[-]

Sorbentlar sifatida ICF va ICB dan foydalanib As (III) va As (V) uchun ikkita sorbsion-desorbtsiya tsikllari uchun ustunlarni tiklash bo'yicha tadqiqotlar o'tkazildi. Bir yuz qirq etti karavotli As (III) va 112 (As (V)) er osti suvlari kolbali tajribalarda ICB yordamida ishlov berilib, mishyak kontsentratsiyasini 500 dan <10kg / l gacha kamaytirdi. Sarflangan sorbentni tiklash uchun ishlatiladigan elektent 0,1 M NaOH ni tashkil qildi. Adsorbent, shuningdek, arsenik bilan ifloslangan er osti suvlari namunalaridan umumiy noorganik mishyakni <10 mkg / l gacha tushirish uchun muvaffaqiyatli ishlatilgan. Yana bir muhim metal bo'lgan xrom ko'plab sanoat qo'llanmalariga ega, masalan, to'qimachilik, elektrokaplama, teri terisi va metallurgiya sanoatida, shuning uchun ushbu sohalarda hosil bo'lgan chiqindilar oltita Cr (VI) yoki trivalent Cr (III) xromga boy. Cr (VI) Cr (III) ga qaraganda toksikroq va shuning uchun atrof-muhitga ko'proq ta'sir ko'rsatmoqda. Xrom odam uchun potentsial zaharli hisoblanadi, chunki u kanserogen hisoblanadi. Xitosanflaklarda Cr (VI) adsorbsiyasi, Aydin va Aksoy tomonidan pH, adsorbent dozasi va boshlang'ich Cr (VI) kontsentratsiyasi kabi jarayon parametrlariga nisbatan tekshirildi [38]. Ushbu omillarning ta'siri mos ravishda 1,5–9,5, 1,8–24,2 g / l va 15–95 mg / l oralig'ida o'rganildi. 13 pH da 30 mg / l konsentratsiyalangan eritmadan 13 g / l adsorbent dozasi bilan maksimal eritmaga erishildi. Ko'rsatilgan sharoitlarda xitosanflaklarning adsorbsion sig'imi 22,09 mg / g sifatida aniqlandi. Shu bilan birga, adsorbsion sig'imi 100 mg / l boshlang'ich Cr (VI) kontsentratsiyasi uchun 102 mg / g sifatida qayd etildi. Soxta ikkinchi darajali kinetik model ma'lumotlar bilan eng yuqori bog'liqlikni namoyish etdi. Natijalar shuni ko'rsatdiki, ikkala monolayer adsorbsiyasi va intrapartaraksimon diffuziya mexanizmlari Cr (VI) adsorbsiya tezligini chekladi. Suvli eritmadan Cr (VI) ni olib tashlash uchun adsorbent sifatida o'zaro bog'liq va o'zaro bog'liq bo'lmagan xitosanning qobiliyati namoyish etildi [39]. Cr (VI) adsorbsion xatti-harakatlarini Langmuir izoterm modelidan foydalanib, 10 dan 1000 mg / L Cr (VI) konsentratsiyasi oralig'ida tasvirlash mumkin. Xitosanning har ikkala turi uchun maksimal adsorbtsiya hajmi o'zaro bog'liq bo'lmagan xitosan uchun 78 mg / g va Cr (VI) ni olib tashlash uchun o'zaro bog'langan xitosan uchun 50 mg / g deb topildi. Maksimal Cr (VI) olib tashlash uchun eng maqbul pH 5. Cr (VI) ni olib tashlash uchun perititli boncuklar xitozan va perlitni o'z ichiga olgan suyuq atala tarkibiga gidroksidi vannaga tomchilatib xitosan bilan qoplangan [40]. Xitosan bilan qoplangan perlitning adsorbsion sig'imi 5000 mg / l Cr (VI) bo'lgan eritmadan 104 mg / g adsorbent ekanligi aniqlandi. Xitosan asosida sig'imi 452 mg / g chitosan bo'lgan. Mualliflar tomonidan bu tabiiy xitosanning tabiiy va modifikatsiyalangan shaklidagi xitosan sig'imidan 11,3 dan 78 mg / g gacha bo'lgan xitosanga nisbatan ancha yuqori ekanligi ma'lum qilindi. Xrom bilan to'ldirilgan boncuklar turli xil konsentratsiyali natriy gidroksid eritmasi bilan qayta tiklandi.

Boddu et al.[41] prepared a composite chitosan biosorbent by coating chitosan, onto nonporous ceramic alumina. Batch and continuous column sorption experiments with this sorbent were carried out at 25 °C to evaluate Cr(VI) adsorption from synthetic and actual chrome plating wastewater samples. Experimental equilibrium data werefitted to Langmuir and Freundlich models. The maximum 29 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy capacity for Cr(VI) obtained from the Langmuir model was 154 mg/g. The adsorption capacities reported in this study on the twice-coated biosorbent was considerably higher than those previously reported values in literature, indicating that the chitosan in the composite biosorbent has greater adsorption capacity than unsupported chitosan and the coating process significantly improved the dsorption capacity of chitosan. This improvement was attributed to the increased surface area and facilitation of transport of chromium ions to the binding sites on chitosan. Quaternary ammonium salt of chitosan (QCS) was synthesized via reaction of a quaternary trimethyl ammonium, glycidyl chloride[42] and examined for Cr(VI) removal. The sorption capacity was found to be pH dependent. The optimum pH range for adsorption was found to be 3.5–4.5, at which Cr(VI) existed frequently as the most easily adsorbed species, HCrO4 − . The Cr(VI) adsorption capacity at pH 9.0 was 30.2 mg/g, while at pH 4.5 the capacity was 68.3 mg/g. The kinetics of Cr(VI) on the cross-linked quaternary chitosan salt (QCS) were found to follow second-order rate mechanism. Cr(VI) ions were eluted from cross-linked QCS by treatment with a 1 mol/L solution of NaCl/NaOH to give a chromium efficiency of more than 95%. Chromium removal onto cross-linked chitosan was studied by Rojas et al.[43]as a function of pH, particle size, adsorbent dose, chromium concentration and chromium oxidation state. The optimum adsorption pH was 4.0, while chromium(VI) was partially reduced in the range pH≤3.0. The chitosan potential for chromium(III) removal was found lower (6 mg/g), while higher uptake was observed for chromium(VI) (215 mg/g). This high capacity was explained due to the large stoichiometry of protonated amine sites in the acidic range of pH. Three cross-linked chitosan-derivatives were used as sorbents for the removal of Cr(VI) from aqueous solutions [25]:(i)Ch,without grafting; (ii)Ch-g-Aam, grafted with acrylamide; and (iii) Ch-g-Aa, grafted with acrylic acid.Ch-g-Aammaterial presented the highest sorption capacity for Cr(VI) removal (935 mg/g at pH 4) among the studied and cited chitosan materials. The FTIR spectra of Cr(VI)-loaded and non-loaded sorbents were also shown to elucidate the mechanism of Cr(VI) sorption onto the prepared chitosan sorbents. The peaks of amino groups of Cr(VI)-loaded chitosan sorbents presented shifts with respect to non-loaded ones (Ch, 1665–1669 cm −1 ; Ch-g-Aam,1672– 1679 cm −1 ; Ch-g-Aa, 1726–1731 cm −1 ), suggesting the electrostatic interaction between HCrO4 − and amino groups of chitosan. Furthermore, two new peaks were observed in FTIR spectra of Cr(VI)-loaded sorbents which attributed to Cr–O and Cr=O bonds of chromate anions, confirming the sorption of Cr(VI) onto the chitosan-derivatives at 789 and 910 cm−1 , 781 and 924 cm−1 ,779 and 907 cm−1 for ν Cr– and ν Cr=O, respectively, in the case ofCh, Ch-g-AamandCh-g-Aa. The regeneration of sorbents was affirmed in four sequential cycles of sorption–desorption experiments, without significant loss in sorption capacity. Chitosan–Fe(0) nanoparticles (chitosan–Fe(0)) were prepared using non-toxic and biodegradable chitosan as a stabilizer and batch experiments were conducted to evaluate the influences of initial Cr(VI) concentration and other factors on Cr(VI) reduction on the surface of the chitosan–Fe(0)[44]. The authors suggested that the overall disappearance of Cr(VI) might include both physical dsorption of Cr(VI) onto the chitosan–Fe(0) surface and subsequent reduction of Cr(VI) to Cr(III). Characterization with high-resolution X-ray photoelectron spectroscopy revealed that after the reaction, relative to Cr(VI) and Fe(0), Cr(III) and Fe(III) were the predominant species on the surface of chitosan–Fe(0). Chitosan also inhibited the formation of Fe(III)–Cr(III) precipitation due to its high efficiency in chelating the Fe(III) ions. This study demonstrated that chitosan–Fe(0) has the potential to become an effective agent for in situ subsurface environmental remediation. A novel aminated chitosan adsorbent with higher adsorption ability for metal cations and metal anions was prepared[45]. Through cross-linking amination reaction, the content of amidocyanogen of aminated chitosan adsorbent was enhanced four times than that of chitosan cross-linked adsorbent.

Boddu va boshq. [41] kompozitsion chitosan biosorbentini xitosan bilan qoplash orqali, non-keramik aluminga. Ushbu sorbent bilan ommaviy va doimiy ustunli sorbsiya tajribalari sintetik va haqiqiy krom qoplamali oqava suv namunalarida Cr (VI) adsorbtsiyasini baholash uchun 25 ° C da o'tkazildi. Eksperimental muvozanat ma'lumotlari Langmuir va Freundlich modellariga o'rnatildi. Maksimal 29 A. Bhatnagar, M. Sillanpäa / Kolloid va interfeys fanidagi yutuqlar 152 (2009) 26–38 Langmuir modelidan olingan Cr (VI) uchun muallifning shaxsiy nusxasi hajmi 154 mg / g. Ikki marta qoplangan biosorbent bo'yicha ushbu tadqiqotda aytilgan adsorbsion sig'im adabiyotda ilgari xabar qilingan qiymatlarga nisbatan ancha yuqori bo'lgan, bu kompozit biosorbent tarkibidagi xitosan qo'llab-quvvatlanmaydigan xitosanga nisbatan ko'proq adsorbsion quvvatga ega ekanligini va qoplama jarayoni chitosanning dorbtsiya qobiliyatini sezilarli darajada yaxshilaganligini ko'rsatmoqda. . Ushbu yaxshilanish xitosanning bog'laydigan joylariga xrom ionlarini tashish yuzasining kengayishi bilan bog'liqdir. Xitosanning to'rtinchi ammoniy tuzi (QCS) to'rtlamchi trimetil ammoniy, glisidil xlorid [42] reaktsiyasi orqali sintez qilindi va Cr (VI) chiqarib tashlanishi tekshirildi. Sorbsiya hajmi pH ga bog'liq ekanligi aniqlandi. Adsorbsiya uchun optimal pH diapazoni 3,5–4,5 deb topildi, bunda Cr (VI) eng oson adsorbsiyalangan turlar HCrO4 sifatida tez-tez mavjud edi. PH 9.0 da Cr (VI) adsorbsiya sig'imi 30,2 mg / g, pH 4,5 da esa 68,3 mg / g. O'zaro bog'langan to'rtlamchi xitosan tuzidagi (QCS) Cr (VI) kinetikasi ikkinchi darajali tezlik mexanizmiga amal qilishi aniqlandi. Kr (VI) ionlari o'zaro bog'langan QCS dan xrom samaradorligini 95% dan ko'proq oshirish uchun NaCl / NaOH ning 1 mol / L eritmasi bilan ishlov berish orqali ajralib chiqdi. Xromning o'zaro bog'langan xitosanga tushirilishi Rojas va boshqalar [43] tomonidan pH, zarrachalar hajmi, adsorbent dozasi, xrom kontsentratsiyasi va xrom oksidlanish holati sifatida o'rganilgan. Optimal adsorbtsiya pH darajasi 4,0, xrom (VI) pH≤3.0 oralig'ida qisman kamaygan. Xromni (III) olib tashlash uchun xitosan potentsiali pastroq (6 mg / g), xrom (VI) ga nisbatan yuqori ko'rsatkich kuzatilgan (215 mg / g). Bu yuqori quvvat pHning kislotali diapazonidagi protonli amin maydonlarining katta stoxiometriyasi tufayli izohlandi. Suvli eritmalardan Cr (VI) ni olib tashlash uchun sorbentlar sifatida uchta o'zaro bog'langan xitosan hosilalari ishlatilgan [25] :( i) Ch, payvandlanmasdan; (ii) akrilamid bilan payvandlangan Ch-g-Aam; va (iii) Akril kislotasi bilan payvandlangan Ch-g-Aa. Ch-g-Aammateryalash o'rganilgan va iqtibos qilingan xitosan materiallari orasida Cr (VI) ni olish uchun eng yuqori sorbtsiya qobiliyatini (pH 4 da 935 mg / g) tashkil etdi. Cr (VI) yuklangan va yuklanmagan sorbentlarning FTIR spektrlari Cr (VI) so'rib olish mexanizmini tayyorlangan xitosan sorbentlariga tushuntirish uchun ham ko'rsatildi. Kr (VI) yuklangan xitosan sorbentlarining aminokislotalari cho'qqilari yuklanmaganlarga nisbatan siljishni ko'rsatdi (Ch, 1665–1669 sm −1; Ch-g-Aam, 1672–1679 sm −1; Ch-g- Aa, 1726–1731 sm −1), bu HCrO4 - va xitosan aminokislotalari orasidagi elektrostatik o'zaro ta'sirni ko'rsatadi. Bundan tashqari, FTIR bilan to'ldirilgan Cr (VI) sorbentlarning FTIR spratlarida Cr-O va Cr = O xromat anionlarining birikmalariga qo'shilib, 789 va 910da xitosan hosilalariga Cr (VI) sorbsiyasini tasdiqlagan. − Cr– va ν Cr = O uchun mos ravishda Ch, Ch-g-AamandCh-g-Aa uchun sm − 1, 781 va 924 sm − 1, 779 va 907 sm − 1. Sorbentlarning regeneratsiyasi sorbsiya-desorbtsiya eksperimentlarining to'rt ketma-ket tsikllarida, yutilish qobiliyatida sezilarli yo'qotishlarsiz tasdiqlandi. Chitosan-Fe (0) nano-zarrachalar (xitosan-Fe (0)) toksik bo'lmagan va biologik parchalanadigan xitosan yordamida stabilizator sifatida tayyorlandi va Cr (VI) kontsentratsiyasining va Cr (VI) boshqa omillarning ta'sirini baholash uchun tajriba o'tkazildi. ) xitosan – Fe (0) [44] yuzasida pasayish. Mualliflar Cr (VI) ning butunlay yo'q bo'lib ketishiga Cr (VI) ning xitosan – Fe (0) yuzasiga fizik tushishi va Cr (VI) ning Cr (III) ga kamayishi ham kiradi. Yuqori aniqlikdagi rentgen fotoelektron spektroskopiyasi bilan xarakterlash reaktsiyadan so'ng Cr (VI) va Fe (0), Cr (III) va Fe (III) ga nisbatan chitosan-Fe (0) yuzasida ustun tur bo'lganligi aniqlandi. ). Chitosan Fe (III) - Cr (III) yog'ingarchiliklarini Fe (III) ionlarini gellatishda yuqori samaradorligi tufayli hosil bo'lishiga to'sqinlik qildi. Ushbu tadqiqot chitosan-Fe (0) situ yer osti atrof-muhitni tiklash bo'yicha samarali agentga aylanishi mumkinligini ko'rsatdi. Metall kationlari va metal anionlari uchun yuqori adsorbtsiya qobiliyatiga ega bo'lgan aminlashtirilgan xitosan adsorbenti tayyorlandi [45]. O'zaro bog'langan aminatsiya reaktsiyasi orqali amidotsianogen amidotsianogenining tarkibi xitosan o'zaro bog'liq adsorbentga qaraganda to'rt baravar ko'paydi.

The adsorption ability of the novel aminated chitosan adsorbent for nickel citrate and Cr(VI) was enhanced remarkably. When the initial concentration of metallic ion was 1000 mg/L, the adsorption capacity of the novel aminated chitosan adsorbent for nickel citrate and Cr(VI) was up to 30.2 mg/g and 28.7 mg/g, respectively. Rhenate sorption on chitin and chitosan has been studied by Kim et al. [46] as an analogue of radioactive ertechnate anion. The mechanism was described by ion-pair formation in the diffuse double layer between NH3 + surface group and rhenate anions in solution. The amount of sorbed rhenate decreased with the increase in pH from 3 to 6.5, indicating a lowering of the sorption capacity of chitosan. At pH 3, a large number of amine groups were in protonated form and could interact with the negatively charged perrhenate anion via electrostatic interactions. At higher pH, the amount of protonated amine groups decreased drastically, limiting the sorption of rhenate. With the increase in the ionic strength from 0.01 to 0.1 M, rhenate sorption on chitosan decreased by 90%. The sorption capacity of chitin and chitosan for rhenate adsorption was also compared. pH 3 was found favorable for adsorption on chitin, however, pH 4.1 was found more favorable in case of chitosan. Even under these conditions, the percentage of rhenate sorbed on chitin was much smaller than the percentage of rhenate sorbed on the chitosan. The main difference between the two organic polymers was that, for chitin, the majority of NH2 groups ere acetylated, so that the amount of protonated amine groups was smaller by far, than in chitosan for the similar experimental conditions. Consequently, chitin had a much smaller surface charge. Thus, a smaller amount of perrhenate anions were located in the diffuse double layer via electrostatic interactions. The weak sorption of rhenate on chitin showed that the sorption of perrhenate occurred only when a large number of protonated amine groups were present on the organic molecule. Acid-washed Ucides shells (AWUS) showed good adsorption potential for anionic gold-cyanide (Au(CN)2 − ), selenate (SeO4 2− ),chromate (CrO4 2− ) and vanadate (VO4 3− )atlowpH[47]. Equilibrium biosorption uptakes by AWUS were up to 0.17 mmol Au/g AWUS (pH 3.4), 0.15 mmol Se/g (pH 3.0), 0.54 mmol Cr/g (pH 2.0) and 0.79 mmol V/g (pH 2.5). An increased ionic strength (IS) suppressed the primary anion uptake as chloride ions competed for biosorbent protonated sites and higher IS reduced the activity of ions in solution. The biosorption mechanism was suggested to involve electrostatic attraction. Chitosan-derivatives have also been explored for the removal and recovery of precious metals. The adsorption of gold (Au(III)) ions onto chitosan and N-carboxymethyl chitosan (NCMC) has been investigated[48]. The percentage adsorption increased first with the rise in pH and then reached a maximum at about pH 4.0 and 6.0, for chitosan and NCMC, respectively. It decreased sharply with a further increase in equilibrium pH. The uptake of Au 3+ on chitosan and NCMC were 30.95 mg/g of chitosan and 33.90 mg/g of NCMC. The Au 3+ ions were readily removed from chitosan and NCMC by treatment with an aqueous EDTA solution. Based on the desorption studies, it was concluded that ion exchange was the controlling mechanism.

Nikel sitrat va Cr (VI) uchun aminlashtirilgan xitosan adsorbentining adsorbsion qobiliyati juda yaxshilandi. Metall ionining dastlabki konsentratsiyasi 1000 mg / l bo'lganida, nikel tsitrati va Cr (VI) uchun yangi aminlangan xitosan adsorbentining adsorbsion quvvati mos ravishda 30,2 mg / g va 28,7 mg / g gacha bo'lgan. Xitin va xitosanda renat sorbsiyasi Kim va boshq tomonidan o'rganilgan. [46] radioaktiv ertexnika anionining analogi sifatida. Mexanizm NH3 + sirt guruhi va eritmadagi renat anionlari orasidagi diffuz ikki qatlamda ion-juft hosil bo'lishi bilan tavsiflangan. Sorbent renat miqdori pH 3 dan 6,5 gacha ko'tarilishi bilan kamaygan, bu xitosanning sorbsion qobiliyatining pasayganligidan dalolat beradi. PH 3 da ko'p miqdordagi amin guruhlari protonlangan holatda bo'lgan va elektrostatik shovqinlar orqali manfiy zaryadlangan perrenat anioni bilan o'zaro ta'sirlashishi mumkin edi. Yuqori pH darajasida protonlangan amin guruhlari miqdori keskin kamayib, renatning sorbsiyasini cheklaydi. Ion kuchining 0,01 dan 0,1 M gacha oshishi bilan xitozanda rhenat sorbsiyasi 90% ga kamaydi. Renit adsorbsiyasi uchun xitin va xitosanning sorbsion sig'imi solishtirildi. pH 3 xitinga adsorbsiyasi uchun qulay deb topildi, ammo pH 4.1 xitozan uchun qulayroq deb topildi. Ushbu sharoitlarda ham xitin bilan sorblangan rhenat ulushi xitosan tarkibidagi sorinlangan renat ulushiga qaraganda ancha oz edi. Ikki organik polimer o'rtasidagi asosiy farq shundan iboratki, xitin uchun NH2 guruhlarining aksariyati atsetilatsiyalanadi, shuning uchun shunga o'xshash eksperimental sharoitda xitozanga qaraganda protonlangan amin guruhlari miqdori kamroq edi. Shunday qilib, xitinning sirt zaryadi ancha oz bo'lgan. Shunday qilib, elektrostatik shovqinlar orqali diffuz ikki qatlamda kamroq miqdordagi perrenat anionlari joylashgan edi. Xitinga renatning zaif sorbentsiyasi shuni ko'rsatdiki, perrenatning sorbsiyasi faqat organik molekulada juda ko'p protonli amin guruhlari mavjud bo'lganda sodir bo'ldi. Kislota bilan yuvilgan Utsid chig'anoqlari (AWUS) anionli oltin-siyanid (Au (CN) 2 -), selenat (SeO4 2−), xromat (CrO4 2−) va vanadat (VO4 3−) atowpH uchun yaxshi adsorbtsiya potentsialini ko'rsatdi [47]. . AWUS tomonidan muvozanatli biosorbtsion oqimlar 0,17 mmol Au / g AWUS (pH 3,4), 0,15 mmol Se / g (pH 3,0), 0,54 mmol Cr / g (pH 2.0) va 0,79 mmol V / g (pH 2,5) edi. Ionning kuchayishi (IS) birlamchi anion zaxirasini bostirdi, chunki xlorid ionlari biosorbent protonlangan joylar uchun raqobatlashdi va yuqori darajadagi IS eritmadagi ionlarning faolligini pasaytirdi. Biosorbtsiya mexanizmiga elektrostatik jalb qilish taklif qilingan. Chitosan hosilalari qimmatbaho metallarni olib tashlash va tiklash uchun ham o'rganilgan. Oltin (Au (III)) ionlarining xitosan va N-karboksimetil xitosan (NCMC) ga adsorbsiyasi tekshirildi [48]. Adsorbtsiya foizi avval pH ko'tarilishi bilan ortdi va keyin chitosan va NCMC uchun mos ravishda pH 4.0 va 6.0 ga etdi. Balans pH darajasining ortishi bilan u keskin pasaygan. Ait 3+ ning xitosan va NCMC ga bo'lgan ta'siri 30,95 mg / g chitosan va 33,90 mg / g NCMC ni tashkil qildi. Au 3+ ionlari suvli EDTA eritmasi bilan ishlov berish orqali xitosan va NCMCdan osongina chiqarildi. Desorbsiya tadqiqotlariga asoslanib, ion almashinuvi nazorat qiluvchi mexanizm degan xulosaga keldi.

Chitosan-derivatives were found very efficient for removing gold from dilute acidic solutions [49]. Maximum uptake capacity reached 600 mg/g (ca. 3 mmol/g). The speciation of gold (under chloride and hydroxide–chloride forms) appeared to be a predominant parameter influencing uptake. In acidic solutions, chitosan was protonated and protonated amine groups were available for the sorption of anionic gold species. The optimum pH range was pH 2–3 for glutaraldehyde crosslinked chitosan, but the sorption capacity strongly decreased with increasing pH. Rubeanic acid grafting decreased the influence of pH on gold sorption. Sulfur grafting increased the polymer chelating sites that were less influenced by pH than ion-exchange sites (protonated amines) involved in ion-pair formation. Sorption kinetics was influenced by pH and the type of chitosan-derivatives. The grafting of sulfur compounds and the hexamethylene diisocyanate cross-linking enhanced sorption kinetics probably due to the presence of highly reactive chelating sites and better diffusion properties. 30 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy Chitosan was also examined for the removal of soluble silver from industrial waste streams [50]. Stirred-batch and column methods were used to remove free (hydrated) silver ion as well as the ammonia, thiocyanate, thiosulfate, and cyanide complexes of silver in simulated wastewater at an initial concentration of 50 mg/L and in a pH range of 2–10. In the case of the free silver ion, Ag+ ,andin particular for Ag(NH3)2 +, the applicable pH range was quite broad (4–8). However, the anions, Ag(SCN)3 2− and Ag(S2O3)2 3− , were bound only at pH 2, and Ag(CN)2 − was not bound to any significant extent at any pH examined in these experiments. The calculated silver ion capacity in a flow-through column at pH 6 was reported ca. 42 mg/g. The chitosan microparticles were prepared using the inverse phase emulsion dispersion method and modified with thiourea (TCS)[51].The results showed that the maximum adsorption capacity was found at pH 2.0 for both Pt(IV) and Pd(II). TCS can selectively adsorb Pt(IV) and Pd(II) from binary mixtures with Cu(II), Pb(II), Cd(II), Zn(II), Ca(II), and Mg(II). The adsorption reaction followed the pseudo-second-order kinetics, indicating the main adsorption mechanism of chemical adsorption. The isotherm adsorption equilibrium was well described by Langmuir isotherms with the maximum adsorption capacity of 129.9 mg/g for Pt(IV) and112.4 mg/g for Pd(II). The adsorption capacity of both Pt(IV) and Pd(II) decreased with increase in temperature. The adsorbent was stable without loss of the adsorption capacity up to at least 5 cycles and the desorption efficiencies were above 95% when 0.5 M EDTA–0.5 M H2SO4 eluent was used. The results also showed that the pre-concentration factor for Pt(IV) and Pd(II) was 196 and 172, respectively, and the recovery was found to be more than 97% for both precious metal ions. Chitosan-derivatives have also been explored for the removal of some radionuclides from water.

Xitosan hosilalari oltinni suyultirilgan kislotali eritmalardan olib tashlash uchun juda samarali deb topildi [49]. Maksimal yutish quvvati 600 mg / g (3 mmol / g) ga etdi. Oltinning spetsifikatsiyasi (xlorid va gidroksid-xlorid shakllari ostida) zararli ta'sir ko'rsatadigan asosiy parametr bo'lib chiqdi. Kislotali eritmalarda xitosan protonlangan va anionli oltin turlarini sorbsiya qilish uchun protonlangan amin guruhlari mavjud edi. Eng yaxshi pH diapazoni glyutaraldegid o'zaro bog'langan xitosan uchun pH 2-3 ni tashkil etdi, ammo pHning oshishi bilan sorbsiya hajmi keskin pasaydi. Ruban kislotasini payvandlash pH ning oltin sorbsiyasiga ta'sirini kamaytirdi. Oltingugurtni payvand qilish ion juftlari shakllanishida ishtirok etadigan ion almashinadigan maydonlarga (protonlangan aminlarga) qaraganda pH kamroq ta'sir ko'rsatadigan polimer xelatlash joylarini ko'paytirdi. Sorption kinetikasi pH va xitosan-hosilalarining turiga ta'sir ko'rsatdi. Oltingugurt birikmalarining payvandlanishi va geksametilen diizosyanatning o'zaro bog'langan kuchaytirilgan sorbsion kinetikasi, ehtimol yuqori reaktiv xelatlash joylarining mavjudligi va yaxshiroq diffuziya xususiyatlariga bog'liqdir. 30 A. Bhatnagar, M. Sillanpäa / Kolloid va interfeys fanidagi yutuqlar 152 (2009) 26–38 Chitosan muallifining shaxsiy nusxasi sanoat chiqindilaridan eriydigan kumushni olib tashlash uchun ham tekshirilgan [50]. Eritilgan (gidratlangan) kumush ionini, shuningdek ammiak, tiosiyanat, tiosulfat va siyanid komplekslarini kumushning 50 mg / l va pH 2 kontsentratsiyasida simulyatsiya qilingan oqava suvlarda olish uchun aralashtirilgan va ommaviy usullardan foydalanilgan. –10. Erkin kumush ioni bo'lgan Ag +, xususan Ag (NH3) 2 + uchun, qo'llaniladigan pH diapazoni ancha keng edi (4–8). Ammo Ag (SCN) 3 2− va Ag (S2O3) 2 3− anionlari faqat pH 2 ga bog'langan, va Ag (CN) 2 - ushbu tajribalarda o'rganilgan har qanday pH darajasida hech qanday darajada bog'lanmagan. Oqim orqali o'tadigan kolonda pH 6 hisoblangan kumush ionining sig'imi qayd qilindi. 42 mg / g. Xitosan mikropartikullari teskari fazali emulsiya dispersiyasi usuli yordamida tayyorlangan va tiourea (TCS) bilan o'zgartirilgan [51]. Natijalar shuni ko'rsatdiki, maksimal adsorbsion sig'imi pt (IV) va Pd (II) uchun pH 2,0 da topilgan. TCS Cu (II), Pb (II), Cd (II), Zn (II), Ca (II) va Mg (II) bilan o'zaro aralashmalardan Pt (IV) va Pd (II) ni tanlab adsorblashi mumkin. Adsorbsiya reaktsiyasi kimyoviy adsorbsiyaning asosiy adsorbsion mexanizmini ko'rsatib, soxta ikkinchi tartibli kinetikaga ergashdi. Izotermning adsorbtsiya muvozanati Pt (IV) uchun 129,9 mg / g va Pd (II) uchun 12,4 mg / g bo'lgan Langmuir izotermalari tomonidan yaxshi tasvirlangan. Haroratning oshishi bilan Pt (IV) va Pd (II) ning adsorbsion qobiliyati pasaygan. Kamida 5 tsiklgacha adsorbtsiya qobiliyatini yo'qotmasdan adsorbent barqaror edi va 0,5 M EDTA – 0,5 M H2SO4 elektent ishlatilganda desorbtsiya samarasi 95% dan yuqori edi. Shuningdek, natijalar shuni ko'rsatdiki, Pt (IV) va Pd (II) ning konsentratsiyadan oldingi koeffitsienti mos ravishda 196 va 172 ni tashkil etdi va tiklanish ikkala qimmatbaho metal ionlari uchun 97% dan ko'proq ekanligi aniqlandi. Chitosan hosilalari, shuningdek, ba'zi radionuklidlarni suvdan olib tashlash uchun ham o'rganilgan.

Chitosan benzoyl thiourea derivative has been synthesized and used successfully for the removal of the hazardous 60 Co and 152 + 154 Eu radionuclides from aqueous solutions by Metwally et al.[52]. The maximum adsorption capacities for Co(II) and Eu(III) were 29.47 (mg/g) and 34.54 (mg/g), respectively. It was found that uptake% of Eu(III) and Co(II) reached its maximum values of 75.0% and 98.0% at pH 3.5 and 8.0, respectively, at 10 −5 M ion concentration. Adsorption of uranium(VI) from aqueous solution onto cross-linked chitosan (CCTS) was investigated in a batch system by Wang et al.[53]. The maximum Langmuir monolayer capacity was found to be 72.6 mg/g. The uranium(VI) adsorption capacity by CCTS was strongly dependent on contact time, pH, and initial uranium(VI) concentration. Kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Readers interested in a detailed discussion of the interaction of metal ions with chitosan should refer to the excellent comprehensive reviews published elsewhere[5–7]. A summary of adsorption capacities of chitin- and chitosan-derivatives for different metal ions and radionuclides has been presented in Table 1.It is evident from the vast literature survey that chitin-, chitosanand its derivatives have been proven very promising biosorbents for the removal of metal ions from water and wastewater. The mechanism of metal adsorption on chitin- and chitosan-derivatives has been proposed to occur via electrostatic interactions in acidic media (ion exchange), metal chelation (coordination) and due to the formation of ion pairs[5–7]. Several parameters influence this reaction such as, ionic charge of the adsorbent, solution pH and the chemistry of the metal ion (ionic charge, ability to be hydrolyzed and to form polynuclear species).

Chitosan benzoyl tiourea hosilasi sintez qilingan va xavfli 60 Co va 152 + 154 Eu radionuklidlarini suvli eritmalardan Metwally va boshqalar tomonidan olib tashlash uchun muvaffaqiyatli ishlatilgan [52]. Co (II) va Eu (III) uchun maksimal adsorbtsiya sig'imi mos ravishda 29,47 (mg / g) va 34.54 (mg / g) ni tashkil etdi. % Eu (III) va Co (II) olishning maksimal qiymatlari pH 3,5 va 8,0 da mos ravishda 10 −5 M ion kontsentratsiyasida 75,0% va 98,0% ga etganligi aniqlandi. Uranning (VI) suvli eritmadan o'zaro bog'langan xitosanga (CCTS) adsorbtsiyasi partiyalar tizimida Vang va boshqalar tomonidan o'rganilgan [53]. Langmuir monolayerining maksimal sig'imi 72,6 mg / g deb topildi. CCTS tomonidan uran (VI) adsorbsion sig'imi kontakt vaqti, pH va uran (VI) kontsentratsiyasiga kuchli bog'liq edi. Kinetik tadqiqotlar shuni ko'rsatdiki, adsorbsiya soxta ikkinchi darajali kinetik modelga ergashdi va bu kimyoviy adsorbsiya tezlikni cheklovchi qadam ekanligini ko'rsatdi. Metall ionlarining xitosan bilan o'zaro ta'siri to'g'risida batafsil muhokama qilishni istagan o'quvchilar boshqa joyda nashr etilgan mukammal batafsil sharhlarga murojaat qilishlari kerak (5-7). 1-jadvalda turli metal ionlari va radionuklidlar uchun xitin- va xitosan-hosilalarning adsorbsion qobiliyatlari to'g'risida qisqacha ma'lumot keltirilgan. Bu katta adabiyot tadqiqotlarida chitin-, xitosan va uning hosilalari olib tashlanishi uchun juda istiqbolli biosorbentslar isbotlanganligi ko'rinib turibdi. suv va oqova suvlardan metall ionlari. Xitin- va xitosan-derivativlarga metal adsorbsiyasi mexanizmi kislotali muhitda elektrostatik ta'sir o'tkazish (ion almashinuvi), metallarning xellashi (koordinatsiya) va ion juftlarining shakllanishi tufayli yuzaga keladi [5-7]. Ushbu reaktsiyaga adsorbentning ion zaryadi, pH eritmasi va metall ionining kimyosi (ion zaryadi, gidrolizlanish va polinukulyar turlarni shakllantirish qobiliyati) kabi bir qator parametrlar ta'sir qiladi.

2.2. Chitin- and chitosan-derivatives for dyes removal

Dyes are important water pollutants which are generally present in the effluents of textile, leather, paper and dye manufacturing industries. The worldwide high level of production and extensive use of dyes generates colored wastewaters which cause water pollution. The colored dye effluents are generally considered to be highly toxic to the aquatic biota and affect the symbiotic process by disturbing the natural equilibrium through reduced photosynthetic activity due to the coloration of water in streams. Some dyes are reported to cause allergy, dermatitis, skin irritation, and cancer in humans. Thus, the removal of dyes from effluents before they are mixed up with unpolluted natural water bodies is important. Various studies on chitin and chitosan for dyes removal from water and wastewater have been conducted in recent years[53–66]. These studies demonstrated that chitosan-based biosorbents are efficient materials and have an extremely high affinity for many classes of dyes.

Table 1 Adsorption capacities of chitin and chitosan-derivatives for various metal ions and radionuclides removal from water.

2.2. Bo'yoqlarni olib tashlash uchun xitin va xitosan hosilalari

Bo'yoqlar, asosan, to'qimachilik, charm, qog'oz va bo'yoq ishlab chiqarish sanoatida mavjud bo'lgan suvni ifloslantiruvchi moddalardir. Dunyo miqyosida yuqori darajada ishlab chiqarish va bo'yoqlardan keng foydalanish suvning ifloslanishiga olib keladigan rangli oqava suvlarni keltirib chiqaradi. Rangli bo'yoqli oqava suvlar odatda suv biotasi uchun juda zaharli hisoblanadi va simbiyotik jarayonga ta'sir qiladi, oqimdagi suvning ranglanishi tufayli fotosintetik faolligi pasayishi natijasida tabiiy muvozanatni buzadi. Ba'zi bo'yoqlar odamlarda allergiya, dermatit, terining tirnash xususiyati va saraton kasalligini keltirib chiqaradi. Shunday qilib, ifloslangan tabiiy suv havzalari bilan aralashtirishdan oldin bo'yoqlarni olib tashlash juda muhimdir. So'nggi yillarda xitin va xitosanni bo'yoqlarni suv va oqava suvlardan tozalash bo'yicha turli tadqiqotlar o'tkazildi [53-66]. Ushbu tadqiqotlar shuni ko'rsatdiki, xitosan asosidagi biosorbentslar samarali materialdir va ko'plab bo'yoq sinflariga juda yuqori darajada yaqinlik qiladi.

1-jadval. Har xil metall ionlari va radionuklidlarni suvdan olib tashlash uchun xitin va xitosan-hosilalarining adsorbtsiya qobiliyatlari.

to the aquatic biota and affect the symbiotic process by disturbing the natural equilibrium through reduced photosynthetic activity due to the coloration of water in streams. Some dyes are reported to cause allergy, dermatitis, skin irritation, and cancer in humans. Thus, the removal of dyes from effluents before they are mixed up with unpolluted natural water bodies is important. Various studies on chitin and chitosan for dyes removal from water and wastewater have been conducted in recent years[53–66]. These studies demonstrated that chitosan-based biosorbents are efficient materials and have an extremely high affinity for many classes of dyes.

suv biotasiga tushadi va oqimlardagi suvning ranglanishi tufayli fotosintetik faollikning pasayishi natijasida tabiiy muvozanatni buzib simbiotik jarayonga ta'sir qiladi. Ba'zi bo'yoqlar odamlarda allergiya, dermatit, terining tirnash xususiyati va saraton kasalligini keltirib chiqaradi. Shunday qilib, ifloslangan tabiiy suv havzalari bilan aralashtirishdan oldin bo'yoqlarni olib tashlash juda muhimdir. So'nggi yillarda xitin va xitosanni bo'yoqlarni suv va oqava suvlardan tozalash bo'yicha turli tadqiqotlar o'tkazildi [53-66]. Ushbu tadqiqotlar shuni ko'rsatdiki, xitosan asosidagi biosorbentslar samarali materialdir va ko'plab bo'yoq sinflariga juda yuqori darajada yaqinlik qiladi.

Wu et al.[58]examined the suitability of chitosan for the removal of reactive dyes. A comparison of the maximum adsorption capacity for reactive red 222 (RR222) by chitosan flakes and beads showed uptake capacities of 293 mg/g forflakes and 1103 mg/g for beads which was explained by the fact that the beads possessed a greater surface area than theflakes. The abilities of removal of three reactive dyes (RR222, RB222, and RY145) and of immobilization of tyrosinase usingflake-type and highly swollen bead-type of chitosans at 30 °C have also been investigated [59]. The capacity of dye adsorption using swollen chitosan beads was aboutfive times, up to 1653 g/kg, as compared to chitosanflakes. The adsorption process could be best described by the pseudo-second-order equation, indicating the controlling nature of chemisorption (chemical reaction). The highly swollen chitosan beads applied in this work, showed promising potential for enzyme immobilization and color removal. The adsorption of reactive dye (reactive red 189) from aqueous solutions on cross-linked chitosan beads was studied in a batch system[60]. The equilibrium isotherms at different particle sizes (2.3– 2.5, 2.5–2.7 and 3.5–3.8 mm) and the kinetics of adsorption with respect to the initial dye concentration (4,320, 5,760 and 7,286 g/m 3 ), temperature (30, 40 and 50 °C), pH (1.0, 3.0, 6.0 and 9.0), and crosslinking ratio (cross-linking agent/chitosan weight ratio: 0.2, 0.5, 0.7 and 1.0) were investigated. The maximum monolayer dsorption capacities obtained from the Langmuir model were very large, (1936, 1686 and 1642 mg/g) for small, medium and large particle sizes, respectively, at pH 3.0 and 30 °C, for the cross-linking ratio of 0.2. The initial dye concentration and the pH of aqueous solutions significantly affected the adsorption capacity of dye RR189 on the cross-linked chitosan. However, the adsorption of the dye on chitosan was slightly influenced by the temperature and the epichlorohydrin (ECH)/ chitosan weight ratio. It was suggested that the rate-limiting step may be the chemical adsorption but not the mass transport. A batch system was also applied to study the adsorption of reactive dye (reactive red 189) from aqueous solutions by cross-linked chitosan beads[61]. The ionic cross-linking reagent sodium tripolyphosphate was used to obtain rigid chitosan beads. To stabilize chitosan in acid solutions, chemical cross-linking reagent epichlorohydrin (ECH), glutaraldehyde and ethylene glycol diglycidyl ether were used and ECH showed the highest adsorptive removal of the dye. The Langmuir model agreed well with experimental data and its calculated maximum monolayer adsorption capacity was found to be 1802–1840 g/kg at pH 3.0, and 30 °C. The electrostatic interactions between the dye and chitosan beads governed the adsorption mechanism. The desorption data showed that the removal percent of dye from the cross-linked chitosan beads was 63% in NaOH solutions at pH 10.0 and 30 °C. It was observed that the desorbed chitosan beads could be reused to adsorb the dye and to reach the same capacity as that before desorption. Chiou et al.[62] examined the adsorption of four reactive dyes, three acid dyes and one direct dye onto cross-linked chitosan beads.

Wu va boshqalar [58] xitosanning reaktiv bo'yoqlarni olib tashlash uchun yaroqliligini ko'rib chiqdilar. Reaktiv qizil 222 (RR222) uchun maksimal adsorbsion sig'im xitosan qopqog'i va boncuklar tomonidan 293 mg / g forflaklar va boncuklar uchun 1103 mg / g bo'lgan sig'imlarni aniqladi, bu munchoqlar nisbatan ko'proq sirt maydoniga ega ekanligi bilan izohlanadi. qorishmalar. Uch reaktiv bo'yoqlarni (RR222, RB222 va RY145) olib tashlash va tirotinazani 30 ° C haroratda parchalanadigan va juda shishgan boncuk tipidagi xitozanlardan foydalanish qobiliyati ham o'rganildi [59]. Shishgan xitosan boncuklardan foydalangan holda bo'yoqning adsorbsiyasi hajmi xitosanflaklarga qaraganda taxminan 1653 g / kg gacha bo'lgan. Adsorbsiya jarayonini eng yaxshi kimyoviy sorbsiyaning (kimyoviy reaktsiya) boshqarilishini ko'rsatuvchi soxta ikkinchi darajali tenglama bilan tasvirlash mumkin. Ushbu ishda qo'llaniladigan juda shishgan xitosan boncuklar, ferment immobilizatsiyasi va ranglarni olib tashlash uchun katta imkoniyatlarni namoyish etdi. Bir-biriga bog'langan xitosan boncuklaridagi suvli eritmalardan reaktiv bo'yoqning adsorbsiyasi (qizil 189-reaktiv) partiyaviy tizimda o'rganilgan [60]. Har xil zarralardagi muvozanat izotermalari (2.3– 2.5, 2.5–2.7 va 3.5–3.8 mm) va bo'yoqlarning dastlabki kontsentratsiyasiga nisbatan adsorbtsiya kinetikasi (4320, 5.760 va 7.286 g / m 3), harorat (30, 40 va 50 ° C), pH (1.0, 3.0, 6.0 va 9.0) va o'zaro bog'liqlik nisbati (o'zaro bog'lanish agenti / chitosan og'irligi nisbati: 0.2, 0.5, 0.7 va 1.0) o'rganildi. Langmuir modelidan olingan maksimal monolayerli dorporbtsiya sig'imi juda katta, (1936, 1686 va 1642 mg / g), mos ravishda pH 3,0 va 30 ° C da kichik, o'rta va katta zarrachalarning o'lchamlari o'zaro bog'liqlik nisbati uchun. 0,2. Dastlabki bo'yoq kontsentratsiyasi va suvli eritmalarning pH o'zaro bog'liq xitozanda RR189 bo'yog'ining adsorbsion sig'imiga sezilarli ta'sir ko'rsatdi. Shu bilan birga, bo'yoqning xitosanga adsorbsiyasi harorat va epiklorohidrin (ECH) / xitosanning vazn nisbatiga ozgina ta'sir ko'rsatdi. Stavkalarni cheklovchi qadam kimyoviy adsorbtsiya bo'lishi mumkin, ammo ommaviy tashish emas. Suvli eritmalardan reaktiv bo'yoqning adsorbtsiyasini o'rganish uchun (189-reaktiv qizil 189) o'zaro bog'langan xitosan boncuklar yordamida tizimli tizim ham qo'llanilgan [61]. Qattiq xitosan boncuklarini olish uchun ionli o'zaro bog'langan reagent natriy tripolifosfat ishlatilgan. Kislota eritmalarida xitosanni barqarorlashtirish uchun kimyoviy o'zaro bog'langan reagent epiklorohidrin (ECH), glutaraldegid va etilen glikol diglikidil efiri ishlatilgan va ECH bo'yoqning yuqori adsorbsion olib tashlanishini ko'rsatgan. Langmuir modeli eksperimental ma'lumotlar bilan yaxshi mos keldi va uning hisoblangan maksimal monolayer adsorbsion quvvati pH 3,0 va 30 ° C da 1802–1840 g / kg deb topildi. Bo'yoq va xitosan boncuklar orasidagi elektrostatik o'zaro ta'sir adsorbsiyalash mexanizmini boshqaradi. Desorbtsiya ma'lumotlari shuni ko'rsatdiki, o'zaro bog'liq bo'lgan xitosan boncuklarından bo'yoqning chiqarilish foizi pH 10,0 va 30 ° C da NaOH eritmalarida 63% ni tashkil qiladi. Tushirilgan xitosan boncuklari bo'yoqni adsorbatsiya qilish va desorbtsiya oldidagi hajmga erishish uchun qayta ishlatilishi mumkinligi kuzatildi. Chiou va boshqalar. [62] To'rt reaktiv bo'yoq, uchta kislotali bo'yoq va bitta to'g'ridan-to'g'ri bo'yoq o'zaro bog'langan xitosan boncuklarına adsorbsiyani o'rganib chiqdi.

The adsorption capacity values ranged from 1911 to 2488 mg/g at pH 3–4. The authors reported that the adsorption conforms to Langmuir isotherm model and pseudo-second-order kinetic model. In addition, adsorption capacity appeared to increase with the decreasing pH of solution. The adsorption capacities of the cross-linked chitosan beads were much higher than those of chitin for anionic dyes. It showed that the major adsorption site of chitosan is an amine group,–NH2, which is easily protonated to form –NH3 + in acidic solutions. The strong electrostatic interaction between the –NH3 + of chitosan and dye anions was used to explain the high adsorption capacity of anionic dyes onto chemically cross-linked chitosan beads. Kinetics of the adsorption of reactive dyes by chitin was studied by Akkaya et al.[63]. The effect of initial concentration, temperature, shaking rate and pH on the adsorption of reactive yellow 2 (RY2) and reactive black 5 (RB5) using chitin was investigated. The authors reported that RY2 and RB5 are significantly adsorbed on chitin. The adsorption capacities were found ca. 38 mg/g for RY2 at 293 K, while 65 mg/g for RY5 at 333 K. It was suggested by the authors that the adsorption kinetics was controlled by surface diffusion as the BET surface area of chitin used in this study was very low. At particularly lower temperatures, surface diffusion was more dominant. The treatment of synthetic reactive dye wastewater (SRDW) by adsorption process was studied using chitin modified by sodium hypochlorite and original chitin in batch experiments[64]. Maximum dye adsorption by chitin increased from 133 mg/g to 167 mg/g with rise in temperatures from 30 to 60 °C. For modified chitin, the capacity decreased from 124 mg/g to 59 mg/g when the temperature increased from 30 °C to 60 °C, respectively. The authors suggested that although modified chitin had lower adsorption capacity as compared to chitin, elution of the dye from modified chitin was easier than chitin. Therefore, modified chitin could be suitable in a column system for dye pre-concentration as well as wastewater minimization. In addition, the column study showed that modified chitin could be used for more than four cycles of adsorption and eluted by distilled water. The main mechanism of dye adsorption onto modified chitin was physical adsorption, while the chemical adsorption was responsible in chitin. Adsorption of reactive orange 16 by quaternary chitosan salt (QCS) was used as a model to demonstrate the removal of reactive dyes from textile effluents by Rosa et al.[65]. The adsorption experiments were conducted at different pH values and initial dye oncentrations. The maximum adsorption capacity determined was 1060 mg of reactive dye/g of adsorbent, corresponding to 75% occupation of the adsorption sites. The results indicated that the adsorption process was not dependent on solution pH, since the most probable mechanism for adsorption was the interaction of the polymer quaternary ammonium groups with the dye sulfonate groups. The adsorption of Remazol black 13 dye onto chitosan in aqueous solutions was investigated[66]. Experiments were carried out as a function of contact time, initial dye concentration (100–300 mg/L), particle size (0.177, 0.384, 1.651 mm), pH (6.7–9.0), and temperature (30–60 °C). The maximum adsorption capacity (qm) was found to be 91.47–130.0 mg/g. The amino group nature of the chitosan provided reasonable dye removal capability. The kinetics of reactive dye adsorption followed the pseudo-first and second-order rate expression which demonstrates that intraparticle diffusion plays a significant role in the adsorption mechanism. The authors also provided scanning electron microscopy (SEM) images to show that the dye was densely and homogeneously adhered to the surface of the carrier, as a result of either natural entrapment in to the porous chitosan material, due to physical adsorption by electrostatic forces or covalent binding between the cellular chitosan and the carrier. Chitosan was cross-linked using glutaraldehyde in the presence of magnetite by Elwakeel[67]. The resin obtained was chemically modified through the reaction with tetraethylenepentamine followed by glycidyl trimethylammonium chloride, to produce chitosan/amino resin (R1) and chitosan bearing both amine and quaternary ammonium chloride moieties (R2), respectively. The uptake of reactive black 5 (RB5) from aqueous solutions using R1 and R2 resins was studied using batch and column methods. The resins showed high affinity for the adsorption of RB5 and an uptake value of 0.63 and 0.78 mmol/g was reported for resins R1 and R2, respectively at 25 °C. The resin was regenerated effectively using NH4OH/NH4Cl buffer (pH 10).

Adsorbtsiya sig'imi ko'rsatkichlari pH 3-4 da 1911 dan 2488 mg / g gacha. Mualliflarning ta'kidlashicha, adsorbsiya Langmuir izotermasi modeliga va soxta ikkinchi darajali kinetik modelga mos keladi. Bundan tashqari, eritmaning pH pasayishi bilan adsorbtsiya hajmi ortib bordi. O'zaro bog'langan xitosan boncuklarının adsorbsion qobiliyati anion bo'yoqlari uchun xitindan yuqori edi. Bu xitosanning asosiy adsorbtsiya zonasi - NH2 kislotali eritmalarda osonlikcha protonlangan NH2 amin guruhi ekanligini ko'rsatdi. Kimyoviy bog'langan xitosan boncuklarına anion bo'yoqlarining yuqori adsorbsion quvvatini tushuntirish uchun xitosan va bo'yoq anionlarining –NH3 + o'zaro kuchli elektrostatik ta'siridan foydalanildi. Reaktiv bo'yoqlarning xitin tomonidan adsorbsiyasi kinetikasi Akkaya va boshqalar tomonidan o'rganilgan [63]. Chitin yordamida reaktiv sariq 2 (RY2) va reaktiv qora 5 (RB5) ning adsorbsiyasiga dastlabki kontsentratsiya, harorat, tebranish darajasi va pHning ta'siri o'rganildi. Mualliflar RY2 va RB5 xitinga sezilarli darajada adsorbsiyalanganligini aytishdi. Adsorbsiya sig'imi topildi 293 K da RY2 uchun 38 mg / g, RY5 uchun esa 65 mg / g, 333 K da esa adsorbsion kinetika sirt diffuziyasi bilan boshqariladi, chunki bu ishda ishlatiladigan xitinning BET sirt maydoni juda past edi. . Ayniqsa past haroratlarda sirt tarqalishi ko'proq ustunlik qildi. Sintetik reaktiv bo'yoq oqava suvlarini (SRDW) adsorbsiya jarayoni bilan davolash natriy gipoxlorit tomonidan o'zgartirilgan xitin va partiyaviy tajribalarda asl xitin yordamida o'rganildi [64]. Xitin bilan bo'yashning maksimal adsorbsiyasi 133 mg / g dan 167 mg / g gacha, harorat 30 dan 60 ° C gacha ko'tarildi. Modifikatsiyalangan xitin uchun harorat mos ravishda 30 ° C dan 60 ° C ga ko'tarilganda 124 mg / g dan 59 mg / g gacha pasaygan. Mualliflar modifikatsiyalangan xitinning xitinga nisbatan adsorbsiya qobiliyatiga ega bo'lishiga qaramay, modifikatsiyalangan xitindan bo'yoqni xitinga qaraganda osonroq ajratib olishni taklif qilishdi. Shuning uchun modifikatsiyalangan xitin bo'yoqlarni oldindan konsentratsiyalash uchun, shuningdek oqava suvlarni minimallashtirish uchun ustun tizimida mos bo'lishi mumkin. Bundan tashqari, ustunli tadqiqotlar shuni ko'rsatdiki, o'zgartirilgan xitinni adsorbsiyaning to'rt tsiklidan ko'proq foydalanish mumkin va distillangan suv bilan yuvib tashlanadi. Modifikatsiyalangan xitinga bo'yoq adsorbsiyasining asosiy mexanizmi fizik adsorbtsiya edi, shu bilan birga kimyoviy adsorbtsiya xitinda bo'lgan. To'rtinchi xitosan tuzi (QCS) tomonidan reaktiv apelsin 16 adsorbsiyasi Roza va boshqalar tomonidan to'qimachilik oqava suvlaridan reaktiv bo'yoqlarni olib tashlashni namoyish qilish uchun namuna sifatida ishlatilgan. Adsorbsiya tajribalari turli xil pH qiymatlarida va boshlang'ich bo'yoqli ontsentratsiyalarda o'tkazildi. Belgilangan maksimal adsorbtsiya hajmi adsorbtsiya maydonlarining 75% egallashiga mos keladigan 1060 mg reaktiv bo'yoq / g adsorbentni tashkil etdi. Natijalar adsorbsiya jarayoni eritmaning pH ga bog'liq emasligini ko'rsatdi, chunki adsorbsiyaning eng mumkin bo'lgan mexanizmi polimer to'rtinchi ammoniy guruhlarining bo'yoq sulfonat guruhlari bilan o'zaro ta'siri edi. Remazol qora 13 bo'yoqning suvli eritmalarida xitosanga adsorbsiyasi o'rganildi [66]. Tajribalar aloqa vaqti, bo'yoqning dastlabki konsentratsiyasi (100–300 mg / l), zarrachalar hajmi (0.177, 0.384, 1.651 mm), pH (6.7–9.0) va harorat (30–60 ° C) funktsiyalari sifatida o'tkazildi. . Maksimal adsorbtsiya hajmi (qm) 91,47-130,0 mg / g ni tashkil qildi. Xitosanning aminokislota tarkibi bo'yoqni olib tashlashning oqilona imkoniyatini ta'minladi. Reaktiv bo'yoq adsorbsiyasining kinetikasi soxta birinchi va ikkinchi darajali tezlikni ifodalashdan iborat bo'lib, bu intrapartisli diffuziya adsorbsiya mexanizmida muhim rol o'ynashini namoyish etadi. Shuningdek, mualliflar elektrostatik kuchlar yoki fizik adsorbsiyasi tufayli gözenekli xitozan materialiga tabiiy kirib borishi natijasida bo'yoq tashuvchining yuzasiga zich va bir hil ravishda yopishganligini ko'rsatish uchun skanerlash elektron mikroskopi (SEM) ni taqdim etdi. hujayra xitosan va tashuvchi o'rtasida kovalent bog'lanish. Chitosan Elwakeel tomonidan magnitit ishtirokida glutaraldegid yordamida o'zaro bog'liq bo'lgan [67]. Olingan qatron tetraetilepentamin bilan reaktsiya natijasida kimyoviy jihatdan modifikatsiyalangan va glisidil trimetilamonyum xlorid bilan xitosan / aminokislotali (R1) va xitosanni o'z ichiga olgan xitosan va xlorid ammoniy xloridlari (R2) ishlab chiqargan. R1 va R2 qatronlaridan foydalangan holda suvli eritmalardan reaktiv qora 5 (RB5) olinishi ommaviy va ustunli usullar yordamida o'rganilgan. Qatronlar RB5 ning adsorbsiyasiga yuqori darajada bog'liqligini va R1 va R2 qatronlari uchun mos ravishda 25 ° C da 0,63 va 0,78 mmol / g ni olish darajasi ma'lum bo'ldi. Qatronlar NH4OH / NH4Cl tampon (pH 10) yordamida samarali ravishda yangilandi.

Chitosan was modified to possess the ability to adsorb cationic dyes from water by Chao et al.[68]. Four kinds of phenol derivatives: 4-hydroxybenzoic acid (BA), 3,4-dihydroxybenzoic acid (DBA), 3,4-dihydroxyphenyl-acetic acid (PA), and hydrocaffeic acid (CA), were used individually as substrates of tyrosinase to graft onto chitosan. These modified chitosans were used in experiments for uptake of the cationic dyes, crystal violet (CV) and bismarck brown Y (BB). The optimum adsorptive uptake for CV and BB occurred at pH 7 and 9, 32 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy respectively at 30 °C. Langmuir type adsorption was found to occur and the maximum adsorption capacities for both dyes were increased with the following order: CTS–CA>CTS–PA>CTS–DBA>CTS–BA. Chitosan-derivatives, by grafting poly (acrylic acid) and poly (acrylamide) through persulfate induced free radical initiated polymerization processes and covalent cross-linking of the prepared materials, were prepared and evaluated as biosorbents for Remacryl Red TGL (a basic dye) removal[69]. It was found that the grafting modifications greatly enhanced the adsorption performance of the biosorbents. Kinetic studies also revealed a significant improvement of sorption rates by the modifications. The amount of adsorbed values derived from the Langmuir model at 298 K were 0.479, 0.727, and 1.068 mmol/g (204.22, 309.82, and 510.74 mg/g) for three forms of chitosan, respectively. Chitosan beads were synthesized for the removal of a cationic dye, malachite green (MG), from aqueous solution[70]. The monolayer adsorption capacities were found to be 93.55 mg/g at 303 K; 74.83 mg/g at 313 K; 82.17 mg/g at 323 K, respectively. The kinetic experiments confirm that sorption process obeys the pseudo-secondorder kinetic model. The temperature strongly influenced the adsorption process. The adsorption of malachite green increased from 18.80% to 99.38% with an increase in pH of the solution from 2.1 to 11.0. Beyond pH 8, the dye adsorption remained almost constant. Batch adsorption experiments were carried out for the removal of methylene blue (MB), a cationic dye, from its aqueous solution using chitosan-g-poly(acrylic acid)/montmorillonite (CTS-g-PAA/MMT) nanocomposites as adsorbent[71]. The adsorption behaviors of the nanocomposite showed that the adsorption kinetics and isotherms were in good agreement with pseudo-second-order equation and the Langmuir equation, respectively, and the maximum adsorption capacity was 1859 mg/g for CTS-g-PAA/MMT with wt.% of 30% and weight ratio of 7.2:1. The desorption studies revealed that the nanocomposite provided the potential for regeneration and reuse after MB dye adsorption. The adsorption using chitosan-based adsorbent for the removal of basic blue 3 (BB 3) from aqueous solutions was studied[72]. This adsorbent exhibited interesting sorption properties toward cationic dye (the maximum adsorption capacity was 166.5 mg/g), depending on the presence of sulfonate groups. The sorption mechanism was a multi-step process, involving adsorption on the external surface, diffusion into the bulk and electrostatic interactions. It was explained by the authors that sulfonate groups contributed to the sorption echanism through electrostatic interactions between SO3 − groups of the sorbent (which are known as strong cation exchangers) and the cationic sites of BB 3. Addition of NaCl enhanced the performance of the adsorbent. N-benzyl mono- and disulfonate derivatives of chitosan were used for the removal of dyes from aqueous solution[73]. The effectiveness of these materials in adsorbing basic blue 9 (BB 9) has been studied as a function of agitation time, initial concentration and solution salinity. Experimental results confirmed the strong cation exchanger character of the sulfonated derivatives and showed that disulfonate derivatives of chitosan exhibited higher sorption capacities toward cationic dye than the monosulfonic one. Sorption of BB 9 reached equilibrium within 20–40 min and the maximum adsorption onto disulfonate derivative was 121.9 mg/g at pH=3. Chitosan intercalated montmorillonite (Chi-MMT) was prepared by dispersing sodium montmorillonite (Na + -MMT) into chitosan solution at 60 °C for 24 h and was examined for three basic dyes viz. basic blue 9 (BB9), basic blue 66 (BB66) and basic yellow 1 BY1)[74]. The Chi-MMT showed the highest adsorption capacity in the range of 46–49 mg/g, when the initial dye concentration was 500 mg/L, being equivalent to 92–99 wt.% of dye removal. The adsorption capacities of Chi-MMT for all basic dyes increased with an increase of initial dye concentration. An increase of adsorption capability of Chi-MMT was attributed to the existence of intercalate-chitosan. It could enlarge the pore structure of Chi-MMT, facilitating the penetration of macromolecular dyes, and also electrostatically interact with the applied dyes.

Chitosan Chao va boshqalar tomonidan suvdan kationik bo'yoqlarni adsorbtsiya qilish qobiliyatiga ega bo'lganligi sababli o'zgartirilgan (68). To'rt turdagi fenol hosilalari: 4-gidroksibenzoy kislotasi (BA), 3,4-dihidroksibenzoy kislotasi (DBA), 3,4-dihidroksifenil-sirka kislotasi (PA) va gidrokofein kislotasi (CA) tirozinazning substratlari sifatida alohida ishlatilgan. xitosan ustiga payvand qilish. Ushbu modifikatsiyalangan xitozanlar kationik bo'yoq, kristall binafsha (CV) va bismark jigarrang Y (BB) ni olish uchun tajribalarda ishlatilgan. CV va BB uchun eng maqbul adsorptiv tutilish pH 7 va 9, 32 A. Bhatnagar, M. Sillanpää / Colloid va Interface Science avanslari 152 (2009) 26–38 Muallifning shaxsiy nusxasi mos ravishda 30 ° C darajasida. Langmuir tipidagi adsorbsiya aniqlandi va ikkala bo'yoq uchun maksimal adsorbsion quvvat quyidagi tartibda oshirildi: CTS – CA> CTS-PA> CTS – DBA> CTS-BA. Polietilen (akril kislota) va poli (akrilamid) payvandlash orqali xitosan hosilalari, erkin radikal boshlangan polimerizatsiya jarayonlari va tayyorlangan materiallarni kovalent o'zaro bog'lash orqali Remacryl Red TGL (asosiy bo'yoq) ni olib tashlash uchun biosorbents sifatida baholandi. [69]. Graf modifikatsiyalari biosorbentsning adsorbsion ish faoliyatini sezilarli darajada oshirgani aniqlandi. Kinetik tadqiqotlar, shuningdek, modifikatsiyalar bo'yicha sorbsiya stavkalari sezilarli yaxshilanganligini aniqladi. 298 K da Langmuir modelidan olingan adsorblangan qiymatlar xitozanning uchta shakli uchun mos ravishda 0,479, 0.727 va 1.068 mmol / g (204.22, 309.82 va 510.74 mg / g) ni tashkil etdi. Chitosan boncuklari kationik bo'yoq, malachit yashil (MG) ni suvli eritmadan olib tashlash uchun sintez qilindi [70]. Monolayerning adsorbsion sig'imi 303 K da 93,55 mg / g; 313 K da 74,83 mg / g; Mos ravishda 323 K da 82,17 mg / g. Kinetik tajribalar, sorbsiya jarayoni soxta ikkinchi darajali kinetik modelga bo'ysunishini tasdiqlaydi. Harorat adsorbsiya jarayoniga kuchli ta'sir ko'rsatdi. Malaxit yashilining adsorbsiyasi 18,80% dan 99,38% gacha, eritmaning pH darajasi 2,1 dan 11,0 gacha ko'tarildi. PH 8 dan tashqari, bo'yoq adsorbsiyasi deyarli doimiy bo'lib qoldi. Xitosan-g-poli (akril kislotasi) / montmorillonit (CTS-g-PAA / MMT) nanokompozitlarini adsorbent sifatida ishlatib, metilen ko'k (MB), kationik bo'yoqni suvli eritmasidan olib tashlash uchun ommaviy adsorbtsiya tajribalari o'tkazildi [71. ]. Nanokompozitning adsorbsion xatti-harakatlari shuni ko'rsatdiki, adsorbtsiya kinetikasi va izotermlari soxta ikkinchi tartibli tenglama va Langmuir tenglamalari bilan mos kelishgan va CTS-g-PAA / MMT uchun maksimal adsorbsiya hajmi 1859 mg / g bo'lgan. 30% dan% vazn va 7,2: 1 nisbatda. Desorbsion tadqiqotlar shuni ko'rsatdiki, nanokompozit MB bo'yoq adsorbsiyasidan keyin qayta tiklanish va qayta foydalanish uchun imkoniyat yaratdi. Suvli eritmalardan asosiy ko'k 3 (BB 3) ni olib tashlash uchun xitosan asosli adsorban yordamida adsorbsiya o'rganildi [72]. Ushbu adsorbent sulfonat guruhlarining mavjudligiga qarab kationik bo'yoqqa nisbatan eng yuqori sorbtsiya xususiyatlarini namoyish etdi (maksimal adsorbtsiya hajmi 166,5 mg / g). Sorbsiya mexanizmi ko'p bosqichli jarayon bo'lib, tashqi yuzada adsorbsiya, quyma va elektrostatik shovqinlarni o'z ichiga olgan edi. Mualliflar tomonidan sulfonat guruhlari SO3 - sorbent guruhlari (kuchli kationlar almashinuvchilari deb nomlanuvchi) va BB 3 kationik joylari o'rtasidagi elektrostatik ta'sir o'tkazish orqali sorbsion echanizmga hissa qo'shganligi tushuntirildi. NaCl qo'shilishi adsorbentning ishlashini yaxshilagan. . Xitosanning N-benzil mono- va disulfonat hosilalari suvli eritmadan bo'yoqlarni olib tashlash uchun ishlatilgan [73]. Ushbu materiallarning asosiy ko'k 9 (BB 9) ni adsorbsiyalashdagi samaradorligi qo'zg'alish vaqti, dastlabki konsentratsiya va eritmaning sho'rlanishi funktsiyasi sifatida o'rganilgan. Eksperimental natijalar sulfatlangan lotinlarning kuchli kation almashtirgich xususiyatini tasdiqladi va xitosanning disulfonat hosilalari monosulfonikiga qaraganda kationik bo'yoqqa nisbatan yuqori sorbtsiya qobiliyatini namoyish etishini ko'rsatdi. BB 9 ning sorbsiyasi 20–40 minut ichida muvozanatga erishdi va disulfonat hosilasiga maksimal adsorbsiya pH = 3 da 121,9 mg / g ni tashkil etdi. Chitosan interkalatsiyalangan montmorillonit (Chi-MMT) natriy montmorillonitni (Na + -MMT) xitosan eritmasiga 24 soat davomida 60 soat davomida eritib yubordi va uchta asosiy bo'yoq vizasi tekshirildi. asosiy ko'k 9 (BB9), asosiy ko'k 66 (BB66) va asosiy sariq 1 BY1) [74]. Chi-MMT eng yuqori adsorbsiya qobiliyatini 46-49 mg / g oralig'ida ko'rsatdi, bo'yoqning dastlabki konsentratsiyasi 500 mg / l ni tashkil etdi, bu bo'yoqni olib tashlashning 92–99 vt% ga teng. Chi-MMT barcha asosiy bo'yoqlar uchun adsorbsion qobiliyati bo'yoqlarning dastlabki konsentratsiyasining ortishi bilan ortdi. Chi-MMT ning adsorbsion qobiliyatining oshishi interkalate-xitosan mavjudligi bilan izohlanadi. Bu Chi-MMT ning gözenek tarkibini kattalashtirishi mumkin, bu makromolekulyar bo'yoqlarning kirib borishini osonlashtiradi, shuningdek qo'llaniladigan bo'yoqlar bilan elektrostatik ta'sir o'tkazadi.

The ability of chitosan as an adsorbent for the removal of acid dyestuff, namely, acid green 25, acid orange 10, acid orange 12, acid red 18, and acid red 73, from aqueous solution has been studied[75]. The monolayer adsorption capacities were determined to be 645.1, 922.9, 973.3, 693.2, and 728.2 mg of dye/g chitosan for acid green 25, acid orange 10, acid orange 12, acid red 18, and acid red 73, respectively. The differences in adsorption capacities might be due to the effect of molecular size and the number of sulfonate groups of each dye. The results demonstrated that monovalent and/or smaller dye molecules had superior adsorption capacities due to an increase in the dye/chitosan ratio in the system. The smaller dye molecules were able to penetrate deeper into the internal pore structure of the chitosan particles. Electrostatic attractions governed the possible acid dye adsorption mechanism onto chitosan. The efficacy of chitosan in the form of hydrobeads to remove congo red, an anionic dye, from water has been examined [76].Itwas reported that chitosan beads is a good adsorbent for the removal of congo red from its aqueous solution and 1 g of chitosan in the form of hydrobeads can remove ca. 93 mg of the dye at pH 6.0. The reason for higher adsorption of congo red on prepared chitosan in this study was explained due to the fact that chitosan being polycationic in nature attracted congo red, an anionic dye, and thus increased dye adsorption. Sodium chloride and sodium dodecyl sulfate (SDS) were found to inhibit the adsorption process. Authors reported that physical forces as well as ionic interaction were responsible for binding of congo red with chitosan. The adsorption performance of chitosan (CS) beads impregnated with triton X-100 (TX-100) as a nonionic surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant was investigated for th removal of anionic dye, congo red (CR), from aqueous olution by Chatterjee et al.[77]. The Sips maximum adsorption capacity in dry weight of the CS/TX-100 beads was 378.79 mg/g and 318.47 mg/g for the CS/SDS beads, higher than the 223.25 mg/g of the CS beads. Modification of CS beads by impregnation with nonionic surfactant, or even anionic surfactant, at low concentrations was found to enhance adsorption of anionic dye. It was suggested by the authors that adsorption of CR onto impregnated beads involved some hydrophobic interactions between CR and surfactant molecules (TX-100 and SDS) impregnated in the beads. The adsorption of eosin Y, as a model anionic dye, from aqueous solution using chitosan nanoparticles prepared by the ionic gelation between chitosan and tripolyphosphate was examined by Du et al. [78]. The adsorption capacity was found to be 3.333 g/g. The adsorption process was endothermic in nature with an enthalpy change (ΔH) of 16.7 kJ/mol at 20–50 °C. The optimum pH value for eosin Y removal was found to be 2–6. The dye was desorbed from the chitosan nanoparticles by increasing the pH of the solution.

Xitosanning kislotali bo'yoq moddalarini, xususan, kislotali yashil 25, kislota apelsin 10, kislota apelsin 12, kislota qizil 18 va kislota qizil 73 ni suvli eritmadan olib tashlash qobiliyati o'rganildi [75]. Monolayerning adsorbsion sig'imi mos ravishda 645.1, 922.9, 973.3, 693.2 va 728.2 mg bo'yoq / g xitosan uchun kislota yashil 25, kislota apelsin 10, kislota apelsin 12, kislota qizil 18, kislota qizil 73 va kislota qizil 73 uchun aniqlandi. Adsorbsiya qobiliyatidagi tafovut molekulyar kattalik va har bir bo'yoqning sulfonat guruhlari soniga bog'liq bo'lishi mumkin. Natijalar shuni ko'rsatdiki, monovalent va / yoki kichikroq bo'yoq molekulalari tizimdagi bo'yoq / xitosan nisbati oshishi tufayli yuqori darajada adsorbtsiya qobiliyatiga ega. Kichik bo'yoq molekulalari xitosan zarralarining ichki gözenekli tuzilishiga chuqurroq kirishga qodir edilar. Elektrostatik diqqatga sazovor joylar xitosanga kislotali bo'yoqning adsorbtsiya mexanizmini boshqargan. Xitosanning kongoni qizil, anionli bo'yoqni suvdan olib tashlash uchun gidrobidlar samaradorligi tekshirildi [76] .Bu xitosan boncuklari kongoni qizil suvli eritmasidan va 1 g dan kongoni olib tashlash uchun yaxshi adsorbent ekanligini aytdi. gidrobidlar ko'rinishidagi xitosan ka ketishini olib tashlashi mumkin. PH 6.0 da 93 mg bo'yoq. Ushbu ishda tayyorlangan xitosanga kongo qizilning yuqori adsorbtsiyasi sababi, chitosan tabiatda polikatsiyaga uchragan kongo qizil, anionik bo'yoqni o'ziga jalb qilganligi va shu bilan bo'yoq adsorbsiyasini ko'payishi bilan izohlangan. Natriy xlorid va natriy detsil sulfat (SDS) adsorbsiya jarayonini inhibe qilganligi aniqlandi. Mualliflarning ta'kidlashicha, jismoniy kuchlar va ionlarning o'zaro ta'siri kongoni qizil rang bilan xitosan bilan bog'lash uchun javobgardir. Anionik sirt faol moddalar sifatida triton X-100 (TX-100) bilan singdirilgan xitosan (CS) boncuklarning adsorbsion ishlashi anionik sirt faol moddasi sifatida, anion sirtini faol moddasi sifatida anionik bo'yoq, kongo qizil (CR), Chatterji va boshqalar tomonidan suvli olovdan [77]. CS / TX-100 boncuklarining quruq og'irligidagi Sips maksimal adsorbtsiya hajmi CS / SDS boncuklar uchun 378,79 mg / g va 318,47 mg / g ni tashkil etdi, bu CS boncuklar 223,25 mg / g dan yuqori. Anonik bo'yoqning adsorbsiyasini kuchaytiradigan past konsentratsiyali CS boncuklarini ion bo'lmagan sirt faol moddalar yoki hatto anion sirt faol moddalar bilan singdirish orqali modifikatsiya qilingan. Mualliflar tomonidan, singdirilgan boncuklarda CR ning adsorbsiyasi CR va sirt faol moddalar molekulalari (TX-100 va SDS) orasidagi munozarali ba'zi o'zaro ta'sirlarni o'z ichiga oladi, deb ta'kidlashdi. Xitosan va tripolifosfat orasidagi ionli gelatlash orqali tayyorlangan xitosan nanopartikullaridan foydalangan holda namunali anionik bo'yoq sifatida eozinning Y adsorbsiyasi Du va boshqalar tomonidan o'rganilgan. [78]. Adsorbsiya hajmi 3,333 g / g ni tashkil qildi. Adsorbtsiya jarayoni tabiatda endotermik bo'lib, 20-50 o C da 16,7 kJ / mol ga teng bo'lgan entalpiya o'zgarishi (ΔH) bilan sodir bo'ldi. Eozin Y ni olib tashlash uchun optimal pH qiymati 2-6 deb topildi. Chitosan nano-zarrachalaridan bo'yoq eritmaning pH miqdorini oshirish orqali tushirilgan.

The desorption percentage was about 60% within 60 min at pH 11.0, whereas 98.5% of the dye could be eluted at pH 12 in 150 min. The capabilities of chitosan and chitosan–EGDE (ethylene glycol diglycidyl ether) beads for removing acid red 37 (AR 37) and acid blue 25 (AB 25) from aqueous solution have also been nvestigated[79]. Chitosan beads were cross-linked with EGDE to enhance its chemical resistance and mechanical strength. It was shown that the adsorption capacities of chitosan for both acid dyes were comparatively higher than those of chitosan–EGDE. The desorption study revealed that after three cycles of adsorption and desorption by NaOH and HCl, both adsorbents retained their promising adsorption abilities. FTIR analysis proved that the adsorption of acid dyes onto chitosan-based adsorbents was physical adsorption. The performance of nanochitosan (with particle size range from 0.0663μm to 1.763μm) as an adsorbent to remove acid dyes from aqueous solution has been explored by the researchers [80]. The monolayer adsorption capacities were determined to be 1.77, 4.33, 1.37 and 2.13 mmol/g nanochitosan for acid orange 10, acid orange 12, acid red 18 and acid red 73, espectively. The differences in 33 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy capacities might be due to the differences in the particle size of dye molecules and the number of sulfonate groups on each dye molecule. The results have demonstrated that monovalent and smaller dye molecular sizes have superior capacities due to the increase in dye/ chitosan surface ratio in the system and deeper penetration of dye molecules into the internal pore structure of nanochitosan. The mechanism of the adsorption process of acid dye on anochitosan was proposed to be the ionic interactions of the colored dye ions with the amino groups on the chitosan. Poly(methylmethacrylate) grafted chitosan was found to be an efficient adsorbent for the removal of three anionic azo dyes (Procion Yellow MX, Remazol Brilliant Violet and Reactive Blue H5G) ver a wide pH range of 4–10 and maximum at pH 7[81]. The adsorption capacity for yellow, violet and blue dyes was 250, 357 and 178 mg/g, respectively. The kinetic study results suggested that adsorption kinetics of the dye molecules were not diffusion controlled, but chemisorption was the main sorption mechanism. The anionic dye, bearing sulfonic groups, is electrostatically attracted by protonated amine groups of the chitosan, thus, neutralized the anionic charges of dyes that can bind together. The removal of the dye reached a maximum at pH 4 with the complete neutralization of the anionic charges. However, with increasing pH, deprotonation at amino group took place that resulted in poor interaction between the dye and the biopolymer and therefore, the decrease in adsorption.

Desorbsiya darajasi pH 11,0 da 60 minut davomida 60% atrofida edi, holbuki, bo'yoqning 98,5% pH 12 da 150 minut ichida elutatsiya qilinishi mumkin. Suvli eritmadan xitosan va chitosan-EGDE (etilen glikol diglisidil efiri) kislotalarini qizil 37 (AR 37) va kislota ko'k 25 (AB 25) eritmalaridan tozalash imkoniyatlari tekshirildi [79]. Chitosan boncukları kimyoviy qarshilik va mexanik kuchini oshirish uchun EGDE bilan o'zaro bog'langan edi. Ikkala kislotali bo'yoq uchun xitosanning adsorbtsiya qobiliyati xitosan-EGDE ga nisbatan ancha yuqori ekanligi ko'rsatildi. Desorbsiyani o'rganish shuni ko'rsatdiki, NaOH va HCl tomonidan adsorbtsiya va desorbtsiyaning uchta tsiklidan so'ng ikkala adsorbent ham o'zlarining istiqbolli adsorbsion qobiliyatini saqlab qolishgan. FTIR tahlillari kislota bo'yoqlarining xitosan asosidagi adsorbentlarga adsorbsiyasi jismoniy adsorbsiya ekanligini isbotladi. Nanoxitosanning (zarracha hajmi 0,0663km dan 1,763km gacha) adsorbent sifatida suvli eritmadan kislota bo'yoqlarini olib tashlash samaradorligi tadqiqotchilar tomonidan o'rganilgan [80]. Monolayerning adsorbsion sig'imi kislota apelsin 10, kislota apelsin 12, kislota qizil 18 va kislota qizil 73 uchun, 1,77, 4.33, 1.37 va 2.13 mmol / g nanoxitosan, aniqlangan. 33 A. Bhatnagar, M. Sillanpäa / Kolloid va interfeys fanidagi yutuqlar 152 (2009) 26–38 Muallifning shaxsiy nusxa olish qobiliyatlari bo'yoq molekulalarining zarracha hajmi va har birida sulfonat guruhlari sonining farqiga bog'liq bo'lishi mumkin. bo'yoq molekulasi. Natijalar shuni ko'rsatdiki, tizimdagi bo'yoq / xitosan sirt nisbati oshishi va bo'yoq molekulalarining nanoxitosanning ichki gözenekli tuzilishiga chuqur kirib borishi tufayli monovalent va kichikroq bo'yoq molekulalari kattaroq imkoniyatlarga ega. Anoxitosan kislotali bo'yoqning adsorbsiya jarayoni mexanizmi xitosan tarkibidagi aminokislota guruhlari bilan rangli bo'yoq ionlarining ionli o'zaro ta'siri sifatida taklif qilingan. Chitosan bilan bog'langan poli (metilmetakrilat) uchta anionli azo bo'yoqlarini (Procion Yellow MX, Remazol Brilliant binafsha va reaktiv ko'k H5G) olib tashlash uchun samarali pH 4-10 va maksimal pH 7 darajalarida samarali adsorbent deb topildi. ]. Sariq, binafsha va ko'k bo'yoqlarning adsorbsion hajmi mos ravishda 250, 357 va 178 mg / g ni tashkil etdi. Kinetik tadqiqot natijalari bo'yoq molekulalarining adsorbsion kinetikasi diffuziya bilan boshqarilmasligini, ammo kimyorbsiyaning asosiy sorbsiya mexanizmi ekanligini ta'kidladi. Sulfonik guruhlarni o'z ichiga olgan anionli bo'yoq xitosanning protonlangan amin guruhlari tomonidan elektrostatik ravishda jalb qilinadi va shu bilan birlashtira oladigan bo'yoqlarning anion zaryadini zararsizlantirdi. Anion zaryadlarini to'liq neytrallashtirish bilan bo'yoqni olib tashlash pH 4 ga maksimal darajada yetdi. Shu bilan birga, pHning oshishi bilan aminokislotada deprotonizatsiya sodir bo'ldi, natijada bo'yoq va biopolimer o'rtasida yomon ta'sir ko'rsatildi va shuning uchun adsorbsiyaning pasayishi kuzatildi.

On the other hand, at much acidic pH (pH<4), protonation took place at the nitrogen and carbonyl groups present in the dyes which decreased the adsorption due to electrostatic repulsion between the same charges. However, in chitosan-graftpoly(methylmethacrylate) (Ch-g-PMMA), the dangling ester groups at the grafted chitosan appeared to be mainly responsible for the adsorption and not the amino groups as was also evident by IR spectrum of dye loaded adsorbent. Further, other than electrostatic interaction some interaction in the form of conformational affects might also be operative. The sensitivity to pH after pH 4 was not seen in the graft copolymer because the major binding took place at PMMA grafts and only a very small amount of NH2were available for binding after grafting. Several other workers also examined the potential of chitosan and its derivatives for different types of dyes removal from water[82–88]. A summary of adsorption capacities of chitin- and chitosan-derivatives for different dyes has been presented inTable 2. Readers interested in a detailed discussion of the interaction of dyes with chitosan and its derivatives should refer to an excellent comprehensive review by Crini and Badot[8]. It is evident from the recent literature survey that chitin- and especially chitosan and its derivatives have been found promising adsorbents for dyes removal. Various classes of dyes have been studied so far and all these studies suggest that chitosan shows higher potential for various dyes. However, it is necessary to continue the identification of the most promising types of chitosan to achieve higher sorption capacities. The mechanism of dye adsorption on chitin- and chitosan-derivatives needs further detailed investigation as different mechanisms have been proposed by different researchers[8], such as surface adsorption, chemisorption, diffusion and adsorption–complexation. Further research is needed to gain a better understanding of adsorption mechanism of dye adsorption on chitin- and chitosan-derivatives. Such studies would provide a better understanding of adsorption phenomenon involve in the uptake of a given dye[8]. 2.3. Chitin- and chitosan-derivatives for phenols removal Among the various aqueous pollutants generally present in wastewaters, phenol and substituted phenols are considered as priority pollutants. Phenols cause unpleasant taste and odor of drinking water and can exert negative effects on different biological processes. The ubiquitous nature of phenols, their toxicity even in trace amounts and the stricter environmental regulations make it necessary to develop processes for the removal of phenols from wastewaters.

Chitin- and chitosan-derivatives have also been investigated for phenol and substituted phenols removal from water and Table 2 Adsorption capacities of chitin and chitosan-derivatives for various dyes removal from water.

Boshqa tomondan, kislotali pH (pH <4) da bo'yoqlar tarkibidagi azot va karbonil guruhlarida protonlash sodir bo'ldi, ular bir xil zaryadlar orasidagi elektrostatik repulsiya tufayli adsorbsiyani kamaytirdi. Biroq, xitosan-graftpoliyada (metilmetakrilat) (Ch-g-PMMA), payvandlangan xitosanning yonib turadigan ester guruhlari aminokislotalar emas adsorbtsiya uchun javobgardir, chunki bu bo'yoq bilan to'ldirilgan adsorbentning IR spektri bilan ham aniqlangan. Bundan tashqari, elektrostatik shovqindan tashqari konformatsion ta'sir ko'rinishidagi ba'zi o'zaro ta'sirlar ham operativ bo'lishi mumkin. PH 4dan keyin pH ga sezgirlik payvand kopolimerida ko'rinmadi, chunki asosiy bog'lanish PMMA payvandlarida sodir bo'lgan va payvandlashdan keyin ulanish uchun juda oz miqdordagi NH2 mavjud. Yana bir qancha ishchilar xitosan va uning hosilalarini turli xil bo'yoqlarni suvdan olib tashlash imkoniyatlarini o'rganib chiqdilar [82-88]. 2-jadvalda turli xil bo'yoqlar uchun xitin va xitosan-hosilalarining adsorbtsiya qobiliyatlari to'g'risida qisqacha ma'lumot keltirilgan. 2-jadvalda bo'yoqlarning xitosan va uning hosilalari bilan o'zaro ta'sirini batafsil muhokama qilishdan manfaatdor bo'lgan o'quvchilar Crini va Badot tomonidan mukammal o'rganib chiqilgan bo'lishi kerak [8. ]. Yaqinda o'tkazilgan adabiyot tadqiqotlaridan ma'lum bo'ladiki, chitin- va ayniqsa chitosan va uning hosilalari bo'yoqlarni olib tashlash uchun istiqbolli adsorbentlar topdilar. Bugungi kunga qadar turli xil bo'yoq sinflari o'rganilgan va bu tadqiqotlar shuni ko'rsatadiki, xitosan turli xil bo'yoqlarning yuqori potentsialini ko'rsatadi. Shu bilan birga, yuqori sorbtsiya qobiliyatiga erishish uchun xitosanning eng istiqbolli turlarini aniqlashni davom ettirish kerak. Xitin va xitosan hosilalari tarkibidagi bo'yoqlarning adsorbsiyasi mexanizmi batafsilroq o'rganishni talab qiladi, chunki turli tadqiqotchilar tomonidan turli xil mexanizmlar taklif qilingan, masalan sirt adsorbsiyasi, ximisorbsiya, diffuziya va adsorbsiya-murakkablashtirish. Chitin- va xitosan-hosilalari bo'yicha bo'yoq adsorbsiyasining mexanizmi to'g'risida ko'proq ma'lumotga ega bo'lish uchun qo'shimcha tadqiqotlar talab etiladi. Bunday tadqiqotlar adsorbsiya fenomeni, bo'yoqni olish bilan bog'liq bo'lgan narsani yaxshiroq tushunishga imkon beradi [8]. 2.3. Fenollarni yo'q qilish uchun xitin va xitosan hosilalari. Odatda suv oqindi suvlarda ifloslantiruvchi moddalar orasida fenol va uning o'rnini bosuvchi fenollar ustuvor ifloslantiruvchi hisoblanadi. Fenollar ichimlik suvining yoqimsiz ta'mini va hidini keltirib chiqaradi va turli biologik jarayonlarga salbiy ta'sir ko'rsatishi mumkin. Fenollarning xilma-xil tabiati, ularning izlari kam bo'lsa ham, ularning toksikligi va ekologik jihatdan qat'iy qoidalar fenollarni oqava suvlardan tozalash jarayonlarini ishlab chiqishni taqozo etadi.

Xitin va xitosan hosilalari suvdan fenol va uning o'rnini bosuvchi fenollarni olib tashlash bo'yicha tadqiqotlar olib borildi va 2-jadval. Xitin va xitosan hosilalarining suvdan turli xil bo'yoqlarni olib tashlash uchun adsorbtsiya qobiliyati.