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Boshqa tomondan, kislotali pH qiymatida metall ionlarining kamayishi adsorbsiyani 27 A. Bhatnagar, M. Sillanpäa / Kolloid va Interfeys fanidagi yutuqlar 152 (2009) 26–38 Muallifning shaxsiy nusxasi pH darajasining pastligi bilan izohlash mumkin. , azotning yagona juftligi bilan muvofiqlashtiradigan metall ionlari faol sayt uchun H3O + bilan raqobatlashishi kerak edi. Bir-biriga bog'langan xitosan boncuklarining quvvat olish qobiliyatini oshirish uchun bir qancha kimyoviy modifikatsiyalar amalga oshirildi. aminitlangan xitosan boncuklar pH 7 da 2,26 mmol Hg 2+ / g quruq massa bo'ldi, bu qiymat turli xil biosorbentslar orasida eng yuqori ushlab turish qobiliyatiga ega deb hisoblangan Boncuklar shuningdek simob va vodorod ionlari o'rtasidagi raqobatbardosh yutilish xususiyatini ko'rsatdi. nihoyat izotermik sorbsiya ma'lumotlariga asoslangan muvozanat modeli yordamida muvaffaqiyatli modellashtirildi Yaqinda Hg (II) suvidan xitosan va uning hosilalari chiqarilishi Miretzky va Cirelli tomonidan keng ko'rib chiqilgan [9]. olib tashlash, Rorrer va boshqalar, natriy gidroksid eritmasiga kislotali xitosan eritmasini qo'shib, xitosan boncuklarının g'ovakliligini oshirish bo'yicha tajribalar o'tkazdilar yog'ingarchilik vannasi [22]. Gazlangan xitosan boncuklar glutaraldegid bilan o'zaro bog'langan va keyin quritilgan holda muzlatilgan. 1 va 3 mm diametrli boncuklar tayyorlandi. 1 mm diametrli boncuklarning sirt maydoni 150 m2 / g dan oshadi va o'rtacha g'ovak o'lchamlari 560 Å va pH 2 da kislota muhitida erimaydi. Adsorbtsiya izotermalari 25 ° C va pH 6,5 kontsentratsiyalari oralig'ida 1-1690 mg Cd 2 + / L pog'onali shaklga ega va 1 va 3 mm o'lchamdagi boncuklar uchun maksimal adsorbsion quvvatlari mos ravishda 518 va 188 mg Cd / g boncuklar ekanligi aniqlandi. Izotermning bosqichli shakli g'ovakli blokirovka mexanizmi bilan izohlangan. O'zgartirilgan xitosan haddan tashqari ko'p yoki kukunli xitosanning ko'plab afzalliklarini namoyish etdi. ichki yuzaning balandligi va boncuklarning o'zaro bog'lanishi, ular past pH eritmalarida erimaydigan bo'lib, bu ularning keng pH oralig'ida yaroqliligini isbotlaydi. Chitosanni perlit rudasiga surtish uchun yangi kompozit xitosan biosorbenti tayyorlandi va Cu (II) va Ni (II) ni olib tashlash uchun tadqiq qilindi [23]. Perlit bilan qoplangan xitosanda Cu (II) va Ni (II) ni maksimal chiqarib tashlash pH 5.0 ga teng. Perlit bilan qoplangan xitosanning maksimal monolayer adsorbsion hajmi Cu (II) uchun 196,07 mg / g ni va Ni (II) uchun 114,94 mg / g ni tashkil etdi. Ipak qurti xrizalidlaridan (ChSC) olingan Chitosan akkumulyator ishlab chiqarish oqava suvlaridan Pb 2+ va Cu2 + ni olib tashlash uchun tekshirildi [24]. Batareya oqava suvlaridan Pb2 + va Cu 2+ ni olib tashlash uchun olingan eng yaxshi toza ChSC deacetilatsiya darajasi (DD), mos ravishda 80% (ChC deacetilation) va 92% (180 min ChSC deatsetilatsiya). Tajriba sharoitida 80% va 92% DD bilan toza CHSC yordamida Pb 2 + va Cu2 + uchun maksimal adsorbsion quvvati mos ravishda 72 mg / g va 87 mg / g ni tashkil etdi: pH 5.0, zarracha hajmi 300 dan 425 mkm gacha, harorat 20,0 ± 0,1 ° C va 250 rpm aralashtirish. Suvli eritmalardan Cu (II) 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-Aamaterat o'rganilgan va ilgari keltirilgan xitosan materiallari orasida Cu (II) ni olib tashlash uchun eng yuqori sorbtsiya qobiliyatini (pH 6 da 318 mg / g) tashkil etdi. Cu (II) va tayyorlangan sorbentlarning o'zaro ta'siri FTIR spektroskopiyasi bilan tasdiqlandi. Cu (II) yuklangan xitosan sorbentlarining aminokislotalar cho'qqilari (Ch, 1665–1660 sm −1; Ch-g-Aam, 1672–1674 sm − 1; Ch-g- Aa, 1674–1670 sm (1), xelatlangan kompleksni nazarda tutadi. Yangi xitosan hosilasi [6,6′-piperazin-1,4-diyldimetilenebis (4-metil-2-formil) fenol] (L) va xitosan (CTS) bilan o'zaro bog'lash orqali sintez qilindi. Krishnapriya va Kandasvami [26]. Mn (II), Fe (II), Co (II), Cu (II), Ni (II) kabi turli xil metal ionlarining o'zaro bog'langan xitosan ligandini (CCTSL) adsorbsion tajribalari (pH bog'liqligi, kinetika va muvozanat) ), Cd (II) va Pb (II) 25 ° C da o'tkazildi. Natijalar adsorbsiya eritmaning pH ga bog'liqligini, pH 6,5 va 8,5 orasidagi maksimal quvvatni ko'rsatdi. O'rganilgan metall ionlari uchun adsorbsion sig'imi tartibi Cu (II)> Ni (II)> Cd (II) ≥Co (II) ≥Mn (II) ≥Fe (II) ≥Pb (II) ekanligi aniqlandi. Kimyoviy sorbsiya adsorbtsiya mexanizmining tezlikni cheklovchi bosqichi sifatida taklif qilindi. Chitosanni polivinilxlorid (PVX) boncuklarına yopishtirish orqali yangi biosorbent ishlab chiqildi [27]. Biosorbentdagi mis (II) va nikel (II) ionlarining muvozanat va ustunli oqim adsorbsion xususiyatlari o'rganildi. Langmuir adsorbsion izotermidan olingan xitosan bilan qoplangan PVX sorbentining maksimal monolayer adsorbsiyalash qobiliyati Cu (II) uchun 87,9 mg / g va Ni (II) uchun 120,5 mg / g deb topildi.

The results indicated that the maximum uptake of Cu(II) ions took place at pH 4.0 while the maximum uptake of Ni(II) ions occurred at an initial pH of 5.0. Column experiments exhibited that it was possible to remove the metal ions from aqueous medium by biosorption on to chitosan-coated PVC beads. The magnetic chitosan nanocomposites were synthesized on the basis of amine-functionalized magnetite nanoparticles[28]. These nanocomposites provide a very efficient, fast, and convenient tool for removing Pb 2+ ,Cu2+, and Cd2+from water. It was suggested that synthesized magnetic chitosan nanocomposites can be used as a recyclable tool for heavy metal ion removal. The adsorption of Al(III) from aqueous solutions onto chitosan was found to be 45.45 mg/g at 30 °C. [29]. The adsorption of Al(III) increased with the rise in adjusted pH of the solution from 3.0 to 4.0 and decreased after pH 4.0. The pseudo-second-order kinetic model was used to describe the kinetics which is based on the assumption that the rate-limiting step may be chemisorption involving valency forces through sharing or exchange of electrons between the –NH2 groups in chitosan and Al(III). It was observed by the authors that before equilibrium was reached, an increase in temperature led to an increase in adsorption rate which indicated a kinetically controlled process, while the adsorption of Al(III) on chitosan was controlled by an exothermic process. Metal anions are another class of aquatic pollutants which pose serious threat to human health even at low concentrations. The removal of metal anions by chitin and chitosan-derivatives has been examined by many researchers. Chitosan was found very efficient for the removal of vanadate anions from dilute solutions through electrostatic attraction and anion exchange in acidic solutions[30]. The optimum pH was found to be in the range 3.0 to 3.5. Sorption capacity under optimum experimental conditions reached 8–9 mmol/g (ca. 400–450 mg/g), which corresponds to a molar ratio of ca. 1.3–1.5 between vanadate and–NH3+ groups. This stoichiometric ratio, together with the shape of the sorption isotherm curves, which was correlated to the predominance of anionic species, indicated that sorption occurred through the reaction of protonated amine sites with decavanadate species (preferentially to other polynuclear anionic species of lower vanadium unit number). In acidic solutions, the predominance of decavanadate solutions lead to almost rectangular sorption isotherm curves. In near neutral solutions, the predominance of nonadsorbable vanadate species resulted in negligible adsorption up to a concentration, dependent on pH, at which decavanadate species appeared in solution. At this limit residual concentration, sorption capacity steeply increased. Above pH 7, the protonation of amine groups was significantly reduced and the polymer was not able to exchange counteranions with vanadate species or to attract anionic species. Thus, the protonation of the polymer revealed a key parameter, as does the distribution of metal species, on the efficiency of vanadium sorption on chitosan. Sorption kinetics was also strongly controlled by the pH and the metal concentration. The predominance of decavanadate species had been correlated to fastest kinetics. Desorption was optimum in alkaline solutions, in which vanadium took the form of vanadate species in solution. Cross-linked chitosan gel beads were used for molybdate sorption and were found to show enhanced sorption performance in batch systems [31]. The authors reported that, in continuous systems, sorption capacities could reach 700 mg/g, a level close to that 28 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy obtained in batch studies. They also suggested that the sorption of molybdate (MoO4 − ) on chitosanflakes depends on the cross-linking. It decreased from the range 300–800 to 150–400 mg Mo/g when the chitosanflakes were cross-linked with glutaraldehyde. Cross-linking of chitosan particles, in glutaraldehyde, epichlorhydrine, or EGDE (ethylene glycol glycidyl ether) enhances the resistance of sorbent beads against acids, alkali or chemicals. This property of glutaraldehyde cross-linked chitosan beads was explored for vanadate and molybdate sorption [32].

Natijalar shuni ko'rsatdiki, Cu (II) ionlarining maksimal yutilishi pH 4,0 darajasida, Ni (II) ionlarining maksimal yutuq darajasi pH 5,0 bo'lganida sodir bo'ldi. Ustunli tajribalar shuni ko'rsatdiki, metall ionlarini suvli muhitdan biosorbtsiya yo'li bilan xitosan bilan qoplangan PVX boncuklarga olib tashlash mumkin. Magnit chitosan nanokompozitlari amin funktsional magnitit nanopartikullari asosida sintez qilindi [28]. Ushbu nanokompozitlar Pb 2+, Cu2 + va Cd2 + ni suvdan olib tashlash uchun juda samarali, tez va qulay vositani ta'minlaydi. Sintezlangan magnit chitosan nanokompozitlaridan og'ir metall ionlarini olib tashlash uchun qayta ishlanadigan vosita sifatida foydalanish tavsiya qilindi. Alit (III) ning suvli eritmalardan xitosanga adsorbsiyasi 30 ° C da 45,45 mg / g ni tashkil qildi. [29]. Al (III) ning adsorbsiyasi eritmaning rN-ni 3,0 dan 4,0 gacha ko'tarilishi bilan ko'tarildi va pH 4,0 dan keyin pasaygan. Soxta ikkinchi darajali kinetik model kinetikani tasvirlash uchun ishlatilgan, bu stavkalarni cheklovchi bosqich xitosan va Al (III) guruhidagi NN2 guruhlari o'rtasida elektronlarni almashish yoki almashish orqali valentlik kuchlari ishtirokidagi kimyosorbtsiya bo'lishi mumkin degan taxminga asoslanadi. . Mualliflar tomonidan muvozanatga erishilgunga qadar haroratning ko'tarilishi adsorbtsiya tezligining oshishiga olib kelganligi, bu kinetik nazorat qilinadigan jarayonni ko'rsatgan, xitosanda Al (III) adsorbsiyasi esa ekzotermik jarayon bilan boshqarilgan. Metall anionlar suv ifloslantiruvchi moddalarning yana bir toifasi bo'lib, ular past konsentratsiyalarda ham inson salomatligiga jiddiy xavf tug'diradi. Metall anionlarning xitin va xitosan-lotinlari bilan olib tashlanishi ko'plab tadqiqotchilar tomonidan ko'rib chiqilgan. Chitosan vanadat anionlarini elektrostatik tortish va kislotali eritmalarda anion almashinuvi orqali suyultirilgan eritmalardan olib tashlash uchun juda samarali deb topildi [30]. Optimal pH darajasi 3,0 dan 3,5 gacha bo'lganligi aniqlandi. Optimal eksperimental sharoitlarda sorbsiya sig'imi 8–9 mmol / g ga (400–450 mg / g) yetdi, bu kolyaning molyar nisbatiga to'g'ri keladi. Vanadat va –NH3 + guruhlari o'rtasida 1.3–1.5. Ushbu stixiyometrik nisbat, anion turlarining ustunligi bilan bog'liq bo'lgan sorbsion izoterm egri shakli bilan birgalikda, sorbsiya protavanli amin maydonlarining dekavanadat turlari bilan reaktsiyasi natijasida sodir bo'lganligini ko'rsatdi (afzalroq pastki polad yadrosi boshqa polinukulyar anion turlariga nisbatan). ). Kislotali eritmalarda dekavanadat eritmalarining ustunligi deyarli to'rtburchaklar shaklida sorbsion izoterm egri hosil bo'lishiga olib keladi. Neytral yechimlarda, so'rilmaydigan vanadat turlarining ustunligi pH ga bog'liq bo'lgan konsentratsiyaga qadar adsorbtsiyaga olib keldi, bunda eritmada dekavanadat turlari paydo bo'ldi. Ushbu chegarada qoldiq kontsentratsiya natijasida sorbsion sig'imi keskin oshdi. PH 7 dan yuqori, amin guruhlarining protonatsiyasi sezilarli darajada kamaydi va polimer kontranionlarni vanadat turlari bilan almashtirishga yoki anion turlarini jalb qilishga qodir emas edi. Shunday qilib, polimerning protonatsiyasi xitosan bo'yicha vanadiy sorbsiyasining samaradorligiga, shuningdek metall turlarining tarqalishiga ham muhim parametrni aniqladi. Sorbtsiya kinetikasi ham pH va metal kontsentratsiyasi tomonidan kuchli nazorat qilingan. Dekavanadate turlarining ustunligi eng tezkor kinetika bilan bog'liq bo'lgan. Desorbsiya ishqoriy eritmalarda eng maqbul bo'lgan, bunda vanadiy eritmada vanadat turini olgan. O'zaro bog'langan xitosan gel boncuklari molibdat sorbsiyasi uchun ishlatilgan va ommaviy tizimlarda yuqori darajada sorbsiya ko'rsatkichlarini namoyish etgan [31]. Mualliflarning ta'kidlashicha, uzluksiz tizimlarda sorbsiya sig'imi 700 mg / g ga yetishi mumkin, bu 28 A. Bhatnagar, M. Sillanpäa / Colloid and Interface Science 152 (2009) 26–38 Muallifning shaxsiy nusxasini olgan. ommaviy tadqiqotlar. Shuningdek, ular molibdatning (MoO4 -) xitosanflaklarga so'rilishi o'zaro bog'lanishga bog'liq degan fikrni ilgari surdilar. Xitosanflaklar glutaraldegid bilan o'zaro bog'langanida, u 300-800 dan 150–400 mg Mo / g gacha pasaygan. Xitozan zarralarini glutaraldegid, epikxlorhidrin yoki EGDE (etilen glikol glisidil eter) bilan o'zaro bog'lash sorbent boncuklarının kislotalar, ishqorlar yoki kimyoviy moddalarga nisbatan qarshiligini oshiradi. Glutaraldegidning o'zaro bog'liq xitosan boncuklarının bu xususiyati vanadat va molibdat sorbsiyasi uchun o'rganilgan [32].

Uptake capacities of 402.5 mg/g for vanadate and 763 mg/g for molybdate were obtained. The sorption into beads (763 mg molybdate/g) was better than into flakes (329.7 mg molybdate/g). Authors reported that both anions (molybdate and vanadate) showed similar sorption behavior which was likely due to the similarities in the chemistry of these ions. A pH of approximately 3 was favorable for the sorption of these metal anions, which was consistent with (i) the electrostatic attraction between the protonated amine sites and the strongly anionic metal species and, (ii) the appearance of polynuclear hydrolyzed metal species in the 3.0–3.5 pH range. Sorption kinetics were mainly controlled by intraparticle diffusion for beads, while forflakes the controlling mechanisms were both external and intraparticle diffusions. The adsorption of sulfate (SO4 2− ) and molybdate (MoO4 − )ionshas also been evaluated by Moret and Rubio[33]on chitin-based material with different deacetylation degrees (DD) at pH 4.5. The capacities were high, 150 mg SO4 2− /g with DD=25%. Chitin also proved to adsorb molybdate ions in the presence of sulfate ions, but reaction required longer equilibration time (60 min for 92% removal). Practical examples of removal of these anions were studied in actual mining effluents, attaining values of the order of 71% SO4 2− and 85% MoO4 − from a Cu–Mo flotationmilleffluent and 80% sulfate removal from a coal AMD-acid mine drainage (Mo free). The regeneration of the adsorbent material was possible through the anions desorption in alkaline medium. Arsenic in natural waters is a worldwide problem. Arsenic toxicity, its health hazards, and the treatment techniques are well known and have been widely reported. Extensive research is being conducted to control/minimize the arsenic contamination in drinking water. Dambies et al.[34]investigated the sorption of As(V) on molybdateimpregnated chitosan gel beads. The sorption capacity of raw chitosan for As(V) was increased by impregnation with molybdate. The optimum pH for arsenic uptake was ca. pH 3. The As(V) sorption capacity, over molybdenum loading, was ca. 160 mg/g. The exhausted sorbent was regenerated by phosphoric acid desorption. Three sorption/desorption cycles were conducted with only a small decrease in sorption capacity. Chitosan powder derived from shrimp shells, was converted into bead form and used to remove As(III) and As(V) from water in both batch and continuous operations[35]. The optimal pH value for As(III) and As(V) removal was ca. 5. Adsorption capacities of 1.83 and 1.94 mg As/g bead for As(III) and As(V), respectively, were reported. The sorption of As(V) onto chitosanflakes has been studied by Kwok et al.[36]. Authors selected 96 h contact time to ensure that equilibrium has been achieved over the whole concentration spectrum. The rate of desorption of arsenate from chitosan increased with the increase of the initial pH from 3.50 to 4.50. The capacity of the arsenate ion on chitosan was governed by the protonation reaction of chitosan and an increase of pH led to a decrease of the protonated groups on chitosan which were available for sorption of arsenate ion and influenced the speciation of arsenate ions in the aqueous phase. The dominant arsenate ions were in the form of H2AsO4 − . It was believed that the removal mechanism of arsenate ions from the aqueous phase might be due to the adsorption of arsenate ions to the protonated amine group on chitosan. A novel pseudo-first order reversible model, incorporating the effect of changing pH profile throughout the adsorption and desorption cycle, was newly developed to describe the sorption and the desorption in the batch kinetic systems of As(V) and chitosan simultaneously. The pH value of the adsorption and desorption reaction of arsenate and chitosan could be predicted from the pH against time profile. The adsorption capacities were reported from 1331 µg arsenate/g chitosan at initial pH 5.5 to 14,160 µg arsenate/g chitosan at initial pH 3.5. A study on the removal of arsenic from groundwater using iron– chitosan composites was conducted[37]. Removal of As(III) and arsenic (V) was studied through adsorption at pH 7.0 under equilibrium and dynamic conditions. The monolayer adsorption capacity from the Langmuir model for iron chitosanflakes (ICF) (22.47±0.56 mg/g for As(V) and 16.15±0.32 mg/g for As(III)) was found to be considerably higher than that obtained for iron chitosan granules (ICB) (2.24± 0.04 mg/g for As(V); 2.32±0.05 mg/g for As(III)). Anions including sulfate, phosphate and silicate at the levels present in groundwater did not cause serious interference in the adsorption behavior of arsenate/ arsenite.

Vanadat uchun 402,5 mg / g va molibdat uchun 763 mg / g oralig'ida qabul qilish quvvatiga ega. Boncuklardagi sorbsiya (763 mg molibdat / g) yoriqlarga qaraganda (329,7 mg molibdat / g) yaxshiroq edi. Mualliflarning ta'kidlashicha, ikkala anion (molibdat va vanadat) shunga o'xshash sorbsion xatti-harakatlarni namoyon etishgan, chunki bu ionlarning kimyosidagi o'xshashliklar tufayli. 3 ga yaqin pH ushbu metal anionlarni so'rib olish uchun qulay bo'lgan, bu (i) protonlangan omin joylari va kuchli anion metallari orasidagi elektrostatik tortishish va (ii) polinukleol gidrolizlangan metall turlarining paydo bo'lishiga mos edi. 3.0–3.5 pH oralig'i. Sorbtsiya kinetikasi, asosan, boncuklar uchun intrapartisle diffuziya bilan boshqarilgan, holbuki, nazorat mexanizmlari tashqi va intrapartalak diffuziyalari bo'lgan. Sulfat (SO4 2−) va molibdat (MoO4 -) ionlarining adsorbsiyasi Moret va Rubio [33] tomonidan pH 4,5 da turli deatsetilasyon darajalari (DD) bo'lgan xitinga asoslangan materialda ham baholandi. Imkoniyatlari yuqori, 150 mg SO4 2− / g, DD = 25%. Chitin, shuningdek, sulfat ionlari ishtirokida molibdat ionlarini adsorblashini isbotladi, ammo reaktsiya uzoqroq muvozanat vaqtini talab qildi (92% olib tashlash uchun 60 minut). Ushbu anionlarni olib tashlashning amaliy misollari haqiqiy kon oqava suvlarida o'rganilib, 71% SO4 2− va 85% MoO4 - Cu-Mo flotatsionilflyuentidan va 80% amid kislotali ko'mir drenajidan sulfat olishdan ( Mo bepul). Adsorbent materialning regeneratsiyasi gidroksidi muhitda anionlarning desorbtsiyasi orqali amalga oshirildi. Tabiiy suvlardagi mish-mish dunyo miqyosidagi muammo. Arsenikning toksikligi, uning sog'liq uchun zararli ekanligi va davolash usullari juda yaxshi ma'lum va ular keng tarqalgan. Ichimlik suvida mishyakning ifloslanishini boshqarish / minimallashtirish bo'yicha keng qamrovli tadqiqotlar olib borilmoqda. Dambies va boshqalar [34] molibdateimpregnatsiyalangan xitosan gel boncuklarında As (V) ning sorbsiyasini o'rganishdi. Xitosanning As (V) uchun sorbsion qobiliyati molibdat bilan singdirish orqali ko'paygan. Mishyakni olish uchun tegmaslik pH darajasi pH 3. As (V) ning sorbsiya sig'imi, molibden yuklanishidan oshib ketdi. 160 mg / g. Ishdan chiqqan sorbent fosforik kislota desorbtsiyasi bilan qayta tiklandi. Uch sorbsiya / desorbtsiya tsikllari sorbtsiya sig'imining ozgina pasayishi bilan o'tkazildi. Qisqichbaqasimon qobiqlardan olingan xitosan kukuni, boncuk shakliga aylantirildi va As (III) va As (V) ni ikkala partiyadan ham, uzluksiz ishlashda ham olib tashlash uchun ishlatildi [35]. As (III) va As (V) ni olib tashlash uchun optimal pH qiymati ca. 5. As (III) va As (V) mos ravishda 1,83 va 1,94 mg As / g boncukning adsorbsion sig'imi haqida xabar qilindi. As (V) ning xitosanflaklarga so'rilishi Kvok va boshqalar tomonidan o'rganilgan [36]. Mualliflar butun kontsentratsiya spektri bo'yicha muvozanatni ta'minlash uchun 96 soatlik aloqa vaqtini tanladilar. Xitosandan arsenatning desorbtsiya darajasi dastlabki pH 3,5 dan 4.50 gacha ko'tarilganda ortdi. Xitosandagi arsenat ionining sig'imi xitosanning protonli reaktsiyasi bilan boshqarilgan va pHning oshishi xitosan tarkibidagi protonli guruhlarning pasayishiga olib kelgan, ular arsenat ionini so'rib olish uchun mavjud bo'lgan va arsenat ionlarining spetsifikatsiyasiga ta'sir qilgan. . Arsenat ionlari H2AsO4 shaklida edi. Arsenat ionlarini suvli fazadan olib tashlash mexanizmi arsenat ionlarining xitosandagi protonlangan aminlar guruhiga adsorbsiyasi bilan bog'liq bo'lishi mumkin deb taxmin qilingan. Adsorbsiya va desorbsiya tsikli davomida pH profilini o'zgartirish ta'sirini o'z ichiga olgan yangi soxta birinchi tartibli qaytariladigan model As (V) va chitosan partiyalarining kinetik tizimlarida sorbsiya va desorbsiyani tavsiflash uchun yangi ishlab chiqilgan. Arsenat va xitosanning adsorbsiyasi va desorbtsiya reaktsiyasining pH qiymatini vaqt profiliga nisbatan pH dan taxmin qilish mumkin edi. Adsorbsiya hajmi 131 mkg arsenat / g chitosan dan boshlang'ich pH 5,5 dan 14,160 mkg arsenat / g xitozan boshlang'ich pH 3,5 ga teng bo'lgan. Temir-xitosan kompozitlaridan foydalanib, er osti suvlaridan mishyakni olib tashlash bo'yicha tadqiqotlar o'tkazildi [37]. As (III) va mishyak (V) ni olib tashlash muvozanat va dinamik sharoitda pH 7.0 da adsorbsiya orqali o'rganildi. Langmuir modelidagi temir xitosanflaklari (ICF) uchun monolayerning adsorbsion sig'imi (As (V) uchun 22,47 ± 0,56 mg / g va As (III) uchun 16,15 ± 0,32 mg / g) temir uchun olinganidan ancha yuqori ekanligi aniqlandi. chitosan granulalari (ICB) (As (V) uchun 2,24 ± 0,04 mg / g; As (III) uchun 2,32 ± 0,05 mg / g). Er osti suvlarida mavjud bo'lgan anionlar, shu jumladan sulfat, fosfat va silikat arsenat / arsenitning adsorbsion holatiga jiddiy aralashuvga olib kelmadi.

The column regeneration studies were carried out for two sorption–desorption cycles for both As(III) and As(V) using ICF and ICB as sorbents. One hundred and forty-seven bed volumes of As(III) and 112 bed volumes of As(V) spiked groundwater were treated in column experiments using ICB, reducing arsenic concentration from 500 to <10μg/L. The eluent used for the regeneration of the spent sorbent was 0.1 M NaOH. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to <10μg/L from arsenic contaminated groundwater samples. Chromium, another important metal, has many industrial applications such as in textile, electroplating, leather tanning and metallurgy industries, and therefore, the wastes generated by these industries are rich in hexavalent Cr(VI) or trivalent Cr(III) forms of chromium. Cr(VI) is more toxic than Cr(III) and has therefore, lead greater environmental concern. Chromium is potentially toxic to humans as it is considered a carcinogen. The adsorption of Cr(VI) on chitosanflakes was investigated against the process parameters such as pH, adsorbent dose and initial Cr(VI) concentration by Aydın and Aksoy [38]. The effects of these factors were studied in the ranges 1.5–9.5, 1.8–24.2 g/L and 15–95 mg/L, respectively. Maximum removal was attained from a solution as concentrated as 30 mg/L at pH 3 with an adsorbent dosage of 13 g/L. The adsorption capacity of chitosanflakes was determined as 22.09 mg/g at these specified conditions. However, the adsorption capacity was recorded as high as 102 mg/g for 100 mg/ L initial Cr(VI) concentration. Pseudo-second-order kinetic model exhibited the highest correlation with data. The results showed that both monolayer adsorption and intraparticle diffusion mechanisms limited the rate of Cr(VI) adsorption. The ability of cross-linked and non-cross-linked chitosan as an adsorbent for Cr(VI) removal from aqueous solution has been demonstrated[39]. Cr(VI) adsorption behavior could be described using the Langmuir isotherm model over the whole concentration range of 10 to 1000 mg/L Cr(VI). The maximum adsorption capacity for both types of chitosan was found to be 78 mg/g for the non-cross-linked chitosan and 50 mg/g for the cross-linked chitosan for the Cr(VI) removal. The optimum pH for maximum Cr(VI) removal was 5. To achieve enhanced removal of Cr(VI), perlite beads were coated with chitosan by drop-wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath[40]. The adsorption capacity of chitosan-coated perlite was found to be 104 mg/g of adsorbent from a solution containing 5000 mg/L of Cr(VI). On the basis of chitosan, the capacity was 452 mg/g of chitosan. It was reported by the authors that this capacity was considerably higher than that of chitosan in its natural and modified forms, which was in the range of 11.3 to 78 mg/g of chitosan. The beads loaded with chromium were regenerated with sodium hydroxide solution of different concentrations.