[-]

The equilibrium and kinetics of chlorophenols sorption by chitosan, polyD-glucosamine, were studied under simulated groundwater conditions [89]. Comparison between two types of chitosan, flakes and highly swollen beads, demonstrated that the maximum pentachlorophenol (PCP) uptake capacities depend on the specific surface area of the particles. Out of the five kinds of chlorophenols, i.e. 2,4,6-trichlorophenol (2,4,6-TCP), 3,4-dichlorophenol (3,4-DCP), 2,3-dichlorophenol (2,3-DCP), 2,6- ichlorophenol (2,6-DCP) and 3-monochlorophenol (3-MCP), flake-type chitosan exhibited maximum sorption efficiency for TCP, followed by DCPs, and finally MCP (the three kinds of DCP, with the same elemental compositions, were sorbed equally). The adsorption of phenol onto chitin was studied as a function of initial pH, temperature and initial phenol concentration [90]. The pH primarily affected the degree of ionization of the phenol and the surface properties of chitin. The functional groups of chitin will be protonated at low-pH values and resulted in a stronger attraction for negatively charged ions in the adsorption medium. Phenol being weakly acidic would be partially ionized in solution. These ions would be negatively charged and would be directly attracted due to electrostatic forces by the protonated amino groups of the chitin. As the pH increased, the overall surface charge of the chitin became negative and adsorption decreased. The equilibrium uptake of phenol by chitin was also affected by temperature which was attributed to the enlargement of pore size or creation of some new active sites on the adsorbent surface due to bond rupture. The highest phenol adsorption capacity was determined as 21.5 mg/g for 300 mg/L initial phenol concentration at pH 1.0 and 40 °C. The application of magnetite-immobilized chitin for pentachlorophenol (PCP) removal was demonstrated by Pang et al.[91]. For chitin immobilization, the optimized conditions were: magnetite to chitin (m:c) ratioat1:2,initialpH6,25°C,200rpmand60mininbatchsystem.The immobilization efficiency (IE) was 99.4% and immobilization capacity (IC) was 2.0 mg chitin/mg magnetite. High initial pH (pH>11) and temperature (>30 °C) lowered the IEand IC. For PCP (10 mg/L) adsorption, the optimized conditions were:1500 mg/L immobilized chitin, initial pH 6, 25 °C, 200 rpm and 60 min in batch system. The removal efficiency (RE) was 57.9% and removal capacity (RC) was 5.4 mg/g. The adsorption ability of immobilized chitin decreased with pH and increased with temperature. However, increasing the amount of immobilized chitin (24,000 mg/L) increased the RE up to 92%. Beads of chitosan–sodium alginate were prepared from chitosan and sodium alginate (an anionic polysaccharide)[92]. These beads were treated with CaCl2in order to improve the stability as well as the sorption capacity of the biosorbent. It was reported that the percent removal of phenol and o-chlorophenol increased rapidly with increase in the dose of chitosan–calcium (CS/Ca) alginate blended beads due to the greater availability of binding sites of the biosorbent. The maximum Langmuir monolayer capacity was reported as 108.69 mg/g for phenol and 97.08 mg/g for o-chlorophenol. Based on the thermodynamic values, the adsorption processes was associated with chemical ion-exchange mechanism. Thefixed bed columns of CS/Ca alginate beads saturated with phenol or chlorophenol was regenerated by passing 0.1 M NaOH solution as an eluent at afixedflow rate of 1 mL/min. Further, results from the limited number of column adsorption–desorption cycle indicated that the adsorption capacity of the CS/Ca alginate beads decreased in the second and third adsorption–desorption cycles. Functional chitosan, chemically modified by salicylaldehyde (CS–SA), β-cyclodextrin (CS–CD), and a cross-linkedβ-cyclodextrin polymer (EPI–CD) were prepared as adsorbents to remove phenol, p-nitrophenol and p-chlorophenol from aqueous solution[93].Itwasfoundthatthe adsorption capacity of phenols onto chitosan was very small (1.98– 2.58 mg/g). However, functional chitosan chemically modified byβ-CD or salicylaldehyde exhibits much better adsorption ability for phenols. CS–CD (20.56–179.73 mg/g) and EPI–CD (41.11–131.50 mg/g) exhibit outstanding adsorption efficiency for these phenols. The adsorption ability of CS–CD was better than EPI–CD. CS–SA presented good adsorption ability for phenols.

Xitosan, poliD-glyukosamin tomonidan xlorofenollarning so'rilishi muvozanati va kinetikasi simulyatsiya qilingan er osti suvlari sharoitida o'rganilgan [89]. Ikki turdagi chitosan, kletchatka va juda shishgan boncuklar o'rtasidagi taqqoslash pentaxlorofenol (PCP) ning maksimal sig'imi zarralarning o'ziga xos sirt maydoniga bog'liqligini ko'rsatdi. Besh turdagi xlorofenollardan, ya'ni 2,4,6-triklorfenol (2,4,6-TCP), 3,4-dixlorofenol (3,4-DCP), 2,3-dixlorofenol (2,3-DCP) ), 2,6- ichlorofenol (2,6-DCP) va 3-monoxlorofenol (3-MCP), kletchatka tipidagi xitosan TCP uchun maksimal sorbsiya samaradorligini namoyish etdi, undan keyin DCPlar va nihoyat MCP (uch turdagi DCP bilan. bir xil elementar kompozitsiyalar, ular teng darajada afsuslangan). Fenolning xitinga adsorbsiyasi boshlang'ich pH, ​​harorat va dastlabki fenol konsentratsiyasi funktsiyasi sifatida o'rganildi [90]. PH asosan fenolning ionlash darajasiga va xitinning sirt xususiyatlariga ta'sir ko'rsatdi. Xitinning funktsional guruhlari past pH qiymatlarida protonlanadi va adsorbsion muhitda manfiy zaryadlangan ionlarning kuchayishiga olib keladi. Kuchsiz kislotali fenol eritmada qisman ionlanadi. Bu ionlar manfiy zaryadlangan va xitinning protonlangan aminokislotalari elektrostatik kuchlari tufayli to'g'ridan-to'g'ri jalb qilingan. PH oshishi bilan xitinning umumiy sirt zaryadi salbiy bo'lib, adsorbsiya kamaydi. Fenolni xitin bilan muvozanatlashishi haroratning o'zgarishiga ta'sir ko'rsatdi, bu haroratni pasayishiga qarab, g'ovak hajmining kattalashishi yoki adsorbent yuzasida yangi faol joylarning paydo bo'lishi bilan bog'liq. Fenolning yuqori adsorbsion sig'imi pH 1,0 va 40 ° C haroratda 300 mg / l boshlang'ich kontsentratsiyasi uchun 21,5 mg / g sifatida aniqlandi. Pentaxlorofenolni (PCP) olib tashlash uchun magnetit-immobilizatsiyalangan chitinni qo'llash Pang va boshq. [91] tomonidan namoyish etildi. Chitin immobilizatsiyasi uchun optimallashtirilgan shartlar quyidagilardir: magnetitdan chitinga (m: c) nisbati1: 2, boshlang'ich pH6,25 ° C, 200rpmand60mininbatchsystem. Immobilizatsiya samaradorligi (IE) 99,4% va immobilizatsiya hajmi (IC) 2,0 mg chitin / mg magnitit. Yuqori boshlang'ich pH (pH> 11) va harorat (> 30 ° C) IEand IC ni pasaytirdi. PCP (10 mg / L) adsorbsiyasi uchun optimallashtirilgan shartlar quyidagilardan iborat edi: 1500 mg / L immobilizatsiyalangan chitin, boshlang'ich pH 6, 25 ° C, 200 rpm va 60 min. Chiqarish samaradorligi (RE) 57,9% ni va tozalash qobiliyati (RC) 5,4 mg / g ni tashkil etdi. Immobilizatsiya qilingan xitinning adsorbsion qobiliyati pH pasaygan va harorat oshgan. Biroq, immobilizatsiya qilingan chitin (24000 mg / L) miqdorini ko'paytirish REni 92% ga oshirdi. Xitosan-natriy alginat boncuklari xitosan va natriy alginat (anion polisakkarid) dan tayyorlangan [92]. Ushbu boncuklar barqarorlikni va biosorbentning sorbsion qobiliyatini yaxshilash uchun CaCl2in bilan ishlov berildi. Fenol va o-xlorofenolning foizli chiqarib tashlanishi xitosan-kaltsiy (CS / Ca) alginat aralashgan boncuklar dozasining biosorbentni bog'laydigan joylari ko'payishi sababli tez ko'paygani haqida xabar berildi. Langmuir monolayerining maksimal hajmi fenol uchun 108,69 mg / g va o-xlorofenol uchun 97,08 mg / g sifatida qayd etildi. Termodinamik qiymatlarga asoslanib adsorbsion jarayonlar kimyoviy ion almashinuvi mexanizmi bilan bog'liq edi. Fenol yoki xlorofenol bilan to'yingan CS / Ca alginat boncuklaridagi to'shalgan ustunlar 0,1 M NaOH eritmasidan ellent sifatida 1 ml / min tezlikda oqadi. Bundan tashqari, ustun adsorbsion-desorbtsiya tsiklining cheklangan soni natijasida, CS / Ca alginat boncuklarının adsorbsion sig'imi ikkinchi va uchinchi adsorbtsiya-desorbtsiya tsikllarida pasayganligini ko'rsatdi. Fenol, p-nitrofenol va p-xlorofenolni olib tashlash uchun adsorbent sifatida salitsilaldegid (CS-SA), β-siklodekstrin (CS-CD) va o'zaro bog'langan-siklodekstrin polimer (EPI-CD) tomonidan kimyoviy jihatdan o'zgartirilgan funktsional xitosan tayyorlandi. suvli eritmadan [93] .Fenollarning xitosanga adsorbsion sig'imi juda oz edi (1.98 - 2.58 mg / g). Ammo, β-CD yoki salitsilaldegid tomonidan kimyoviy jihatdan o'zgartirilgan funktsional xitozan fenollarga nisbatan yaxshiroq adsorbsion xususiyatga ega. CS-CD (20.56–179.73 mg / g) va EPI-CD (41.11–131.50 mg / g) ushbu fenollar uchun yuqori darajada adsorbtsiya samaradorligini namoyish etadi. CS-CD ning adsorbsion qobiliyati EPI-CD ga qaraganda yaxshiroq edi. CS-SA fenollarga yaxshi adsorbtsiya qobiliyatini taqdim etdi

The adsorption of phenols onto EPI–CD, CS–CD and CS–SA was predominated by hydrophobic interaction, hydrogen bonding andπ–πinteraction, respectively. The low temperature was found favorable for the adsorption of phenols. Ethanol was used for phenols desorption from adsorbent and 80–94.2% adsorbate was removed from the adsorbent. The regenerated adsorbent could adsorb 69.4–78.9% adsorbate compared with thefirst adsorption capacity, and it could be reused six times. Laccase from Coriolus versicolor was immobilized on chitosan using glutaraldehyde as a cross-linking agent [94]. After immobilization, laccase retained 52.2% of its original activity and was used to study 2,4-dichlorophenol (2,4-DCP) removal from aqueous solutions. Favorable cross-linking of laccase with chitosan occurred using 5% glutaraldehyde for 8 h. The ratio of laccase to cross-linked chitosan was 20 mg/g after 6 h of reaction. The recovery of immobilized laccase activity was 52.2%. The optimum pH for immobilized laccase was 4.5, which was less than the optimum pH for the free enzyme (5.0). The immobilized enzyme also demonstrated greater stability at room temperature over time. When used to remove 2,4-DCP from wastewater, the optimum conditions for the immobilized enzyme were a pH of 5.5 and a temperature range of 35–45 °C. The immobilized enzyme retained removal efficiency above 50% for up to six usages. Chitosan–abrus precatorius (CS/Ab) blended beads were used as adsorbent for the removal of phenolic compounds from aqueous solution[95]. The maximum monolayer adsorption capacity of phenol, 2-chlorophenol and 4-chlorophenol on to the (CS/Ab) beads was found to be 156 mg/g, 204 mg/g and 278 mg/g, respectively. A summary of adsorption capacities of chitin- and chitosan-derivatives for different henolsispresentedinTable 3. As compared to metal ions and dyes, there are comparatively less reports available, demonstrating the usefulness of chitin- and chitosan and its derivatives for the removal of phenols. Most of these studies are limited only to chloro- or nitro-phenols. Additionally, chitin-, chitosan and its derivatives show low affinity for phenols removal and there is a strong need to conduct extensive research to enhance the removal efficiencies/adsorption capacities of these biosorbents for different phenols after appropriate treatment. Furthermore, the mechanism of phenols adsorption on chitin- and chitosan-derivatives also needs to be studied in detail as most of the articles focused only on the dsorption potential (adsorption capacity) of chitin- and chitosan-derivatives for phenols removal and little efforts have been made to elucidate the sorption mechanism. 2.4. Chitin- and chitosan-derivatives for anions removal Inorganic anions are one of the important classes of aquatic pollutants and various inorganic anions have been found in potentially harmful concentrations in numerous drinking water sources. The removal of these pollutants from drinking water suppliesisanemergingissue.Inrecent years, chitin- and chitosan-derivatives have been successfully utilized for some anions removal from water. The adsorption of nitrate by chitosan hydrobeads was examined by Chatterjee and Woo[96].Themaximum adsorption capacity was 92.1 mg/g at 30 °C. Intraparticle diffusion played significant role at the initial stage of the adsorption process.

Fenollarning EPI-CD, CS-CD va CS-SA tarkibiga adsorbsiyasi mos ravishda gidrofobik ta'sir o'tkazish, vodorod bilan bog'lanish va π-o'zaro ta'sirga ega edi. Past harorat fenollarning adsorbsiyasi uchun qulay deb topildi. Etanol adsorbentdan fenollar desorbtsiyasi uchun ishlatilgan va adsorbentdan 80-94,2% adsorbent olib tashlangan. Qayta tiklangan adsorbent birinchi adsorbsiya sig'imiga nisbatan 69.4–78.9% adsorbtsiyani yutishi mumkin va undan olti marta foydalanish mumkin. Coriolus versicolor-dan olingan vaktsinalar o'zaro bog'lash vositasi sifatida glutaraldegid yordamida xitosanga immobilizatsiya qilindi [94]. Immobilizatsiya qilinganidan so'ng, laktsiya asl faolligining 52,2 foizini saqlab qoldi va suvli eritmalardan 2,4-dixlorofenol (2,4-DCP) ni o'rganish uchun ishlatilgan. Laktaza bilan xitosanni o'zaro bog'lash 5% glutaraldegid yordamida 8 soat davomida amalga oshirildi. Laktoza o'zaro bog'langan xitosanga nisbati 6 soatlik reaktsiyadan keyin 20 mg / g ni tashkil etdi. Immobilizatsiya qilingan lakaza faolligining tiklanishi 52,2% ni tashkil etdi. Immobilizatsiya qilingan laktsiya uchun optimal pH 4,5 ni tashkil qildi, bu erkin ferment uchun tegmaslik pHdan (5.0) past edi. Immobilizatsiya qilingan ferment vaqt o'tishi bilan xona haroratida ko'proq barqarorlikni namoyish etdi. Oqim suvlardan 2,4 DCPni olib tashlash uchun ishlatilganida, immobilizatsiya qilingan ferment uchun pH 5,5 va harorat oralig'i 35-45 ° C darajasida bo'lgan. Immobilizatsiya qilingan ferment oltita foydalanish uchun 50% dan yuqori samarani saqlab qoldi. Aralashtirilgan chitosan-abrus precatorius (CS / Ab) suvli eritmadan fenolik birikmalarni olib tashlash uchun adsorbent sifatida ishlatilgan [95]. (CS / Ab) boncuklarda fenol, 2-xlorofenol va 4-xlorofenolning maksimal monolayer adsorbsion hajmi mos ravishda 156 mg / g, 204 mg / g va 278 mg / g bo'lganligi aniqlandi. Xitol- va chitosan-hosilalarining turli xil henolsprententinetable 3-jadval uchun adsorbsion qobiliyatlari to'g'risida qisqacha ma'lumot. Metall ionlari va bo'yoqlarga nisbatan, chitin- va xitosan va uning hosilalari fenollarni olib tashlash uchun foydaliligini namoyish etuvchi nisbatan kam ma'lumotlar mavjud. Ushbu tadqiqotlarning aksariyati faqat xlor- yoki nitro-fenollar bilan cheklangan. Bundan tashqari, xitin-, chitosan va uning hosilalari fenollarni olib tashlash uchun past darajada bog'liqlikni namoyish etadi va tegishli davolanishdan keyin ushbu biosorbentslarning turli fenollar uchun olib tashlash samaradorligini / adsorbsion qobiliyatini oshirish uchun keng tadqiqotlar o'tkazish zarurati mavjud. Bundan tashqari, xitin va xitosan-hosilalari bo'yicha fenollarning adsorbsiyasi mexanizmini ham batafsil o'rganish kerak, chunki maqolalarning aksariyati faqat xitin va xitosan hosilalarining fenollarni olib tashlash uchun dorbtsiya potentsialiga (adsorbsion sig'imga) qaratilgan va ozgina kuch sarflamoqda. sorbsiya mexanizmini tushuntirish uchun qilingan. 2.4. Anionlarni yo'q qilish uchun xitin va xitosan hosilalari Anorganik anionlar suvni ifloslantiruvchi moddalarning muhim sinflaridan biri bo'lib, turli xil noorganik anionlar ichimlik suvining ko'plab manbalarida zararli konsentratsiyalarda topilgan. Ushbu ifloslantiruvchi moddalarni ichimlik suvi etkazib berishdan tozalash ishlari olib borilmoqda. So'nggi yillarda xitin va xitosan hosilalari ba'zi anionlarni suvdan tozalash uchun muvaffaqiyatli ishlatilgan. Nitratning xitosan gidro-gidrobadlari tomonidan adsorbtsiyasi Chatterji va Wu tomonidan tekshirildi [96] .Temaksimal maksimal adsorbsiya hajmi 30 ° C da 92,1 mg / g ni tashkil etdi. Intraparticle diffuziyasi adsorbsiya jarayonining dastlabki bosqichida muhim rol o'ynadi.

Nitrate adsorption was found to increase with a decrease in the pH of the solution which was explained due to the fact that a decrease in the pH of the solution resulted in more protons being available to protonate the chitosan amine group. This resulted in an enhancement of nitrate adsorption by chitosan beads due to increased electrostatic interactions between negatively charged nitrate group and positively charged amine group. Above pH 6.4, an appreciable amount of nitrate adsorption by chitosan beads indicated the involvement of physical forces. Desorption of nitrate from the loaded beads was accomplished by increasing the pH of 35 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy the solution to the alkaline range, and a desorption ratio of 87% was achieved around pH 12.0. The adsorption of nitrate onto chitosan beads modified by crosslinking with epichlorohydrin (ECH) and surface conditioning with sodium bisulfate was investigated by Chatterjee et al. [97]. The maximum adsorption capacity was found at a cross-linking ratio of 0.4 and conditioning concentration of 0.1 mM NaHSO4. The maximum adsorption capacity was 104.0 mg/g for the conditioned cross-linked chitosan beads at pH 5, while it was 90.7 mg/g for normal chitosan beads. The nitrate adsorption was found strongly pH dependent, and the maximum nitrate removal was found at pH 3. The high adsorption capacities in acidic solutions (pH 3–5) were due to the strong electrostatic interactions between its adsorption sites and nitrate. The applicability of neodymium-modified chitosan as adsorbents for the removal of excessfluoride ions from water was studied by Yao et al.[98]. The effect of various physico-chemical parameters such as temperature (283–323 K), pH (5–9), adsorbent dose (0.2–2.0 g/L), particle size (0.10–0.50 mm) and the presence of co-anions (NO3 − ,Cl − and SO4 2− ) on removal offluoride ions were studied. The maximum equilibrium sorption was 11.4–22.3 mg/g. The sorption process was found to be complex, and both the boundary of liquid film and intraparticle diffusion contributed to the rate-determining step. The used adsorbents could be regenerated in 24 h by 4 g/L of sodium hydroxide. A novel adsorbent namely magnesia/chitosan (MgOC) composite was prepared to removefluoride from drinking water by Sundaram et al.[99]. The maximum Langmuir monolayer capacity was found ca. 11 mg/g. The mechanism offluoride removal of both MgO and MgOC composite was mainly governed by adsorption. The higher defluoridation capacity (DC) of MgOC composite might be attributed to the fact that chitosan also contributed in the enhancement of DC by removingfluoride through hydrogen bonding. It was suggested that MgOC composite being biocompatible, biodegradable, cost effective, shaped into any desired form which possesses higher defluoridation capacity with minimum contact time, can be used as a promising sorbent forfluoride removal. The metal-binding property of chitosan was used to incorporate titanium (Ti) metal and applied as an adsorbent forfluoride adsorption by Jagtap et al.[100]. Ti loading was varied from 5 to 50 wt.%. It was observed that an increase in titanium loading from 5 to 15% improved fluoride removal from 61 to 89%. A 15% Ti loading was optimum as it showed the highestfluoride removal and reduces thefluoride level to permissible limits. Further increasing titanium loading showed a negative effect onfluoride removal and this might be due to overlapping of active sites. The maximum Langmuir monolayer capacity was found to be 7.2 mg/g. Thefluoride uptake was maximum at pH 7 and decreased in acidic and alkaline pH. The presence of co-existing anions has a negative effect onfluoride adsorption. The adsorbent was found to have very fast kinetics in thefirst 30 min and then the rate slowed down as equilibrium was approached. A comparison offluoride removal in simulated and field water shows a high adsorption capacity in simulated water.

Nitrat adsorbsiyasi eritmaning pH pasayishi bilan ko'payganligi aniqlandi, chunki bu eritmaning pH darajasining pasayishi xitosan aminlar guruhini protonlash uchun ko'proq protonlar mavjud bo'lishiga olib keldi. Natijada manfiy zaryadlangan nitrat guruhi va musbat zaryadlangan aminlar guruhi o'rtasida elektrostatik o'zaro ta'sir kuchayishi natijasida xitosan boncuklar tomonidan nitrat adsorbsiyasining kuchayishiga olib keldi. Nitrat pH 6.4 dan yuqori darajada, xitosan boncuklar tomonidan nitrat adsorbtsiyasi jismoniy kuchlarning jalb qilinganligini ko'rsatadi. Yuklangan boncuklardan nitratning desorbtsiyasi 35 A. Bhatnagar, M. Sillanpäa / Kolloid va interfeys fanidagi yutuqlarning pH miqdorini ko'paytirish orqali amalga oshirildi 152 (2009) 26–38 Muallifning shaxsiy nusxasi ishqoriy diapazoni eritmasi va desorbtsiya nisbati. 87% ning pH 12.0 atrofida erishildi. Xitosan boncuklaridagi nitratning adsorbsiyasi epiklorohidrin (ECH) bilan o'zaro bog'lanish va natriy bisulfat bilan sirtni kondensatsiyalash orqali Chatterji va boshqalar tomonidan o'rganilgan. [97]. Maksimal adsorbtsiya sig'imi 0,4 va konditsioner kontsentratsiyasi 0,1 mM NaHSO4 bo'lgan o'zaro bog'liqlikda aniqlandi. Maksimal adsorbtsiya hajmi pH 5 da shartli o'zaro bog'langan xitosan boncuklar uchun 104,0 mg / g, oddiy xitosan boncuklar uchun esa 90,7 mg / g edi. Nitratning adsorbsiyasi kuchli pH ga bog'liq va nitritning maksimal chiqarib tashlanishi pH 3 da aniqlandi. Kislotali eritmalardagi yuqori adsorbsion qobiliyat (pH 3-5) uning adsorbsion joylari va nitrat o'rtasidagi kuchli elektrostatik o'zaro ta'sir tufayli yuzaga keldi. Neodimiy modifikatsiyalangan xitosanning ortiqcha ftorid ionlarini suvdan olib tashlash uchun adsorbent sifatida qo'llanishi Yao va boshq. [98] tomonidan o'rganilgan. Har xil fizik-kimyoviy parametrlarning ta'siri, masalan harorat (283–323 K), pH (5–9), adsorbent dozasi (0.2–2.0 g / l), zarrachalar hajmi (0,10–0,50 mm) va qo'shilishning mavjudligi. Olovli ionlarni olib tashlash bo'yicha anionlar (NO3 -, Cl - va SO4 2−) o'rganildi. Maksimal muvozanat sorbsiyasi 11.4–22.3 mg / g ni tashkil etdi. Sorbtsiya jarayoni murakkab deb topildi va suyuqlik plyonkasining chegarasi va intrapartal yadroli tarqalishi tezlikni aniqlash bosqichiga yordam berdi. Ishlatilgan adsorbentlarni 24 soat ichida 4 g / l natriy gidroksid bilan tiklash mumkin. Sundaram va boshq. Tomonidan yangi adsorbent, ya'ni magniy / chitosan (MgOC) kompozitsiyasi ichimlik suvidan ftoridni chiqarib tashlash uchun tayyorlangan. Langmuir monolayerining maksimal sig'imi topildi. 11 mg / g. MgO va MgOC kompozitsiyalarini offloriddan tozalash mexanizmi asosan adsorbsiya bilan boshqarildi. MgOC kompozitining deflyorizatsiya darajasi (DC) yuqori bo'lishi xitosanning vodorod bilan bog'lanish orqali ftoridni chiqarib tashlash orqali DCning kuchayishiga hissa qo'shganligidir. MgOC kompozitsiyasini biokompozitsiyali, biologik tarzda parchalanadigan, tejamkor, istalgan shaklda shakllantirilgan, eng kam aloqa vaqti bilan yuqori deflyorizatsiya qobiliyatiga ega bo'lgan forfloridni so'rib olish uchun istiqbolli sorbent sifatida ishlatish tavsiya etildi. Xitosanning metallni bog'laydigan xususiyati titandan (Ti) metalni olish uchun ishlatilgan va Jagtap va boshqalar tomonidan 100% adsorbent forflorid adsorbsiyasi sifatida qo'llanilgan. Ti yuklamasi 5 dan 50 wt% gacha o'zgargan. Titan yuklanishining 5% dan 15% gacha ko'tarilishi ftoridlarning chiqarilishini 61 foizdan 89 foizga yaxshilaganligi kuzatildi. 15% Ti yuklanishi eng maqbul edi, chunki u ftororidni yo'q qilishning eng yuqori ko'rsatkichini ko'rsatdi va ftorid darajasini ruxsat etilgan chegaralarga qadar kamaytirdi. Keyinchalik ortib boruvchi titanning chiqishi floridni yo'q qilishga salbiy ta'sir ko'rsatdi va bu faol maydonlarning bir-birining ustiga chiqishi bilan bog'liq bo'lishi mumkin. Langmuir monolayerining maksimal sig'imi 7,2 mg / g deb topildi. Ftoridlarni qabul qilish maksimal pH 7 darajasida va kislotali va gidroksidi pHda pasaygan. Birgalikda mavjud bo'lgan anionlarning mavjudligi ftorid adsorbsiyasiga salbiy ta'sir qiladi. Adsorbentning dastlabki 30 minutda juda tez kinetikasi borligi aniqlandi va keyin muvozanat yaqinlashganda kurs sekinlashdi. Simulyatsiya qilingan va dala suvlarida solishtirma offloridlarni chiqarib tashlash simulyatsiya qilingan suvda yuqori adsorbsion quvvatni namoyish etadi.

Protonated chitosan beads (PCB) were examined for fluoride removal by Viswanathan et al.[101]. Sorption process was found to be independent of pH and altered in the presence of other co-existing anions. The maximum Langmuir monolayer capacity was found in the range of 4.72–7.32 mg/g. The sorption process followed pseudosecond-order and intraparticle diffusion kinetic models. The adsorption mechanism was explained on the basis of FTIR analysis, where a slight widening of–NH2stretching band in FTIR spectra of thefluoride sorbed PCB was observed which confirmed the presence of hydrogen bonding between protonated amine (NH3 + ) andfluoride, suggesting that the PCB removedfluoride by means of hydrogen bonding which was due to electrostatic interactions between positively charged surface and negatively chargedfluoride ions. 0.1 M HCl was identified as the best eluent. Field trial results indicated that PCB could be employed as a best sorbent forfluoride removal. The same researchers also prepared multifunctional chitosan beads after chemical modification by introducing multifunctional groups, viz., NH3+and COOH groups by means of protonation and carboxylation in order to utilize both amine and hydroxyl groups forfluoride removal [102]. The protonated cum carboxylated chitosan beads (PCCB) showed a maximum DC of 1800 mg F −/kg, whereas, raw chitosan beadsdisplayed only 52 mg F−/kg dsorption capacity. The mechanism of fluoride removal by PCCB was explained by H-bonding. The fluoride adsorption potential of novel nano-hydroxyapatite/ chitin (n-HApCh) composite was explored by Sundaram et al.[103]. The effect of pH, interfering anions and contact time were examined. n-HApCh composite possesses higher defluoridation capacity (DC) of 2840 mg F− /kg than nano-hydroxyapatite (n-HAp) which showed a DC of 1296 mg F − /kg. The enhancement in DC of n-HApCh composite over n-HAp was explained due to biosorption by chitin, adsorption by physical forces andfluoride ion entrapped infibrilliar capillaries and spaces of polysaccharide network of the chitin moiety. Recently, Xie et al. [104] investigated the removal of perchlorate from aqueous solution by protonated cross-linked chitosan. The maximum Table 3 Adsorption capacities of chitin and chitosan-derivatives for various phenols removal from water.

Protonli xitosan boncuklari (PCB) Visvanatan va boshqalar tomonidan floridni yo'q qilish uchun tekshirildi. [101] Sorbtsiya jarayoni pH ga bog'liq emasligi va boshqa birgalikda mavjud bo'lgan anionlar mavjudligida o'zgarganligi aniqlandi. Langmuir monolayerining maksimal sig'imi 4.72-7.32 mg / g oralig'ida topildi. Sorbtsiya jarayoni soxta sekundosekund tartibida va intrapartikula diffuz kinetik modellarida kuzatilgan. FTIR analizi asosida adsorbsiya mexanizmi tushuntirildi, bunda ftorli sorblangan PCB spektrida NH2-chiziqning biroz kengayishi kuzatildi, bu protonlangan amin (NH3 +) va ftorid o'rtasida vodorod bog'lanishining mavjudligini tasdiqladi, bu esa PCB chiqarib tashlangan floridni tasdiqlaydi. musbat zaryadlangan sirt va manfiy zaryadlangan ftorid ionlari o'rtasidagi elektrostatik o'zaro ta'sir natijasida vodorod bog'lanishi orqali. 0,1 M HCl eng yaxshi elektent sifatida aniqlandi. Dala sinovlari natijalari shuni ko'rsatdiki, PCB eng yaxshi sorbent sifatida ishlatilishi mumkin. Xuddi shu tadqiqotchilar kimyoviy modifikatsiyadan keyin ko'p funktsiyali guruhlar, viz., NH3 + va COOH guruhlarini protonatsiya va karboksilatsiyalash orqali amin va gidroksil guruhlarini ftorlarni chiqarib tashlash uchun foydalanish orqali tayyorlashdi [102]. Protonli karbonatlangan xitosan boncuklar (PCCB) maksimal DC 1800 mg F - / kg ni ko'rsatdi, holbuki, xom xitosan boncuklari atigi 52 mg F− / kg dsorbtsiya sig'imiga ega. Ftoridlarni PCCB yordamida yo'q qilish mexanizmi H-bog'lanishi bilan izohlandi. Yangi nano-gidroksiapatit / chitin (n-HApCh) kompozitsiyasining ftorid adsorbsion potentsiali Sundaram va boshqalar tomonidan o'rganilgan [103]. PH, aralashuvchi anionlar va aloqa vaqtining ta'siri o'rganildi. n-HApCh kompozitsiyasi nano-gidroksiapatitdan (n-HAp) nisbatan 2840 mg F− / kg ga teng bo'lgan deflyidizatsiya (DC) ga ega, bu DC ning 1296 mg F - / kg ni tashkil etadi. N-HApCh kompozitsiyasining n-HAp ga nisbatan DC ga ko'payishi xitinning biosorbtsiyasi, jismoniy kuchlar tomonidan adsorbsiyalanishi va inflorilli kapillyarlarning kirib borgan ftorid ionlari va chitin tutqichining polisaxarid tarmog'idagi bo'shliqlar bilan izohlanadi. Yaqinda Xie va boshqalar. [104] perkloratning suvli eritmadan protonlangan o'zaro bog'langan xitosan tomonidan olib tashlanishini tadqiq qildi. 3-jadval. Har xil fenollarni suvdan olib tashlash uchun xitin va xitosan-hosilalarining adsorbtsiya qobiliyatlari.

Table 4

Adsorption capacities of chitosan-derivatives for different anions removal.



monolayer adsorption capacity was found to be 45.45 mg/g. The presence of other anions inhibited the perchlorate adsorption. The adsorbent was well regenerated by sodium hydroxide solution with pH 12 and reused for about 15 cycles. Electrostatic attraction as well as physical forces was suggested as the main driven forces for perchlorate adsorption. A summary of adsorption capacities of chitinand chitosan-derivatives for different anions is provided inTable 4. Recent studies have shown that chitosan and its derivatives can be successfully applied for the removal of anions (especiallyfluoride and nitrate). However, as mentioned previously, it is necessary to continue identification of the most promising types of chitosan for anions removal. Additionally, mechanistic studies with anions need to be performed in detail to propose the binding mechanism. There is, as yet, little information in the literature on this topic, which needs to be explored more in detail. 2.5. Chitin- and chitosan-derivatives for miscellaneous pollutants removal Two types of chitosan microparticles (CMs) and their silvercomplex CMs (SCMs) were prepared using different cross-linking agents, i.e. glutaraldehyde and epichlorohydrin, in order to investigate the adsorption and release behaviors of a typical pesticide, methyl parathion (MP)[105]. The maximum adsorption capacities of Ag(I) on glutaraldehyde-cross-linked CM (CM # 1) and pichlorohydrin-crosslinked CM (CM # 2) were found to be 140 mmol/g and 290 mmol/g, and those of MP on SCM # 1 and SCM # 2 were 180 mmol/g and 60 mmol/g, respectively. It was also confirmed that SCM # 1 has better absorptivity for MP than SCM # 2, in spite of its lower adsorption capacity of Ag(I). The ratios of MP/Ag adsorbed on the SCMs are 1.3 and 0.2 for SCM # 1 and SCM # 2, respectively. The removal of two fungicides, 4,4′-iso-Propylidene diphenol (BPA), and diphenylolpropane 4,4′- ioxyaceticacid (BPAc) has been investigated by Şişmanoğlu, [106]. The Langmuir maximum monolayer coverage was reported to be 4.30 ×10 −3 mol/g for BPA and 2.62 × 10 −3 mol/g for BPAc. The pseudo-first-order model and intraparticle diffusion were used to describe the adsorption behavior of BPA and BPAc onto chitin. The ability of chitin and chitosan to adsorb humic acid has been studied [107]. The adsorption capacities of humic acid at room temperature (27 °C) were 27.30 mg/g for chitin and 28.88 mg/g for chitosan. It was suggested that chitin and chitosan can be utilized to remove humic acid. Chitosan was successfully coated on PET granules through a dip and phase inversion process and the coated granules were examined for the performance and mechanism of humic acid removal through a series of batch adsorption tests[108]. Chitosan-coated granules were found to have positive zeta potential values at pH<6.6, mainly due to the protonation of the amino groups in chitosan. Adsorption of humic acid onto chitosan-coated granules was pH dependent and significant amounts of humic acid could be adsorbed under acidic and neutral pH conditions. The adsorption process involved a two-step process: protonation of the amino groups in chitosan, followed by attachment of humic acid onto the protonated amino sites on the surface. Under low-pH conditions, the adsorption process was transport-controlled, but under high-pH conditions, both transport and attachment played an important role in humic acid adsorption onto chitosan-coated granules. While chitosan has been widely studied for metal removal from aqueous solution, it is also possible to extend the application of chitosan as an adsorbent to remove charged organic compound such as humic acid from water and wastewater. The effects of pH and ionic strength on the adsorption capacity for fulvic acid (FA) by chitosan hydrogel beads were examined[109]. The maximum adsorption capacity of FA on chitosan hydrogel beads was 1.67 mg/g at pH 6.0. FTIR along with XPS analyses revealed that the amine groups on the beads were involved in the sorption of FA and the organic complex between the protonated amino groups and FA was formed after FA uptake. Electrostatic interaction and surface complexation were found to be involved in the complex sorption of FA on the chitosan hydrogel beads. Chitin and chitosan have also been examined for the removal of endocrine disrupting chemicals, estrone (E1) and 17β-estradiol (E2) from water[110]. It was reported that it took about 1 and 2 days for E1 to achieve the equilibration onto chitin and chitosan, respectively. The limited adsorption capacity was observed by chitin and chitosan for estrogenic compounds. The authors reported that chitin was slightly more effective than chitosan in adsorbing E1, suggesting that the process is primarily adsorption rather than ion exchange in nature. The feasibility of chitosan, with different molecular weights, to simultaneously remove various pollutants from the discharge of an eel culture pond was evaluated[111].

monolayerning adsorbsion sig'imi 45,45 mg / g ni tashkil etdi. Boshqa anionlarning mavjudligi perkloratning adsorbsiyasini inhibe qildi. Adsorbent pH 12 bilan natriy gidroksid eritmasi bilan yaxshi qayta tiklandi va taxminan 15 tsiklda ishlatildi. Perklorat adsorbsiyasining asosiy harakatlantiruvchi kuchi sifatida elektrostatik va jismoniy kuchlarni jalb qilish taklif qilindi. 4-jadvalda turli xil anionlar uchun xitinand xitosan-hosilalarining adsorbsion qobiliyatlari to'g'risida qisqacha ma'lumot 4-jadvalda keltirilgan. So'nggi tadqiqotlar shuni ko'rsatdiki, xitosan va uning hosilalari anionlarni (ayniqsa ftorid va nitrat) olib tashlash uchun muvaffaqiyatli qo'llanilishi mumkin. Ammo, yuqorida aytib o'tilganidek, anionlarni olib tashlash uchun xitosanning eng istiqbolli turlarini aniqlashni davom ettirish kerak. Bundan tashqari, bog'lovchi mexanizmni taklif qilish uchun anion bilan mexanik tadqiqotlarni batafsil bajarish kerak. Ushbu mavzudagi adabiyotlarda hali batafsil ma'lumot yo'qligi sababli juda kam ma'lumotlar mavjud. 2.5. Turli xil ifloslantiruvchi moddalarni olib tashlash uchun xitin va xitosan lotinlari Ikki turdagi chitosan mikropartikullari (CM) va ularning kumushsimon CMlari (SCM) turli xil o'zaro bog'liqlashtiruvchi vositalar, ya'ni glutaraldegid va epixlorohidrinlardan foydalanib, adsorbsiya va bo'shatish harakatlarini o'rganish maqsadida tayyorlangan. tipik pestitsid, metil paratyon (MP) [105]. Glutaraldegid bilan bog'langan CM (CM # 1) va piklorohidrin bilan bog'langan CM (CM №2) ning maksimal (adsorbtsiya) qobiliyatlari 140 mmol / g va 290 mmol / g, va MP bo'yicha SCM №1 va SCM №2 navbati bilan 180 mmol / g va 60 mmol / g ni tashkil etdi. Shuningdek, № 1-SCM Ag (I) ning adsorbsion qobiliyatiga qaramay, 2-SCM-ga qaraganda MP uchun yaxshi singdiruvchanlikka ega ekanligi tasdiqlandi. SCM-larga qo'shilgan MP / Ag nisbati mos ravishda 1,3 va 0,2-sonli SCM-lar uchun 2 va 0,2 ni tashkil qiladi. Ikki fungitsid, 4,4′-izo-Propiliden difenol (BPA) va difenilolpropan 4,4′- iosiyatsetatsid (BPAc) ning olib tashlanishi Shishmanog'lu tomonidan o'rganilgan [106]. Langmuir maksimal monolayer qoplamasi BPA uchun 4.30 × 10 −3 mol / g va BPAc uchun 2.62 × 10 −3 mol / g bo'lganligi ma'lum qilindi. Soxta birinchi tartibli model va intraparticle diffuziyasi BPA va BPAclarning xitinga adsorbsion harakatlarini tavsiflash uchun ishlatilgan. Xitin va xitosanning hümik kislotani adsorbsiyalash qobiliyati o'rganildi [107]. Xona kislotasining xona haroratida (27 ° C) adsorbsion sig'imi xitin uchun 27,30 mg / g va xitosan uchun 28,88 mg / g ni tashkil etdi. Xitin va xitosanni hümik kislotani olib tashlash uchun ishlatish mumkinligi taklif qilindi. Chitosan PET granulalariga daldırma va fazali inversiya jarayoni orqali muvaffaqiyatli surtildi va qoplangan granulalar bir qator partiyali adsorbsion sinovlar orqali hümik kislotani olish mexanizmi va ishlash mexanizmi uchun tekshirildi. Chitosan bilan qoplangan granulalar pH <6,6 da musbat zeta potentsial qiymatiga ega ekanligi aniqlandi, bu asosan xitosanadagi aminokislotalarning protonatsiyasi tufayli. Xit kislotasining xitosan bilan qoplangan granulalarga adsorbsiyasi pH ga bog'liq edi va kislotali va neytral pH sharoitida ko'p miqdorda hümik kislota adsorbsiyalanishi mumkin. Adsorbsiya jarayoni ikki bosqichli jarayonni o'z ichiga oldi: xitosan tarkibidagi aminokislotalar protonatsiyasi, so'ngra sirtdagi protinatsiyalangan aminokislotalarga hümik kislota biriktirilishi. Kam pH sharoitida adsorbsiya jarayoni transport orqali boshqariladigan edi, lekin yuqori pH sharoitida ham transport, ham birikma xit kislotani xitosan bilan qoplangan granulalarga adsorbsiyasida muhim rol o'ynadi. Xitosan suvli eritmadan metallni olib tashlash uchun keng o'rganilgan bo'lsa-da, xitosanni adsorbent sifatida suv va oqava suvdan zararli kislota kabi zaryadlangan organik birikmani olib tashlash uchun qo'llashni kengaytirish mumkin. Xitosan gidrojel boncuklari tomonidan pH va ionli quvvatning fulvik kislota (FA) uchun adsorbtsiya sig'imiga ta'siri o'rganildi. FA ning xitosan gidrojel boncuklaridagi maksimal adsorbsion quvvati pH 6.0 da 1,67 mg / g ni tashkil etdi. FTIR va XPS tahlillari boncuklardagi amin guruhlari FA ning sorbsiyasiga jalb qilinganligini va protonlangan aminokislotalar orasidagi organik kompleksni va FA faolligi ortidan hosil bo'lganligini aniqladi. Elektrostatik shovqin va sirtning murakkablashishi FA ning xitosan gidrogel boncuklaridagi murakkab sorbsiyasiga aloqadorligi aniqlandi. Xitin va xitosan shuningdek, endokrinni buzadigan kimyoviy moddalarni, estron (E1) va 17β-estradiol (E2) ni suvdan tozalash uchun tekshirildi [110]. Xabar qilinishicha, E1 uchun mos ravishda chitin va xitosanning muvozanatlashuviga erishish uchun 1 va 2 kun kerak bo'lgan. Cheklangan adsorbtsiya hajmi estrogenik birikmalar uchun xitin va xitosan tomonidan kuzatilgan. Mualliflarning ta'kidlashicha, chitin E1 adsorbsiyasida xitosanga qaraganda bir oz samaraliroq bo'lib, bu jarayon tabiatda ion almashinishidan ko'ra adsorbsiyadan iborat degan xulosaga keladi. Turli xil molekulyar og'irliklarga ega bo'lgan xitosanning bir vaqtning o'zida turli xil ifloslantiruvchi moddalarni dukkakli suv havzasi chiqarishidan tozalash imkoniyati baholandi [111].

Experimental results indicated that chitosan with high molecular weight was best in removing turbidity, suspended solids, and biological and chemical oxygen demand (BOD and COD). In contrast, chitosan of low molecular weight excelled at removing NH3and PO4 3− from wastewater. Additionally, chitosan with high molecular weight did well at eliminating suspended solids of various particle sizes relative to chitosan with low molecular weight. The best removal percentage achieved by chitosan for removing turbidity, suspended solids, BOD, COD, NH3,PO4 3− ,andbacteriawas 87.7%, 62.6%, 52.3%, 62.8%, 91.8%, 99.1%, and 99.998% removal, respectively. When chitosan with a high molecular weight was added at 12 mg/L, the quality of treated wastewater successfully complied with government discharge standards. 3. Conclusions and future perspectives This review focuses on the recent developments related to detoxification of water and wastewater using chitin- and chitosanderivatives and reports the main advances published over the last 10– 15 years. It should be noted that the maximum adsorption capacities reported in this paper provide some idea of sorbent effectiveness for each type of pollutant, and mainly depends on experimental conditions. The use of chitin-, chitosan and its derivatives for removing various pollutants from water and wastewater presents many attractive features such as the outstanding adsorption capacity, especially for metal ions and dyes, and the fact that these materials are low cost, nontoxic and biocompatible. However, their potential for other pollutants, e.g. phenols, anions, pesticides, humic substances needs extensive research. Although the amount of available literature data for chitin/ chitosan application in water and wastewater treatment is increasing at a tremendous pace, there are still several gaps which need to befilled. Some of the important issues can be summarized below: (1) Selection and identification of an appropriate form of chitin/ chitosan is one of the key issues to achieve the maximum removal/adsorption of specific type of pollutant depending upon the adsorbent–adsorbate characteristics. (2) The conditions for the production of chitosan loaded with high amino groups on its surface need to be optimized, which consequently would increase the maximum removal of pollutants. (3) Cost factor should not be ignored. Low production cost with higher removal efficiency would make the process economical and efficient. (4) Mechanistic studies with organic pollutants (phenols and dyes) and inorganic anions need to be performed in detail to propose a correct binding mechanism of these pollutants with chitinand chitosan-derivatives. (5) Regeneration studies need to be performed in detail with the pollutants-laden adsorbent (chitin- and chitosan-derivatives) to recover the metals as well as adsorbent. It will enhance the economic feasibility of the process. (6) The potential of chitin/chitosan-derivatives under multi-component pollutants needs to be assessed. This would make a 37 A. Bhatnagar, M. Sillanpää / Advances in Colloid and Interface Science 152 (2009) 26–38 Author's personal copy significant impact on the potential commercial application of chitosan to industrial systems. (7) There is scarce data available for the adsorption of metal ions in the presence of phenols, dye and other contaminants and vice-versa. Therefore, more research should be conducted in this direction. (8) It is further suggested that the research should not limit to only lab scale batch studies, but pilot-plant studies should also be conducted utilizing chitin- and chitosan-derivatives to check their feasibility on commercial scale. (9) The effectiveness of the treatment depends not only on the properties of the adsorbent and adsorbate, but also on various environmental conditions and variables used for the adsorption process e.g., pH, ionic strength, temperature, existence of competing organic or inorganic compounds in solution, initial adsorbent concentration, contact time and speed of rotation etc. These parameters should be taken into account while examining the potential of chitin/chitosan-derivatives. (10) The development in thefield of adsorption process using chitin/ chitosan-derivatives essentially requires further investigation of testing these materials with real industrial effluents. If it is possible to develop such adsorbents having all the abovementioned characteristics, then these adsorbents may offer significant advantages over currently available commercially expensive activated carbons and, in addition contribute to an overall waste minimization strategy

Eksperimental natijalar shuni ko'rsatdiki, yuqori molekulyar og'irlikdagi xitosan xiralashishni, to'xtatilgan qattiq moddalarni va biologik va kimyoviy kislorodga bo'lgan talabni (BOD va COD) yo'q qilishda eng yaxshisi. Bunga javoban, kam molekulyar og'irlikdagi xitosan NH3 va PO4 3− ni oqava suvlardan tozalashda a'lo darajada. Bundan tashqari, yuqori molekulyar og'irlikdagi xitosan past molekulyar og'irlikdagi xitosanga nisbatan turli zarrachalar o'lchamidagi to'xtatilgan qattiq moddalarni yo'q qilishda yaxshi natijalarga erishdi. Xitosanning xiralashgan, qotib qolgan qattiq moddalarni, BOD, COD, NH3, PO4 3− va bakteriyalarni olib tashlash uchun eng yaxshi olib tashlash foizi mos ravishda 87,7%, 62,6%, 52,3%, 62.8%, 91.8%, 99.1% va 99.998% ni tashkil qiladi. Yuqori molekulyar og'irlikdagi xitosan 12 mg / l ga qo'shilganda, tozalangan oqava suvning sifati davlat chiqarish standartlariga muvaffaqiyatli javob berdi. 3. Xulosa va kelajakdagi istiqbollar Ushbu sharh chitin- va xitosanderivativlardan foydalangan holda suv va oqava suvlarni zararsizlantirish bilan bog'liq so'nggi voqealarga bag'ishlangan va oxirgi 10-15 yil ichida e'lon qilingan asosiy yutuqlar to'g'risida. Shuni ta'kidlash kerakki, ushbu hujjatda keltirilgan maksimal adsorbsion qobiliyat har bir ifloslantiruvchi vosita uchun sorbentning samaradorligi to'g'risida ba'zi bir fikrlarni beradi va asosan tajriba sharoitlariga bog'liq. Xitin-, xitosan va uning hosilalarini turli xil ifloslantiruvchi moddalarni suv va oqava suvlardan tozalash uchun ishlatish, ayniqsa, metall ionlari va bo'yoqlari uchun yuqori darajada adsorbtsiya qobiliyati va ushbu materiallarning arzonligi, toksik bo'lmagan va biokompozitsion xususiyatlarga ega. Biroq, ularning boshqa ifloslantiruvchi moddalar uchun potentsiali, masalan. fenollar, anionlar, pestitsidlar, hümik moddalar keng qamrovli tadqiqotlarga muhtoj. Xitin / xitosanni suvda va oqova suvlarni tozalashda qo'llash uchun mavjud adabiyotlar hajmi juda katta sur'atlarda o'sib borayotgan bo'lsa-da, hali ham bir qancha bo'shliqlar mavjud. Ba'zi muhim masalalarni qisqacha umumlashtirish mumkin: (1) Chitin / xitosanning tegishli shaklini tanlash va aniqlash, adsorbent-adsorbtsiya xususiyatlariga qarab, ifloslantiruvchi moddalarning muayyan turini maksimal darajada yo'q qilish / adsorbsiyalashga erishish uchun muhim masalalardan biridir. (2) Sirtida yuqori aminokislotalar bilan to'ldirilgan xitosanni ishlab chiqarish uchun sharoitlarni optimallashtirish kerak, bu esa ifloslantiruvchi moddalarni maksimal darajada olib tashlashni kuchaytiradi. (3) Xarajatlar omiliga e'tibor bermaslik kerak. Chiqarish samaradorligi yuqori bo'lgan ishlab chiqarishning past qiymati bu jarayonni iqtisodiy va samaraliroq qiladi. (4) Organik ifloslantiruvchi moddalar (fenollar va bo'yoqlar) va noorganik anionlar bilan xitinandit xitosan-hosilalari bilan bu ifloslantiruvchi moddalarni to'g'ri bog'lash mexanizmini taklif qilish uchun batafsil tekshirish kerak. (5) Regeneratsiya tadqiqotlari, shuningdek metallarni va adsorbentni tiklash uchun ifloslantiruvchi moddalar bilan to'ldirilgan adsorbent (chitin- va xitosan-hosilalari) bilan batafsil bajarilishi kerak. Bu jarayonning iqtisodiy maqsadga muvofiqligini oshiradi. (6) Ko'p komponentli ifloslantiruvchi moddalar ta'sirida xitin / chitosan-hosilalarining baholanishi kerak. Bu 37 A. Bhatnagar, M. Sillanpäa / Kolloid va interfeys fanidagi yutuqlar 152 (2009) 26–38 Muallifning shaxsiy nusxasi xitosanning sanoat tizimlarida potentsial tijorat maqsadlarida qo'llanilishiga sezilarli ta'sir ko'rsatishi mumkin. (7) Fenollar, bo'yoqlar va boshqa ifloslantiruvchi moddalar mavjud bo'lganida va aksincha, metall ionlarining adsorbsiyasi to'g'risida kam ma'lumotlar mavjud. Shuning uchun ushbu yo'nalishda ko'proq tadqiqotlar o'tkazish kerak. (8) Bundan tashqari, tadqiqot faqat laboratoriya miqyosidagi tadqiqotlar bilan chegaralanib qolmasligi kerak, ammo tajriba-o'simlik tadqiqotlari tit miqyosida ularning maqsadga muvofiqligini tekshirish uchun chitin- va xitosan-derivativlaridan foydalanib o'tkazilishi kerak. (9) Davolanishning samaradorligi nafaqat adsorbent va adsorbsiyaning xususiyatlariga, balki adsorbsiya jarayoni uchun ishlatiladigan turli xil atrof-muhit sharoitlariga va o'zgaruvchilarga, masalan, pH, ion kuchiga, haroratga, raqobatdagi organik yoki noorganik birikmalarning mavjudligiga bog'liq. eritma, dastlabki adsorbent kontsentratsiyasi, aloqa vaqti va aylanish tezligi va boshqalar. Ushbu parametrlar xitin / chitosan-hosilalarining potentsialini o'rganishda hisobga olinishi kerak. (10) Xitin / chitosan-lotinlaridan foydalanib adsorbsiya jarayoni sohasidagi rivojlanish ushbu materiallarni haqiqiy sanoat oqova suvlari bilan sinashni yanada chuqurroq o'rganishni talab qiladi. Agar yuqorida sanab o'tilgan barcha xususiyatlarga ega bo'lgan bunday adsorbentlarni ishlab chiqish mumkin bo'lsa, unda ushbu adsorbentlar hozirgi paytda mavjud bo'lgan tijorat narxida faollashtirilgan uglerodlarga nisbatan katta afzalliklarga ega bo'lishi mumkin va qo'shimcha ravishda chiqindilarni minimallashtirishning umumiy strategiyasiga hissa qo'shishi mumkin.