| With the rapid development of industry in China,the problem of water shortage,drought and desertification of land and water pollution have become prominent gradually.How to effectively solve the water shortage and water pollution with heavy metals becomes a focus in many scholars,research in and abroad.?-cyclodextrin(?-CD)has more hydroxyl groups and be hydrophobic in cavity,hydrophilic in external cavity in chemical structure,so it is suitable for the development of biodegradable polymers.This paper introduce a novel P-CD based adsorbent which is synthesized through self-assembly technology and inverse suspension co-polymerization,to use ?-CD as raw material,acrylic acid(AA)and acrylamide(AM)as monomer,polyvinyl alcohol(PVA)as cross-linking agent.Meanwhile the synthesis conditions were optimized to determine the optimum synthesis conditions.The chemical structure and physical characteristics of the adsorbent is measured by FTIR,SEM and DSC.According to the structural characteristics of the two adsorbents,the corresponding performance of them was researched and analyzed the kinetics of adsorption of the products of the adsorption mechanism of metal ions.The main research results are following:(1)A novel ?-CD based adsorbent is synthesized with inverse suspension co-polymerization through self-assembly technology,and the results showed that the optimal synthesis conditions are followings:the mass ratio of ?-CD:AA:PVA is 1:5:1,the initiator content(representing the percentage of the total mass of raw materials)is 0.35%,cross-linking agent content(representing the percentage of the total mass of raw materials)is 0.04%,Span-80 content(representing the percentage of the total mass of raw materials)is 6.67%,and the reaction time is 4 h.The product's asorbent ratio of distilled water is 1629.39 g/g,and the ratio of bibulous multiple in chloride is 91.48 g/g in these synthesis conditions.The analysis of FTIR showed that the present of-OH?C=O and C-O-C groups and the absent of C=C in the product confirmed that ?-CD react with AA and PVA through graft copolymerization.The SEM results showed that the product has prefect three-dimensional network structure,and the horizontal grid size is about 30 ?m after absorbing.The DSC showed that the resin has a good stability below 300 ?,and the resin is thermoplastic and has some salt tolerance.The order of bibulous multiple in Chloride is NaCl>KCl>CaCl2>FeCl3,and in Sulfate is Na2SO4>K2SO4>Fe2(SO4)3>FeSO4,and Suction effect of Chloride is better than Sulfate.The higher the pH value,the better the Suction effect.(2)To use ?-CD,AA and AM as raw material,(3-CD-based adsorbent was synthesized by self-assembly graft polymerization.The optimum conditions for synthesis was as the following:the mass ratio of AA and AM was 7:1;the mass ratio of ?-CD and the monomer was 1:3;the contents of initiator and cross-linking agent were 0.3%and 0.04%,respectively(accounting for the total mass of monomer);the reaction solvents were 25 mL deionized water and 50 mL cyclohexane.Under the optimum conditions and in solution which concentrations of Cd2+,Cu2+ and Pb2+ were 80 mg/L,the adsorption capacity of the products were 78.94 mg/g,107.37 mg/L and 80.04 mg/L,respectively.Adsorption rate for distilled water,running water and physiological saline were 1554.16 g/g,940.82 g/g,and 104.53 g/g,respectively.The resin was good at both removal of metal ions and absorption water.The results of FTIR indicated that ?-CD,AA and AM had been polymerized.The product surface and better three-dimension structure were observed by SEM.As the resin adsorpted the metal ions,there was competing absorption according to XPS.In DSC spectra,there was no heat(absorption)peak,when the temperature was higher than 80?.It was indicated that the resin had good stability at high temperature.(3)In this research,the mechanism of ?-CD-based resin adsorption was described by quasi-first-order kinetic model,quasi-second-order kinetic model,Elovich equation and intraparticle diffusion models.The result revealed that:in the adsorption of Cu2+,the process conformed to quasi-second-order kinetic model in the case of low concentration(25 mg/L,50 mg/L)and intraparticle diffusion models in the case of high concentration(100 mg/L,150 mg/L);Fitted process by Elovich equation,the correlation coefficient R2 was high and from the size of the initial concentration.These illustrated that resin on the adsorption of Cu2+ with the Elovich equation to explain was the more reasonable.That is adsorption of Cu2+ was affected by ion exchange and the some complexations of Cu2+ with the adsorbent surface were occurred.In the adsorption of Pb2+,the process fitted to quasi-second-order kinetic model,Elovich equation and intraparticle diffusion models in the case of moderate concentrations(50 mg/L,100 mg/L),which indicated that,the resin on absorption of Pb2+ was more regularity at this concentration and accompanied with ion exchange and complexation.The resin on the adsorption of four different initial concentrations Cd2+ was in line with quasi-second-order kinetic equations and intraparticle diffusion equation,which demonstrated that the process was with chemical adsorption and physical adsorption and was independent of the concentration gradient. |
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