Preparation And Adsorption Properties Of The Novel Chelating Resins From Amino Acids Grafted PGMA

The water pollution of heavy metal ions has already become a serious threat to human being's healthy and life safety. It will have a significance and wide application prospect in environmental protection or resource recycling to find a Low-Cost-High-Performance adsorbent material. Chelating resin is a cross-linking functional polymer material, which can form a coordinate bond with heavy metal ions because of its functional groups. It can selectively chelate specific metal ions from effluent containing metal ions, and it will release metal ions at suitable conditions. It has been widely used because of its good capacity of adhesion, higher ions selectivity, low cost and excellent regeneration ability.PGMA was synthesized via the suspension polymerization of GMA in the presence of divinylbenzene as a cross-linking agent in this paper. At a second step, the amino acids?L-cysteine, L-aspartate, L-serine, L-phenylalanine? were grafted on PGMA microspheres,which formed four kinds of chelating resin with similar structure ?L-Cys-PGMA,L-Ser-PGMA, L-Phe-PGMA, L-Asp-PGMA?. Series of synthesis conditions were optimized to determine the optimal process parameters. The chelating resin's structure, grafting efficiency, surface morphology and thermal stability were characterized by Fourier Transform Infrared Spectrometer, Elemental Analysis, Scanning Electron-microscope, Thermo gravimetric.The optimal adsorption conditions of L-cysteine grafting PGMA chelating resin for heavy metal ions (Ni²⁺, Co²⁺,Pb²⁺, Hg²⁺) were investigated such as resin dosage, adsorption time, solution pH, stirring speed, initial metal concentration. Dynamics ?pseudo-first-order,pseudo-second-order, intraparticle diffusion?, isothermal adsorption ?Langmuir, Freundlich?and thermodynamics were used to fit the experimental data to understand the adsorption mechanisms and the rate-limiting step. Regeneration and swelling properties of L-Cys-PGMA were studied finally. The results shown that the reasonable doses were 5g/L, 5g/L, 2g/L, 1g/L,the values of suitable pH were 6.5, 6.0, 6.0, 5.0, the optimal initial concentrations were 140 mg/L, 200 mg/L, 190 mg/L, 180 mg/L, the reasonable adsorption time was 6h, the stirring speed was 100r/min, respectively. Their maximum adsorption capacities of the resin for the four metal ions were 20.07mg/g, 34.13 mg/g, 88.14 mg/g,122.67 mg/g under optimum conditions. The adsorption data can be fitted perfectly with pseudo-second-order equation,which indicated that the process was chemical sorption. And adsorption was mainly controlled by the intraparticle diffusion. The adsorption isotherms followed the Langmuir model within the concentration range of 0?200mg/L, which indicated that adsorption was monolayer preferential adsorption. The thermodynamic studies testified that the adsorption processes were spontaneous, endothermic and with the increase of entropy. In addition, the recycling efficiency of resin was still higher than 85% after repeatedly used 8 times, and it also has an appropriate swelling ratio in water. L-Cys-PGMA has higher adsorption ability to four metal ions comparing with L-Ser-PGMA and L-Phe-PGMA as well as L-Asp-PGMA.