Preparation And Adsorption Properties Of Chelating Resin From Magnetic Chitosan Derivative

Chelating resin is a kind of functional polymer materials,which can chelate with metal ions to form coordination compound.The chelating functional groups were directly bound to the polymer supports via chemical bonding methods in the chelating resin.According to adsorption mechanisms for heavy metal ions,the stable structures of coordinatebonds were formed between the functional atoms of chelating resin and the metal ions.And their structures were similar to small molecular compound.Therefore,the diffusion inside the sorbent between functional groups of resins and metal ions are particularly important in the adsorption process.As the chelating resin have the advantages of the strong adhesion of coatings to metal,the high selectivity,low cost and so on,it can be widely applied to removal,retrieve,separation and enrichment of metal ions in waste water.The dicyandiamide modified magnetic chitosan chelating resin?CMCTS?and furfural modified magnetic chitosan chelating resin?FMCTS?were synthesized with chitosan as raw material,Fe₃O₄ as carrier,dicyandiamide and furfural as modifier,and glutaraldehyde as crosslinking agent in this paper.It was easy to separate the chelating resins from waste water,reclamation and recycling of the resins because of chelating resins/Fe₃O₄ particles having magnetism.The atoms N and O were introduced the polymer molecule chains in order to improve the capacity of the resin ion-selective recognition and adsorption capacity to the metal ions.The synthesized chelating resins were characterized by the infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?,thermal gravimetric analysis?TGA?,scanning electron microscopy?SEM?,energy dispersive spectrum?EDS?analysis and specific surface area?BET?analysis.The influence of the contact time,initial concentration of metal ions,dose of adsorbent and pH of solution on the adsorption capacity of heavy metal ions on the chelating resin were investigated.The results show that the adsorption capacity of the four metal ions[Co?II?,Ni?II?,Pb?II?and Hg?II?]obtained the largest when pH values were 5,5,5 and 4;the initial concentrations of metal ions were 60 mg/L,200 mg/L,60 mg/L and 200 mg/L;the dose of adsorbent was 1 g/L,1 g/L,2 g/L and 2 g/L,respectively;the adsorption time was 8 h.The adsorption capacity and removal efficiency of CMCTS was better than FMCTS and CTS.The pseudo-first-order model,pseudo-second-order model and intraparticle diffusion model were used to estimate CMCTS adsorption kinetics parameters.The results of kinetic study indicated that the adsorption behavior of four metal ions followed pseudo-second-order kinetic model,which proved that the rate controlling step was chemical adsorption.The Langmuir and Freundlich isotherm model were used to fit the equilibrium data.The results showed that Langmuir model fitted better with the equilibrium data,which indicated that the adsorption was single layered adsorption and favorable adsorption.The adsorption process of the four heavy metal ions on the CMCTS was spontaneous and endothermic,and raise temperaturewasadvantageoustotheadsorptionprocess.Theresultsof adsorption-regeneration experiment showed that CMCTS was a good renewable and potential application valuable sorbent.