Crosslinked Chitosan Based Magnetic Nanomaterials Used As Adsorbents For Pb²⁺ Removal From Aqueous Solution

With the development of the sociology and the industry,the heavy metal pollutions become more and more serious.Heavy metal pollutions are harmful,hard to deal with and easy to enrich.These pollutions become one of the main ecological problems.Traditional treating methods are normally hard to operate,cost a lot and can't treat thoroughly.The second pollutions also appear in traditional methods.So finding new treat methods is the direction of solving the problems of heavy metal pollutions.Magnetic nanomaterials have a broad application prospect for its high efficiency,low cost and easy operations.In this work,derivatives of chitosan coated Fe₃O₄ were prepared,including a2-thenaldehyde chitosan coated Fe₃O₄?CSB@Fe₃O₄?and an epichlorohydrin crosslinked 2-furanaldehyde chitosan coated Fe₃O₄?ECCSB@Fe₃O₄?.This work used typical characterization methods such as XRD,FT-IR,SEM,TEM,VSM on these materails.Adsorption behaviors were also investigated in this work.In this work,Fe₃O₄ were prepared by co-precipitation method and were used as the core of nanomaterials.2-thenaldehyde chitosan was synthesized by the Schiff base reaction between 2-thenaldehyde and chitosan.Epichlorohydrin crosslinked2-furanaldehyde chitosan was synthesized by the crosslinked reaction between epichlorohydrin and chitosan and Schiff base reaction between 2-furanaldehyde and epichlorohydrin crosslinked chitosan.In alkaline conditions,CSB@Fe₃O₄ and ECCSB@Fe₃O₄ were prepared by coating of Fe₃O₄ with CSB and ECCSB respectively.XRD characterization results showed that Fe₃O₄ particles had typical inverse spinel structure and that Fe₃O₄ didn't show significant structure and crystal phase changes.VSM characterization results showed that CSB@Fe₃O₄ and ECCSB@Fe₃O₄ had high-level saturation magnetization.And there were good separation results using permanent magnet.FT-IR results of CSB@Fe₃O₄,ECCSB@Fe₃O₄,Pb loaded CSB@Fe₃O₄ and Pb loaded CSB@Fe₃O₄ showed that CSB@Fe₃O₄ and ECCSB@Fe₃O₄ had amount of–OH,-NH₂ and ether bond O as active groups.After Pb loaded,these groups'absorption peak intensity decreased,which showed that these active groups played important roles in the adsorption of Pb.These groups should be coordination groups.TEM results of CSB@Fe₃O₄ and ECCSB@Fe₃O₄ showed that these two nanomaterials were ellipsoid or spherical and had a structure of core-shell structure which were loose and uniform.After Pb loaded,these two materials showed agglomerate phenomenon.The coordination effects of Pb and adsorption materials should cause this agglomerate.In this work,adsorption behaviors of CSB@Fe₃O₄ and ECCSB@Fe₃O₄ were also investigated.The best experimental conditions,including the dose(0.5 g/50 mL Pb²⁺solution and 0.4 g/50 mL Pb²⁺solution,respectively)and the pH?5.0?,were determined.The reason of the pH should be that higher pH would affect Pb²⁺'s form of existence and that lower pH would affect active groups.Adsorption kinetics showed that these two materials got adsorption equilibrium at almost 105 min and that the pseudo-2nd-order kinetic model was better for the adsorption processes.That is to say chemical adsorption dominated.Adsorption isotherms showed that Langmuir isotherm was better for the adsorption processes,which indicated that chemisorption of single molecular layer dominated.At the temperature of 323 K,the saturated adsorption capacities of CSB@Fe₃O₄ and ECCSB@Fe₃O₄ were 83.33 mg/g and 86.20mg/g,respectively.