Adsorption Of Heavy Metal By Modified Chitosan And Preparation Of Its Functional Materials

The problem of environmental pollution caused by heavy metal ions in industrial wastewater has attracted more and more attention.In this paper,the adsorbent for heavy metal ions was prepared by chemical modification of chitosan.The adsorption effect of modified chitosan for Cu²⁺,Ni²⁺and influencing factors of adsorption process were investigated.In order to recover and reuse the adsorbed heavy metals,the modified metal/modified chitosan composites were prepared by in-situ reduction with modified chitosan as carrier and template,and with adsorbed heavy metals as the metal source.The catalytic properties of composites were explored.The main contents and results are as follows:1.The chemical modification method of chitosan was studied.The chemical modification process mainly included protection of amino groups on the chitosan molecular chain by benzaldehyde,introduction of amino groups by grafting triethylenetetramine,and deprotection in hydrochloric acid solution to release amino,etc.The modification conditions were investigated by single factor experiments,and the appropriate modification conditions of chitosan were obtained.Chitosans before and after modification were characterized by FT-IR,XRD,SEM-EDS methods.The results showed that the amino group was successfully introduced into the molecular chain after modification,and the adsorption effect of modification chitosan for Cu²⁺and Ni²⁺was better than that of unmodified chitosan.2.The adsorption effects of modified chitosan for Cu²⁺and Ni²⁺in monometallic solution under different adsorption conditions were investigated.The results showed that the adsorption capacity of modified chitosan for Cu²⁺and Ni²⁺could reach96.62mg/g and 51.40mg/g under the appropriate adsorption conditions,respectively.In the bimetals solution,Cu²⁺had a certain inhibition on the adsorption of Ni²⁺.However,Ni²⁺had no effect on the adsorption of Cu²⁺.The solution pH had a great influence on the adsorption performance of modified chitosan.The adsorption mechanism of modified chitosan for Cu²⁺and Ni²⁺was mainly attributed to coordination effect of amino groups with Cu²⁺and Ni²⁺.3.With the modified chitosan loaded with heavy metals as raw material,the modified metal/modified chitosan composites were prepared through chemical reduction method by introducing NaBH₄.The effects of metal loading amount and other factors on the catalytic performance of the composites were investigated by using the catalytic conversion of 4-nitrophenol as a model reaction.The results showed thatthe prepared composites had better catalytic performance,and catalytic rate constants were 0.964 min^-11 and 0.208 min^-1,respectively when the loading amount of Cu and Ni on modified chitosan were 68.28 mg/g and 51.40 mg/g.The catalytic performance of Cu/MCTS was obviously better than that of Ni/MCTS.The conversion of 4-nitrophenol could still reach 90%after 5 cycles of catalytic cycling implying that composite Cu/MCTS had certain recyclability.Meanwhile,the composite Cu/MCTS also showed a good catalytic decolorization effect on azo dye methyl orange.The research results of this paper provide ideas for the removal and recovery of heavy metals in wastewater.