Study On The Polyethylenimine Grafted Dithiocarbamate Heavy Metal Ion Adsorbing Material

With the rapid development of global industry,heavy metal water pollution has become increasingly serious.How to effectively and cost-effectively control heavy metal water pollution has become the focus of global attention.Polyethyleneimine has a small amount of formula,and the molecular fragment contains more primary and secondary amino groups,while primary and secondary amino groups have strong chelating ability for heavy metal ions,so they have good adsorption capacity,but polyethyleneimine is readily soluble in water.Therefore,we have to design a dithiocarbamate material based on polyethyleneimine which can be stable in water and has good adsorption properties for heavy metal ions Cu²⁺,Cd²⁺,and Pb²⁺.The adsorbing material was prepared by cross-linkage of polyethyleneimine with glutaraldehyde,reduction with sodium borohydride,and then reaction with CS₂ to form a spongy polyethyleneimine grafted dithiocarbamate adsorbing material.The main results of this paper are as follows:1.The IR spectrum verified that the structure of the prepared polyethyleneimine grafted dithiocarbamate polymer adsorbent was just as we expected.The TGA results show that the prepared adsorbent material has good thermal stability.XRD results show that it does not have a crystal structure.2.The SEM results show that the surface of the material has many micropores,similar to a sponge-like layered structure.It is beneficial for heavy metal ions to enter the interior of the adsorbent and thus to increase adsorption capability of the polymer adsorbent.3.When the mass ratio of polyethyleneimine to glutaraldehyde is 6:1,the mass ratio with sodium borohydride is 13:4,the mass ratio to carbon disulfide is 8:5,the crosslinking temperature is 60 ^oC,and the reduction temperature is 60 ^oC.and the reaction temperature with carbon disulfide is 0 ^oC,the prepared polymer adsorbent has the best adsorption performance for heavy metal ions.4.With the increase of the initial concentration of heavy metal ions or the increase of pH,the adsorption capacity of macromolecular adsorbents for heavy metal ions first increases rapidly and then slows down.As the temperature increases,the adsorption capacity of the adsorbent material for heavy metal ions gradually increases.As the ion concentration increases,the adsorption capacity of the adsorbent for heavy metal ions gradually decreases.The investigation of the adsorption time shows that the adsorption rate of the adsorbed material on heavy metal ions was fast,and saturated adsorption was achieved in about 40 minutes.5.Optimal adsorption conditions:at a temperature of 25 ^oC,a pH of 5.5,an adsorption time of 45 min,and initial concentrations of heavy metal ions Cu²⁺,Cd²⁺,and Pb²⁺of 300 mg/L,250 mg/L,and 550 mg/L,the saturated adsorption capacities of the polymer adsorbent were 3.38 mmol/g,1.88 mmol/g,and 2.19 mmol/g,respectively.6.Thermodynamic studies show that the adsorption of heavy metal ions by polymer adsorption material is a spontaneous endothermic reaction and conforms to the Langmuir adsorption model.The kinetic study reflects the dominant chemical adsorption,which belongs to the rate-control step and conforms to the second-order kinetic equation.7.After five times of re-use,the desorption rate of heavy metal ions by the polymer adsorbent can still be above 80%.The adsorption capacity for heavy metal ions can reach about 80%of the first adsorption capacity.