Preparation And Application Performance Of Heavy Metal Trapping Agent BC-DTC

The sodium 3,6-di-tert-butyl-9H-carbazole-9-carbodithioate（C21H24NS2Na,abbreviated as BC-DTC）,a new type of heavy metal trapping agent with dithiocarbamic acid groups,was synthesized with 2-chloro-2-methylpropane,carbazole,carbon disulfide and sodium hydroxide at relatively mild reaction conditions.The influence trend of each factor on the synthesis of BC-DTC was determined by single factor condition analysis,and the optimal synthesis process of BC-DTC was determined by the response surface optimization method.The molecular structure of the synthetic intermediate product and final product of the heavy metal trapping agent was characterized by FT-IR,¹H NMR,¹³C NMR and GC-MS.The treatment efficiencies of single simulated heavy metal ion wastewater by BC-DTC were investigated,including Cu²⁺,Zn²⁺,Pb²⁺,Cd²⁺,Fe²⁺.The effects of the dosage of BC-DTC,the initial concentration of wastewater,and the initial p H value on the performance of BC-DTC in capturing heavy metal ions were investigated.And further studied the treatment effect of BC-DTC on mixed heavy metal ion wastewater,and explored the competitive capture effect of BC-DTC on different heavy metal ions.The experimental results showed the resultsas follow:（1）In this study,a DTC heavy metal trapping agent BC-DTC,with tert-butyl and aromatic ring structure,was synthesized by Friede-Crafts reaction and electrophilic substitution reaction.The synthesis of BC-DTC was proved to be successfully by characterization methods including FT-IR,¹H NMR,¹³C NMR and GC-MS.In a single factor experiment,it was proved that the better synthesis yield of BC-DTC was82.04%.According to the results of response surface optimization,the optimal synthesis process conditions for BC-DTC are as follows:the sodium hydroxide/3,6-bis（tert-butyl）carbazole molar ratio is 1.900,the carbon disulfide/3,6-bis（tert-butyl）carbazole molar ratio is 1.890,the synthesis time is 87.53min,and the synthesis temperature is 33.45℃.The theoretical conversion rate under this condition was 94.49%and compared with the optimal conversion rate obtained by the single factor experiment,it has increased by 12.45%.（2）In this study,heavy metal ions including Cu²⁺,Zn²⁺,Pb²⁺,Cd²⁺,Fe²⁺were as esearch target to investigate the trapping performance of BC-DTC on heavy metal ions under different initial conditions.BC-DTC showed excellent trapping performance for different heavy metal ions.Under different initial conditions,Cu²⁺,Pb²⁺,Fe²⁺ effluents all meet the standards,and Zn²⁺and Cd²⁺effluents are difficult to fully meet the standards at higher initial concentrations.However,with the increase of the dosage of BC-DTC,the p H of the simulated wastewater environment increased,and Zn²⁺appears reverse dissolution phenomenon.In the study of leaching toxicity,all the heavy metal precipitates showed good stability.（3）In this study,the infrared characterization of the heavy metal precipitates confirmed that the role of BC-DTC and the heavy metal ions is to generate the corresponding heavy metal chelated precipitates.The competitive ability of BC-DTC to capture the heavy metal ions is as follows:Cu>Pb>Cd>Zn>Fe,and the stability of the heavy metal chelates is as follows:Zn>Cd>Fe>Cu>Pb.