Study On Preparation And Application Performance Of The New Heavy Metal Chelating Agent

This paper studies the preparation of N, N’-bis(2-mercaptoethyl)isophthalamide (NBMIPA) and N1, N2, N4, N5-terrakis(2-mercaptoethyl)benzene-1,2,4,5-tetracarboxamide (TMBTCA) that a new type chelating heavy metal chelating agent. Two trapping agent were characterized by IR, MS,1H NMR to determine their structure. Investigated the application performance of the trapping agent for heavy metal ions and preliminary explored its cheater trapping mechanism.(1) The NBMIPA was synthesized with isophthaloyl chloride and mercaptoethylamin hydrochloride as raw materials. The best conditions for the synthesis reaction in a solvent of chloroform:the amount of solvent chloroform90mL, mercaptoethylamine hydrochloride4.62g, isophthalic acid chloride3.04g, reacted at ice bath by5h with the N2protection. Under this condition, the yield of product was79.2%, m.p.128.7to129.1℃, the purity of the product was99.12%, and the test has a better reproducibility. The structure of the product was characterized by IR, MS,1H NMR, which determine the target product is NBMIPA.(2) The TMBTC was directly synthesized by pyromellitic dianhydride and cysteamine hydrochloride as the raw material in the solvent DMF, the best conditions for the synthesis reaction:the DMF75mL, the molar ratio of pyromellitic dianhydride to cysteamine hydrochloride was1:4.8, after reacting1h adding4A molecular sieves1.5g, reacted at5℃by7h. were characterized by IR, MS,’H NMR to determine their structure. Under this condition, the yield of product was75.92%, m.p.66.2to67.5℃, the purity of the product was97.76%, and the test has a better reproducibility. The structure of the product was characterized by IR, MS,1H NMR, which determine the target product is TMBTCA.(3) The NBMIPA has trapping effects for Cu2+, Zn2+, Hg2+, Cd2+, Pb2+, Cr3+, Ni2+heavy metal ions at room temperature, when the molar ratio (trapping agent dosage compared to the amount of heavy metal) about4.5, the removal rate of Cu2+and Hg2+are more than99.5%, also to the removal rate of Zn2+, Cd2+and Pb2+are more than99.5%.(4) The TMBTCA has trapping effects for Cu2+, Cd2+, Pb2+, Ag+heavy metal ions at room temperature, when feeding molar ratio greater than2.5, the removal rate of Cu2+, Pb2+Ag+reached99.5%. The wastewater solution of Cu2+, Pb2+, Ag+is able to reach the national emission standards after treatment of TMBTCA.(5) The solitary electronics of S atoms and heavy metal ions to form coordination bonds in the molecular of the heavy metal trapping agent NBMIPA and TMBTCA, which resulting S-M instead of S-H.