Compound heavy metal chelating agent containing dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer

A preparation method of a compound heavy metal chelating agent, wherein:

• the compound heavy metal chelating agent comprises dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and alkylene diamine-N,N′-sodium bisdithiocarboxylate, wherein:
• the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer has a chemical formula of C[CH2OCH2CH2OCOCH2CH2N(CSSM)(CH2)n NHCSSM]4;
• the alkylene diamine-N,N′-sodium bisdithiocarboxylate has a chemical formula of (MSSC)2N(CH2)nN(CSSM)2, here n is a positive integer between 2 and 12, M is Na+, K+ or NH4+;
• a molar ratio of the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and the alkylene diamine-N,N′-sodium bisdithiocarboxylate is in a range from 1:1.0 to 1:10.0;
• the preparation method comprises steps of:
• (1) performing a first addition reaction, which comprises adding a first low-carbon alcohol solution drop by drop into a second low-carbon alcohol solution at 20-25° C. under nitrogen protection, wherein the first low-carbon alcohol solution contains ethoxylated pentaerythritol tetraacrylate (EPTA), the second low-carbon alcohol solution contains excessive alkylenediamine (ADA) with a chemical formula of H2N(CH2)n NH2, here n is a positive integer between 2 and 12;
• and then obtaining a mixed low-carbon alcohol solution which contains (N-(n-aminoalkylene))-3-aminopropionate hyperbranched polymer and unreacted alkylenediamine by stirring for 20-48 h at 20-35° C.;
• and
• (2) performing a second addition reaction, which comprises adding alkaline aqueous solution and carbon disulfide drop by drop after cooling the mixed low-carbon alcohol solution obtained by the step (1) to 10-25° C., stirring for 3-8 h at 20-35° C., standing at room temperature for 3-24 h, precipitating a solid product, filtering and drying to obtain the compound heavy metal chelating agent, wherein:
• a molar ratio of the EPTA, the ADA, the alkali and the carbon disulfide is in a range of 1:
• (5.0-14.0):
• (10.0-28.0):
• (10.0-28.0).