Study on the Treatment of Wastewater Containing Mercury by Macromolecular Heavy Metal Flocculant Mercaptoacetyl Polyethyleneimine

A novel water-soluble macromolecular heavy metal flocculant mercaptoacetyl polyethyleneimine (MAPEI) was synthesized by reacting polyethyleneimine (PEI) with thioglycolic acid (TGA). Removal of Hg²⁺ and turbidity from aqueous solutions by induced flocculation of MAPEI was investigated. It was showed that MAPEI is efficient for the removal of Hg²⁺ and turbidity simultaneously. The highest removal rate of mercury ions can reach above 95%. Factors such as pH, MW of PEI, co-existing ions and so on that could affect the process were studied. In the process of treating wastewater containing both turbidity and mercury ions, mercury ions and turbidity have a synergic removal effect with each other. Compared with TGA, MAPEI shows obvious advantages, including higher removal efficiency, larger floes and higher floe sedimentation velocity. In addition, compared with PEI, MAPEI can remove both turbidity and mercury ions very well while PEI removes only turbidity efficiently.