Keywords: 
• heavy metal chelating flocculant /
• complexing heavy metal wastewater /
• Pb2+ /
• Cd2+ /
• removal rate

Abstract: A new heavy metal chelating flocculant (HMCF) was synthesized using triethylene tetramine (TETA)， epichlorohydrin， sodium hydroxide and carbon disulfide as raw materials. Its removal effeciency for free and complexing Pb2+ and Cd2+ in wastewater and the stability of its chelated precipitates were investigated， and the structures of HMCF and its chelated precipitates were characterized by FT-IR and ultraviolet spectroscopy. The images and compositions of the flocs were investigated by using scanning electron microscope and energy spectrum analysis. The results show that， for the treatment of free Pb2+ and Cd2+， the molar ratios of －CSS- to Pb2+ and Cd2+ are 1.8∶1 and 2∶1， respectively， and the residual Pb2+ and Cd2+ are all belowed Integrated Wastewater Discharge Standard of China (GB 8978-1996)；while for the treatment of complexing Pb2+ and Cd2+， the molar ratios of －CSS- to Pb2+ and Cd2+ increase in the order (according to the type of complexing agent): thiourea＜citric acid＜EDTA， of which the molar ratios of －CSS- to Pb2+ for complexing Pb2+ are 2∶1，2.2∶1 and 2.4∶1， respectively， and the molar ratios of －CSS- to Cd2+ for complexing Cd2+ are 2.2∶1，2.4∶1 and 2.6∶1， respectively. The chelated precipitates of HMCF-Pb and HMCF-Cd are very dense and stable under weak acid and alkali conditions. The results of energy spectrum analysis show that －CSS- reacts with Pb2+ and Cd2+ to form chelates according to a molar ratio of 2∶1.