Preparation of Macromolecular Heavy Metal Coagulant and Treatment of Wastewater Containing Copper

Abstract

Many treatment technologies for wastewater containing heavy metals have been developed in recent years, but these technologies have some disadvantages, such as poor removing efficiency and complex operation. For this reason, a macromolecular heavy metal coagulant polyethyleneimine-sodium xanthogenate (PEX) was prepared by grafting a xanthogenate group to polyethyleneimine. It was determined that PEX has the function of removing both turbidity and copper ions. It was also determined that copper ions and turbidity have a cooperative removal effect with each other in the process of treating wastewater containing both turbidity and copper ions by PEX. The investigation showed that PEX is an amphoteric polyelectrolyte. At lower pH values, the amino groups of the macromolecule are electrically positive; therefore, turbidity is removed because of electroneutralization coagulation; at higher pH values, both amino groups and xanthogenic radical groups contribute to the removal of heavy metals, as a result of chelation. Compared with traditional chemical precipitation by calcium oxide and coagulation by an ordinary inorganic coagulant, PEX showed obvious advantages, for example, removing both turbidity and copper ions, higher removal efficiency, lower suitable pH value, and higher floc settlement velocity.