Studies Regarding the Copper Ions Removal from Waste Waters

Waste waters resulted from industry usually contain heavy metals salts. During the neutralization process with sodium hydroxide and sodium carbonate, these salts are transformed into compounds such as insoluble hydroxides or basic salts. The precipitation process represents one of the most used methods for the removal of heavy metals from waste waters. In the present paper, studies on the removal of copper ions from waste waters resulted from industry through precipitation, using 15% NaOH and 20% Na2CO3 solutions as precipitation agents, are presented. The studies were carried out on synthetic solutions containing copper in various concentrations (5, 10, and 15 g Cu2+/L). Several aspects of the precipitation process were studied: the dependence of the pH of the reaction mass on the volume of precipitation agent, the evolution of the volume of suspensions in time, and the dependence on the pH of the residual concentration of copper ions. The optimum pH value for the removal of copper ions from the waste waters for both precipitation agents is 7. For all initial copper ions concentrations, pH = 7 assures residual concentrations smaller than the maximum value admitted by the legislation. The copper ions removal using the 20% Na2CO3 solutions was also studied on a pilot installation. Copper residual concentration decreased with installation functioning time; a constant residual concentration of ~1.1 mg Cu2+/L was reached.