HYDROXIDE PRECIPITATION OF COMPLEXED METALS

In this study, theoretical analysis of the complexed metal treatment b y conventional hydroxide precipitation is made. The analysis is aimed to evaluate the mechanism of ligand-sharing effect of metals which are added to wastewater to ensure effective removal of complexed heavy me tals. Theoretical expression of the analysis is made using phase diagr ams. Cadmium, copper and nickel are selected as heavy metals. EDTA, NT A and succinic acid are selected as organic complex formers of differe nt strengths. Calcium is used as the ligand binding agent. Theoretical solutions are made for, single metal-single ligand system and several metal and ligand combinations in the closed system and single metal-s ingle ligand in the open system. Theoretical solutions are interpreted considering the solubility, stability and ionization constants and th eir relative magnitudes. Experimental studies are conducted to check t he theoretical predictions. Result indicate that high pH precipitation is applicable to the cases where organic ligand can be effectively bo und by calcium or any other coagulant or pH adjustment agent thus free ing the heavy metal to form hydroxide or carbonate solids. Theoretical diagrams can be used to predict the favorable conditions for precipit ation and as a guide to determine the operating conditions.