Pretreatment of complexed metal wastewaters

This study investigates the applicability of hydroxide precipitation to complexed metal wastewaters using inorganic cations that may function as ligand sharing agents. Within this context Ca²⁺, Fe²⁺, Fe³⁺, Mn²⁺ and Mg²⁺ cations with the metals Cd and Cu and EDTA and NTA as ligands are used to define the systems for which theoretical and experimental evaluations are made. Results indicate that calcium is the only cation that effectively binds the ligands that makes it possible to apply the hydroxide precipitation. Fe²⁺ and Mn²⁺ are not effective due to their rapid oxidation. Mg²⁺ is found partly effective but may not be adequate for pretreatment purposes.