Use of the solubility domain approach for the modeling of the hydroxide precipitation of heavy metals from wastewater

The use of the solubility domain approach for providing representative effluent treatment quality assurance standards for the hydroxide precipitation of Zn2+, Pb2+, and Fe3+ from various wastewater composition types has been modeled and experimentally validated. Solubility domain calculations were based on the precipitated phases isolated from systems representing the upper and lower limits of potential effluent chemical compositions. All such phases resembled their mineralized counterparts with a lower degree of structural order. For all systems modeled, the experimentally observed solubilities were generally encompassed within the predicted solubility domains. Validation of the approach using real treatment data demonstrated the effectiveness of the solubility domain method in predicting optimum operating condition ranges for wastewater treatment. Prediction accuracy was largely dependent on the nature of the solubility-limiting phase. With the exception of carbonate-rich systems, changes to the aqueous-phase complexation had a minimal impact on solubility in comparison to selection of the solubility-limiting phases.