What is the optimal pH range for coagulating hexavalent chrome using hydroxide treatment?

The optimal pH range for coagulating hexavalent chrome using hydroxide treatment is most effective between 7.5 and 8.5. This pH range is important because hydroxide ions play a critical role in the transformation of hexavalent chromium (Cr(VI)) into less soluble forms, such as trivalent chromium (Cr(III)). The reaction is influenced by the pH, with higher hydroxide concentrations leading to more effective coagulation and precipitation of chromium compounds.

At pH levels within this optimal range, precipitates can form more efficiently, enhancing the removal of chromium from wastewater. This is pivotal in reducing the toxicity and environmental impact of wastewater containing hexavalent chromium. Operating outside of this pH range, such as at lower pH levels or excessively high levels, may not achieve sufficient coagulation efficiency or could even hinder the process, leading to higher residual chromium levels in the treated effluent.