Cyanide Removal and Recovery by Electrochemical Crystallization Process

Alkaline chlorination, an efficient but high chemical cost process, is commonly employed for cyanide (CN−) removal from CN-rich wastewater streams. CN− and recovery through the precipitation of Prussian Blue (Fe4III[FeII(CN)6]3, PB) or Turnbull’s (Fe3II[FeIII(CN)6]2, TB) were realized using iron salts, leading to a cost-effective sustainable process producing valuable product. However, PB TB highly affected by pH dissolved oxygen (DO). CN-containing water crystallization and/or investigated that was electrochemically generated sacrificial anode under various values, initial levels (10 to100 mg/L) DO (aeration, mechanical mixing, N2 purging). It shown complexation with Fe ions prevented vaporization HCN acidic pH. At 7 concentration 10 mg/L, efficiency increases linearly increasing Fe:CN− molar ratios, reaching 80% at ratio 5. A clear blue precipitate observed between range 5–7. concentration, resulting in residual concentrations 8, 7.5 12 mg/L effluent 0.8 10, 50 100 mg CN−/L, respectively. polishing treatment H2O2 oxidation lower meet discharge limit <1 CN−/L.