Cyanide Removal from Laboratory Wastewater Using Sodium Hypochlorite and Calcium Hypochlorite

Removal of cyanide (CN - ) from laboratory wastewater using sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca(OCl) 2 ) were performed at the reaction time of 30 minutes. The product of chlorination at an alkaline pH of 12.3 was CNO - which could be oxidized further to N 2 . Colorimetric method was used to determine the amount of CN - before and after chemical treatments. The optimum doses of chemicals used were determined. It was found that 100% removal of this contaminant could be achieved. The optimum doses and chemical costs of NaOCl and Ca(OCl) 2 varied depending on the initial cyanide concentration. The optimum doses of NaOCl and Ca(OCl) 2 for 100% CN - removal were Y = 17.3X and Y = 3.32 X, respectively (where X = initial CN - concentration in mg/l, and Y = chemical dose in mg/l). The chemical costs of NaOCl and Ca(OCl) 2 were Y = 0.69 X and Y = 0.50X, respectively (where X = initial CN - concentration in mg/l, and Y = cost, baht/m 3 of wastewater). Ca(OCl) 2 is more effective than NaOCl