Cyanide Removal from Laboratory Wastewater Using Sodium Hypochlorite and Calcium Hypochlorite

บทคัดย่อ

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 N₂. 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/m³ of wastewater). Ca(OCl)₂ is more effective than NaOCl
considering the cost and dosage used.