Optimization of mercury removal from chloralkali industrial wastewater by starch xanthate

Abstract Mercury precipitation with starch xanthate (SX) has been investigated batchwise both in test solutions and wastewater samples. The process has been studied taking into account such parameters as: ionic strength, pH, xanthate dosage, chloride and chlorine concentration. The results have shown that the precipitation of mercury‐starch xanthate in the range of pH 11+12, at a SX/Hg ratio of around 1 allows the removal of mercury from chloralkali wastewater down to a value of the order of 200 μgl‐1. Preliminary oxidation of the sample with chlorine is required before xanthate is added in order to reduce the residual mercury concentration to less than 10 μgl‐1. Mercury can be recovered in highly concentrated solutions following the attack of mercury starch xanthate sludge by chlorine in acid conditions.