Study on Flotation Separation and Determination of Mercury (II) by Sodium Bromide-Ammonium Thiocyanate-Octadecyl Trimethyl Ammonium Bromide System

The flotation separation and determination behaviours of mercury (Ⅱ) by sodium bromide -ammonium thiocyanide-octadecyl trimethyl ammonium bromide system were studied. The effects of different parameters,such as the dosages of NH4SCN and octadecyl trimethyl ammonium bromide (OTMAB),various salts and acidity etc. on the flotation yield of Hg2+have been investigated to select the experimental conditions.The results showed that in the presence of 1.0g NaBr and when the dosage of 0.1 mol/L NH4SCN was 0.50 mL and 0.01 mol/L OTMAB solution was 1.00 mL respectively, the formed water-insoluble ternary association complex of (OTMAB)2[Hg(SCN)4] floated above water phase and liquid-solid phases were formed with clear interface. In this condition, Cd2+,Mn2+,Ni2+,Co2+,Fe2+and Pb2+could not be floated and Hg2+could be floated quantitatively at pH2.0.Therefore, the quantitative separation of Hg2+from the above metal ions could be achieved. A new method of determination of trace mercury by flotation separation was established.The proposed method has been successfully applied to the determination of Hg2+in the sample of synthetic water and the flotation yield was 94.2%~97.9%.