Removal Of Cs(?) From Water By Ferrocyanide Coprecipitation Flotation

In 2011,a nuclear accident occurred at Fukushima Nuclear Power Station in Japan,which produced tons of radioactive wastewater.The main radionuclides in wastewater are cesium-137 and cesium-134.How to effectively treat a large number of radioactive wastewater and avoid pollution and harm to the environment is very necessary.In this paper,the simulated experimental study on the treatment of cesium-containing radioactive wastewater by co-precipitation flotation of ferrocyanide was carried out.The removal efficiency of cesium ion from water by four different ferrocyanides under different experimental conditions(surfactant concentration,precipitator concentration and gas solubilized water flow rate)was investigated by controlling variable method.The results show that the ferrocyanide formed by copper ion,cobalt ion and cadmium ion has a good effect as precipitator.The molar ratio of precipitator to cesium ion in the original solution is 1.4,the flow rate of gas solubilized water is 50L/h,and the concentration of surfactant is 200 mg/L.The removal rate of cesium ion is over 99%.Potassium nickel ferrocyanide are used as precipitant,and the removal rate of cesium ion is lower than that of the other three ferrocyanides.The flotation effect of potassium nickel ferrocyanide can be improved by adding flocculant.2 mg/L polyacrylamide can increase the removal rate of cesium ion by precipitation of potassium nickel ferrocyanide to over 99%.Under the same conditions,the median diameters of potassium nickel ferrocyanide,potassium copper ferrocyanide,potassium cobalt ferrocyanide and potassium cadmium ferrocyanide particles were 2.681,4.936,4.010 and 4.773(micron),respectively.The particle size of potassium and nickel ferrocyanide is the smallest.The particle size of ferrocyanide is different when the ratio of divalent metal ions to potassium ferrocyanide is changed.It is found that the particle size of ferrocyanide increases with increasing the proportion of divalent metal ions.The size of particle will affect the effect of flotation.The smaller the particle size,the more difficult the flotation will be.It is found that the composition of precipitation is different with different proportion of metal salts and potassium ferrocyanide.The higher the proportion of nickel nitrate,the higher the proportion of nickel ion and the lower the proportion of potassium ion in the product.The chemical composition of the precipitate formed in proportion 1.4 is K1.30Ni1.16Fe(CN)6,the chemical composition of the precipitate formed in proportion 1.6 is K1.18Ni1.30Fe(CN)6,and the chemical composition of the precipitate formed in proportion 1.8 is K0.83Ni1.44Fe(CN)6.Comparing the composition of ferrocyanide before and after cesium ion absorption,it is proved that the mechanism of this process is mainly ion exchange between potassium ion and cesium ion.