Remediation Of Heavy Metals Contaminated Soil By Using Flotation Technique

Soil as an environmental factor, it is not only the original source of human material, but also the acceptance and purification of human production and living waste. However, with the rapid development of economic, some major environmental pollution incidents occurred frequently, such as, explosion and leakage, that leading to high-intensity heavy metals pollution which is doing harm to people's healthy, ecological environment and social security.In this paper, the influence of surfactant collector type (non-ionic and anionic), collector dosage, pulp pH, flotation time and particle size on heavy metals removal efficiency and flotation selectivity was studied.Through analysis the forms of heavy metals in soil, the heavy metals sulfide is easy to flotation, so the research pay more attention to the effect on sulfidisation. For setting up the new type of flotation separation equipment, different types of the flotation equipment should be taken into account.The main results are given as follows:To find out the suitable foaming agent, using ionic surfactant sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) as foaming agent, because it's both the bubble and capture functions. Three foaming surfactants are used in experiment of foaming property, interfacial tension, the heavy metals removal efficiency and heavy metals concentration factors to select the proper surfactants which is anionic surfactant SDS as foaming agent on flotation experiment, the best conditions are SDS concentration of 6mg/g, pH 6, the gas velocity of 0.15m3/h. In this situation, the removal efficiency of four heavy metals is 20% ~ 30%.It can be seen from above results, SDS have low removal efficiency on heavy metals. In order to improve heavy metals removal efficiency, adding to two types of collector (potassium amyl xanthate and kerosene). When using potassium amyl xanthate as collector on flotation experiment, the best conditions are KAX dosage of 1mg/g, pH 10. When using kerosene as collector on flotation experiment, the best conditions are kerosene dosage of 15mg/g, pH 8, the gas velocity of 0.15m3/h, flotation time of 10min.It is easy to select the sulphide heavy metals according to the results of heavy metals forms before and after the flotation experiment. To improve heavy metals removal efficiecy by using sulfidisation as pretreatment technology. The results showed that the suitable sodium sulfide dosage is 3 times the concentration of heavy metals in soil. In this situation, heavy metals removal efficiency is about 80%.By researching the form of flotation separation equipment and method of intake, it can be seen that two-stage separation device are better than single-stage separation device. It has not significant impact on heavy metals removal efficiency by using countercurrent and cross-flow.