| Chrome slag is one of the solid wastes produced in the lixiviation process of producing sodium buchromateCNaiCriO?). The main harmful component in chromium slag is the hexavalent chrome[Cr(VI)]. Although many things have been done to recycle the chrome slag in China and some other foreign countries, people still haven't find an efficient way to treat chrome slag. The pollution of chrome slag is still a serious problem threatening people's health and the environment.In order to search for a new method of treating chrome slag, which can not only decrease the pollution of it but also recover it, two groups of experiment have been carried out in this research. One group is the extraction of hexavalent chrome[Cr(VI)] by leaching it from chrome slag, the other is the synthesization of yellow chrome through reaction of leachate with Pb(CH3COO)2 [or Pb(NO3)2].Firstly, we sampled some newly produced chrome slag and weathered chrome slag for leaching experiment. The influence of soaking time, granularity of slag, quantity of slag, volume of water equipment on the concentration and quantity of Cr(VI) in the leachate are studied respectively in the experiments. It is indicated that:(1) The soaking time, granularity of the slag, quantity of the chrome slag and water, and the pH of water, all can influence the concentration and quantity of Cr(VI) in the leachate can be increased by prolonging the soaking time, milling the chrome slag, adjusting the quantity of chrome slag and water for leaching, and decreasing the pH of water.(2) The most important use of bumping is increasing the leaching speed evidently, which can save much time.(3) The inner diameter of the equipment can influence the percentage of Cr(VI) in the leachate, but decreased the concentration and quantity of Cr(VI) in the leachate for the first leaching.(4) More than 60%of the Cr(VI) can be leached into the leachate if propermethod was adopted.And then, synthesizing of middle chrome, light chrome and lemon chrome through the reaction of leachate with Pb(CH3COO)2 and Pb(NO3)2 were studied respectively. Influence of the concentration of Cr(VI) in the leachate and quantity of Pb(CH3COO)2 of Pb(NO3)2 on the reaction of synthesizing yellow chrome was also studied. Finally, according to the criterion and standard method in GB3184-82, some yellow chrome synthesized in the experiments was sampled and the concentration of PbCrO4 in these samples was determined. The following conclusion can be drawn from these experiments.(1) The concentration of sodium bichromate (Na2Cr2O7) in the reaction of synthesizing yellow chrome need not to be as high as 150~250gL-1, which is asserted by predecessors. In this research, the concentration of PbCrO4 in the reaction can be as low as 58g-L-1 without any ill influence on the experiment. Therefore, some leachate can be used to produce yellow chrome directly without concentration.(2) In the reaction of producing yellow chrome, the quantity of Pb(CH3COO)2 or Pb(NO3)2 should be 1.10-1.15 times of the theoretic value. The residual Pb2+ can be removed by phosphorite to avoid bringing new pollution.(3) It is feasible to produce yellow chrome by using the leachate of chrome slag. And the concentration of red chrome (PbCrO4) can meet the standard of criterion in GB3184-82.In conclusion, not only the methods and relative situation of extracting Cr(VI) from chrome slag but also the feasibility of producing yellow chrome by using chrome slag's leachate were studied in this dissertation. All these study will provide necessary theoretical basis for the industrialization of producing yellow chrome from the chrome slag's leachate.
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