Abstract: The aim of the work is to detoxify one of the solid wastes containing hexavalent chromium （Cr6+） discharged from the production process of potassium chromate by oxidization of chromite ore in liquid phase，developed by The Institute of Process Engineering，Chinese Academy of Sciences. Aqueous solution of ammonium sulphate，sodium sulphate，ammonium chloride，sodium chloride or their mixtures were adopted to extract Cr6+ from the waste.The method of mixture design was used to plan the experiments and the results indicated that the constituents of the solutions had no substantial different effect on the extraction of Cr6+ and the leaching yields of Cr6+ were parallel to that of the USEPA Method 3060A.Furthermore，the method of uniform design was used to plan the experiments to optimize leaching time，solution concentration，and leaching temperature. Modeling and simulation showed that the optimal concentration of the ammonium sulphate was about 1.5 mol/L，and the leaching yield raised substantially with the increase of leaching temperature.

Key words: chromium slag, hexavalent chromium, leaching, salt aqueous solution