Detoxification And Leaching Behaviour Of Chromite Ore Processing Residue(COPR)

The COPR contains a large amount of toxic Cr?VI?.The Cr?VI?is a carcinogenic inducer,it has strong oxidizing property and is liable to cause damage to the organism.The non treatment of COPR will cause serious environmental pollution and harm human health.In the treatment of detoxification of COPR,detoxification by wet process is widely used.But this method has the disadvantages of large amount of reducing agent,high cost and complex component after detoxification and difficult to use.In this paper,two aspects of detoxification and leaching are carried out for COPR.Firstly,the composition of COPR was characterized systematically,and the theoretical basis for detoxification and leaching of COPR was obtained.Then the detoxification of COPR by SO₂ reduction and a new method for detoxification of COPR under acid conditions was investigated.At the end of the leaching rules chromium in COPR and other materials were studied.The main results of the full text are as follows:?1?The phase composition of COPR was determined.The main phase of the COPR was?Fe,Mg??Cr,Fe?₂O₄ and MgFeAlO₄.The content of Cr₂O₃ was 11.34%.Fe₂O₃ was39.49%;Al₂O₃ was 31.35%.?2?The process of the detoxification of COPR by SO₂ reduction was proposed.The influence of stirring speed,temperature,liquid solid ratio,pressure and reaction time on the detoxification of COPR was studied.In the optimum process conditions,the removal rate of Cr?VI?in COPR is 90%.When mechanical activation was combined with SO₂ reduction and detoxification of COPR,the removal rate of Cr?VI?in COPR was 98.1%and the residual Cr?VI?content in COPR can be reduced to less than 25 mg·kg^-1.?3?A new detoxification process of COPR,which utilizes the residual Chromite ore?Fe,Mg??Cr,Fe?₂O₄ in COPR to react with the Cr₂O₇^2-in it in an acid environment was proposed.The influence of mechanical grinding,sulphuric acid concentration,liquid-solid ratio,temperature and reaction time on the process were studied.In the optimum process conditions,the removal rate of Cr?VI?in COPR was 98.3%and the residual Cr?VI?content in COPR can be reduced to less than 25 mg·kg^-1.?4?Chromium in COPR was recycled and detoxificated.The leaching behavior was studied by the speed,temperature,liquid to solid ratio and so on.Under the best condition of water washing and recovery,particle size of 101¹50?m of the chromium in the COPR leaching rate was 75%.The content of Cr?VI?in COPR can be reduced to 13.7mg·kg^-1after washing and detoxification of COPR.?5?The use of chromium in COPR containing as oxidant can promote the leaching of various components in tide.?6?The influence of sulphuric acid concentration,temperature,liquid-solid ratio and reaction time on the leaching of components in COPR was studied.In the optimum condition of acid leaching,the leaching rate of Fe was 83.8%,Al was 59.8%,the total Cr was 55.4%,and the dissolution rate of COPR was 84.6%.It was found that in the process of acid leaching,the dissolution of COPR was mainly the dissolution of MgFeAlO₄,and then the dissolution of chromite.Compared with MgFeAlO₄,the increase of temperature has obvious effect on the acid dissolution of chromite in the COPR.