Leaching kinetics of acid-soluble Cr(Ⅵ) in chromite ore processing residue (COPR) using hydrofluoric (HF) acid solution as a leaching agent was investigated for potential remediation of COPR with industrial waste wat...Leaching kinetics of acid-soluble Cr(Ⅵ) in chromite ore processing residue (COPR) using hydrofluoric (HF) acid solution as a leaching agent was investigated for potential remediation of COPR with industrial waste water containing HF. The results show that HF can effectively destabilize the Cr(VI)-bearing minerals,resulting in the mobilization of Cr(Ⅵ) from COPR into the leachate. Particle size significantly influences the leaching of acid-soluble Cr(Ⅵ) from COPR,followed by leaching time,whereas the effects of HF concentration and leaching temperature are slight and the influence of stirring rate is negligible. The leaching process of acid-soluble Cr(VI) from COPR is controlled by the diffusion through the product layer. The apparent activation energy is 8.696 kJ/mol and the reaction orders with respect to HF concentration and particle size is 0.493 8 and-2.013 3,respectively.展开更多
Coal is the world's most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-grade coal for fulfilling energy d...Coal is the world's most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-grade coal for fulfilling energy demands of modern civilization. However, due to its high ash and moisture content, low-grade coal exerts the substantial impact on their consumption like pyrolysis, liquefaction, gasification and combustion process. The present research aimed to develop the efficient technique for the production of clean coal by optimizing the operating parameters with the help of response surface methodology. The effect of three independent variables such as hydrofluoric acid(HF) concentration(10–20% by volume), temperature(60–100 °C), and time(90–180 min), for ash reduction from the low-grade coal was investigated. A quadratic model was proposed to correlate the independent variables for maximum ash reduction at the optimum process condition by using central composite design(CCD) method. The study reveals that HF concentration was the most effective parameter for ash reduction in comparison with time and temperature. It may be due to the higher F-statistics value for HF concentration, which effects to large extent of ash reduction. The characterization of coal was evaluated by Fourier transform infrared spectroscopy(FTIR) analysis and Field-emission scanning electron microscopy with energy-dispersive X-ray(FESEMEDX) analysis for confirmation of the ash reduction.展开更多
以吉林汪清地区某隐晶质石墨选矿精矿为原料,采用QWJ气流涡旋粉碎机成套系统进行球形化处理,共整形16次,最佳整形次数为6次。并对球形化石墨进行提纯,采用HF和HCl的混酸法确定混酸与石墨液固比5 m L/g,HF体积分数33%,反应温度50℃,时间3...以吉林汪清地区某隐晶质石墨选矿精矿为原料,采用QWJ气流涡旋粉碎机成套系统进行球形化处理,共整形16次,最佳整形次数为6次。并对球形化石墨进行提纯,采用HF和HCl的混酸法确定混酸与石墨液固比5 m L/g,HF体积分数33%,反应温度50℃,时间3 h,浸出4次,得到最终精矿固定碳含量99. 82%。展开更多
基金Project(2009FJ1009) supported by Major Program of Hunan Provincial Science and Technology, ChinaProject(2005CB6237) supported by the National Basic Research Program of China
文摘Leaching kinetics of acid-soluble Cr(Ⅵ) in chromite ore processing residue (COPR) using hydrofluoric (HF) acid solution as a leaching agent was investigated for potential remediation of COPR with industrial waste water containing HF. The results show that HF can effectively destabilize the Cr(VI)-bearing minerals,resulting in the mobilization of Cr(Ⅵ) from COPR into the leachate. Particle size significantly influences the leaching of acid-soluble Cr(Ⅵ) from COPR,followed by leaching time,whereas the effects of HF concentration and leaching temperature are slight and the influence of stirring rate is negligible. The leaching process of acid-soluble Cr(VI) from COPR is controlled by the diffusion through the product layer. The apparent activation energy is 8.696 kJ/mol and the reaction orders with respect to HF concentration and particle size is 0.493 8 and-2.013 3,respectively.
文摘Coal is the world's most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-grade coal for fulfilling energy demands of modern civilization. However, due to its high ash and moisture content, low-grade coal exerts the substantial impact on their consumption like pyrolysis, liquefaction, gasification and combustion process. The present research aimed to develop the efficient technique for the production of clean coal by optimizing the operating parameters with the help of response surface methodology. The effect of three independent variables such as hydrofluoric acid(HF) concentration(10–20% by volume), temperature(60–100 °C), and time(90–180 min), for ash reduction from the low-grade coal was investigated. A quadratic model was proposed to correlate the independent variables for maximum ash reduction at the optimum process condition by using central composite design(CCD) method. The study reveals that HF concentration was the most effective parameter for ash reduction in comparison with time and temperature. It may be due to the higher F-statistics value for HF concentration, which effects to large extent of ash reduction. The characterization of coal was evaluated by Fourier transform infrared spectroscopy(FTIR) analysis and Field-emission scanning electron microscopy with energy-dispersive X-ray(FESEMEDX) analysis for confirmation of the ash reduction.
文摘以吉林汪清地区某隐晶质石墨选矿精矿为原料,采用QWJ气流涡旋粉碎机成套系统进行球形化处理,共整形16次,最佳整形次数为6次。并对球形化石墨进行提纯,采用HF和HCl的混酸法确定混酸与石墨液固比5 m L/g,HF体积分数33%,反应温度50℃,时间3 h,浸出4次,得到最终精矿固定碳含量99. 82%。
