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 was...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
This investigation was conducted by using alkaline slag and crop straw biochars to reduce acidity of an acidic Ultisol through incubation and pot experiments with lime as a comparison. The soil was amended with differ...This investigation was conducted by using alkaline slag and crop straw biochars to reduce acidity of an acidic Ultisol through incubation and pot experiments with lime as a comparison. The soil was amended with different liming materials: lime(1 g kg-1),alkaline slag(2 and 4 g kg-1), peanut straw biochar(10 and 20 g kg-1), canola straw biochar(10 and 20 g kg-1) and combinations of alkaline slag(2 g kg-1) and biochars(10 g kg-1) in the incubation study. A pot experiment was also conducted to observe the soybean growth responses to the above treatments. The results showed that all the liming materials increased soil p H and decreased soil exchangeable acidity. The higher the rates of alkaline slag, biochars, and alkaline slag combined with biochars, the greater the increase in soil p H and the reduction in soil exchangeable acidity. All the amendments increased the levels of one or more soil exchangeable base cations. The lime treatment increased soil exchangeable Ca2+, the alkaline slag treatment increased exchangeable Ca2+and Mg2+levels, and the biochars and combined applications of alkaline slag with biochars increased soil exchangeable Ca2+, Mg2+and K+and soil available P. The amendments enhanced the uptake of one or more nutrients of N, P, K, Ca and Mg by soybean in the pot experiment. Of the different amendments, the combined application of alkaline slag with crop straw biochars was the best choice for increasing base saturation and reducing soil acidity of the acidic Ultisol. The combined application of alkaline slag with biochars led to the greatest reduction in soil acidity, increased soil Ca, Mg, K and P levels, and enhanced the uptake of Ca, Mg, K and P by soybean plants.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.
基金Supported by the National Basic Research Program(973 Program)of China(No.2014CB441003)the National Natural Science Foundation of China(No.41271010)
文摘This investigation was conducted by using alkaline slag and crop straw biochars to reduce acidity of an acidic Ultisol through incubation and pot experiments with lime as a comparison. The soil was amended with different liming materials: lime(1 g kg-1),alkaline slag(2 and 4 g kg-1), peanut straw biochar(10 and 20 g kg-1), canola straw biochar(10 and 20 g kg-1) and combinations of alkaline slag(2 g kg-1) and biochars(10 g kg-1) in the incubation study. A pot experiment was also conducted to observe the soybean growth responses to the above treatments. The results showed that all the liming materials increased soil p H and decreased soil exchangeable acidity. The higher the rates of alkaline slag, biochars, and alkaline slag combined with biochars, the greater the increase in soil p H and the reduction in soil exchangeable acidity. All the amendments increased the levels of one or more soil exchangeable base cations. The lime treatment increased soil exchangeable Ca2+, the alkaline slag treatment increased exchangeable Ca2+and Mg2+levels, and the biochars and combined applications of alkaline slag with biochars increased soil exchangeable Ca2+, Mg2+and K+and soil available P. The amendments enhanced the uptake of one or more nutrients of N, P, K, Ca and Mg by soybean in the pot experiment. Of the different amendments, the combined application of alkaline slag with crop straw biochars was the best choice for increasing base saturation and reducing soil acidity of the acidic Ultisol. The combined application of alkaline slag with biochars led to the greatest reduction in soil acidity, increased soil Ca, Mg, K and P levels, and enhanced the uptake of Ca, Mg, K and P by soybean plants.