Digesting aluminum-bearing minerals and converting ferric oxide to magnetite simultaneously in Bayer digestion process is crucially important to deal with high-iron diasporic bauxite economically for alumina productio...Digesting aluminum-bearing minerals and converting ferric oxide to magnetite simultaneously in Bayer digestion process is crucially important to deal with high-iron diasporic bauxite economically for alumina production.The reaction behaviors of hydrothermal reduction of ferric oxide in alkali solution were studied by both thermodynamic calculation and experimental investigation.The thermodynamic calculation indicates that Fe3O4 can be formed by the conversion of Fe2O3 at proper redox potentials in alkaline solution.The experimental results show that the formation ratio of Fe3O4 either through the reaction of Fe and Fe2O3 or through the reaction of Fe and H2O in alkaline aqueous solution increases remarkably with raising the temperature and alkali concentration,suggesting that Fe（OH）3- and Fe（OH）4- form by dissolving Fe and Fe2O3,respectively,in alkaline aqueous solution and further react to form Fe3O4.Moreover,aluminate ions have little influence on the hydrothermal reduction of Fe2O3 in alkaline aqueous solution,and converting iron minerals to magnetite can be realized in the Bayer digestion process of diasporic bauxite.展开更多
This paper studied the effect of ferric chloride on waste sludge digestion,dewatering and sedimentation under the optimized doses in co-precipitation phosphorus removal process.The experimental results showed that the...This paper studied the effect of ferric chloride on waste sludge digestion,dewatering and sedimentation under the optimized doses in co-precipitation phosphorus removal process.The experimental results showed that the concentration of mixed liquid suspended solid(MLSS) was 2436 mg.L-1 and 2385 mg.L-1 in co-precipitation phosphorus removal process(CPR) and biological phosphorous removal process(BPR),respectively.The sludge reduction ratio for each process was 22.6% and 24.6% in aerobic digestion,and 27.6% and 29.9% in anaerobic digestion,respectively.Due to the addition of chemical to the end of aeration tank,the sludge content of CPR was slightly higher than that of BPR,but the sludge reduction rate for both processes had no distinct difference.The sludge volume index(SVI) and sludge specific resistance of BPR were 126 ml.g-1 and 11.7×1012 m.kg-1,respectively,while those of CPR were only 98 ml.g-1 and 7.1×1012 m.kg-1,indicating that CPR chemical could improve sludge settling and dewatering.展开更多
基金Project(51374239)supported by the National Natural Science Foundation of China
文摘Digesting aluminum-bearing minerals and converting ferric oxide to magnetite simultaneously in Bayer digestion process is crucially important to deal with high-iron diasporic bauxite economically for alumina production.The reaction behaviors of hydrothermal reduction of ferric oxide in alkali solution were studied by both thermodynamic calculation and experimental investigation.The thermodynamic calculation indicates that Fe3O4 can be formed by the conversion of Fe2O3 at proper redox potentials in alkaline solution.The experimental results show that the formation ratio of Fe3O4 either through the reaction of Fe and Fe2O3 or through the reaction of Fe and H2O in alkaline aqueous solution increases remarkably with raising the temperature and alkali concentration,suggesting that Fe（OH）3- and Fe（OH）4- form by dissolving Fe and Fe2O3,respectively,in alkaline aqueous solution and further react to form Fe3O4.Moreover,aluminate ions have little influence on the hydrothermal reduction of Fe2O3 in alkaline aqueous solution,and converting iron minerals to magnetite can be realized in the Bayer digestion process of diasporic bauxite.
基金Supported by the Major National Water Sci-Tech Projects of China(2009ZX07210-009)the Department of Environmental Protection of Shandong Province(2006032,2060403)
文摘This paper studied the effect of ferric chloride on waste sludge digestion,dewatering and sedimentation under the optimized doses in co-precipitation phosphorus removal process.The experimental results showed that the concentration of mixed liquid suspended solid(MLSS) was 2436 mg.L-1 and 2385 mg.L-1 in co-precipitation phosphorus removal process(CPR) and biological phosphorous removal process(BPR),respectively.The sludge reduction ratio for each process was 22.6% and 24.6% in aerobic digestion,and 27.6% and 29.9% in anaerobic digestion,respectively.Due to the addition of chemical to the end of aeration tank,the sludge content of CPR was slightly higher than that of BPR,but the sludge reduction rate for both processes had no distinct difference.The sludge volume index(SVI) and sludge specific resistance of BPR were 126 ml.g-1 and 11.7×1012 m.kg-1,respectively,while those of CPR were only 98 ml.g-1 and 7.1×1012 m.kg-1,indicating that CPR chemical could improve sludge settling and dewatering.
