This study investigated the heat-acid activated red mud used for hexavalent chromium (Cr6+) removal from aqueous solution. The results showed that the heat-acid activated red mud enhanced hexavalent chromium removal c...This study investigated the heat-acid activated red mud used for hexavalent chromium (Cr6+) removal from aqueous solution. The results showed that the heat-acid activated red mud enhanced hexavalent chromium removal capacity from 0.003 to 0.015 mg·g﹣1. Adsorption experiments were conducted as a function of adsorbent dosage, contact time, pH and reaction temperature. The removal efficiency was found to increase gradually when solution pH decreased and maximum removal was achieved at pH 2. The physico-chemical characteristics of heat-acid activated red mud were studied by using instrumental technique like Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF). The experimental data fitted well to Langmuir isotherm model. Thermodynamic parameters indicated the adsorption process was exothermic reaction. The cost-effective performance and, simple operation suggest the heat-acid activated red mud can be taken as a promising sorbents for removal of Cr6+ from wastewater.展开更多
Red mud is a slimy caustic residue generated from alumina production. Taking into account the rela- tively considerable content and availability of scandium, red mud can be viewed as an important and promising scandiu...Red mud is a slimy caustic residue generated from alumina production. Taking into account the rela- tively considerable content and availability of scandium, red mud can be viewed as an important and promising scandium resource rather than a solid waste. This paper is primarily to review the investigations of scandium recov- ery from red mud based on the most widely used hydrometallurgical processes including acid leaching, sol- vent extraction and ion exchange adsorption. It is thought that recovery of scandium from red mud should be con- sidered as a direct objective rather than a by-product in the development of overall flowsheet. In order to achieve environmentally-friendly processes with high scandium recovery and low cost, more attention is required to be paid to optimizing the selective leaching of scandium to decrease mineral acid consumption and alleviate pollution, and developing new solvent extraction systems and novel ion exchange adsorption materials with high selectivity and recognition for scandium.展开更多
Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic aci...Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H^＋concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4：1 and room temperature 25 ℃（only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 ℃）. Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204,15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y^3＋ and 42.60% Fe^3＋ are extracted from sulfuric acid leaching liquor（adjusted to pH = 2.0） after seven-stage counter current extraction with O/A ratio of 1：1 at room temperature, while other metals ions such as Al^3＋, Ca^2＋, Mg^2＋and Mn^2＋ are almost not extracted. The Y^3＋ in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with O/A ratio of 10：1 at room temperature, while only 2.26% co-extracted Fe^3＋ is stripped. The Y^3＋ of loaded strip liquor can be precipitated by oxalic acid to further separate Y^3＋ and Fe^3＋. The precipitation efficiency of Y^3＋ in loaded strip liquor can be 98.56% while Fe^3＋ is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 ℃ for 3 h to obtain the oxide of Y in which the purity of Y_2 O_3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%.Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting,the yttrium yield is 82.04%.展开更多
The boron mud is solid waste from a borax factory in Liaoning province, China. The main chemical compositions of the boron mud powder are MgO 43.36%, SiO2 25.99%, Fe2O3 5.55% (shown in Table 1), and its mineral phases...The boron mud is solid waste from a borax factory in Liaoning province, China. The main chemical compositions of the boron mud powder are MgO 43.36%, SiO2 25.99%, Fe2O3 5.55% (shown in Table 1), and its mineral phases are mainly forsterite, magnesite and phlogopite.展开更多
文摘This study investigated the heat-acid activated red mud used for hexavalent chromium (Cr6+) removal from aqueous solution. The results showed that the heat-acid activated red mud enhanced hexavalent chromium removal capacity from 0.003 to 0.015 mg·g﹣1. Adsorption experiments were conducted as a function of adsorbent dosage, contact time, pH and reaction temperature. The removal efficiency was found to increase gradually when solution pH decreased and maximum removal was achieved at pH 2. The physico-chemical characteristics of heat-acid activated red mud were studied by using instrumental technique like Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF). The experimental data fitted well to Langmuir isotherm model. Thermodynamic parameters indicated the adsorption process was exothermic reaction. The cost-effective performance and, simple operation suggest the heat-acid activated red mud can be taken as a promising sorbents for removal of Cr6+ from wastewater.
基金financially supported by the National Natural Science Foundation of China (Nos. 51234008 and 51574024)the China Postdoctoral Science Foundation (No. 2016M590046)
文摘Red mud is a slimy caustic residue generated from alumina production. Taking into account the rela- tively considerable content and availability of scandium, red mud can be viewed as an important and promising scandium resource rather than a solid waste. This paper is primarily to review the investigations of scandium recov- ery from red mud based on the most widely used hydrometallurgical processes including acid leaching, sol- vent extraction and ion exchange adsorption. It is thought that recovery of scandium from red mud should be con- sidered as a direct objective rather than a by-product in the development of overall flowsheet. In order to achieve environmentally-friendly processes with high scandium recovery and low cost, more attention is required to be paid to optimizing the selective leaching of scandium to decrease mineral acid consumption and alleviate pollution, and developing new solvent extraction systems and novel ion exchange adsorption materials with high selectivity and recognition for scandium.
基金Project supported by Science and Technology Planning Project of Guangdong Province(20168070701022,20168090931003,20168020240004,2017B090907026)National Natural Science Foundation of China(51704081)+1 种基金Ocean Investigation and Research Project of China Geological Survey(GZH201100303-05)Science and Technology Program of Guangzhou(201504010010,201607020022)
文摘Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H^＋concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4：1 and room temperature 25 ℃（only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 ℃）. Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204,15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y^3＋ and 42.60% Fe^3＋ are extracted from sulfuric acid leaching liquor（adjusted to pH = 2.0） after seven-stage counter current extraction with O/A ratio of 1：1 at room temperature, while other metals ions such as Al^3＋, Ca^2＋, Mg^2＋and Mn^2＋ are almost not extracted. The Y^3＋ in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with O/A ratio of 10：1 at room temperature, while only 2.26% co-extracted Fe^3＋ is stripped. The Y^3＋ of loaded strip liquor can be precipitated by oxalic acid to further separate Y^3＋ and Fe^3＋. The precipitation efficiency of Y^3＋ in loaded strip liquor can be 98.56% while Fe^3＋ is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 ℃ for 3 h to obtain the oxide of Y in which the purity of Y_2 O_3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%.Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting,the yttrium yield is 82.04%.
文摘The boron mud is solid waste from a borax factory in Liaoning province, China. The main chemical compositions of the boron mud powder are MgO 43.36%, SiO2 25.99%, Fe2O3 5.55% (shown in Table 1), and its mineral phases are mainly forsterite, magnesite and phlogopite.
