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
Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to ...Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to assess the effect of particle size,sulfuric acid concentration,pressure,reaction time and temperature on the extraction of zinc and the dissolution of silica.Under the optimum conditions employed,up to 99.25% of zinc extraction and 0.20% silica dissolution are obtained.The main minerals in leaching residue are quartz and small amounts of undissolved oxide minerals of iron,lead and aluminum are associated with quartz.展开更多
Limestone(CaCO3),which could promote sulfur fixation,was added to coal gangue during roasting in a circulating fluidized bed(CFB)boiler.CaO and CaSO_(4) were the main Ca-bearing minerals while metakaolinite was the ma...Limestone(CaCO3),which could promote sulfur fixation,was added to coal gangue during roasting in a circulating fluidized bed(CFB)boiler.CaO and CaSO_(4) were the main Ca-bearing minerals while metakaolinite was the major Al-bearing mineral in CFB slag.The effect of CaSO_(4) and CaO on the separation of alumina and silica from metakaolinite by reduction roasting−alkaline leaching process was studied.Results showed that metakaolinite was completely converted into hercynite and silica solid solutions(i.e.,quartz and cristobalite solid solutions)by reduction roasting with hematite.More than 95%of silica in the reduced specimen was removed by alkaline leaching.The addition of CaSO_(4) and CaO remarkably decreased the separation efficiency of alumina and silica in metakaolinite,which could be attributed to the formation of Si-bearing minerals:(1)Fayalite and anorthite were formed during the reduction roasting process;(2)Fayalite was stable while anorthite was converted into sodalite and wollastonite during the alkaline leaching process.This study demonstrates that sulfur in coal gangue should be fixed by treating the exhaust gas instead of controlling the combustion process of CFB to achieve the comprehensive recovery of silica and alumina from the CFB slag.展开更多
The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem for many existing sewage structures. In this study, the properties of concrete using the blast furnace slag hav...The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem for many existing sewage structures. In this study, the properties of concrete using the blast furnace slag have been examined. It was shown that by using the blast furnace slag fine aggregate and blast furnace slag fine powder, it is possible to enhance the resistance of mortar and concrete to sulfuric acid. The resistance to sulfuric acid of mortar and concrete can be improved by using a blast-furnace slag fine aggregate in the total amount of fine aggregate. When mortar or concrete reacts to sulfuric acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film could retard the penetration of sulfuric acid, thus, improving the resistance to sulfuric acid. Furthermore, it has been proved that the relationship between the erosion depth by sulfuric acid attack and the product of immersion period and concentration of sulfuric acid can be expressed linearly. However, this relationship is dependent on the type of materials of concrete.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Project(2007CB613605) supported by the National Basic Research Program of China
文摘Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to assess the effect of particle size,sulfuric acid concentration,pressure,reaction time and temperature on the extraction of zinc and the dissolution of silica.Under the optimum conditions employed,up to 99.25% of zinc extraction and 0.20% silica dissolution are obtained.The main minerals in leaching residue are quartz and small amounts of undissolved oxide minerals of iron,lead and aluminum are associated with quartz.
基金the financial supports from the National Natural Science Foundation of China (Nos. 52004194, 51874219)the China Postdoctoral Science Foundation (No. 2019M662733)。
文摘Limestone(CaCO3),which could promote sulfur fixation,was added to coal gangue during roasting in a circulating fluidized bed(CFB)boiler.CaO and CaSO_(4) were the main Ca-bearing minerals while metakaolinite was the major Al-bearing mineral in CFB slag.The effect of CaSO_(4) and CaO on the separation of alumina and silica from metakaolinite by reduction roasting−alkaline leaching process was studied.Results showed that metakaolinite was completely converted into hercynite and silica solid solutions(i.e.,quartz and cristobalite solid solutions)by reduction roasting with hematite.More than 95%of silica in the reduced specimen was removed by alkaline leaching.The addition of CaSO_(4) and CaO remarkably decreased the separation efficiency of alumina and silica in metakaolinite,which could be attributed to the formation of Si-bearing minerals:(1)Fayalite and anorthite were formed during the reduction roasting process;(2)Fayalite was stable while anorthite was converted into sodalite and wollastonite during the alkaline leaching process.This study demonstrates that sulfur in coal gangue should be fixed by treating the exhaust gas instead of controlling the combustion process of CFB to achieve the comprehensive recovery of silica and alumina from the CFB slag.
文摘The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem for many existing sewage structures. In this study, the properties of concrete using the blast furnace slag have been examined. It was shown that by using the blast furnace slag fine aggregate and blast furnace slag fine powder, it is possible to enhance the resistance of mortar and concrete to sulfuric acid. The resistance to sulfuric acid of mortar and concrete can be improved by using a blast-furnace slag fine aggregate in the total amount of fine aggregate. When mortar or concrete reacts to sulfuric acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film could retard the penetration of sulfuric acid, thus, improving the resistance to sulfuric acid. Furthermore, it has been proved that the relationship between the erosion depth by sulfuric acid attack and the product of immersion period and concentration of sulfuric acid can be expressed linearly. However, this relationship is dependent on the type of materials of concrete.
