The mineralogical characteristics of three kinds of gibbsitic high-iron bauxite and the effects of various digestion conditions on the enrichment and separation of iron minerals were investigated. The results show tha...The mineralogical characteristics of three kinds of gibbsitic high-iron bauxite and the effects of various digestion conditions on the enrichment and separation of iron minerals were investigated. The results show that adding an appropriate organic reductant such as glycerol can promote the digestion of concomitant diaspore, boehmite and alumogoethite as well as the conversion of goethite to hematite in the reductive Bayer digestion. Processing Bauxite A with A/S of 25.41 can directly produce qualified iron concentrates(TFe>56%) by the reductive Bayer digestion, and thus realize the zero red mud discharge. For Bauxite B and Bauxite C with A/S of 7.82 and 3.35, the iron recoveries of 65.13% and 79.13% can be achieved with the corresponding TFe of 52.05% and 50.16% in the iron concentrates by gravity separation, respectively, resulting in the red mud discharge reduction of ~50% or above.展开更多
A systematic investigation on the interaction between Bayer red mud particles generated from Chinese diaspore bauxite and commercial sodium polyacrylate(SPA) or polyacrylamide(PAM) was performed by red mud settling te...A systematic investigation on the interaction between Bayer red mud particles generated from Chinese diaspore bauxite and commercial sodium polyacrylate(SPA) or polyacrylamide(PAM) was performed by red mud settling tests,conductivity-pH titration and Ubbelodhe viscosimetric measurement.The results indicate that the treatment with red mud by SPA gives a lower red mud settling rate and lower supernatant turbidity than the treatment with red mud by PAM.There is an optimum polymer dosage of 300 g/t(based on the weight of dry red mud) when red mud slurry is treated by SPA or PAM,so 'bridging' adsorption is one of the main interactions between red mud and SPA or PAM.With the increase of NaOH concentration,the hydrolysis degree of PAM dissolved in NaOH solution increases and its molecular weight almost does not change,but the settling rate of red mud treated by it drops rapidly.The settling rate of red mud treated by PAM dissolved in 10 g/L NaOH solution is 0.61 m/h while by PAM dissolved in distilled water it is 1.31 m/h,because the adsorption ability of the hydrolyzed PAM onto red mud surface declines primarily due to the formation of-CONH2～-COO-～-CONH2 intramolecular hydrogen bond。展开更多
Acid/basic potentiometric titration can be used to quantify the red mud surface charge properties.The amount of surface active -OH groups and surface charge density on the red mud particles generated from Chinese dias...Acid/basic potentiometric titration can be used to quantify the red mud surface charge properties.The amount of surface active -OH groups and surface charge density on the red mud particles generated from Chinese diaspore bauxite were evaluated from the acid/basic potentiometric titration data in 0.1 mol/L or 0.5 mol/L NaCl solution.The results show that the adsorption of sodium polyacrylate(SPA) on the red mud surface causes the increase of the surface active -OH groups,which makes the point of zero charge(PZC) shift to a lower pH value.However,the adsorption of polyacrylamide(PAM) causes little change.As the concentration of NaCl solution increases,the surface charge becomes more positive in acidic solution and more negative in alkaline solution,which can be attributed to the presence of a porous surface gel coating on the red mud particles.展开更多
This present research work is on the characterization of bauxite red mud (waste material) from Ngaoundal for the manufacture of ceramic products. After the extraction process, the raw material was characterized using ...This present research work is on the characterization of bauxite red mud (waste material) from Ngaoundal for the manufacture of ceramic products. After the extraction process, the raw material was characterized using Scanning Electron Microscopy (SEM). Morphology, mineral phases and chemical composition were determined by using energy-dispersive X-ray (EDX) analysis, X-ray diffractometer (XRD), X-ray fluorescence (XRF). Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA), Infra-Red (IR), Particle size (PS) were also used. Results of red mud analysis show that major oxides were Fe<sub>2</sub>O<sub>3</sub> (37.21%), Al<sub>2</sub>O<sub>3</sub> (19.6%), SiO<sub>2</sub> (7.68%), TiO<sub>2</sub> (1.07%), Na<sub>2</sub>O (4.71%), and CaO (2.75%). These last oxides require low temperature to melt and act as binders which link particles of red mud during the sintering process. Presence of alkaline oxides is an appeal to reduce energy consumption during ceramic manufacture process and to protect our environment for sustainable development. Physical and mechanical properties of fired red mud showed that the firing shrinkage, bulk density, and flexural strength increase with firing temperature. Porosity and water absorption had the same pattern and they decreased with the increase of temperature. Chemical stability reveals that 10% material loss is obtained after 7 days of treatment under acid-base conditions.展开更多
A common issue with filters designed to remove nutrients from runoff is their reduced effectiveness in high-flow conditions. To overcome this challenge, it was determined that nutrient removal from broiler-house fan d...A common issue with filters designed to remove nutrients from runoff is their reduced effectiveness in high-flow conditions. To overcome this challenge, it was determined that nutrient removal from broiler-house fan dust could be more effective if nutrient removal was conducted at the nutrient source. The objective of this study was to evaluate the effectiveness of containment trays (CTs) holding locally sourced by-products installed adjacent to broiler house fans at the University of Arkansas Savoy broiler production facility to capture nutrients released from dust during rainfall over four years (2013 to 2017). By-products used were locally sourced, iron-based red mud (RM) generated during the manufacture of steel belts for tires and alum-based drinking water treatment residual (WTR), where both materials have large phosphorus (P) sorption capacities. Four-year mean annual concentrations of dissolved P of through-flow from RM CTs were consistently below 0.7 mg·L-1 and below 1.6 mg·L-1 for WTR CT through-flow. This equated to an average 11- and 4-fold decrease for RM and WTR, relative to concentrations in runoff from same-sized plots adjacent to sidewall fans, demonstrating their potential to trap P at the source and decrease P runoff to nearby flowing waters. While there was no significant decline in RM or WTR effective-ness over the four-year study, further work needs to be conducted to determine the lifespan of CTs. Use of RM and WTR in CTs at poultry broiler production facilities, along with their subsequent land application, has the potential to reduce the amount of by-product materials that are currently landfilled.展开更多
基金Project(2019M652799)supported by China Postdoctoral Science FoundationProject(51604309)supported by the National Natural Science Foundation of China。
文摘The mineralogical characteristics of three kinds of gibbsitic high-iron bauxite and the effects of various digestion conditions on the enrichment and separation of iron minerals were investigated. The results show that adding an appropriate organic reductant such as glycerol can promote the digestion of concomitant diaspore, boehmite and alumogoethite as well as the conversion of goethite to hematite in the reductive Bayer digestion. Processing Bauxite A with A/S of 25.41 can directly produce qualified iron concentrates(TFe>56%) by the reductive Bayer digestion, and thus realize the zero red mud discharge. For Bauxite B and Bauxite C with A/S of 7.82 and 3.35, the iron recoveries of 65.13% and 79.13% can be achieved with the corresponding TFe of 52.05% and 50.16% in the iron concentrates by gravity separation, respectively, resulting in the red mud discharge reduction of ~50% or above.
基金Supported by National Basic Research Project (973) of China (No.2005CB623702)
文摘A systematic investigation on the interaction between Bayer red mud particles generated from Chinese diaspore bauxite and commercial sodium polyacrylate(SPA) or polyacrylamide(PAM) was performed by red mud settling tests,conductivity-pH titration and Ubbelodhe viscosimetric measurement.The results indicate that the treatment with red mud by SPA gives a lower red mud settling rate and lower supernatant turbidity than the treatment with red mud by PAM.There is an optimum polymer dosage of 300 g/t(based on the weight of dry red mud) when red mud slurry is treated by SPA or PAM,so 'bridging' adsorption is one of the main interactions between red mud and SPA or PAM.With the increase of NaOH concentration,the hydrolysis degree of PAM dissolved in NaOH solution increases and its molecular weight almost does not change,but the settling rate of red mud treated by it drops rapidly.The settling rate of red mud treated by PAM dissolved in 10 g/L NaOH solution is 0.61 m/h while by PAM dissolved in distilled water it is 1.31 m/h,because the adsorption ability of the hydrolyzed PAM onto red mud surface declines primarily due to the formation of-CONH2～-COO-～-CONH2 intramolecular hydrogen bond。
基金Project(2005CB623702) supported by the National Basic Research Program of China
文摘Acid/basic potentiometric titration can be used to quantify the red mud surface charge properties.The amount of surface active -OH groups and surface charge density on the red mud particles generated from Chinese diaspore bauxite were evaluated from the acid/basic potentiometric titration data in 0.1 mol/L or 0.5 mol/L NaCl solution.The results show that the adsorption of sodium polyacrylate(SPA) on the red mud surface causes the increase of the surface active -OH groups,which makes the point of zero charge(PZC) shift to a lower pH value.However,the adsorption of polyacrylamide(PAM) causes little change.As the concentration of NaCl solution increases,the surface charge becomes more positive in acidic solution and more negative in alkaline solution,which can be attributed to the presence of a porous surface gel coating on the red mud particles.
文摘This present research work is on the characterization of bauxite red mud (waste material) from Ngaoundal for the manufacture of ceramic products. After the extraction process, the raw material was characterized using Scanning Electron Microscopy (SEM). Morphology, mineral phases and chemical composition were determined by using energy-dispersive X-ray (EDX) analysis, X-ray diffractometer (XRD), X-ray fluorescence (XRF). Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA), Infra-Red (IR), Particle size (PS) were also used. Results of red mud analysis show that major oxides were Fe<sub>2</sub>O<sub>3</sub> (37.21%), Al<sub>2</sub>O<sub>3</sub> (19.6%), SiO<sub>2</sub> (7.68%), TiO<sub>2</sub> (1.07%), Na<sub>2</sub>O (4.71%), and CaO (2.75%). These last oxides require low temperature to melt and act as binders which link particles of red mud during the sintering process. Presence of alkaline oxides is an appeal to reduce energy consumption during ceramic manufacture process and to protect our environment for sustainable development. Physical and mechanical properties of fired red mud showed that the firing shrinkage, bulk density, and flexural strength increase with firing temperature. Porosity and water absorption had the same pattern and they decreased with the increase of temperature. Chemical stability reveals that 10% material loss is obtained after 7 days of treatment under acid-base conditions.
文摘A common issue with filters designed to remove nutrients from runoff is their reduced effectiveness in high-flow conditions. To overcome this challenge, it was determined that nutrient removal from broiler-house fan dust could be more effective if nutrient removal was conducted at the nutrient source. The objective of this study was to evaluate the effectiveness of containment trays (CTs) holding locally sourced by-products installed adjacent to broiler house fans at the University of Arkansas Savoy broiler production facility to capture nutrients released from dust during rainfall over four years (2013 to 2017). By-products used were locally sourced, iron-based red mud (RM) generated during the manufacture of steel belts for tires and alum-based drinking water treatment residual (WTR), where both materials have large phosphorus (P) sorption capacities. Four-year mean annual concentrations of dissolved P of through-flow from RM CTs were consistently below 0.7 mg·L-1 and below 1.6 mg·L-1 for WTR CT through-flow. This equated to an average 11- and 4-fold decrease for RM and WTR, relative to concentrations in runoff from same-sized plots adjacent to sidewall fans, demonstrating their potential to trap P at the source and decrease P runoff to nearby flowing waters. While there was no significant decline in RM or WTR effective-ness over the four-year study, further work needs to be conducted to determine the lifespan of CTs. Use of RM and WTR in CTs at poultry broiler production facilities, along with their subsequent land application, has the potential to reduce the amount of by-product materials that are currently landfilled.
基金Project (2022YFC2904405) supported by the National Key Research and Development Program of ChinaProjects (22078055,52074083) supported by the National Natural Science Foundation of China。
