The Experts below are selected from a list of 2136 Experts worldwide ranked by ideXlab platform
Shengguo Xue - One of the best experts on this subject based on the ideXlab platform.
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long term natural restoration creates soil like microbial communities in Bauxite Residue a case for 50 year field study
Land Degradation & Development, 2021Co-Authors: Tian Tang, Feng Zhu, William Hartley, Xiaomeng Wei, Shengguo XueAbstract:Ecological reconstruction on Bauxite Residue disposal areas is regarded as an effective approach to eliminate potential environmental risks. Establishment of microbial communities and associated functions may improve physical and chemical properties, and may stimulate soil formation in Bauxite Residue. Spontaneous colonization at a disposal area in Shandong Province, China, over 50 years, indicated that natural weathering can ameliorate Residues, and in turn, support the establishment of vegetation communities. Residue samples were collected from unrestored, poorly restored and well restored areas to investigate the development of microbial communities and associated functions. Microbiota significantly developed after long term natural restoration. Microbial biomass, respiration and enzyme activities significantly increased in restored Bauxite Residue, whereas the metabolic quotient significantly decreased. In addition, the long‐term natural restoration significantly shaped the microbial structure from alkalophilic and halophilic assemblages (Firmicutes and Actinobacteria) to neutrophilic assemblages (Acidobacteria and Planctomycetes). Both microbial communities and associated functions in well restored Residue had high similarity with that in natural soil, indicating that long term restoration created diverse soil‐like microbial communities and functions. Redundancy analysis (RDA) revealed that TN, followed by Na+, ESP, SOC, AP and pH were the major influence factors in the development of microbial communities in Bauxite Residue. These findings provide us a biogeochemical perspective to reveal soil formation in Bauxite Residue and suggest that nutrient supplement and regulation of salinity‐alkalinity may benefit for the establishment of microbial communities and functions in Bauxite Residue.
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Improvement of aggregate‐associated organic carbon and its stability in Bauxite Residue by substrate amendment addition
Land Degradation & Development, 2020Co-Authors: Tao Tian, William Hartley, Feng Zhu, Zheng Liu, Shengguo XueAbstract:Bauxite Residue has extreme alkalinity, poor aggregate stability, and low organic carbon content, which limits plant growth on large expanses of Bauxite Residue disposal areas. Soil formation of Bauxite Residue is one of the effective approaches to transform Bauxite Residue into a soil‐like medium for revegetation. In order to improve aggregate stability and organic carbon content in the short term, addition of substrate amendments is crucial to accelerate soil formation of Bauxite Residue. Nevertheless, the effect of different amendments on the stability, organic and humic substances distribution in Bauxite Residue aggregate is unclear. Therefore, a column experiment was used to investigate the distribution and stability of aggregate, and aggregate‐associated carbon by adding phosphogypsum and vermicompost (PVC), and biosolids and microorganism (BSM). The average particle sizes of CK (control check), PVC, and BSM treatments were observed to be ~114, ~157, and ~188 nm, respectively. Compared with CK treatment, the contents of organic carbon, humic acid, and fulvic acid following PVC treatment increased by 1.65, 1.59, and 1.57 times, respectively, and the increased contents of organic carbon, humic acid, and fulvic acid following BSM treatment reached 2.90, 2.69, and 2.60 times, respectively. Results demonstrated that amendment additions enhanced aggregate stability and carbon sequestration, but the effects of BSM treatment were better than those of PVC treatment. The findings offer an evidence that BSM treatment is a feasible approach to accelerate soil formation of Bauxite Residue, which shows promising applications to reclaim Bauxite Residue disposal areas.
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Alkalinity neutralization and structure upgrade of Bauxite Residue waste via synergistic pyrolysis with biomass
Journal of environmental sciences (China), 2020Co-Authors: Lu Tang, Feng Zhu, Jun Jiang, Jing-ju Zhou, Shengguo XueAbstract:Bauxite Residues, a large volume solid waste, are in urgent need of effective disposal and management. Especially, strategies to alleviate the high alkalinity of Bauxite Residue remain a big challenge. Here, we developed a synergistic pyrolysis to neutralize the alkalinity of Bauxite Residue and upgrade the structure of biomass simultaneously. By cooperating the catalytic feature from Bauxite Residue, rice straw, a cellulose-enriched biomass, could prefer to produce acidic components under a hypothermal pyrolysis temperature (below 250 °C) and partial oxygen-contained atmosphere as evidenced by the synchronous TGA-FTIR analysis. In return, these in-situ produced acidic components neutralized the Bauxite Residue profoundly (pH decreased from 11.5 to 7.2) to obtain a neutral product with long-term water leaching stability. Also, a higher pyrolysis temperature led to neutral biochar-based products with well-defined carbonization characteristics. Thus, the biomass-driven pyrolysis strategy provides a potential to dispose the alkalinity issue of Bauxite Residue and further opportunities for the sustainable reuse and continuing management of Bauxite Residue.
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Variation on leaching behavior of caustic compounds in Bauxite Residue during dealkalization process.
Journal of environmental sciences (China), 2020Co-Authors: Feng Zhu, Shengguo Xue, William Hartley, Jia-xin Liao, Jun JiangAbstract:Bauxite Residue, a byproduct of alumina manufacture, is a serious environmental pollutant due to its high leaching contents of metals and caustic compounds. Four typical anions of CO32-, HCO3-, Al(OH)4- and OH- (represented caustic compounds) and metal ions (As, B, Mo and V) were selected to assess their leaching behavior under dealkalization process with different conditions including liquid/solid ratio (L/S ratio), temperature and leaching time. The results revealed that washing process could remove the soluble composition in Bauxite Residue effectively. The leaching concentrations of typical anions in Bauxite Residue decreased as follows: c(CO32-) > c(HCO3-) > c[Al(OH)4-] > c(OH-). L/S ratio had a more significant effect on leaching behavior of OH-, whilst the leaching concentration of Al(OH)4- varied larger underleaching temperature and time treatment. Under the optimal leaching, the total alkaline, soluble Na concentrations, exchangeable Ca concentrations were 79.52, 68.93, and 136.0 mmol/L, respectively, whilst the soluble and exchangeable content of As, B, Mo and V in Bauxite Residue changed slightly. However, it should be noted that water leaching has released metal ions such as As, B, Mo and V in Bauxite Residue to the surrounding environment. The semiquantitative analysis of XRD revealed that water leaching increased the content of gismondine from 2.4% to 6.4%. The SEM images demonstrated the dissolution of caustic compounds on Bauxite Residue surface. The correlation analysis indicated that CO32- and HCO3- could effectively reflect the alkalinity of Bauxite Residue, and may be regarded as critical dealkalization indicators to evaluate alkalinity removal in Bauxite Residue.
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The reuse of Bauxite Residue as a cathode for heterogeneous electro-Fenton
Journal of Cleaner Production, 2020Co-Authors: Shengguo Xue, Lu Tang, Tian Tang, Jun JiangAbstract:Abstract Bauxite Residue is an alkaline waste generated from aluminum smelting and generally treated by land-fill, severely challenging the surrounding environmental safety. Here, this work demonstrated that Bauxite Residue could be reused as a superior cathode for heterogeneous electro-Fenton (EF) process to degrade organic pollutants. With Bauxite Residue and straw as raw materials, a Fe-C-N contained catalyst was successfully prepared via a pyrolysis route in the presence of urea. This Fe-C-N contained catalyst exhibited promising electrocatalytic performance to reduce O2 to produce H2O2 and activate H2O2 to generate .OH simultaneously. As a heterogeneous EF cathode, 97% of rhodamine B (10 mg L−1) could be degraded within 45 min at pH 3 with a catalyst dosage of 0.2 mg mL−1, which was comparable to those reported advanced EF cathodes. The appropriate reduction of Fe-contained minerals and carbonization of straw with N doping were attributed to the superior catalytic properties. Thus, the current study provides a feasible strategy to reuse Bauxite Residue and upgrade them into value-added electrode material.
Feng Zhu - One of the best experts on this subject based on the ideXlab platform.
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long term natural restoration creates soil like microbial communities in Bauxite Residue a case for 50 year field study
Land Degradation & Development, 2021Co-Authors: Tian Tang, Feng Zhu, William Hartley, Xiaomeng Wei, Shengguo XueAbstract:Ecological reconstruction on Bauxite Residue disposal areas is regarded as an effective approach to eliminate potential environmental risks. Establishment of microbial communities and associated functions may improve physical and chemical properties, and may stimulate soil formation in Bauxite Residue. Spontaneous colonization at a disposal area in Shandong Province, China, over 50 years, indicated that natural weathering can ameliorate Residues, and in turn, support the establishment of vegetation communities. Residue samples were collected from unrestored, poorly restored and well restored areas to investigate the development of microbial communities and associated functions. Microbiota significantly developed after long term natural restoration. Microbial biomass, respiration and enzyme activities significantly increased in restored Bauxite Residue, whereas the metabolic quotient significantly decreased. In addition, the long‐term natural restoration significantly shaped the microbial structure from alkalophilic and halophilic assemblages (Firmicutes and Actinobacteria) to neutrophilic assemblages (Acidobacteria and Planctomycetes). Both microbial communities and associated functions in well restored Residue had high similarity with that in natural soil, indicating that long term restoration created diverse soil‐like microbial communities and functions. Redundancy analysis (RDA) revealed that TN, followed by Na+, ESP, SOC, AP and pH were the major influence factors in the development of microbial communities in Bauxite Residue. These findings provide us a biogeochemical perspective to reveal soil formation in Bauxite Residue and suggest that nutrient supplement and regulation of salinity‐alkalinity may benefit for the establishment of microbial communities and functions in Bauxite Residue.
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Improvement of aggregate‐associated organic carbon and its stability in Bauxite Residue by substrate amendment addition
Land Degradation & Development, 2020Co-Authors: Tao Tian, William Hartley, Feng Zhu, Zheng Liu, Shengguo XueAbstract:Bauxite Residue has extreme alkalinity, poor aggregate stability, and low organic carbon content, which limits plant growth on large expanses of Bauxite Residue disposal areas. Soil formation of Bauxite Residue is one of the effective approaches to transform Bauxite Residue into a soil‐like medium for revegetation. In order to improve aggregate stability and organic carbon content in the short term, addition of substrate amendments is crucial to accelerate soil formation of Bauxite Residue. Nevertheless, the effect of different amendments on the stability, organic and humic substances distribution in Bauxite Residue aggregate is unclear. Therefore, a column experiment was used to investigate the distribution and stability of aggregate, and aggregate‐associated carbon by adding phosphogypsum and vermicompost (PVC), and biosolids and microorganism (BSM). The average particle sizes of CK (control check), PVC, and BSM treatments were observed to be ~114, ~157, and ~188 nm, respectively. Compared with CK treatment, the contents of organic carbon, humic acid, and fulvic acid following PVC treatment increased by 1.65, 1.59, and 1.57 times, respectively, and the increased contents of organic carbon, humic acid, and fulvic acid following BSM treatment reached 2.90, 2.69, and 2.60 times, respectively. Results demonstrated that amendment additions enhanced aggregate stability and carbon sequestration, but the effects of BSM treatment were better than those of PVC treatment. The findings offer an evidence that BSM treatment is a feasible approach to accelerate soil formation of Bauxite Residue, which shows promising applications to reclaim Bauxite Residue disposal areas.
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Alkalinity neutralization and structure upgrade of Bauxite Residue waste via synergistic pyrolysis with biomass
Journal of environmental sciences (China), 2020Co-Authors: Lu Tang, Feng Zhu, Jun Jiang, Jing-ju Zhou, Shengguo XueAbstract:Bauxite Residues, a large volume solid waste, are in urgent need of effective disposal and management. Especially, strategies to alleviate the high alkalinity of Bauxite Residue remain a big challenge. Here, we developed a synergistic pyrolysis to neutralize the alkalinity of Bauxite Residue and upgrade the structure of biomass simultaneously. By cooperating the catalytic feature from Bauxite Residue, rice straw, a cellulose-enriched biomass, could prefer to produce acidic components under a hypothermal pyrolysis temperature (below 250 °C) and partial oxygen-contained atmosphere as evidenced by the synchronous TGA-FTIR analysis. In return, these in-situ produced acidic components neutralized the Bauxite Residue profoundly (pH decreased from 11.5 to 7.2) to obtain a neutral product with long-term water leaching stability. Also, a higher pyrolysis temperature led to neutral biochar-based products with well-defined carbonization characteristics. Thus, the biomass-driven pyrolysis strategy provides a potential to dispose the alkalinity issue of Bauxite Residue and further opportunities for the sustainable reuse and continuing management of Bauxite Residue.
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Variation on leaching behavior of caustic compounds in Bauxite Residue during dealkalization process.
Journal of environmental sciences (China), 2020Co-Authors: Feng Zhu, Shengguo Xue, William Hartley, Jia-xin Liao, Jun JiangAbstract:Bauxite Residue, a byproduct of alumina manufacture, is a serious environmental pollutant due to its high leaching contents of metals and caustic compounds. Four typical anions of CO32-, HCO3-, Al(OH)4- and OH- (represented caustic compounds) and metal ions (As, B, Mo and V) were selected to assess their leaching behavior under dealkalization process with different conditions including liquid/solid ratio (L/S ratio), temperature and leaching time. The results revealed that washing process could remove the soluble composition in Bauxite Residue effectively. The leaching concentrations of typical anions in Bauxite Residue decreased as follows: c(CO32-) > c(HCO3-) > c[Al(OH)4-] > c(OH-). L/S ratio had a more significant effect on leaching behavior of OH-, whilst the leaching concentration of Al(OH)4- varied larger underleaching temperature and time treatment. Under the optimal leaching, the total alkaline, soluble Na concentrations, exchangeable Ca concentrations were 79.52, 68.93, and 136.0 mmol/L, respectively, whilst the soluble and exchangeable content of As, B, Mo and V in Bauxite Residue changed slightly. However, it should be noted that water leaching has released metal ions such as As, B, Mo and V in Bauxite Residue to the surrounding environment. The semiquantitative analysis of XRD revealed that water leaching increased the content of gismondine from 2.4% to 6.4%. The SEM images demonstrated the dissolution of caustic compounds on Bauxite Residue surface. The correlation analysis indicated that CO32- and HCO3- could effectively reflect the alkalinity of Bauxite Residue, and may be regarded as critical dealkalization indicators to evaluate alkalinity removal in Bauxite Residue.
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The dynamic development of bacterial community following long-term weathering of Bauxite Residue.
Journal of environmental sciences (China), 2019Co-Authors: Li Chen, Feng Zhu, William Hartley, Yifan Zhang, Shengguo XueAbstract:Bauxite Residue is the industrial waste generated from alumina production and commonly deposited in impoundments. These sites are bare of vegetation due to the extreme high salinity and alkalinity, as well as lack of nutrients. However, long term weathering processes could improve Residue properties to support the plant establishment. Here we investigate the development of bacterial communities and the geochemical drivers in Bauxite Residue, using Illumina high-throughput sequencing technology. Long term weathering reduced the pH in Bauxite Residue and increased its nutrients content. The bacterial community also significantly developed during long term weathering processes. Taxonomic analysis revealed that natural weathering processes encouraged the populations of Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes, whereas reducing the populations of Firmicutes and Actinobacteria. Redundancy analysis (RDA) indicated that total organic carbon (TOC) was the dominant factors affecting microbial structure. The results have demonstrated that natural weathering processes improved the soil development on the abandoned Bauxite Residue disposal areas, which also increased our understanding of the correlation between microbial variation and Residue properties during natural weathering processes in Bauxite Residue disposal areas.
William Hartley - One of the best experts on this subject based on the ideXlab platform.
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long term natural restoration creates soil like microbial communities in Bauxite Residue a case for 50 year field study
Land Degradation & Development, 2021Co-Authors: Tian Tang, Feng Zhu, William Hartley, Xiaomeng Wei, Shengguo XueAbstract:Ecological reconstruction on Bauxite Residue disposal areas is regarded as an effective approach to eliminate potential environmental risks. Establishment of microbial communities and associated functions may improve physical and chemical properties, and may stimulate soil formation in Bauxite Residue. Spontaneous colonization at a disposal area in Shandong Province, China, over 50 years, indicated that natural weathering can ameliorate Residues, and in turn, support the establishment of vegetation communities. Residue samples were collected from unrestored, poorly restored and well restored areas to investigate the development of microbial communities and associated functions. Microbiota significantly developed after long term natural restoration. Microbial biomass, respiration and enzyme activities significantly increased in restored Bauxite Residue, whereas the metabolic quotient significantly decreased. In addition, the long‐term natural restoration significantly shaped the microbial structure from alkalophilic and halophilic assemblages (Firmicutes and Actinobacteria) to neutrophilic assemblages (Acidobacteria and Planctomycetes). Both microbial communities and associated functions in well restored Residue had high similarity with that in natural soil, indicating that long term restoration created diverse soil‐like microbial communities and functions. Redundancy analysis (RDA) revealed that TN, followed by Na+, ESP, SOC, AP and pH were the major influence factors in the development of microbial communities in Bauxite Residue. These findings provide us a biogeochemical perspective to reveal soil formation in Bauxite Residue and suggest that nutrient supplement and regulation of salinity‐alkalinity may benefit for the establishment of microbial communities and functions in Bauxite Residue.
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Improvement of aggregate‐associated organic carbon and its stability in Bauxite Residue by substrate amendment addition
Land Degradation & Development, 2020Co-Authors: Tao Tian, William Hartley, Feng Zhu, Zheng Liu, Shengguo XueAbstract:Bauxite Residue has extreme alkalinity, poor aggregate stability, and low organic carbon content, which limits plant growth on large expanses of Bauxite Residue disposal areas. Soil formation of Bauxite Residue is one of the effective approaches to transform Bauxite Residue into a soil‐like medium for revegetation. In order to improve aggregate stability and organic carbon content in the short term, addition of substrate amendments is crucial to accelerate soil formation of Bauxite Residue. Nevertheless, the effect of different amendments on the stability, organic and humic substances distribution in Bauxite Residue aggregate is unclear. Therefore, a column experiment was used to investigate the distribution and stability of aggregate, and aggregate‐associated carbon by adding phosphogypsum and vermicompost (PVC), and biosolids and microorganism (BSM). The average particle sizes of CK (control check), PVC, and BSM treatments were observed to be ~114, ~157, and ~188 nm, respectively. Compared with CK treatment, the contents of organic carbon, humic acid, and fulvic acid following PVC treatment increased by 1.65, 1.59, and 1.57 times, respectively, and the increased contents of organic carbon, humic acid, and fulvic acid following BSM treatment reached 2.90, 2.69, and 2.60 times, respectively. Results demonstrated that amendment additions enhanced aggregate stability and carbon sequestration, but the effects of BSM treatment were better than those of PVC treatment. The findings offer an evidence that BSM treatment is a feasible approach to accelerate soil formation of Bauxite Residue, which shows promising applications to reclaim Bauxite Residue disposal areas.
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Variation on leaching behavior of caustic compounds in Bauxite Residue during dealkalization process.
Journal of environmental sciences (China), 2020Co-Authors: Feng Zhu, Shengguo Xue, William Hartley, Jia-xin Liao, Jun JiangAbstract:Bauxite Residue, a byproduct of alumina manufacture, is a serious environmental pollutant due to its high leaching contents of metals and caustic compounds. Four typical anions of CO32-, HCO3-, Al(OH)4- and OH- (represented caustic compounds) and metal ions (As, B, Mo and V) were selected to assess their leaching behavior under dealkalization process with different conditions including liquid/solid ratio (L/S ratio), temperature and leaching time. The results revealed that washing process could remove the soluble composition in Bauxite Residue effectively. The leaching concentrations of typical anions in Bauxite Residue decreased as follows: c(CO32-) > c(HCO3-) > c[Al(OH)4-] > c(OH-). L/S ratio had a more significant effect on leaching behavior of OH-, whilst the leaching concentration of Al(OH)4- varied larger underleaching temperature and time treatment. Under the optimal leaching, the total alkaline, soluble Na concentrations, exchangeable Ca concentrations were 79.52, 68.93, and 136.0 mmol/L, respectively, whilst the soluble and exchangeable content of As, B, Mo and V in Bauxite Residue changed slightly. However, it should be noted that water leaching has released metal ions such as As, B, Mo and V in Bauxite Residue to the surrounding environment. The semiquantitative analysis of XRD revealed that water leaching increased the content of gismondine from 2.4% to 6.4%. The SEM images demonstrated the dissolution of caustic compounds on Bauxite Residue surface. The correlation analysis indicated that CO32- and HCO3- could effectively reflect the alkalinity of Bauxite Residue, and may be regarded as critical dealkalization indicators to evaluate alkalinity removal in Bauxite Residue.
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The dynamic development of bacterial community following long-term weathering of Bauxite Residue.
Journal of environmental sciences (China), 2019Co-Authors: Li Chen, Feng Zhu, William Hartley, Yifan Zhang, Shengguo XueAbstract:Bauxite Residue is the industrial waste generated from alumina production and commonly deposited in impoundments. These sites are bare of vegetation due to the extreme high salinity and alkalinity, as well as lack of nutrients. However, long term weathering processes could improve Residue properties to support the plant establishment. Here we investigate the development of bacterial communities and the geochemical drivers in Bauxite Residue, using Illumina high-throughput sequencing technology. Long term weathering reduced the pH in Bauxite Residue and increased its nutrients content. The bacterial community also significantly developed during long term weathering processes. Taxonomic analysis revealed that natural weathering processes encouraged the populations of Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes, whereas reducing the populations of Firmicutes and Actinobacteria. Redundancy analysis (RDA) indicated that total organic carbon (TOC) was the dominant factors affecting microbial structure. The results have demonstrated that natural weathering processes improved the soil development on the abandoned Bauxite Residue disposal areas, which also increased our understanding of the correlation between microbial variation and Residue properties during natural weathering processes in Bauxite Residue disposal areas.
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changes in distribution and microstructure of Bauxite Residue aggregates following amendments addition
Journal of Environmental Sciences-china, 2019Co-Authors: Shengguo Xue, Jun Jiang, Feng Zhu, Qiongli Wang, William HartleyAbstract:Abstract Bauxite Residue is a highly alkaline byproduct which is routinely discarded at Residue disposal areas. Improving soil formation process to revegetate the special degraded lands is a promising strategy for sustainable management of the refining industry. A laboratory incubation experiment was used to evaluate the effects of gypsum and vermicompost on stable aggregate formation of Bauxite Residue. Aggregate size distribution was quantified by fractal theory, whilst Residue microstructure was determined by scanning electron microscopy and synchrotron-based X-ray micro-computed tomography. Amendments addition increased the content of macro-aggregates (> 250 μm) and enhanced aggregate stability of Bauxite Residue. Following gypsum and vermicompost addition, fractal dimension decreased from 2.84 to 2.77, which indicated a more homogeneous distribution of aggregate particles. Images from scanning electron microscopy and three-dimensional microstructure demonstrated that amendments stimulate the formation of improved structure in Residue aggregates. Pore parameters including porosity, pore throat surface area, path length, and path tortuosity increased under amendment additions. Changes in aggregate size distribution and microstructure of Bauxite Residue indicated that additions of gypsum and vermicompost were beneficial to physical condition of Bauxite Residue which may enhance the ease of vegetation.
Jun Jiang - One of the best experts on this subject based on the ideXlab platform.
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Alkalinity neutralization and structure upgrade of Bauxite Residue waste via synergistic pyrolysis with biomass
Journal of environmental sciences (China), 2020Co-Authors: Lu Tang, Feng Zhu, Jun Jiang, Jing-ju Zhou, Shengguo XueAbstract:Bauxite Residues, a large volume solid waste, are in urgent need of effective disposal and management. Especially, strategies to alleviate the high alkalinity of Bauxite Residue remain a big challenge. Here, we developed a synergistic pyrolysis to neutralize the alkalinity of Bauxite Residue and upgrade the structure of biomass simultaneously. By cooperating the catalytic feature from Bauxite Residue, rice straw, a cellulose-enriched biomass, could prefer to produce acidic components under a hypothermal pyrolysis temperature (below 250 °C) and partial oxygen-contained atmosphere as evidenced by the synchronous TGA-FTIR analysis. In return, these in-situ produced acidic components neutralized the Bauxite Residue profoundly (pH decreased from 11.5 to 7.2) to obtain a neutral product with long-term water leaching stability. Also, a higher pyrolysis temperature led to neutral biochar-based products with well-defined carbonization characteristics. Thus, the biomass-driven pyrolysis strategy provides a potential to dispose the alkalinity issue of Bauxite Residue and further opportunities for the sustainable reuse and continuing management of Bauxite Residue.
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Variation on leaching behavior of caustic compounds in Bauxite Residue during dealkalization process.
Journal of environmental sciences (China), 2020Co-Authors: Feng Zhu, Shengguo Xue, William Hartley, Jia-xin Liao, Jun JiangAbstract:Bauxite Residue, a byproduct of alumina manufacture, is a serious environmental pollutant due to its high leaching contents of metals and caustic compounds. Four typical anions of CO32-, HCO3-, Al(OH)4- and OH- (represented caustic compounds) and metal ions (As, B, Mo and V) were selected to assess their leaching behavior under dealkalization process with different conditions including liquid/solid ratio (L/S ratio), temperature and leaching time. The results revealed that washing process could remove the soluble composition in Bauxite Residue effectively. The leaching concentrations of typical anions in Bauxite Residue decreased as follows: c(CO32-) > c(HCO3-) > c[Al(OH)4-] > c(OH-). L/S ratio had a more significant effect on leaching behavior of OH-, whilst the leaching concentration of Al(OH)4- varied larger underleaching temperature and time treatment. Under the optimal leaching, the total alkaline, soluble Na concentrations, exchangeable Ca concentrations were 79.52, 68.93, and 136.0 mmol/L, respectively, whilst the soluble and exchangeable content of As, B, Mo and V in Bauxite Residue changed slightly. However, it should be noted that water leaching has released metal ions such as As, B, Mo and V in Bauxite Residue to the surrounding environment. The semiquantitative analysis of XRD revealed that water leaching increased the content of gismondine from 2.4% to 6.4%. The SEM images demonstrated the dissolution of caustic compounds on Bauxite Residue surface. The correlation analysis indicated that CO32- and HCO3- could effectively reflect the alkalinity of Bauxite Residue, and may be regarded as critical dealkalization indicators to evaluate alkalinity removal in Bauxite Residue.
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The reuse of Bauxite Residue as a cathode for heterogeneous electro-Fenton
Journal of Cleaner Production, 2020Co-Authors: Shengguo Xue, Lu Tang, Tian Tang, Jun JiangAbstract:Abstract Bauxite Residue is an alkaline waste generated from aluminum smelting and generally treated by land-fill, severely challenging the surrounding environmental safety. Here, this work demonstrated that Bauxite Residue could be reused as a superior cathode for heterogeneous electro-Fenton (EF) process to degrade organic pollutants. With Bauxite Residue and straw as raw materials, a Fe-C-N contained catalyst was successfully prepared via a pyrolysis route in the presence of urea. This Fe-C-N contained catalyst exhibited promising electrocatalytic performance to reduce O2 to produce H2O2 and activate H2O2 to generate .OH simultaneously. As a heterogeneous EF cathode, 97% of rhodamine B (10 mg L−1) could be degraded within 45 min at pH 3 with a catalyst dosage of 0.2 mg mL−1, which was comparable to those reported advanced EF cathodes. The appropriate reduction of Fe-contained minerals and carbonization of straw with N doping were attributed to the superior catalytic properties. Thus, the current study provides a feasible strategy to reuse Bauxite Residue and upgrade them into value-added electrode material.
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changes in distribution and microstructure of Bauxite Residue aggregates following amendments addition
Journal of Environmental Sciences-china, 2019Co-Authors: Shengguo Xue, Jun Jiang, Feng Zhu, Qiongli Wang, William HartleyAbstract:Abstract Bauxite Residue is a highly alkaline byproduct which is routinely discarded at Residue disposal areas. Improving soil formation process to revegetate the special degraded lands is a promising strategy for sustainable management of the refining industry. A laboratory incubation experiment was used to evaluate the effects of gypsum and vermicompost on stable aggregate formation of Bauxite Residue. Aggregate size distribution was quantified by fractal theory, whilst Residue microstructure was determined by scanning electron microscopy and synchrotron-based X-ray micro-computed tomography. Amendments addition increased the content of macro-aggregates (> 250 μm) and enhanced aggregate stability of Bauxite Residue. Following gypsum and vermicompost addition, fractal dimension decreased from 2.84 to 2.77, which indicated a more homogeneous distribution of aggregate particles. Images from scanning electron microscopy and three-dimensional microstructure demonstrated that amendments stimulate the formation of improved structure in Residue aggregates. Pore parameters including porosity, pore throat surface area, path length, and path tortuosity increased under amendment additions. Changes in aggregate size distribution and microstructure of Bauxite Residue indicated that additions of gypsum and vermicompost were beneficial to physical condition of Bauxite Residue which may enhance the ease of vegetation.
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phosphogypsum stabilization of Bauxite Residue conversion of its alkaline characteristics
Journal of Environmental Sciences-china, 2019Co-Authors: Shengguo Xue, Graeme J Millar, Chuxuan Li, Jun Jiang, Meng Li, Xiangfeng KongAbstract:Abstract Reduction of the high alkalinity of Bauxite Residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the Bauxite Residue. Under optimal water washing conditions (liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during phosphogypsum application were investigated. Phosphogypsum addition effectively lowered pH levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+ and Ca2 + in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca2 + became the dominant element in the solid phase (phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that phosphogypsum could promote the formation of stable macro-aggregates, whilst the content of Ca2 + increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions. This research provided a feasible method to promote soil formation of Bauxite Residue by phosphogypsum amendment.
Dimitrios Panias - One of the best experts on this subject based on the ideXlab platform.
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Optimization of Microwave Reductive Roasting Process of Bauxite Residue
Metals, 2020Co-Authors: Chiara Cardenia, Efthimios Balomenos, Dimitrios PaniasAbstract:In this study, microwave-assisted heating is presented as a suitable method to transform the hematite and goethite contained in Bauxite Residue into magnetite, wüstite, and metallic iron, with a short processing time. The final target was the production of a sinter with strong magnetic properties, allowing the magnetic separation of Fe from the Residue. The influence of microwave energy on the sample, the effect of irradiation time, and the carbon/Bauxite Residue mass ratio (C/BR) were the parameters that have been analyzed to optimize the process. Their optimized combination allowed transforming 79% of the iron present in the sinter into metallic iron. However, hercynite was also formed, and the presence of this mineralogical phase could be considered a possible drawback for its magnetic properties.
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Electrolytic iron production from alkaline Bauxite Residue slurries at low temperatures
Johnson Matthey Technology Review, 2020Co-Authors: Sevasti Koutsoupa, Stavroula Koutalidi, E. Bourbos, Efthymios Balomenos, Dimitrios PaniasAbstract:The primary iron metallurgy is characterized by significant direct CO2 emissions, due to the carbothermic reduction of the iron ore. This paper deals with the electrification of primary iron production by developing a new and innovative process for the carbon-free production of metallic iron from Bauxite Residue (BR) which is a by-product of the alumina industry. It is based on the electroreduction of iron oxides from BR suspensions in concentrated sodium hydroxide solutions, at low temperature and normal pressure. The iron oxide source, used in the present study is Bauxite Residue provided by Mytilineos S.A., Metallurgy Business Unit-Aluminium of Greece. The research study is a preliminary screening of BR as a potential raw material for iron production by performing experiments in a small-scale electrolysis cell. The first results presented here, show that iron can be produced by the reduction of iron oxides in the Bauxite Residue with high Faradaic efficiency (>70%). Although significant optimization is needed, the novel process shows great promise.
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Sintering Optimisation and Recovery of Aluminum and Sodium from Greek Bauxite Residue
Minerals, 2019Co-Authors: Pritii Wai Yin Tam, Dimitrios Panias, Vicky VassiliadouAbstract:Bauxite Residue is treated for the recovery of aluminum and sodium by sintering with the addition of soda, metallurgical coke and other reagents such as CaO, MgO and BaO. A thorough thermodynamic analysis using Factsage 7.0™ software was completed together with XRD mineralogy of sinters with different fluxes and reagents additions. Through both thermodynamic interpretation and mineralogical confirmations, it was observed that the type of desilication product in Bauxite Residue influences the total aluminum recovery through the sintering process and formation of sodium aluminum silicate exists in equilibrium with sodium aluminate, unless silica is consumed by additives (such as CaO, MgO, BaO etc.) forming other more thermodynamically favorable species and liberating alumina. Addition of barium oxide improves the aluminum and sodium recovery to 75% and 94% respectively. Complex sinter product formation that are triggered due to high calcium content in the Greek Bauxite Residue reduces aluminum recovery efficiency. Optimised and feasible recovery of aluminum and sodium for Greek Bauxite Residue was proved to be 70% and 85% respectively, when sintered with 50% excess stoichiometric soda. It was observed that stoichiometric carbon addition in inert atmosphere only assisted recovery up to 75% of aluminum and 83% of sodium, though there are benefits gained from pre-reducing iron from hematite for downstream recovery.
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A Study of the Occurrence of Selected Rare-Earth Elements in Neutralized–Leached Bauxite Residue and Comparison with Untreated Bauxite Residue
Journal of Sustainable Metallurgy, 2019Co-Authors: Rodolfo Marin Rivera, Koen Binnemans, Johannes Vind, Annelies Malfliet, Vicky Vassiliadou, Dimitrios Panias, Ghania Ounoughene, Tom Van GervenAbstract:This study investigates the chemical associations of the selected rare-earth elements (Sc, Y, Ce, La, and Nd) with major element phases in the postprocessed Bauxite Residues and compares them with the untreated Bauxite Residue. The treatment of Bauxite Residue considers our previous published process which involved the neutralization with CO_2, followed by leaching with H_2SO_4. Neutralized Bauxite Residue resulted with larger aggregates than the untreated Bauxite Residue after making contact with CO_2 as the consequence of additional CaCO_3 formation. Neutralization with CO_2, however, has a negligible effect on the distribution of the rare-earth elements (REEs) with respect to the untreated Bauxite Residue, but a large amount of rare earths remained unreacted after acid leaching. Electron probe microanalysis (EPMA) confirmed the chemical associations of Sc(III) and Ce(IV) with Fe(III)- and Al(III)-containing minerals in the postprocessed Bauxite Residues, i.e., Bauxite Residues subjected to CO_2-neutralization and neutralization–acid leaching processes. The occurrence of Nd(III) is positively correlated to that of La(III) in the untreated Bauxite Residue, but both of them may be associated with the same mineralogical phase as Ce(IV) after processing. Y(III) may remain associated with the Al/Si-minerals, cancrinite and chamosite. Ergo, the extractability of Sc, Y, Ce, La, and Nd from neutralized Bauxite Residue is more difficult in H_2SO_4 media due to the presence of coarser particles compared to those of the untreated Bauxite Residue, but also due to the formation of a solid product layer (i.e., CaSO_4) that is presumably adsorbed on the surface of Fe(III)-rich phases (hematite and goethite) and Al(III)-containing minerals (diaspore, gibbsite, boehmite, and chamosite).
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a study of the occurrence of selected rare earth elements in neutralized leached Bauxite Residue and comparison with untreated Bauxite Residue
Journal of Sustainable Metallurgy, 2019Co-Authors: Rodolfo Marin Rivera, Koen Binnemans, Johannes Vind, Annelies Malfliet, Vicky Vassiliadou, Dimitrios Panias, Ghania Ounoughene, Tom Van GervenAbstract:This study investigates the chemical associations of the selected rare-earth elements (Sc, Y, Ce, La, and Nd) with major element phases in the postprocessed Bauxite Residues and compares them with the untreated Bauxite Residue. The treatment of Bauxite Residue considers our previous published process which involved the neutralization with CO2, followed by leaching with H2SO4. Neutralized Bauxite Residue resulted with larger aggregates than the untreated Bauxite Residue after making contact with CO2 as the consequence of additional CaCO3 formation. Neutralization with CO2, however, has a negligible effect on the distribution of the rare-earth elements (REEs) with respect to the untreated Bauxite Residue, but a large amount of rare earths remained unreacted after acid leaching. Electron probe microanalysis (EPMA) confirmed the chemical associations of Sc(III) and Ce(IV) with Fe(III)- and Al(III)-containing minerals in the postprocessed Bauxite Residues, i.e., Bauxite Residues subjected to CO2-neutralization and neutralization–acid leaching processes. The occurrence of Nd(III) is positively correlated to that of La(III) in the untreated Bauxite Residue, but both of them may be associated with the same mineralogical phase as Ce(IV) after processing. Y(III) may remain associated with the Al/Si-minerals, cancrinite and chamosite. Ergo, the extractability of Sc, Y, Ce, La, and Nd from neutralized Bauxite Residue is more difficult in H2SO4 media due to the presence of coarser particles compared to those of the untreated Bauxite Residue, but also due to the formation of a solid product layer (i.e., CaSO4) that is presumably adsorbed on the surface of Fe(III)-rich phases (hematite and goethite) and Al(III)-containing minerals (diaspore, gibbsite, boehmite, and chamosite).
