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Xiaofei Li

Bio: Xiaofei Li is an academic researcher from Central South University. The author has contributed to research in topics: Bauxite & Alkalinity. The author has an hindex of 5, co-authored 7 publications receiving 342 citations.

Papers
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Journal ArticleDOI
TL;DR: Future research should focus on transformation chemistry and its associated mechanisms and for the development of a clear and economic process to reduce alkalinity and soda in bauxite residue.
Abstract: Bauxite residue is a hazardous solid waste produced during the production of alumina. Its high alkalinity is a potential threat to the environment which may disrupt the surrounding ecological balance of its disposal areas. China is one of the major global producers of alumina and bauxite residue, but differences in alkalinity and associated chemistry exist between residues from China and those from other countries. A detailed understanding of the chemistry of bauxite residue remains the key to improving its management, both in terms of minimizing environmental impacts and reducing its alkaline properties. The nature of bauxite residue and the chemistry required for its transformation are still poorly understood. This review focuses on various transformation processes generated from the Bayer process, sintering process, and combined Bayer-sintering process in China. Problems associated with transformation mechanisms, technical methods, and relative merits of these technologies are reviewed, while current knowledge gaps and research priorities are recommended. Future research should focus on transformation chemistry and its associated mechanisms and for the development of a clear and economic process to reduce alkalinity and soda in bauxite residue.

120 citations

Journal ArticleDOI
TL;DR: SEM images suggest that mineral acid transformations promote macro-aggregate formation, and the positive promotion of citric acid, confirming the removal or reduction in soluble and exchangeable Na.

120 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on the origin and transformation of alkalinity in bauxite residues using typical industrial waste and propose key research directions with an emphasis on alkaline regulation by industrial waste, whilst also providing a scientific reference point for their potential use as amendments to enhance soil formation and establish vegetation on Bauxite residue disposal areas.
Abstract: Bauxite residue is a highly alkaline material generated from the production of alumina in which bauxite is dissolved in caustic soda. Approximately 4.4 billion tons of bauxite residues are either stockpiled or landfilled, creating environmental risks either from the generation of dust or migration of filtrates. High alkalinity is the critical factor restricting complete utilization of bauxite residues, whilst the application of alkaline regulation agents is costly and difficult to apply widely. For now, current industrial wastes, such as waste acid, ammonia nitrogen wastewater, waste gypsum and biomass, have become major problems restricting the development of the social economy. Regulation of bauxite residues alkalinity by industrial waste was proposed to achieve ‘waste control by waste’ with good economic and ecological benefits. This review will focus on the origin and transformation of alkalinity in bauxite residues using typical industrial waste. It will propose key research directions with an emphasis on alkaline regulation by industrial waste, whilst also providing a scientific reference point for their potential use as amendments to enhance soil formation and establish vegetation on bauxite residue disposal areas (BRDAs) following large-scale disposal.

103 citations

Journal ArticleDOI
TL;DR: Climate, stacking time, and biological factors appear to improve the structure of bauxite residue, and natural processes decreased pH, electrical conductivity, and exchangeable sodium percentage, while exchangeable Ca and Mg were significantly beneficial to aggregation of water-stable aggregates.
Abstract: Bauxite residue often has chemical and physical limitations to support plant growth, and improving its matrix properties is crucial to support sustainable vegetation in the long term. Spontaneous vegetation colonization on deposits in Central China, over a period of 20 years, has revealed that natural weathering processes may convert bauxite residue to a soil-like medium. Residue samples from different stacking ages were collected to determine the effect of natural processes on matrix properties over time. It was demonstrated that natural processes decreased pH (10.98 to 9.45), electrical conductivity (EC) (3.73 to 0.36 mS/cm), and exchangeable sodium percentage (ESP) (72.51 to 28.99 %), while increasing bulk density (1.91 to 1.39 g/cm(3)), improving the mean weight diameter (MWD) of water-stable aggregates (0.24 to 0.52 mm), and the proportion of >0.25-mm water-stable aggregates (19.91 to 50.73 %). The accumulation of organic carbon and the reduction of ESP and exchangeable Na had positive effects on soil aggregate formation, while exchangeable Ca and Mg were significantly beneficial to aggregation of water-stable aggregates. Climate, stacking time, and biological factors appear to improve the structure of bauxite residue. Our findings demonstrate soil genesis occurring following natural weathering processes of bauxite residues over time.

79 citations

Journal ArticleDOI
TL;DR: It was concluded that natural processes of regeneration, stabilization, and attenuation have improved the hostile physical environment of bauxite residue allowing plant establishment to take place.
Abstract: Freshly stacked bauxite residue in Central China has little vegetative growth probably as a result of its poor physical condition and chemical properties which deter plant establishment. Over the last 20 years, spontaneous plant colonization on the deposits has revealed that natural weathering processes may improve bauxite residue to the extent that it can support vegetation. Bauxite residue samples were collected from a chronosequence and analyzed to determine the effect of natural processes over time. The freshly stacked residue showed considerable physical degradation, having a high bulk density, low porosity, and poor aggregate stability. Through natural processes over a 20-year period, the texture changed from a silty loam to a sandy loam, porosity was enhanced (43.88 to 58.24 %), while improvements in both aggregate stability (43.32 to 93.20 %) and structural stability (1.33 to 5.46 %) of the stacked residue were observed. Plant growth had a positive effect on pH, exchangeable sodium percentage, soil organic carbon, water-stable aggregation, and structural stability, probably due to the presence of plant roots and associated microbial activity. It was concluded that natural processes of regeneration, stabilization, and attenuation have improved the hostile physical environment of bauxite residue allowing plant establishment to take place.

41 citations


Cited by
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Journal ArticleDOI
Yuancheng Li1, Xiaobo Min1, Yong Ke1, Degang Liu1, Chong-Jian Tang1 
TL;DR: This study demonstrated that RGM may be utilized in cement composites and showed that the RGM had long-term stability and the characteristics satisfied the requirements of MU10 fly ash bricks.

195 citations

Journal ArticleDOI
TL;DR: Overall red mud amendment is likely to contribute to lowering the PTE availability in contaminated soil, suggesting the toxicity from PTEs was reduced by red mud, as well as indirect effects due to changes in soil properties.

167 citations

Journal ArticleDOI
TL;DR: Future research should focus on transformation chemistry and its associated mechanisms and for the development of a clear and economic process to reduce alkalinity and soda in bauxite residue.
Abstract: Bauxite residue is a hazardous solid waste produced during the production of alumina. Its high alkalinity is a potential threat to the environment which may disrupt the surrounding ecological balance of its disposal areas. China is one of the major global producers of alumina and bauxite residue, but differences in alkalinity and associated chemistry exist between residues from China and those from other countries. A detailed understanding of the chemistry of bauxite residue remains the key to improving its management, both in terms of minimizing environmental impacts and reducing its alkaline properties. The nature of bauxite residue and the chemistry required for its transformation are still poorly understood. This review focuses on various transformation processes generated from the Bayer process, sintering process, and combined Bayer-sintering process in China. Problems associated with transformation mechanisms, technical methods, and relative merits of these technologies are reviewed, while current knowledge gaps and research priorities are recommended. Future research should focus on transformation chemistry and its associated mechanisms and for the development of a clear and economic process to reduce alkalinity and soda in bauxite residue.

120 citations

Journal ArticleDOI
TL;DR: SEM images suggest that mineral acid transformations promote macro-aggregate formation, and the positive promotion of citric acid, confirming the removal or reduction in soluble and exchangeable Na.

120 citations

Journal ArticleDOI
TL;DR: In this paper, the acid neutralizing capacity of bauxite residue was investigated by incubation with hydrochloric acid and batch neutralization experiments, which revealed a characteristic buffering behavior that could be controlled by its alkaline components.

112 citations