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Yujun Wu

Bio: Yujun Wu is an academic researcher from Central South University. The author has contributed to research in topics: Bauxite & Alkalinity. The author has an hindex of 3, co-authored 6 publications receiving 86 citations.

Papers
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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: In this paper, the authors show that the extent of bauxite residue efflorescence is affected by many factors, including porosity, initial water content, and particle size.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the neutralization of bauxite residue following the application of biomass as an alkali modifier by natural fermentation, and found that the biomass fermentation was the main cause for the decrease in residue pH.
Abstract: Biomass fermentation has been proposed as a simple and economical strategy to alleviate the high alkalinity of bauxite residue. This study investigates the neutralization of bauxite residue following the application of biomass as an alkali modifier by natural fermentation. Fresh bauxite residue samples were collected from Pingguo refinery (Aluminum Corporation of China). Samples were treated with straw mulching (SC), straw mixing (SM), bagasse mulching (BC), and bagasse mixing (BM), respectively. Treatments were analyzed for pH, EC, metal cations, and soluble alkali (OH−, Al(OH)4− and CO32−). The mineral phase and Na speciation were analyzed by X-ray diffraction (XRD) and near-edge X-ray absorption fine structure (Na-XANES). Optimum application rate for either straw or bagasse was 20% (w/w), reducing leachate pH from 10.26 to 8.56. During biomass transformation, the alkaline mineral grossular was completely dissolved, while calcite and cancrinite were dissolved to a lesser degree. No treatment changed the spatial distribution of Na+, but the basic anions (OH−, CO32−, and Al(OH)4−) were significantly reduced. Following treatment application, soluble alkali in the residues was significantly reduced while the alkaline minerals were slightly dissolved. This was determined as the main cause for the decrease in residue pH.

9 citations

Journal ArticleDOI
TL;DR: 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 alkalination removal in bauxites residue.
Abstract: 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.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the dissolution of alkaline solids in bauxite residue (BR) and gypsum amendment, as well as their environmental behaviors, were determined through a 1-year simulated rainfall leaching experiment.

6 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the compressive strength of slag with D50 − 3.1μm activated by 4% Na2O-E of NS reached 36.2MPa and 77.3MPa at 28-d and 90-d age.

92 citations

Journal ArticleDOI
TL;DR: This review focuses on several typical processes for the management of bauxite residue alkalinity in recent decades around the world and describes the Bayer process in detail, where emphasis is put on the formation of alkaline substances in bauxites residue and its release process in long-term storage.

74 citations

Journal ArticleDOI
TL;DR: The results enhance the understanding of soil formation in bauxite residue and reveal the potential benefit of human intervention in ecological reconstruction at disposal areas.

66 citations

Journal ArticleDOI
TL;DR: In this article, a novel process employing natural biomass without addition of chemicals was proposed for remediation of red mud Hydrothermal carbonization (HTC) of local fallen leaves was conducted to obtain solution containing bio-acids (SBA) and hydrochar.

47 citations