Comparison of several different neutralisations to a bauxite refinery residue: Potential effectiveness environmental ameliorants

Clark, Malcolm W.; Johnston, Max; Reichelt‐Brushett, Amanda

doi:10.1016/j.apgeochem.2015.01.015

Cited by 43 publications

(16 citation statements)

References 60 publications

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“…Following this CaSO4·2H2O (0.2 g) (2 %) was rapidly added to three samples treated with the three different acids, respectively (HGBR, SGBR, CGBR). The supernatant liquors were then shaken by hand and pH measured immediately by a calibrated pH probe [30]. Samples were then placed on a shaker operating at 120 rpm (25 o C).…”

Section: Field Sampling and Sample Preparationmentioning

confidence: 99%

“…Residual sodium hydroxide (NaOH), sodium aluminate (NaAl(OH)4) and sodium carbonate (Na2CO3) that can't be completely separated by counter-current decantation (CCD) water washing remain in the residue and are responsible for the soluble alkalinity. The leaching of alkaline ions (OH -, Al(OH)4 -, CO3 2-) provides some buffering capacity around pH 11 to 8.3 [29,30].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, with consumption of free OH -, Al(OH)4 -will precipitate as gibbsite (Al(OH)3) and possible dawsonite (Eqs. 11-13) [35,44,45]. Use of CO2 would also reduce the emission of industrial carbon dioxide, which could create an additional benefit.…”

Section: Introductionmentioning

confidence: 99%

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Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Kong

Xue

et al. 2017

Journal of Hazardous Materials

150

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Graphical abstractHighlights  Speciation and transformation of solid and soluble alkalinities were investigated. SEM, NEXAFS, and STXM were used to observe particle morphology and alkaline Na speciation and distribution. Gypsum combination promoted leaching of Na-bearing solids and the replacement of exchangeable Na. The use of organic citric acid to transform bauxite residue alkalinity.ABSTRACT: Bauxite residue (BR) is a highly alkaline solid hazardous waste produced from bauxite processing for alumina production. Alkaline transformation appears to reduce the environmental risk of bauxite residue disposal areas (BRDAs) whilst potentially providing opportunities for the sustainable reuse and on-going management of BR. Mineral acids, a novel citric acid and a hybrid combination of acid-gypsum treatments were investigated for their potential to reduce residue pH and total alkalinity and transform the alkaline mineral phase. XRD results revealed that with the exception of andradite, the primary alkaline solid phases of cancrinite, grossular and calcite were transformed into discriminative products based on the transformation used. Supernatants separated from BR and transformed bauxite residue (TBR) displayed distinct changes in soluble Na, Ca and Al, and a reduction in pH and total alkalinity. 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. NEXAFS analysis of Na K-edge revealed that the chemical speciation of Na in TBRs was consistent with BR.Three acid treatments and gypsum combination had no effect on Na speciation, which affects the distribution of Na revealed by sodium STXM imaging.

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Section: Field Sampling and Sample Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Kong

Xue

et al. 2017

Journal of Hazardous Materials

150

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“…However, these rapid developments have caused numerous environment issues (Clark et al 2015;Wu et al 2015) especially as China is the largest producer of alumina in the world (Si et al 2013;Liu et al 2014b). Bauxite residue (red mud) is an alkaline solid generated during the process of alumina production.…”

Section: Introductionmentioning

confidence: 99%

Proposal for management and alkalinity transformation of bauxite residue in China

Xue

Kong

Zhu

et al. 2016

Environ Sci Pollut Res

132

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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.

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“…Currently, research has focused on conversion of the high alkalinity of bauxite residue prior to disposal and as an amelioration technique for encouraging revegetation and further land development (Kong, Li, et al, ; Xue, Kong, et al, ). Seawater neutralization, waste acid dosing, gypsum amendment, and carbon dioxide sequestration are often used to ameliorate its alkalinity, but nevertheless, there still remains insufficient long‐term success as a result of economics and side effects (Clark, Johnston, & Reichelt‐Brushett, ; Couperthwaite, Johnstone, Millar, & Frost, ; Jones, Haynes, & Phillips, ; Kishida, Harato, Tokoro, & Owada, ; Rai et al, ; Sushil & Batra, ; Tuazon & Corder, ; Wong & Ho, ; Wong & Ho, ). Furthermore, such methods have only concentrated on artificial amelioration of alkaline substances with less attention being given to natural development of alkalinity and its occurrence on BRDAs.…”

Section: Introductionmentioning

confidence: 99%

Development of alkaline electrochemical characteristics demonstrates soil formation in bauxite residue undergoing natural rehabilitation

et al. 2017

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Mining and mineral processing industries have generated a large amount of polymineral wastes, causing the destruction and degradation of huge areas of landscapes at extensive geographical locations. Rehabilitation of these mine waste landscapes is critical to social and economic sustainability of mining and metallurgy operations, such as alumina refineries. The Bayer process to refine alumina generates large amounts of highly alkaline bauxite residues that are hazardous to plant growth. Innovative methodologies are urgently needed to address this economic and environmental challenges, one of which is soil formation from bauxite residues. Mineral weathering appears the prerequisite to the initiation of soil formation and development of functional soil properties in bauxite residue disposal areas. The present study investigated natural changes of mineralogy, zeta potential, isoelectric point, surface protonation, active alkaline groups, and associated implications for rehabilitation of the bauxite residue disposal area. Alkaline calcite, hydrogarnet, and sodalite minerals were slowly transformed or dissolved with declining levels over weathering time. Amorphous and semiamorphous minerals also decreased with a corresponding decrease in specific surface area and sorption sites. Zeta potential curve of fresh residue had steeper slope than those of aged residues. The isoelectric point of fresh residue was significantly higher, but those of aged residues were significantly lower, with a significant decrease of isoelectric point with increasing time. These attributes in mineralogy and electrochemical characteristics such as transformation of alkaline minerals, and decreases of surface protonation and active alkaline groups, may be used to help the assessment of soil formation status in the bauxite residues of different age and associated rehabilitation requirements.

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Comparison of several different neutralisations to a bauxite refinery residue: Potential effectiveness environmental ameliorants

Cited by 43 publications

References 60 publications

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Proposal for management and alkalinity transformation of bauxite residue in China

Development of alkaline electrochemical characteristics demonstrates soil formation in bauxite residue undergoing natural rehabilitation

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