Proposal for management and alkalinity transformation of bauxite residue in China

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.

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

“…The volume of bauxite residue generated per ton of alumina product is approximately 0.5-2 tons [3][4][5]. Raising demand for alumina worldwide has increased the rate of bauxite residue production.…”

Influence of natural regeneration on fractal features of residue microaggregates in bauxite residue disposal areas

“…In the aluminium industry, bauxite residue is an alkaline solid by‐product generated when alumina is extracted from bauxite ore by the Bayer process (Goloran, Phillips, & Chen, ; Kong, Guo et al, ). The global inventory has reached 3.4 billion tons, with an annual increase of 120 million tons (Kong, Li et al, ; Xue, Kong, et al, ). Large volumes of bauxite residue are deposited in bauxite residue disposal areas, which cause potential environmental risks, as these bare areas are sensitive to erosion by wind and water, and can be regarded as a potential source of contamination due to their high alkalinity and salinity (Gelencsér et al, ; Ruyters et al, ).…”

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

“…The management of bauxite residue is a seriously challenging waste problem that is a major concern to alumina refineries. Globally, there is no economic alternative to landfill, therefore almost all bauxite residue continues to be stored indefinitely in land‐based bauxite residue disposal areas (BRDAs; Burke et al, ; Xue, Kong, et al, ; Zhu, Liao, et al, ). The liabilities and environmental risks including freshly formed alkaline dust and efflorescence, leaching of caustic liquor, trace metal, and remediation costs (Buckley, Curtin, & Courtney, ; Higgins, Curtin, & Courtney, ; Higgins, Curtin, Pawlett, & Courtney, ; Liu, Chen, Li, Yu, & Yan, ; Samal, Ray, & Bandopadhyay, ; Santini & Banning, ; Xue, Zhu et al, ) have all afforded incentives to find selectable management and appropriate rehabilitation options.…”

“…These are fine grain sized and structurally complex combined with high sodicity and soluble alkalinity. Furthermore, Ca minerals are commonly produced during caustic regeneration with calcium hydroxide precipitating carbonate alkalinity (Pan et al, ; Xue, Kong, et al, ). Subsequently, these minerals appear as alkaline minerals in bauxite residue.…”

“…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, ).…”