Reducing the leachability of iron-arsenic speiss using modified alumina refinery residue

Reducing the leachability of iron-arsenic speiss using modified alumina refinery residue

This study investigates whether the addition of chemical
reagents derived from alumina refinery residue, a solid
waste byproduct generated when extracting alumina from
bauxite, can reduce the leachability of metals and metalloids from iron-arsenic speiss, a lead smelting solid waste byproduct. Due to its high concentrations in iron-arsenic speiss, a primary focus of this study was on arsenic, although other metals such as lead and antimony were also investigated. The research particularly sought to investigate whether alumina refinery residue could reduce leachable arsenic to Australian disposal limits for a low level contaminated waste solid; leachability was determined by using the Toxicity Characteristic Leaching Procedure as the extracting mechanism.

Findings indicate that some forms of modified alumina refinery residues reduce the leachability of arsenic by greater than 99.9% (for example from 235 mg/L to 0.17 mg/L) allowing the treated speiss to be legally disposed to landfill, but when combined with oxidation and acidification these percentages dropped to an average of 87%, with reductions in leachable arsenic from 235 mg/L to an average of 30 mg/L.

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