Hydrotalcite formation for contaminant removal from mining wastewaters

Douglas, G., Wendling, L. and Pleysier, R. (2009). Hydrotalcite formation for contaminant removal from mining wastewaters. In: Proceedings, International Mine Water Conference 2009. International Mine Water Conference 2009, Pretoria, South Africa, (407-414). 19-23 October 2009.

Author Douglas, G.
Wendling, L.
Pleysier, R.
Title of paper Hydrotalcite formation for contaminant removal from mining wastewaters
Conference name International Mine Water Conference 2009
Conference location Pretoria, South Africa
Conference dates 19-23 October 2009
Proceedings title Proceedings, International Mine Water Conference 2009
Place of Publication Pretoria, South Africa
Publisher International Mine Water Association (IMWA)
Publication Year 2009
Sub-type Fully published paper
ISBN 9780980262353
Start page 407
End page 414
Total pages 8
Language eng
Formatted Abstract/Summary
Hydrotalcites are a class of Mg-Al layered double hydroxide minerals with the ideal 3:1 Mg:Al endmember chemical composition Mg6Al2(A)(OH)16.n(H2O) (A = CO3 2-, SO4 2-, Cl-, etc). Hydrotalcites may occur naturally and are a common
secondary mineral formed in soils during natural attenuation of acidic, metal-laden contaminated sites. Many acidic
wastewaters generated during mineral processing often contain either Mg and/or Al in sufficient abundance that the
potential exists for hydrotalcite formation providing there is addition of alkali to achieve a pH >5 and Mg and/or Al to attain a Mg:Al ratio between 2:1 and 3:1. Some Fe, typically present in acidic wastewaters, may also be accommodated within the hydrotalcite structure. Advantageously, hydrotalcites form rapidly and readily dewater. The utility of hydrotalcites, which could be precipitated as part of managing mine wastewaters, lies in their ability to incorporate a wide range of cationic (Cu2+, Ni2+, UO22+), metalloid (SeO42-, AsO4 3-), and (oxy)anionic contaminants (CrO4 2-, MnO4-). Silication to form a chlorite-like phase or calcination to form a spinel-like phase may increase precipitate stability prior to disposal. CSIRO has investigated the treatment of a variety of acidic wastewaters which has resulted in the patenting of processes for both in-situ formation of hydrotalcites as a potential closure strategy for solution mining, and for the treatment of natural and acidic mining wastewaters. The broad spectrum removal of contaminants, including U which is often present as a variety of geochemical species, also lends hydrotalcites and their derivatives to use as a potential containment material in nuclear waste repositories. In this study, Ranger Mine process water, an acidic, Mg-SO4 brine derived from the leaching of U ore from chloritic schist, was treated with Na-aluminate (NaAl(OH)4) sourced from a commercial Bayer Process liquor, in combination with NaOH or Ca(OH)2. Detailed analyses of precipitates formed during neutralisation of the process water confirm the presence of hydrotalcites as the primary mineral with the abilityto simultaneously remove a suite of  contaminants from solution during precipitation.
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Conference Paper
Collection: School of Agriculture and Food Sciences
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Created: Tue, 04 Feb 2014, 14:46:29 EST by Laura Wendling on behalf of School of Agriculture and Food Sciences