Research Articles

Synthesis of zeolite-P from coal fly ash derivative and its utilisation in mine-water remediation

Viswanath R.K. Vadapalli, Wilson M. Gitari, Annabelle Ellendt, Leslie F. Petrik, Gillian Balfour
South African Journal of Science | Vol 106, No 5/6 | a231 | DOI: https://doi.org/10.4102/sajs.v106i5/6.231 | © 2010 Viswanath R.K. Vadapalli, Wilson M. Gitari, Annabelle Ellendt, Leslie F. Petrik, Gillian Balfour | This work is licensed under CC Attribution 4.0
Submitted: 19 April 2010 | Published: 09 June 2010

About the author(s)

Viswanath R.K. Vadapalli, Department of Chemistry, University of the Western Cape, South Africa
Wilson M. Gitari, Department of Ecology and Resources Management, University of Venda, South Africa
Annabelle Ellendt, Environmental and Nano Sciences Group, Department of Chemistry, University of the Western Cape, South Africa
Leslie F. Petrik, Environmental and Nano Sciences Group, Department of Chemistry, University of the Western Cape, South Africa
Gillian Balfour, Environmental and Nano Sciences Group, Department of Chemistry, University of the Western Cape, South Africa


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Abstract

Solid residues resulting from the active treatment of acid mine drainage with coal fly ash were successfully converted to zeolite-P under mild hydrothermal treatment conditions. Scanning electron microscopy showed that the zeolite-P product was highly crystalline. The product had a high cation exchange capacity (178.7 meq / 100 g) and surface area (69.1 m2/g) and has potential application in waste-water treatment. A mineralogical analysis of the final product identified zeolite-P, as well as mullite and quartz phases, which indicated incomplete dissolution of the fly ash feedstock during the ageing step. Further optimisation of the synthesis conditions would be required to attain complete utilisation of the feedstock. The zeolite-P was tested for decontamination potential of circumneutral mine water. High removal efficiency was observed in the first treatment, but varied for different contaminants. The synthesised zeolite-P exhibited a high efficiency for the removal of heavy metal cations, such as aluminium, iron, manganese, zinc, copper and nickel, from contaminated mine water, even with repeated use. For potassium, calcium, strontium and barium, the removal was only efficient in the first treatment and decreased rapidly with subsequent treatments, indicating preferential adsorption of the other metals. A continuous release of sodium was observed during decontamination experiments, which decreased with subsequent treatments, confirming that sodium was the main exchangeable charge-balancing cation present in the zeolite-P product.

Keywords

acid mine drainage; circumneutral mine waters; fly ash; low temperature synthesis; solid residues; zeolite-P

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