Journal article
The long-term stability of a metal-laden BauxsolTM reagent under different geochemical conditions
Geochemistry: Exploration, Environment, Analysis, Vol.9, pp.101-112
2009
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Abstract
<p><p id="x-x-x-x-p-1">Although Bauxsol™ technology is gaining acceptance for treatment of acid rock drainage and industrial effluents, most leaching studies of spent reagent have used material that has been stored in well-oxygenated conditions for no more than a few weeks. Consequently, few long-term stability data are available to predict potential metal release under various geochemical conditions. This study investigates the simulated aging of a metal-laden Bauxsol™ reagent under oxic, anoxic and anoxic-reducing conditions. Long-term stability under oxic conditions was simulated by sealing samples in 50 ml centrifuge tubes with a small quantity of water (to facilitate metal transfer and mineral recrystallization reactions), and allowing the contents to age at 65°C over about 3 months. Anoxic conditions were maintained for 6 months in 200-l drums of seawater, using nitrogen to displace any dissolved oxygen; Eh remained between +50 and +100 mV and dissolved oxygen was maintained at2S; the dissolved oxygen content remained0.3 mg/l and the water Eh less than −350 mV. <p id="x-x-x-x-p-2">The proportion of most metals extractable with pH 2.88 buffered acetic acid extractant (used to indicate relative leachability) decreased by between 25 and >75% during aging under all tested conditions (i.e. the longer the samples were left, the less metal could be extracted) although minor short-term (2–4 weeks) increases in metal mobility were detected with anoxic and anoxic-reducing samples. The data show that metals bound by Bauxsol™ reagents become increasingly resistant to leaching over time. The precipitation of insoluble sulphides, low solubility carbonates, hydroxycarbonates or hydroxysulphates, and solid-state diffusion process may explain the observed decreases. A measured increase of <em>c.</em> 16% in the mean volume of hematite crystallites over 3 months in oxic conditions also admits the possibility that metals may be incorporated as impurities in growing oxide and oxyhydroxide crystals.</p>
Details
- Title
- The long-term stability of a metal-laden BauxsolTM reagent under different geochemical conditions
- Creators
- Malcolm W Clark - Southern Cross UniversityJ BerryD McConchie - Southern Cross University
- Publication Details
- Geochemistry: Exploration, Environment, Analysis, Vol.9, pp.101-112
- Identifiers
- 3338; 991012821862402368
- Academic Unit
- School of Environment, Science and Engineering; Faculty of Science and Engineering
- Resource Type
- Journal article