Treatment of mine water for iron (II) oxidation.
Mohajane, Goodwill Boitumelo
Mohajane, Goodwill Boitumelo
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Abstract
The treatment of acid mine water is relatively expensive due to the prohibitive costs of lime, scaling, long iron (II) residence time and energy costs for the aeration system. The aim of this study was to investigate the most cost-effective iron (II) oxidation in the treatment of acid mine water. The oxidation investigated using hydrogen peroxide/vacuum in an open and closed reactors, limestone OPeN system, ultrasound and pressurised oxygen/limestone reactor respectively. It was found that 1:1 of hydrogen peroxide to iron (II) was sufficient to precipitate Fe (OH)3(s) for both open and vacuum systems.
Total acidity was removed completely from both coal and gold acidic mine water containing 177 to 5 700 mg/L iron (II), while sludge scaling was prevented. The rate of iron (II) oxidation was found to be four times faster with the application of ultrasound when compared to limestone addition with stirring. The pipe reactor batch studies showed that the rate of Fe (II) oxidation depended on the iron (II) concentration, oxygen pressure, amount of recycled sludge, limestone dosage and the mixing rate. It was concluded that the OPeN system can address the major disadvantage of the high-density sludge process. Ultrasound and hydrogen peroxide were found to shorten the residence time for iron (II) oxidation.
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Submitted in partial fulfilment of the requirements for the degree, Magister Technologiae: Water care in the Department of Environmental, Water and Earth Sciences, Faculty of Science at the Tshwane University of Technology.
Date
2017-10-01
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Tshwane University of Technology
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Keywords
Oxidation, Mine water, Iron, Ultrasound, Limestone