title: Treatment of iron(II)-rich acid mine water with limestone and oxygen.
abstract: The main components of acid mine water are free acid, sulphate, and Fe²⁺. Limestone is the most cost-effective alkali that can be used for neutralization. The purpose of this investigation was to identify conditions where Fe²⁺ is removed with limestone and simultaneously oxidized with oxygen to Fe³⁺, in a polyvinyl chloride pipe under pressure. Gypsum scaling is prevented by passing rubber balls through the pipe of the so-called Oxygen-Pipe-Neutralization (OPeN) process pilot plant. Two synthetic waters were treated: (A) acid mine water containing 123 mg L⁻¹ Fe²⁺ representing gold mine water, and (B) acid mine water containing 6,032 mg L⁻¹ Fe²⁺ representing coal mine water. Batch studies were carried out in a pipe reactor and showed that the rate of Fe²⁺ oxidation depended on the Fe²⁺ concentration, oxygen pressure, amount of recycled sludge, limestone dosage and the mixing rate. Continuous studies in an OPeN process pilot plant resulted in 100% removal of total acidity from synthetic coal mine water and a 98% removal from synthetic gold mine water. Fe²⁺ was removed completely as precipitated Fe(OH)₃ from both synthetic coal and gold mine water at around pH 7 at 200 and 100 kPa oxygen pressure, respectively.
authors: Department of Environmental, Water and Earth Sciences, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa E-mail: boitumelogbmohajane@gmail.com.
authors: G B
authors: GB
authors: Mohajane
authors: Department of Environmental, Water and Earth Sciences, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa E-mail: boitumelogbmohajane@gmail.com.
authors: J P
authors: JP
authors: Maree
authors: Department of Chemistry, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa.
authors: N
authors: N
authors: Panichev
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D008906:Mining; D010100:Oxygen / Q000737:chemistry*; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D002119:Calcium Carbonate; D007220:Industrial Waste; D007501:Iron; D010100:Oxygen; D062065:Wastewater; D014874:Water Pollutants, Chemical