Effective Desalination of Acid Mine Drainage Using an Advanced Oxidation Process: Sodium Ferrate (VI) Salt

Abstract

The screening and treatment of acid mine drainage (AMD) using Na2FeO4 was explored. Elemental composition was performed, using an Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) for the raw and treated AMD. The AMD samples were collected from three different sampling sites:(Raw Tailing Water 1 (RTW1), Raw Tailing Water 2 (RTW2) and Raw Tailing Water 3 (RTW3)) in Pretoria, South Africa, with acidic pH ranging between 2.50 and 3.13. Total dissolved solids and the electrical conductivity of AMD samples ranged between 960 and 1000 mg L−1, 226 and 263 µS. cm−1, respectively. The final pH of treated water samples increased up to ≥9.5 after treatment with sodium ferrate (VI) (Na2FeO4). Liquid Na2FeO4 was quantitatively produced through a wet oxidation method and was fully characterized, using Fourier Transform Infra-Red (FTIR), X-ray Diffraction spectroscopy (XRD) and UV-Vis instruments. Na2FeO4 showed dual functions by removing metals and raising the pH of the treated water. Concentrations of most trace elements did not comply with WHO and DWAF guideline standards in raw AMD while after treatment with Na2FeO4, the concentrations were below guidelines for domestic and irrigation purposes.