Characterization and reusability suggestions of the sludge generated from a synthetic acid mine drainage treatment using sodium ferrate (VI)

Alexis Munyengabe; Caliphs Zvinowanda; John Ngoni Zvimba; James Ramontja

doi:10.1016/j.heliyon.2020.e05244

Characterization and reusability suggestions of the sludge generated from a synthetic acid mine drainage treatment using sodium ferrate (VI)

Heliyon. 2020 Oct 13;6(10):e05244. doi: 10.1016/j.heliyon.2020.e05244. eCollection 2020 Oct.

Authors

Alexis Munyengabe¹, Caliphs Zvinowanda¹, John Ngoni Zvimba², James Ramontja¹

Affiliations

¹ Department of Chemical Sciences, Faculty of Science, Doornfontein Campus, University of Johannesburg, Corner Beit and Nind Streets, P.O. Box: 17011, Johannesburg, 2028, South Africa.
² Water Use and Waste Management, Water Research Commission, Bloukrans Building, Lynnwood Bridge Office Park, 4 Daventry Street, Lynnwood Manor, South Africa.

Abstract

Mining activities are the main cause of generation of the voluminous sludge waste, loaded with metals precipitated from the treatment of acid mine drainage (AMD) and this is always disposed to the landfill. This study aimed at characterizing and suggesting the reusability potential of AMD sludge to reduce the environmental problem caused by its accumulation so that it could become a valuable material. The sludge was obtained after treating a synthetic AMD with a green oxidant sodium ferrate (VI) (Na₂FeO₄) that was prepared by a wet oxidation method. Chemical and physical characterization of a dried sludge generated after treatment was then performed using the Fourier Transform-Infrared and X-Ray powder Diffraction spectroscopy. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy also served to identify the surface morphology of the sludge. The sludge presented a high weight percentage of Fe and O and lower concentrations of other metals such as Al, Mn, Si, and Na. Nitrogen adsorption/desorption isotherms or Brunauer-Emmett-Teller (BET) was used to assess the surface area, pore volume and diameter of the sludge. The BET results showed that the surface area of the sludge obtained after treating the synthetic AMD using Na₂FeO₄ was 31.50 ± 0.03 m²/g with pore diameter and volume of 52.50 nm and 0.41 cm³/g, respectively. However, the produced sludge could serve as an adsorbent to remove pollutants from water or to synthesize different magnetic nanocomposites due to its high surface area (>natural zeolite) and high composition of Fe and O.

Keywords: Characterization; Chemistry; Earth sciences; Engineering; Environmental science; Materials science; Reusability suggestions; Sodium ferrate (VI); Synthetic AMD.