Presented paper

IMWA2019 Students work

Cavitation of Acid Mine Drainage-Magnesite Mixtures: A Promising Acid Mine Drainage Treatment Technology

Gitari, WilsonMugera; Novela, Rirhandzu J; Ayinde, Wasiu B
University of Venda, South Africa

Acid mine drainage (AMD) is an acidic effluent resulting from exposure of sulphidic rock to oxygen and water during mining operations. These effluents are strongly acidic and are often characterize by high concentrations metals ions such as Fe, Mn, Al and SO42- among others. Acid mine drainage has the potential to contaminate ground and surface water resources and other aquatic ecosystems. These effluents require treatment to prescribed standards before discharge into natural water courses. The aim of this work was to evaluate the potential of cavitation of acid mine drainage-magnesite mixtures as an emerging innovative treatment tool. Cavitation of the AMD-magnesite mixtures was induced using a sonotrode and the chemical species removal, and neutralization potential of the magnesite evaluated. This was process was repeated using the conventional agitation by a magnetic stirrer. Several operational parameters were optimized, these include pH, reaction time, magnesite dosage and chemical species removal. pH, EC, TDS and chemical species attenuation recorded over time. XRF and SEM were utilized in characterization of the raw and reacted magnesite. SEM showed new morphologies indicating formation of new mineral phases while XRF results indicated increased concentration of Fe, S, Al and Mn in residues indicating formation of Fe, S, Al and Mn bearing mineral phases and deposition on unreacted magnesite grains. Contact of magnesite with AMD at S/L of 1g/100 mL for 60 mins of conventional agitation led to decrease in EC and increase in pH to 9.4. Al, Mn, Fe and Zn were removed to levels > 99% while SO42- were removed to levels ≥ 50 %. Cavitation treatment of the same AMD-magnesite mixtures for 60 mins led to an increase in pH to 8.6 and sulphate removal ≥ 60%. Cavitation treatment was observed to induce fast kinetics, final alkaline pH was attained in a shorter time than conventional shaking and was also superior interms of sulphate removal. Cavitation treatment was observed to introduce superior mechanistic aspects that enhanced sulphate removal and can be enhanced through selective seeding with various salts to enhance sequential chemical species removal and recovery of beneficial salt products