Acid mine drainage is generated when mining activities expose sulphidic rock to water and oxygen leading to generation of sulphuric acid effluents rich in Fe, Al, SO 4 and Mn with minor concentrations of Zn, Cu, Mg, Ca, Pb depending on the geology of the rock hosting the minerals. These effluents must be collected and treated before release into surface water bodies. Mining companies are in constant search for cheaper, effective and efficient mine water treatment technologies. This study assessed the potential of applying magnesite as an initial remediation step in an integrated acid mine drainage (AMD) management system. Neutralization and metal attenuation was evaluated using batch laboratory experiments and simulations using geochemical modelling. Contact of AMD with cryptocrystalline magnesite for 60 min at 1 g: 100 mℓ S/L ratio led to an increase in pH, and a significant increase in metals attenuation. Sulphate concentration was reduced to ≈1 910 mg/ℓ. PH redox equilibrium (in C language) (PHREEQC) geochemical modelling results showed that metals precipitated out of solution to form complex mineral phases of oxy-hydroxysulphates, hydroxides, gypsum and dolomite. The results of this study showed that magnesite has potential to neutralize AMD, leading to the reduction of sulphate and precipitation of metals.
This study evaluated the feasibility of integrating amorphous magnesite and bentonite clay (composite) as an alternative technology for removing arsenic from industrial effluents. The removal of arsenic from industrial effluents by using magnesiteÀbentonite clay composite was carried out in batch mode. The effects of equilibration time, adsorbent dosage, adsorbate concentration, and pH on removal of arsenic were investigated. The experiments demonstrated that %100% arsenic removal is optimum at 30 minutes of agitation, 2 g of adsorbent dosage (2 g: 100 mL, S/L ratio), and 20 mg L ¡1 of arsenic concentration. The adsorption data fitted well to both Langmuir and Freundlich adsorption models, hence proving monolayer and multilayer adsorption. The kinetic studies revealed that the data fitted better to a pseudo-second-order reaction than to a pseudo-first-order reaction, hence proving chemisorption. At optimized conditions, the composite was able to remove arsenic to below World Health Organization water quality guidelines, hence depicting that the composite is effective and efficient in removing arsenic from contaminated water. Based on that, this comparative study proves that the composite is a promising adsorbent with high adsorption capacity for arsenic and can be a suitable substitute for the conventional treatment methods.
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