Pre-treatment of Coal Dump Leachate With MgO For Pigment Recovery
Letjiane, Leny (1,3); Maree, Johannes Philippus (2,3); Onyango, Maurice (1); Adeniyi, Amos (1)
1: Tshwane University of Technology; 2: University of Limpopo,; 3: ROC Water Technologies
Mine water rich in metals requires sustainable and cost effective treatment that leads to recovery of resources. Consequently, this investigation was aimed at identifying a process for recovering clean water and saleable products such as pigments from iron-rich acid mine water. For this, MgO was used to remove iron as Fe(OH)3, which was converted through drying at 80°C to goethite (yellow) and at 700°C to haematite (red). Na2CO3 was used for removal of the remaining metals (Mn2+ and Ca2+) as carbonates. The pre-treated water is desalinated with RO to produce a permeate (TDS = 105 mg/L) and a brine of 85 069 mg/L. The brine is further concentrated by freeze crystallization up to a TDS of 336 820 mg/L. This is concentrated enough for the recovery of MgSO4.7H2O.