Treatment of acid-alkali mixed mine wastewater with oxidation process

Acid mine drainage(AMD) in a copper mine is characterized as low pH and high concentrations of metal ions such as Fe3+,Fe2+ and Cu2+,while flotation wastewater often contains amounts of residual flotation reagents,which lead to high COD(chemical oxygen demand) value.AMD and flotation wastewater were firstly pre-mixed at a ratio of 1∶1 and then were treated by use of NaClO,O3 and Fe2+/H2O2 oxidation techniques respectively.The experimental results indicate that H2O2 as the oxidants is feasible and effective for the treatment of the mixed wastewater,while NaClO and O3 oxidation exhibites poor degradation efficiency towards COD removal.91.6% COD of the mixed wastewater can be removed when the optimum H2O2 dosage(340 mg/L) was applied.The high reactive free radical generated from the Fenton reaction may be responsible for COD elimination.Fenton reaction mechanism was discussed by fitting a two-step kinetic model.