| Summary: | Mining of pyrite-rich ore deposits produces large volumes of acid mine drainage, which has low pH and high concentrations of heavy metals and sulfates. Upcoming Swedish environmental regulations aim to decrease maximum allowed concentrations of metals in water discharged to natural water bodies. Conventional processes are not able to achieve the upcoming requirements, which leads to demand for new solutions. This thesis identifies water treatment methods that could potentially be used to treat mine drainage from Kristineberg mine in northern Sweden to comply with the proposed requirements. This work evaluates chemical methods of acid mine drainage treatment with particular focus on precipitation of metals as hydroxides and sulfides. Co-precipitation and adsorption of metals by ferric hydroxide and manganese dioxide as polishing step after neutralization were also investigated. The work was done by modelling and laboratory experiments with mine drainage obtained from Kristineberg mine area. It was found that neutralization of mine drainage and hydroxide precipitation of metals could not reach the proposed requirements for arsenic and copper. Applying Fenton reagent and manganese oxidation as a polishing step improved removal of all metals, but residual As and Cu concentrations were still slightly higher than required. Sulfide precipitation of metals after removal of iron and aluminium as hydroxides showed better removal of copper, but removal of nickel was not achieved. Removal of uranium was also worse than that achieved by neutralization. However, because sulfide precipitation produces less sludge and makes metals recovery possible, the study concluded that it is a more attractive option for Kristineberg mine drainage treatment. But additional studies are required to find optimum conditions for nickel removal. Conducting bench-scale experiments with hydrogen sulfide gas as a sulfide source is recommended. The study found that both neutralization with polishing and sulfide precipitation would reach lower ...
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