Abstract: A method and apparatus for precipitating manganese from acidic sulfate solutions, and more specifically from zinc leach solutions, without removing zinc. A zinc- and manganese-containing solution is treated with an SO2—O2 gas mixture at the appropriate pH and temperature, thereby causing manganese to precipitate as a trivalent and/or tetravalent manganese hydroxides and/or oxides that report to the leach residue or are removed separately from solution by solid/liquid separation. These trivalent and/or tetravalent manganese compounds may be used as oxidants in other parts of the leach circuit.

Abstract: The present invention relates to an apparatus for removing volatile impurities such as mercury and selenium from a weak acid solution resulting from scrubbing gases created in the production of sulfuric acid by roasting of sulfide concentrates. The apparatus comprises a calcine filtering unit for removing calcine from the weak acid solution, a sodium sulfide mixing unit for precipitating mercury from the weak acid solution, a sodium dithionite mixing unit for precipitating selenium from the weak acid solution, and a mercury-selenium filtering unit for filtering the precipitated mercury and selenium from the weak acid solution. The present invention further relates to a treatment plant utilizing such an apparatus, a process for removing volatile impurities from a weak acid solution, and a selenium cake obtained by utilizing the resent invention.