Systems and methods are provided for processing metal sulfate compounds and sequestering CO2. These systems and processes involve one or more electrochemical cells for producing an alkali-containing catholyte and involve a CO2 absorption reactor operatively connected to the electrochemical cell and to a CO2 source. The CO2 absorption reactor receives the alkali-containing catholyte and CO2 gas for forming an alkaline carbonate solution. The alkaline carbonate solution is directed to a vessel where it reacts with an acidic sulfate solution comprising metal ions resulting in precipitation of solid metal carbonate compounds. The acidic sulfate solution may comprise sulfide leachates from acid mine drainage, sulfide mine tailings and/or reacted pyrite concentrate. The acidic sulfate solution may be circulated through an optional SO2 reduction reactor prior to reaction in the vessel. The SO2 reduction reactor reduces trivalent metal compounds present in the acidic sulfate solution to divalent metal compounds.