Methods and systems using electrochemical cells for processing metal sulfate compounds from mine waste and sequestering CO2

A method for processing aqueous metal sulfate compounds and sequestering CO2, comprising:

• providing an electrochemical cell producing an alkali-containing catholyte;
• providing a CO2 absorption reactor operatively connected to said electrochemical cell and to a source of CO2;
• feeding said CO2 absorption reactor with said alkali-containing catholyte for forming an alkaline carbonate solution;
• and
• reacting in a vessel an acidic sulfate solution comprising metal ions with said alkaline carbonate solution for precipitating solid metal carbonate compounds.

A system for reducing trivalent metal compounds to divalent metal compounds and sequestering CO2, comprising:

• a SO2 reduction reactor operatively connected to a source of CO2 and SO2 gas, and to a source of trivalent metal compounds, said SO2 reduction reactor reducing trivalent metal compounds to produce a solution comprising divalent metal compounds;
• an electrochemical cell producing an alkali-containing catholyte;
• a CO2 absorption reactor operatively connected to said electrochemical cell and to the SO2 catalytic reduction reactor, said CO2 absorption reactor receiving said alkali-containing catholyte from the electrochemical cell and CO2 from the SO2 reduction reactor for forming an alkaline carbonate solution;
• and
• a vessel for receiving said alkaline carbonate solution and for receiving said solution comprising divalent metal compounds, said vessel allowing precipitation of solid divalent metal carbonate compounds.

A method for reducing trivalent metal compounds to divalent metal compounds and sequestering CO2, comprising:

• reducing trivalent metal compounds into a SO2 reduction reactor to obtain an acidic sulfate solution comprising divalent metal compounds;
• providing an electrochemical cell producing an alkali-containing catholyte;
• circulating said alkali-containing catholyte into a CO2 absorption reactor operatively connected to said electrochemical cell for forming an alkaline carbonate solution;
• and
• reacting in a vessel said acidic sulfate solution with said alkaline carbonate solution for precipitating solid carbonate compounds containing divalent metal.