Production of alkali metal carbonates and/or bicarbonates from alkali metal sulphates

A method of producing a carbonate or a bicarbonate of an alkali metal, in solid form, from a sulphate of the alkali metal, and elemental sulphur or sulphuric acid, the method including:

• in a first reaction step, reacting, in aqueous medium, a sulphate of an alkali metal with one or more alkaline earth metal sulphides, thus forming an aqueous solution of one or more sulphides of the alkali metal and one or more sulphates of the alkaline earth metal in solid form;
• in a second reaction step, in the aqueous solution of one or more sulphides of the alkali metal, reacting the one or more sulphides of the alkali metal with carbon dioxide (CO2) in gaseous form, thus forming an aqueous solution of a bicarbonate of the alkali metal and gaseous hydrogen sulphide;
• in a recovery step, recovering a carbonate or the bicarbonate of the alkali metal, in solid form, from the aqueous solution of the bicarbonate of the alkali metal;
• in an alkaline earth metal sulphide regeneration step, regenerating one or more alkaline earth metal sulphides by subjecting one or more sulphates of the alkaline earth metal, formed in the first reaction step, to carbothermal reduction and thus obtaining one or more regenerated alkaline earth metal sulphides;
• and
• in a hydrogen sulphide processing step, converting the hydrogen sulphide to elemental sulphur or to sulphuric acid.