The present application pertains to methods for making
metal oxides and / or
citric acid and / or capturing
carbon dioxide. In one embodiment, the application pertains to a process for producing
calcium oxide,
magnesium oxide, or both from a material comprising
calcium and
magnesium. The process may include reacting a material comprising
calcium carbonate and
magnesium carbonate. Separating, concentrating, and calcining may lead to the production of oxides such as
calcium oxide or magnesium
oxide. In other embodiments the application pertains to methods for producing an alkaline-earth oxide and a
carboxylic acid from an alkaline earth cation -
carboxylic acid anion salt. Such processes may include, for example, reacting an alkaline-earth cation -
carboxylic acid anion salt with aqueous
sulfur dioxide to produce aqueous alkaline-earth
sulfite or
bisulfite and an aqueous carboxylic acid solution. Other useful steps may include desorbing, separating, and / or calcining.