The specification discloses a desulfurization process for use in a fossel fuel combustion process involving the generation of a flue gas product containing sulfur oxides and halogen compounds wherein an alkali metal compound is contacted with the gas resulting in the removal of sulfur oxides from the gas and formation of a water-soluble residue comprising alkali metal sulfates and alkali metal halides, which residue is collected from the gas before the gas is released to the environment. The process is adapted to recover the alkali metal ions from the collected residue for use in supplying the alkali metal ions that are contacted with the gas and for limiting the presence co-collected halogen ions within the recovered alkali metal ions. The process comprises dissolving the collected residue in water to form an aqueous solution thereof having a pH of less than about 8 so that sulfate ions, halogen ions and alkali metal ions are present in the solution. Thereafter, the solution is contacted with a weak base anion-exchange resin having bicarbonate groups associated therewith that exchange with sulfate and halogen ions in the solution so that the sulfate and halogen ions become associated with the resin and the bicarbonate groups become associated with the alkali metal ions in the solution. As a result, the alkali metal ions are separated from the sulfate ions and halogen ions for use in supplying the alkali metal compound that is contacted with the gas.