A method for removing sulfide from an aqueous alkali solution in which hydrogen peroxide is introduced into a sulfide-containing aqueous alkali solution associated with an alkali mineral recovery operation. The method is particularly useful for the processing of sulfide-containing aqueous alkali solutions containing NaHCO3 and Na2CO3, where bicarbonate in the sulfide-depleted alkali solution is decomposed to form Na2CO3, with concurrent evolution of gaseous carbon dioxide byproduct but without formation of gaseous H2S as a pollutant, and where Na2CO3 values are subsequently recovered from the sulfide-depleted carbonate-rich alkali solution via a crystallization operation.