摘要:
In a method for increasing the purity of alkali metal hydroxides, alkaline earth metal compounds are used to render contaminants insoluble, thereby lessening the entry of contaminants into a solution of alkali-metal hydroxide, or promoting removal of contaminants from a contaminated solution of alkali-metal hydroxide. The invention is particularly applicable to increasing the purity of alkali metal hydroxides regenerated from the spent liquor resulting from sulphur-free alkaline pulping of wood or of other natural material containing cellulose fibres.