A method for reducing the calcium content of sodium the basis of conventional waste - sulfite lyes

摘要

The amount of calcium contained in sodium-base waste sulfite liquor is reduced by precipitating the calcium as calcium sulfite and separating the precipitate from the remaining waste sulfite liquor solution. The precipitation is caused by dissolving in the waste suflite liquor (1) additional calcium, i.e., beyond the amount of calcium initially contained in the waste sulfite liquor; (2) a sodium or an ammonium compound or a combination thereof selected from the group consisting of sodium oxide, sodium sulfite, sodium carbonate, sodium bisulfite, sodium hydroxide, anhydrous ammonia, ammonium sulfite, aqueous ammonia, ammonium carbonate, ammonium magnesium carbonate and ammonium hydroxide; and (3) a source of sulfite ions.