Method of separating sodium hydroxide from white liquor

摘要

The present invention relates to a method of processing white liquor (3) obtained from the causticization step of a pulp mill, in which method infeed white liquor (3) principally contains sodium hydroxide (6) and sodium sulfide (7). The method according to the invention is characterized in that the sodium hydroxide (6) contained in the white liquor (3) is separated from the white liquor (3) either entirely or partly by means of a diffusion dialysis membrane process (4). The invention is further characterized in that the sodium hydroxide (6) separated from the white liquor (3) is advantageously entirely returned back to the chemical circulation of the pulp mill.