| abstract |
Treatment of sulphite pulp waste liquors is carried out by (a) adding H3PO4 or a substance which forms H3PO4 by hydrolysis, (b) boiling the mixt. to drive off SO2, and (c) recovering H3PO4. The H3PO4 converts sulphites, e.g. Ca(HSO3)2, to SO2 which is removed together with other volatile materials (furfural, cymene, MeCOOH and HCOOH) during step (b). The product remaining after H3PO4 recovery can be used as a fuel, an ion exchanger or water filter, and additive for plastics, rubber or asphalt, or as a soil improver or as a soil improver or animal feed additive. |