Abstract: A process is provided for isolating vanillin from alkaline aqueous solutions containing unwanted, chemically-related phenolic impurities, such as orthovanillin, acetovanillone, para-hydroxybenzaldehyde, syringaldehyde and the like, wherein the alkaline aqueous solution is subjected to an extractive process including as a step, extractive bisulfitation. The step of extractive bisulfitation involves the formation of an alkali-metal bisulfite complex of vanillin in the presence of a substantially water-insoluble organic solvent, such as a water-insoluble alkanol, e.g., normal-butyl alcohol.

Abstract: In a typical pulp mill bleaching process, a pulp slurry is subjected to one or more chlorination treatments, each being followed by a caustic extraction stage. To decrease the volume of effluents, water re-use is practiced with a portion of the first caustic extraction stage filtrate being reused for direct countercurrent washing to increase the concentration of the filtrate and the balance thereof being removed as a concentrated caustic extraction effluent. According to the novel feature, the caustic extraction effluent removed, having a pH of about 9 to 12, is combined with an acidic solution having a pH of less than about 1.5 to form a combined effluent having a volume of less than about 2500 gallons per air dried ton of bleached pulp and a pH below about 2.8, whereby a precipitate is formed which removes organic color bodies from the combined effluent. Part or all of the acidic solution is preferably a concentrated chlorination effluent obtained by recycle of the chlorination stage washer filtrate.