Process for producing peracids from aliphatic hydroxy carboxylic acids

In a wood pulp processing system of the type producing both pulp and a stream of lactic acid-containing black liquor solution, the processor for production of peracid bleaching agents from hydroxy acid contained in the black liquor solution, comprising:

• adjusting the pH of said black liquor solution to the range of about 8-9 by exposing the solution to CO.sub.2 carbon dioxide to form an alkaline precipitate;
• separating solids from the black liquor solution to produce a residual solution containing lower aliphatic hydroxy acids selected from the group consisting of lactic acid, glycolic acid, 2-hydroxybutanoic acid, xyloisosaccharinic acid, and glucoisosaccharinic acid;
• decarboxylating said lower aliphatic hydroxy acids to corresponding gaseous aliphatic aldehydes by admixing a powdered semiconductor with said residual solution to form a slurry, said semiconductor being selected from the group consisting of doped n-TiO.sub.2, both platinized and unplatinized, n-WO.sub.3, a-Fe.sub.2 O.sub.3 and other insoluble semiconductors having bandgaps equal to or higher than a-Fe.sub.2 O.sub.3, and then irradiating said slurry by a means for causing photoelectro-chemical reaction at the site of the semiconductor material resulting in decarboxylation of the carboxylic acid and produuction of CO.sub.2 and corresponding aldehydes;
• removing said gaseous aldehydes from the residual solution by sweeping gas flow as soon as they are generated to prevent further oxidation to carboxylic acids;
• reacting said gaseous aldehydes with oxygen to form corresponding peracids;
• and
• applying said peracids as bleaching agents to said pulp produced in the pulp processing system.