SORPTION AND EXTRACTION OF LACTIC AND SUCCINIC ACIDS AT PH-GREATER-THAN-PK(A1) .1. FACTORS GOVERNING EQUILIBRIA

Many fermentations to produce carboxylic acids operate most effectivel y at pH above pK(a1) of the acid product, under which conditions the a cid is largely in the carboxylate form. One approach to acid recovery from such solutions is to use solid sorbents or liquid extractants tha t are strongly enough basic to provide substantial capacity even at mo derately high values of pH. Data are presented for sorption of lactic and succinic acids by several commercially available basic polymeric s orbents. Performance at pH > pK(a1) is a function of sorbent basicity, and apparent pK(a) or monomer pK(a) can be used to predict sorbent pe rformance. Data are also presented for the extraction of the acids by two commercial amine extractants, Alamine 336 and Amberlite LA-2, in v arious diluents. The extractants sustain capacity to higher pH in dilu ents that stabilize the acid-amine complex. Secondary amines provide h igher capacities than do tertiary amines in diluents that solvate the additional proton. Competitive uptakes of sulfate, phosphate, and carb oxylate were also measured.