STUDY ON THE CONCENTRATION OF ACIDS BY MEMBRANE DISTILLATION

The membrane distillation (MD) process was applied for the concentrati on of different mineral acids, such as, sulfuric phosphoric, hydrochlo ric and nitric acids. The MD of a citric acid solution as an example o f an organic acid was also investigated. The experiments were carried out keeping the warm feed and cold solution temperatures at 333 and 29 3 K, respectively. The data obtained indicate that the volume flux of a permeate decreased with an increase of acid concentration in the fee d. The reduction of acid content in the permeate, close to 100%, for n on-volatile acids was independent of the acid concentration in the fee d. The amounts of hydrochloric or nitric acids in the permeate increas ed with a rise of the acid concentration in the feed, reaching the aze otropic composition. The effect of the polarisation phenomena on the c oncentration process of sulfuric acid is discussed.