Study on concentration of aqueous sulfuric acid solution by multiple-effect membrane distillation

Multiple-effect membrane distillation (MEMD) process, by using a hollow fiber-based AGMD module and an external heat exchanger, was studied to concentrate dilute sulfuric acid solution. Latent heat of distillate was in-situ recovered by directly heating the cold feed within the AGMD module of special configuration. Permeation flux (J(w)) and performance ratio (PR) parameters were used to characterize the operation performance of MEMD process. PR value obtained in the MEMD process was much higher than that obtained in traditional and the other modified membrane distillation process. The effects of heated feed-in temperature, cold feed-in temperature, feed-in flow rate and feed-in concentration on the MEMD performance were experimentally investigated. The dilute sulfuric acid in 2 wt.% could be concentrated up to about 40 wt.% by using MEMD process. The maximum value of PR and J(w) could reach 11.5 and 5.3 L/m(2)h, respectively. When the feed concentration was up to 20 wt.%, the value of PR and J(w) could still be 4.9 and 1.9 L/m(2)h, respectively. In a long-term stability test lasting for >30 days, the electrical conductivity of the distillate was always less than 150 mu s/cm, which demonstrated that the performance of MEMD modules was kept in good condition. (C) 2012 Elsevier B.V. All rights reserved.