Multiple-effect membrane distillation （MEMD） process for enriching semi-volatile organic acids from their individual aqueous solutions was performed by using a hollow fiber-based air gap membrane distillation （AGMD...Multiple-effect membrane distillation （MEMD） process for enriching semi-volatile organic acids from their individual aqueous solutions was performed by using a hollow fiber-based air gap membrane distillation （AGMD） module with the function of internal heat recovery. Aqueous solutions of glyoxylic acid, glycolic acid, lactic acid, pyrnvic acid, malonic acid and glutaric acid were used as model feed. For a feed of 1% （mass fraction）, each acid could be enriched for 8--20 times, which depended on the surface tension of the concentrate. The operation performance of MEMD process was characterized by permeation flux J, performance ratio PR and acid rejection rate R. The effects of cold feed-in temperature, heated feed-in temperature, feed-in volumetric flow rate and feed-in concen- tration on MEMD performance were experimentally evaluated. Maximum values of J, PR and R were 4.8 L/（h-m2）, 9.84 and 99.93%, respectively. Moreover, MEMD process demonstrated a fairly good stability in a long-term experiment lasting for 30 d when aqueous solution of 4% （mass fraction） lactic acid was used as a feed.展开更多
Multiple-effect membrane distillation （MEMD） using a hollow fiber-based air-gap membrane distillation module was experimentally examined for concentrating dilute aqueous hydrochloric acid. The effects of the hot and...Multiple-effect membrane distillation （MEMD） using a hollow fiber-based air-gap membrane distillation module was experimentally examined for concentrating dilute aqueous hydrochloric acid. The effects of the hot and cold feed-in temperatures, and the feed-in volumetric flow rates on the performance of the MEMD process were studied. The performance was evaluated using the performance ratio （PR）, the average selectivity of water over HCl （βavg） and the permeation flux （N）. Two types of porous fibers made from polypropylene were used to fabricate the MEMD modules. The experimental data indicated that hollow fibers with high porosity were preferred for the MEMD process. The PR, βavg and N all decreased as the feed concentration increased. When the feed concentration was below 12 wt-%, the PR was 6.0 - 9.6 and βavg was 10 190. When the concentration of HCl reached 18 wt-%, the PR and βavg were about 4.4 and 2.3, respectively. However, βavg sharply decreased to around 1.0 when the feed was further concentrated. During an operational stability test that lasted for 30 days, the performance of the MEMD modules remained good.展开更多
文摘Multiple-effect membrane distillation （MEMD） process for enriching semi-volatile organic acids from their individual aqueous solutions was performed by using a hollow fiber-based air gap membrane distillation （AGMD） module with the function of internal heat recovery. Aqueous solutions of glyoxylic acid, glycolic acid, lactic acid, pyrnvic acid, malonic acid and glutaric acid were used as model feed. For a feed of 1% （mass fraction）, each acid could be enriched for 8--20 times, which depended on the surface tension of the concentrate. The operation performance of MEMD process was characterized by permeation flux J, performance ratio PR and acid rejection rate R. The effects of cold feed-in temperature, heated feed-in temperature, feed-in volumetric flow rate and feed-in concen- tration on MEMD performance were experimentally evaluated. Maximum values of J, PR and R were 4.8 L/（h-m2）, 9.84 and 99.93%, respectively. Moreover, MEMD process demonstrated a fairly good stability in a long-term experiment lasting for 30 d when aqueous solution of 4% （mass fraction） lactic acid was used as a feed.
文摘Multiple-effect membrane distillation （MEMD） using a hollow fiber-based air-gap membrane distillation module was experimentally examined for concentrating dilute aqueous hydrochloric acid. The effects of the hot and cold feed-in temperatures, and the feed-in volumetric flow rates on the performance of the MEMD process were studied. The performance was evaluated using the performance ratio （PR）, the average selectivity of water over HCl （βavg） and the permeation flux （N）. Two types of porous fibers made from polypropylene were used to fabricate the MEMD modules. The experimental data indicated that hollow fibers with high porosity were preferred for the MEMD process. The PR, βavg and N all decreased as the feed concentration increased. When the feed concentration was below 12 wt-%, the PR was 6.0 - 9.6 and βavg was 10 190. When the concentration of HCl reached 18 wt-%, the PR and βavg were about 4.4 and 2.3, respectively. However, βavg sharply decreased to around 1.0 when the feed was further concentrated. During an operational stability test that lasted for 30 days, the performance of the MEMD modules remained good.
