Air-sweep vacuum membrane distillation using fine silicone, rubber, hollow-fiber membranes

Abstract

An air-sweep vacuum membrane distillation process can be used for water purification or the desalination of salt water. The process simply consists of a hollow-fiber membrane module and a diaphragm vacuum pump without a condenser for the water recovery or trap. The only operating parameter of the apparatus is the sweeping air flow rate. A membrane module using fine silicone, rubber, hollow-fiber membranes 40 μm thick was used for the water recovery experiments from pure water or salt water. The experimental results were compared with that using a membrane module with porous polypropylene hollow-fiber membranes. The fine silicone rubber membrane module could produce condensed water at a rate comparable to the porous membrane module. For each membrane, the apparent permeability of the water vapor was evaluated from the results of another vacuum membrane distillation experiment. Based on the apparent permeability and a simple vapor-phase driving force model, model calculations were made that well predicted the experimental results of air-sweep membrane distillation.