Experimental Study for Benzene/Water Removal by Air Gap Membrane Distillation

Abstract

Benzene, a hazardous chemical, is one of the effluents which are eliminated by various industries as waste products into the water bodies. Various techniques are used for the separation of benzene from waste water such as liquid-liquid extraction, adsorption, absorption and pervaporation, and membrane distillation (MD). In this work, the air gap membrane distillation technique is used for the removal of benzene from benzene-water solution. Microporous hydrophobic polytetrafluoroethylene (PTFE) membrane was used in the membrane module in the AGMD setup. The effect of various parameters, such as feed bulk temperature and air gap width, were studied on permeate flux and membrane selectivity. It was observed that on increasing the feed bulk temperature from 40°C to 60°C, the permeate flux increases exponentially from 2.95 kg/m2·h to 4.63 kg/m2·h at an air gap of 3 mm. However, on increasing the air gap width from 3 mm to 11 mm, the permeate flux decreased tremendously from 4.63 kg/m2·h to 0.93 kg/m2·h at 2 lpm of feed flow rate under a constant feed temperature of 60°C. It was also found that the selectivity of benzene in permeate increases from 40.57 to 63.74, on increasing the feed bulk temperature from 40°C to 60°C, which clearly indicates the separation of benzene by using air gap membrane distillation. The UV-Vis spectrophotometer is used for determining the concentration of benzene in permeate at the wavelength of 255 nm. The membrane morphology of the hydrophobic PTFE membrane was studied using FE-SEM, prior and after the experimental runs for continuous 200 hours.