Comparative evaluation of the radioactivity removal efficiency of different commercially available reverse osmosis membranes

Abstract

Reverse osmosis (RO) is a water purification process that uses a semi-permeable membrane to remove ions from potable water. It has high rejection throughput, low energy consumption, and negligible pollution load when compared to conventional treatment methods. Comparative percentage salt rejection (SR) efficiency for surrogates of cesium and molybdenum was performed using commercially available membranes. Polyamide, polysulfone, polyamide–polysulfone composite, and cellulose acetate were subjected to various operating conditions in a domestically developed high-pressure membrane test cell. Five different concentrations of surrogate salts ranging from 100 to 500 ppm and varied pressures of 15–17 kg/cm2 combined with varying temperatures of the feed solution from 25°C to 45°C were used in this experimental work. It was found that the %SR efficiency of these membranes increased with the increase in salt concentration and feed temperature. However, a significant decrease in SR was observed with increasing pressure. A comparative study of these commercially available RO membranes was also performed against short-lived radioisotope Technetium-99m, and was determined by activity counts of feed and filtered samples using a well counter. The results suggest that the rejection efficiency was found to be highest in the case of polyamide–polysulfone composite, followed by polysulfone, polyamide, and cellulose acetate.

Keywords

• cellulose acetate membrane
• high-pressure membrane test cell
• radio-contamination
• technetium-99m pertechnetate
• thin film composite
• well counter