Pervaporative desalination by phosphomolybdic acid/PVA hybrid membrane

Abstract

Water is indeed a precious natural resource and essential for all living organisms. Despite the Earth's abundant water resources, only a small portion is freshwater suitable for drinking and utilization. This accounts for approximately 0.3% of the Earth's total water capacity, equivalent to about 105 thousand km3. As a result, desalination has emerged as a viable solution to produce clean water by converting seawater, which is an almost limitless supply. Among the various desalination processes, pervaporation (PV) has attracted significant attention due to its numerous advantages, including low energy consumption, simplicity in operation, low cost, and high separation performance within a short period. The current study proposes the application of pervaporation for desalination purposes. Specifically, a hydrophilic polymer, polyvinyl alcohol (PVA), is chosen for membrane synthesis in the desalination process. Polymeric membranes are comparatively easier to produce and more cost-effective than other types of membranes. However, polymeric membranes tend to exhibit a swelling behavior, resulting in high flux and low selectivity. To address this challenge, recent advancements have led to the development of hybrid membranes, known as organic-inorganic composite membranes. In this study, phosphomolybdic acid (PMA) is chosen as an additive material. The effects of the amount of phosphomolybdic acid, salt concentration, and operation temperature on desalination performance are examined. Optimal operating conditions are determined, resulting in a salt rejection rate of 99.99% and a flux value of 2.45 kg/m2 h. These findings demonstrate the potential of the proposed membrane system for efficient desalination applications. © 2023 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.