Unsupported hydrophobic electrospun membranes for water desalination using direct contact membrane distillation

Abstract

Water is the most fundamental element of life. However, the boost in economic development, industrialization, and uncontrolled population growth are causing a severe threat to fresh water finite resources that are naturally available on earth, especially in the Middle East and North Africa (MENA) region. Due to limited accessibility to fresh water, desalination is believed to be a promising method to supply the continuously increasing fresh water needs. Desalination is a process that removes the excess amount of salts and minerals from seawater to make it drinkable. Over the last few decades, membrane-based technologies have gained considerable popularity due to their high separation efficiencies, relatively low costs, and ease of operation. In this project, we developed an unsupported electrospun hydrophobic poly(vinylidene fluoride)‐co‐hexafluoropropylene (PVDF-HFP) membrane for direct contact membrane distillation (DCMD) for seawater desalination. The driving force of separation in DCMD is a partial vapor pressure difference on both sides of the hydrophobic membrane that is imposed by the temperature difference between liquid feed and permeate flows. The hydrophobic porous membrane acts as a barrier and separates the hot salty water (liquid feed) from the cold water (permeate). The electrospinning effective parameters were found to be polymer’s concentration, applied voltage, and tip to collector distance. The fabricated membranes were characterized using various techniques such as SEM, capillary flow porometry, and contact angle measurement. The electrospun membrane was heat pressed and treated in ethanol at 65 C to improve its performance. The modified electrospun membrane showed very high permeate flux (15 Kg-m².hr) and salt rejection rate of 99.99percent. The proposed modified PVDF-HFP electrospun membrane was found to be a good candidate in the DCMD process. The performance of the electrospun membrane was compared to that of a commercially available PTFE membrane for benchmarking.