Structure-Performance Engineering of Recycled Acrylic Membranes for Air Gap Membrane Distillation

Air Gap Membrane Distillation (AGMD) is an emerging and promising technology in separation processes, but its industrial adoption is limited by relatively low permeate flux. Conventional AGMD systems typically utilise thin film-cast polymeric membranes. However, electrospun nanofibrous membranes have become more popular since they possess a highly interconnected porous structure, which is able to increase mass transfer performance and availability. In this study, recycled acrylic (RA) waste powder was used to prepare a precursor solution to fabricate two types of membranes: thin film-cast membranes and electrospun nonwoven nanofibrous membranes to be evaluated in the AGMD process for water desalination application. The fabricated RA-based membranes underwent characterisation by scanning electronic microscopy (SEM), mechanical properties, water contact angle (WCA), and Fourier transform infrared spectroscopy (FTIR). Based on the results obtained, the nanofiber membrane exhibited a higher contact angle, porosity, and elasticity than the thin film cast membrane. RA-based membranes were tested in the AGMD system at different feed temperatures (45 °C, 55 °C, and 65 °C). The electrospun nanofibrous membrane performed better than the thin-film cast membrane in both permeate flux and salt rejection. The temperature of the feed increased correspondingly with the flux of permeate as well as the salt rejection. The cast membrane of thin film attained a flux of permeate of 1.48 kg/(m²‧h) with 99.98 % salt rejection. Conversely, the electrospun nanofibrous membrane had better performance with a significantly higher permeate flux rate of 7.69 kg/(m²‧h) and an almost ideal salt rejection of 99.99 %.