Direct contact membrane distillation for seawater desalination: Evaluation of the long-term operation performance of omniphobic mullite ceramic hollow fiber membrane

In the recent past, the use of membrane distillation (MD) has become a flexible method of treating saline water and industrial wastewater. The inability of traditional polymeric membranes, however, to resist wetting and irreversible fouling of pores is a critical bottleneck to the industrial viability of MD, as it affects the liquid-vapor interface and ends the separation process. Even though the hierarchical surface morphologies, which are frequently developed through hydrothermal techniques, have been suggested to address these challenges, there is still a major deficiency in the simultaneous chemical strength and omniphobic stability in ceramic-based networks. This paper will overcome these drawbacks by designing an omniphobic mullite-based ceramic hollow fiber membrane (Omni-FAS) and comparing its functionality to that of a hydrophobic one. In this study, the performance of omnophobic mullite-based ceramic hollow fiber membrane (Omni-FAS) and a hydrophobic mullite-based ceramic hollow fiber membrane (Mu-FAS) was evaluated using direct contact membrane distillation (DCMD) with 30 g/L NaCl and 8 mg/L humic acid being used as a feed. The rejection rate and water flux values of Omni-FAS were observed to be fairly constant at 99.99% and 21.5 kg/m²/h, respectively, during the period of about 75 h of the MD process, showing that the Omni-FAS had long-term stability. The ML-FAS showed a significant decline in performance after 10 h of the MD process (rejection declined to 84% at the conclusion of the process time). The surface-modified membrane was free of fouling, as was demonstrated by the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) profiles. This was due to the enhanced anti-fouling property of CO₃O₄ spider web-like (SWL) particles, a pointer to the fact that even in the presence of organic contamination, the prepared omniphobic mullite ceramic hollow fiber membrane of SWL structure could be used in DCMD and seawater desalination.