MagMD · Magneto-responsive hydrophobic membrane and membrane distillation: insight into the real-time fouling and wetting mitigation mechanism

Magneto-responsive hydrophobic membrane and membrane distillation: insight into the real-time fouling and wetting mitigation mechanism

Water scarcity and pollution are the key global threats, they are the internal driving force for water/wastewater research, treatment, and application in chasing od the sustainable development goals (SDGs) and carbon neutrality. Membrane technology plays a crucial role in water-energy nexus in terms of seawater desalination, water reuse, and industrial wastewater treatment and zero liquid discharge (ZLD). However, the membrane fouling remains the key Achilles' heel for membrane process, driving the quest for fouling mitigation to achieve long end-of-life, low operation costs, and low carbon footprint. Specially, scaling is the main fouling mechanism during hypersaline wastewater desalination. In this project, the scaling mechanisms in both temperature- and pressure-driven membrane process were demonstrated and compared with a goal to promote the application of membrane in hypersaline treatment. A 3-stage flux decline mechanism in vacuum membrane distillation (VMD) was identified, in where the bulk crystallization was the dominating mechanism. However, the surface crystallization and following pore-blocking prevailed in NF, and the combination of Si and Mg showed a significant impact on cake layer formation. Meanwhile, the role of organic matters and the key scalants in scaling was revealed in membrane process. By which we proposed a mixed scaling mechanism in hypersaline desalination, it could offer scientific support to the desalination world. Secondly, we investigated the combination of magnetic nanoparticles and magnetic field in MD, to mitigate the membrane fouling and pore wetting issue with a new perspective. The multiple effects of magnetism including the vibration, nano-heating, anti-scaling, anti-biofouling effects were envisioned as combined with membrane. Then, a one-pot hydrothermal method was developed to synthesize metal-organic frameworks (MOFs) with high water (0.4 g·g⁻¹ at 20% RH) and ammonia adsorption capacities. Magnetic nanoparticles (Fe₃O₄) were prepared via solvothermal synthesis, exhibiting strong magnetism and dispersibility. Composite membranes integrating these nanoparticles and MOFs showed enhanced hydrophobicity, reduced flux decline, and improved ammonia adsorption, leading to stable long-term MD performance. Furthermore, we studied the effect of magnetic field on the MD process for Urine treatment. A low-frequency magnetic field integrated with MD mitigated fouling, slowed flux decline, and delayed organic/nitrogen accumulation. Composite membranes with magnetic MOFs further improved performance, achieving >99% rejection of TOC, TP, and PO₄³⁻, and >90% rejection of TN and ammonia in 24-hour runs. This work will pave a new way for hydrophobic/ Janus membrane preparation by bring in the magnetism, and shape a new road to the hypersaline wastewater desalination and resource recovery for the proposing of new MagMD process and the demonstration of mixed scaling mechanism.

Data: CORDIS, © European Union