Progress and perspectives for synthesis of sustainable antifouling composite membranes containing in situ generated nanoparticles

Polymeric membranes enhanced by nanoparticles have received great attention over the past decade due to their abilities to meet the growing demand in addressing the global scarcity and pollution of water resources. Many efforts have been devoted to improve the membrane performance using this strategy, and to develop novel applications via molecular-level design for nanoparticle-polymer systems. Recent advances in applying in situ preparative techniques in polymeric membrane can potentially lead to new classes of nano-enhanced membranes for advanced water purification. Considering the increasing interest in this field related to the potential for controlling the dispersion and stability of nanoparticles, we review the progress of in situ preparative techniques for water purification. Categories of in situ preparative techniques are elaborated in detail, primarily focusing on the mechanism of the sol-gel process and in situ chemical reduction, which are considered as the most common applications of in situ preparative techniques. We also describe the effect of binding styles of nanoparticles (in situ formation in the membrane matrix or on the membrane surface) on the structure-property relationship in nano-enhanced membranes, discussing recent applications of in situ formed metal nanoparticles, metal oxide nanoparticles, polymeric nanoparticles and other nanoparticles in water treatment. Finally, we suggest the antifouling mechanisms of in situ preparative techniques and give a further perspective for the next-generation nano-enhanced membranes. Further development of nano-enhanced membranes must go hand in hand with strict regulations for drinking water consumption and environmental safety.