Recent trends in application of nanoscale zero-valent metals and metal single atoms in membrane processes

Various nanomaterials (NMs) with special characteristics such as high reactivity, improved catalysis, and adsorption properties have gained considerable attention to improve the performance and characteristics of membranes especially in the field of wastewater treatment. Engineered nanoscale zero-valent metals (nZVMs) and metal single atoms (MSAs) indicate the superior performance in membrane technologies, due to their cost-effectiveness of production and strong catalytic capability in the removal of pollutants. This paper critically reviews the nZVMs and MSAs incorporation in membranes processes with considering the different features of the bare, supported, or modified nanomaterials and bimetallic systems. Various fabrication techniques of nZVMs modified membranes including phase inversion, interfacial polymerization, blending in the coated layer, and other fabrication methods were summarized. Nanoscale zero-valent iron (nZVI) as the most extensively studied nZVMs, due to their low cost and effective properties in the removal of pollutants were highlighted and different applications of those in membrane processes as a reactive medium for wastewater treatment focusing on polymeric membrane systems were discussed. Furthermore, the effects of numerous nZVMs and MSAs used in membrane processes and various supporting techniques were explained and the key factors of the different operation conditions for contaminants removal are critically compared. Also, an account of dynamic simulations of MSAs applications in different membrane processes and future research directions based on the findings have been reviewed throughout the study.