A Critical Review on Silica Nanoparticles for the Adsorptive Removal of Per- and Polyfluoroalkyl Substances (PFAS) from Aqueous Systems

PFAS are a group of man-made pollutants that last a long period of time in the environment, and they are harmful to humans, very stable, and can build up in living systems, and are therefore considered dangerous because of the potential health problems associated with exposure to PFAS. Traditional cleanup methods for PFAS, such as granular activated carbon, ion exchange media, and membrane technologies, have limitations in terms of selectivity, efficiency, and cost, particularly for short-chain PFAS. This paper will present new information about the use of silica nanoparticles (SiNPs) as alternative adsorbents for removing PFAS from water. Mesoporous SiNPs have a large surface area and tunable pore size and numerous different functions on their surface that create an ideal environment for the adsorption of PFAS through mechanisms like electrostatic attraction, hydrophobicity, and pore confinement. The ability to increase adsorption capabilities of SiNPs was enhanced by adding amine, quaternary ammonium, or hydrophobic groups to the surface of SiNPs, which allowed SiNPs to remove PFAS extremely quickly in lab-like conditions. This paper will also provide comparisons between destructive and non-destructive treatment technologies and weigh the advantages and disadvantages between achieving complete mineralisation vs. achieving it in a practical, cost-effective manner. It will show a comprehensive understanding from experimental results and molecular modelling of the structural interaction design of SiNPs to enable the development of the best possible adsorbents. Some challenges exist with these materials, including their decreased efficiency when exposed to complex waters, limited research available regarding the regeneration of SiNPs, the potential release of nanoparticles into the environment, and the limited availability of technoeconomics and life-cycle assessment data for SiNPs that need to be able to guide future developments.