Due to chemical and physiological inertness and wide usage in nearly every aspect of our daily life, per- and poly-fluoroalkyl substances (PFAS) are now ubiquitous in the environment, including drinking water sources. As most biological and chemical destruction methods have so far shown limited efficiencies, adsorption, a simple and cost-effective treatment, is widely adopted for the removal of PFAS from water/wastewater. This paper aims to review the recent progress in PFAS adsorption using various adsorbents. The performance of different types of adsorbents, including the traditional carbonaceous materials and resins as well as the newly-synthesized minerals, biomaterials, and polymers, in PFAS removal was summarized. Furthermore, the adsorption characteristics and mechanisms were critically reviewed. Real-life adsorption applications (large-scale setups, adsorption-involved treatment trains and point-of-use/point-of-entry systems) were also examined. Learned lessons, current challenges and recommendations on future research were provided regarding results of tests in real environmental matrices, pilot and/or field scale studies of promising newly-developed adsorbents, and the improvement of the removal of alternative PFAS (mostly short-chained ones).

Heterogeneous catalytic ozonation has been increasingly studied for the degradation and mineralization of refractory organic water pollutants in recent years. Compared with homogeneous catalysts, an important advantage of heterogeneous catalysts is that they can be easily separated from the treated water, making the process economically viable. While many studies have focused on the development and evaluation of metal oxide-based catalytic ozonation, possible leaching of metal ions and the subsequent effect on the contaminants' degradation are sometimes overlooked. Here, we examined metal leaching from several solid catalysts and further investigated the influence of the leached metal ions on the mineralization of two model compounds (oxalate and nitrobenzene) during continuous ozonation. Metallic ion leaching was observed from both commercially-available catalysts and catalysts prepared via wet-chemistry methods in the lab. The water matrix has been demonstrated to play an important role in metal leaching. The homogeneous catalytic effect resulting from the leached metal ions was found to be significant. A mechanism involving the formation of an unstable Cu(III)/oxalate complex through the reaction between ˙OH and Cu(II)/oxalate was proposed to explain the experimental observations. Our results indicate that the stability of the solid catalysts and the effects of the leached ions must be carefully examined during the catalytic ozonation of organic contaminants. Through this study we highlight the importance of rigorous, accepted protocols for evaluating and reporting heterogeneous catalyst performance in water/wastewater treatment within the research community.

The adsorption of short-chain PFAAs has recently received increasing attention due to their potential for replacing the long-chain homologs.