Aqueous‐Phase Photocatalytic Degradation of Emerging Forever Chemical Contaminants

Abstract

Heterogeneous photocatalysis is an emerging area of catalysis increasingly fraught with pains caused by the battle between hype and real-world application. Inspired by abundant yet diffuse solar energy and applications such as clean water and energy, ample motivation has provided the background for this situation. However, substantial fundamental (e. g., charge transfer, recombination), engineering (e. g., observed rates, photon management), and practical barriers (e. g., use of precious metals, competing technologies) have limited implementation. In this review, these are all outlined, in conjunction with typical strategies for improvements, with an emphasis on the use of semiconductor photocatalysts for the degradation of emerging forever chemical contaminants in water. The selected classes of forever chemical contaminants are (micro)-plastics, per-and polyfluoroalkyl substances (PFAs), siloxanes, and dioxanes. Each has been identified as a key or emerging contaminant and often travel widely while accumulating in the atmosphere due to the lack of natural remediation processes. Recommendations to the field and opportunities for contributions are highlighted throughout and as part of the outlook to the future.

Towards Solving the PFAS Problem: The Potential Role of Metal‐Organic Frameworks

“…[25,32] The collective desire by government agencies, chemical industries, and academia to eliminate the persistent and highly toxic PFAS from the environment has resulted in much research for ideal photocatalytic materials. [33][34][35][36][37] Although MOF-based photocatalytic research for PFAS solutions is still in its infancy. Hou et al recently fabricated lignin-based nanofiber (lignin/PVA/bi-MOFs) composite membranes that contain bimetallic Co/Fe MOFs for the photodegradation of PFOA in the presence of peroxymonosulfate as an advanced oxidizer, using sunlight irradiation.…”

“…Hence, the combination of excellent adsorption capacities and photocatalytic properties offers the potential for accelerated degradation of organic wastes [25,32] . The collective desire by government agencies, chemical industries, and academia to eliminate the persistent and highly toxic PFAS from the environment has resulted in much research for ideal photocatalytic materials [33–37] …”

“…[ 25 , 32 ] The collective desire by government agencies, chemical industries, and academia to eliminate the persistent and highly toxic PFAS from the environment has resulted in much research for ideal photocatalytic materials. [ 33 , 34 , 35 , 36 , 37 ]…”

Per-/Poly-fluoroalkyl Substances (PFASs) Treatment and Mechanistic Insights: Photo-catalyst and Photo-Electro-catalyst Materials Application

“…The decomposition reaction of PFASs (e.g., PFCA) is initiated by a Kolbe decarboxylation in an electron acceptor forming perfluoroalkyl radicals. Photogenerated holes and hydroxyl radicals are the primary electron acceptors in the photocatalytic degradation system [49,50]. During the photocatalysis process, the photogenerated holes on the surface of the photocatalyst rapidly generated hydroxyl radicals in water.…”