# Light-Induced Advanced Oxidation Processes as PFAS Remediation Methods: A Review
## 3 Advanced Oxidation Processes (AOPs) for PFAS
### Heterogeneous Photocatalysis Materials
#### 3.1.2 Other Photocatalysts
Because of these properties, the Bi/BiOI\({}_{0.8}\)F\({}_{0.2}\) composite presented the best activity for the decomposition of PFOA (40 mg/L) in just 2 h of illumination of simulated solar light with a \(\sim\)10 times higher degradation rate than that of pure BiOF and BiOI. As per the results of the EPR spectra and scavenging experiment, superoxide radicals (O\({}_{2}^{-\bullet}\)) are dominant species for dissociating the bonds of PFOA. The p-n heterojunction of BiOI@Bi\({}_{5}\)O\({}_{7}\)I (Figure 4a) was formed to improve charge separation by the facile heat treatment of BiOI in the air at a moderate temperature of 390 \({}^{\circ}\)C [92]. The resulting p-n heterojunction causes photogenerated electrons to be immediately driven to the conduction band of BiO\({}_{7}\)I while leaving the holes in the valence band of BiOI, thereby spatially separating h\({}^{+}\)/e\({}^{-}\) pair. This heterojunction is efficient in degrading 80% of PFOA in 6 h under irradiation with visible light, with the HO\({}^{\bullet}\) radical as the oxidizing agent. Similar charge separation was observed in the case of the Bi\({}_{5}\)O\({}_{7}\)I/ZnO n-n heterojunction microsphere, but here photogenerated holes were found to be responsible for attacking carboxylic groups of PFOA [93]. A novel Bi\({}_{3}\)O(OH)(PO\({}_{4}\)) (BOHP) compound, despite having a larger bandgap and lower surface area than BiPO\({}_{4}\) and \(\beta\)-Ga\({}_{2}\)O\({}_{3}\), showed \(\sim\)15 times higher photocatalytic activity towards the degradation of PFOA [94]. The highly positive surface charge of BOHP induces an incremental rise in the adsorption behavior of PFOA on the surface. Along with this, the favorable redox potential of the BOHP also participates in enhancing PFOA mineralization. The performance of BOHP was amplified by [PERSON] et al. [95], forming composites with carbon spheres (CS) and upgrading the stability of BOHP by suppressing the photo corrosion of the composites via acting as an electron sink. The adsorption capacity of PFOA was also improved through CS, which contributes to the adsorption of PFOA. Carbon spheres were also found to be beneficial for an iron (hydro)oxide photocatalyst (FeO), where a 1:1 composite of FeO/CS was developed by the same research group that presented the BOHP/CS composites (Figure 4b) [96]. Here, CS aids in forming ferrihydride on the surface, which improves the adsorption of PFOA via binuclear and bidentate complexation and increases direct electron extraction from PFOA under stimulated solar light. FeO/CS was able to photodegrade 95.2% of PFOA, with 57.2% defluorination in 4 h in neutral pH. The wide-bandgap semiconductor boron nitride (BN) was also reported for photocatalytic degradation of PFOA under UV light (Figure 5a) [97]. Boron nitride followed a similar photo-oxidation pathway as TiO\({}_{2}\), mainly involving holes to bifurcate PFOA but with rate twice that of TiO\({}_{2}\). The exfoliation of BN layers through ball milling further improved the degradation rate. Tungstic heteropoly acid (H\({}_{3}\)PW\({}_{12}\)O\({}_{40}\)) supported on high-surface-area bimodal mesoporous silica (BMS) displayed an enhanced defluorination rate of PFOA compared to direct photolysis under vacuum UV light irradiation with a wavelength of 185 nm [98]. Recently, a Z-scheme-based heterojunction was discovered to be highly effective in photocatalytic applications, considering its ability to cause charge separation at the junction to increase the lifetime of photogenerated charges. [PERSON] et al. [99] fabricated a Z-scheme heterojunction of core-shell CeO2@NiAl-LDHs (Figure 5b) to proficiently remove PFOA from wastewater. A built-in electric field in the Z-scheme heterojunction causes instantaneous separation of photogenerated charges to record photodegradation of 90.2% of PFOA under stimulated solar light.