Surface fluorination on TiO2 catalyst induced by photodegradation of perfluorooctanoic acid

Structural dependence of PFAS oxidation in a boron doped diamond-electrochemical system

Driven by long-term persistence and adverse health impacts of legacy perfluorooctanoic acid (PFOA), production has shifted towards shorter chain analogs (C4, perfluorobutanoic acid (PFBA)) or fluorinated alternatives such as hexafluoropropylene oxide dimer acid (HFPO-DA, known as GenX) and 6:2 fluorotelomer carboxylic acid (6:2 FTCA). Yet, a thorough understanding of treatment processes for these alternatives is limited. Herein, we conducted a comprehensive study using an electrochemical approach with a boron doped diamond anode in Na2SO4 electrolyte for the remediation of PFOA common alternatives, i.e., PFBA, GenX, and 6:2 FTCA. The degradability, fluorine recovery, transformation pathway, and contributions from electro-synthesized radicals were investigated. The results indicated the significance of chain length and structure, with shorter chains being harder to break down (PFBA (65.6 ± 5.0%) < GenX (84.9 ± 3.3%) < PFOA (97.9 ± 0.1%) < 6:2 FTCA (99.4 ± 0.0%) within 120 min of electrolysis). The same by-products were observed during the oxidation of both low and high concentrations of parent PFAS (2 and 20 mg L-1), indicating that the fundamental mechanism of PFAS degradation remained consistent. Nevertheless, the ratio of these by-products to the parent PFAS concentration varied which primarily arises from the more rapid PFAS decomposition at lower dosages. For all experiments, the main mechanism of PFAS oxidation was initiated by direct electron transfer at the anode surface. Sulfate radical (SO4•-) also contributed to the oxidation of all PFAS, while hydroxyl radical (•OH) only played a role in the decomposition of 6:2 FTCA. Total fluorine recovery of PFBA, GenX, and 6:2 FTCA were 96.5%, 94.0%, and 76.4% within 240 min. The more complex transformation pathway of 6:2 FTCA could explain its lower fluorine recovery. Detailed decomposition pathways for each PFAS were also proposed through identifying the generated intermediates and fluorine recovery. The proposed pathways were also assessed using 19F Nuclear Magnetic Resonance (NMR) spectroscopy.

Photocatalysts for chemical-free PFOA degradation - What we know and where we go from here?

Perfluorooctanoic acid (PFOA) is a toxic and recalcitrant perfluoroalkyl substance commonly detected in the environment. Its low concentration challenges the development of effective degradation techniques, which demands intensive chemical and energy consumption. The recent stringent health advisories and the upgrowth and advances in photocatalytic technologies claim the need to evaluate and compare the state-of-the-art. Among these systems, chemical-free photocatalysis emerges as a cost-effective and sustainable solution for PFOA degradation and potentially other perfluorinated carboxylic acids. This review (I) classifies the state-of-the-art of chemical-free photocatalysts for PFOA degradation in families of materials (Ti, Fe, In, Ga, Bi, Si, and BN), (II) describes the evolution of catalysts, identifies and discusses the strategies to enhance their performance, (III) proposes a simplified cost evaluation tool for simple techno-economical analysis of the materials; (IV) compares the features of the catalysts expanding the classic degradation focus to other essential parameters, and (V) identifies current research gaps and future research opportunities to enhance the photocatalyst performance. We aim that this critical review will assist researchers and practitioners to develop rational photocatalyst designs and identify research gaps for green and effective PFAS degradation.

Photodegradation and photocatalysis of per- and polyfluoroalkyl substances (PFAS): A review of recent progress

Per- and polyfluoroalkyl substances (PFAS) are oxidatively recalcitrant organic synthetic compounds. PFAS are an exceptional group of chemicals that have significant physical characteristics due to the presence of the most electronegative element (i.e., fluorine). PFAS persist in the environment, bioaccumulate, and have been linked to toxicological impacts. Epidemiological and toxicity studies have shown that PFAS pose environmental and health risks, requiring their complete elimination from the environment. Various separation technologies, including adsorption with activated carbon or ion exchange resin; nanofiltration; reverse osmosis; and destruction methods (e.g., sonolysis, thermally induced reduction, and photocatalytic dissociation) have been evaluated to remove PFAS from drinking water supplies. In this review, we will comprehensively summarize previous reports on the photodegradation of PFAS with a special focus on photocatalysis. Additionally, challenges associated with these approaches along with perspectives on the state-of-the-art approaches will be discussed. Finally, the photocatalytic defluorination mechanism of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) following complete mineralization will also be examined in detail.

Nanomaterial-Based Advanced Oxidation/Reduction Processes for the Degradation of PFAS

This review focuses on a critical analysis of nanocatalysts for advanced reductive processes (ARPs) and oxidation processes (AOPs) designed for the degradation of poly/perfluoroalkyl substances (PFAS) in water. Ozone, ultraviolet and photocatalyzed ARPs and/or AOPs are the basic treatment technologies. Besides the review of the nanomaterials with greater potential as catalysts for advanced processes of PFAS in water, the perspectives for their future development, considering sustainability, are discussed. Moreover, a brief analysis of the current state of the art of ARPs and AOPs for the treatment of PFAS in water is presented.

Photocatalysis of aqueous PFOA by common catalysts of In2O3, Ga2O3, TiO2, CeO2 and CdS: influence factors and mechanistic insights

Gallium oxide (Ga₂O₃), titanium dioxide (TiO₂), cerium dioxide (CeO₂), indium oxide (In₂O₃) and cadmium sulfide (CdS) were commonly used under UV light as photocatalysis system for the pollutants' degradation. In this study, these five catalysts were applied for the photodegradation of perfluorooctanoic acid (PFOA), a well-known perfluoroalkyl substance (PFAS). As a result, the PFOA photodegradation performance was sequenced as: Ga₂O₃ > TiO₂ > CeO₂ > In₂O₃ > CdS. To further explain the photocatalysis mechanism, the effects of initial pH, photon energy and band gap were evaluated. The initial pH of 3 ± 0.2 hinders the catalytic reaction of CdS, resulting in low degradation of PFOA, while it has no significant effect on Ga₂O₃, TiO₂, CeO₂ and In₂O₃. In addition, quantum yield was sequenced as TiO₂ > CeO₂ > Ga₂O₃ > In₂O₃, which may not be the main factor determining the degradation effect. Notably, the band gap energy from large to narrow was as: Ga₂O₃ > TiO₂ > CeO₂ > In₂O₃ > CdS, which exactly matched their degradation performance.

Photocatalytic degradation of perfluoroalkyl substances in water by using a duo-functional tri-metallic-oxide hybrid catalyst

The recalcitrant nature of perfluoroalkyl substances (PFASs) urges scientists to discover solutions to permanently remove PFAS contaminations from water with less energy in contrast to incineration. Herein, a duo-functional tri-metallic-oxide (f-TMO) hybrid photocatalyst was developed via a facile process, which displayed both high adsorption capacity and high defluorination rate of a series of PFASs including PFOA, PFOS, PFHpA, PFHxA and PFBA due to the generated holes/electrons (h⁺/e^-) and multi-radicals such as O₂^•- and SO₄^•-. Particularly the Langmuir adsorption capacities up to 827.84 and 714.46 mg g^-1 along with the adsorption efficiency of 99.8% and 99.4% for PFOS and PFOA were respectively achieved. A defluorination ratio of as high as 74.8% with PFOA and a ratio up to 67.6% with PFOS were respectively received. Over 98% PFOA molecules were degraded within as fast as 15 min under initial concentrations ranging from 1 ppb to 1000 ppb, which demonstrates an excellent degradation kinetics. As for the sulfonic acid of PFOS, an as high as 95.5% degradation efficiency was obtained within 300 min. The degradation rates were 4.5 mg L^-1 h^-1 for PFOA and 0.54 mg L^-1 h^-1 for PFOS, respectively. In parallel, the f-TMO photocatalyst still exhibited a >96.2% degradation efficiency after eight regeneration cycles. The high physical adsorption capacity and high defluorination rate make this f-TMO catalyst promising applications in removing various PFASs from a broad range of residential and industrial water systems.

Efficient removal of PFOA with an In2O3/persulfate system under solar light via the combined process of surface radicals and photogenerated holes

The environmental persistence, high toxicity and wide spread presence of perfluorooctanoic acid (PFOA) in aquatic environment urgently necessitate the development of advanced technologies to eliminate PFOA. Here, the simultaneous application of a heterogeneous In₂O₃ photocatalyst and homogeneous persulfate oxidation (In₂O₃/PS) was demonstrated for PFOA degradation under solar light irradiation. The synergistic effect of direct hole oxidation and in-situ generated radicals, especially surface radicals, was found to contribute significantly to PFOA defluorination. Fourier infrared transform (FTIR) spectroscopy, Raman, electrochemical scanning microscope (SECM) tests and density functional theory (DFT) calculation showed that the pre-adsorption of PFOA and PS onto In₂O₃ surface were dramatically critical steps, which could efficiently facilitate the direct hole oxidation of PFOA, and boost PS activation to yield high surface-confined radicals, thus prompting PFOA degradation. Response surface methodology (RSM) was applied to regulate the operation parameters for PFOA defluorination. Outstanding PFOA decomposition (98.6%) and near-stoichiometric equivalents of fluorides release were achieved within illumination 10 h. An underlying mechanism for PFOA destruction was proposed via a stepwise losing CF₂ unit. The In₂O₃/PS remediation system under solar light provides an economical, sustainable and environmentally friendly approach for complete mineralization of PFOA, displaying a promising potential for treatment of PFOA-containing water.

Photooxidative decomposition and defluorination of perfluorooctanoic acid (PFOA) using an innovative technology of UV-vis/ZnxCu1-xFe2O4/oxalic acid

Per- and polyfluoroalkyl substances (PFAS) are a large group of perfluorinated organic molecules that have been in use since the 1940s for industrial, commercial, and consumer applications. PFAS are a growing concern because some of them have shown persistent, bioaccumulative and toxic effects. Herein, we demonstrate an innovative technology of UV-vis/Zn_xCu_1-xFe₂O₄/oxalic acid for the degradation of perfluorooctanoic acid (PFOA) in water. The magnetically retrievable nanocrystalline heterogeneous ferrite catalysts, Zn_xCu_1-xFe₂O₄ were synthesized using a sol-gel auto-combustion process followed by calcination at 400 °C. The combination of Zn_xCu_1-xFe₂O₄ and oxalic acid generate reactive species under UV light irradiation. These reactive species are then shown to be capable of the photodegradation of PFOA. The degree of degradation is tracked by identifying transformation products using liquid chromatography coupled with quadrupole time-of-flight mass spectroscopy (LC-QTOF-MS).

Light-Induced Advanced Oxidation Processes as PFAS Remediation Methods: A Review

PFAS substances, which have been under investigation in recent years, are certainly some of the most critical emerging contaminants. Their presence in drinking water, correlated with diseases, is consistently being confirmed by scientific studies in the academic and health sectors. With the aim of developing new technologies to mitigate the water contamination problem, research activity based on advanced oxidation processes for PFAS dealkylation and subsequent mineralization is active. While UV radiation could be directly employed for decontamination, there are nevertheless considerable problems regarding its use, even from a large-scale perspective. In contrast, the use of cheap, robust, and green photocatalytic materials active under near UV-visible radiation shows interesting prospects. In this paper we take stock of the health problems related to PFAS, and then provide an update on strategies based on the use of photocatalysts and the latest findings regarding reaction mechanisms. Finally, we detail some brief considerations in relation to the economic aspects of possible solutions.

Decomposition of highly persistent perfluorooctanoic acid by hollow Bi/BiOI1-xFx: Synergistic effects of surface plasmon resonance and modified band structures

Perfluorooctanoic acid (PFOA) is highly stable due to the strong CF bond and extremely difficult to be removed by conventional photocatalysts. In this study, Bi doped BiOI_1-xF_x solid solutions with hollow microsphere structure were prepared through a facile one-step hydrothermal method. Compared with pure BiOI and BiOF, the band gap of the Bi/BiOI_1-xF_x solid solutions was significantly reduced, thus promoting the visible light absorbance. The cavity structure of the BiOI_1-xF_x solid solutions enhanced the surface areas and active sites for reaction. The local electromagnetic field dominated by surface plasmon resonance (SPR) effect of Bi metal on the surface favored the separation of the photoinduced charge pairs. As a consequence, Bi/BiOI_0.8F_0.2 (x = 0.20, the doping amount of fluorine was 20 %) composite displayed the best photocatalytic performance for decomposing PFOA, and 40 mg/L PFOA could be removed within 2 h illumination. The degradation rate constant (k = 0.0375 min^-1) of PFOA by Bi/BiOI_0.8F_0.2 was about tenfold of that by pure BiOI and BiOF. Superoxide radical (·O₂-) predominated in the degradation of PFOA by Bi/BiOI_0.8F_0.2, and the possible degradation pathway of PFOA by Bi/BiOI_0.8F_0.2 was proposed. This work provides a highly efficient catalyst for the practical application in removal of highly persistent PFOA.

Rapid photochemical decomposition of perfluorooctanoic acid mediated by a comprehensive effect of nitrogen dioxide radicals and Fe3+/Fe2+ redox cycle

Developing efficient methods to degrade perfluorochemicals (PFCs), an emerging class of highly recalcitrant contaminants, are urgently needed in recent years, due to their persistence, high toxicity, and resistance to most regular treatment procedures. Here, a UV-photolysis system is reported for efficient mineralization of perfluorooctanoic acid (PFOA) via irradiation of ferric nitrate aqueous solution, where in-situ generating •NO₂ and the effective Fe³⁺/Fe²⁺ redox cycle synergistically play great roles on rapidly mediating the mineralization of PFOA. A fast PFOA removal kinetics with first-order kinetic constants of 2.262 h^-1 is observed at initial PFOA concentration of 5 ppm (50 mL volume), reaching ∼ 92 % removal efficiency within only 0.5-h irradiation. Near-stoichiometric fluoride ions liberation and high total organic carbon (TOC) removal efficiency (∼100 %) further validated the capability for completely destructive removal of PFOA. A tentative pathway for PFOA destruction is proposed. This work, by UV photolysis of abundant existing iron/nitrate-based systems in natural environment, provides an economical, sustainable and highly efficient approach for complete mineralization of perfluorinated chemicals.

TiO2 quantum dots loaded sulfonated graphene aerogel for effective adsorption-photocatalysis of PFOA

With the pollution of perfluoroalkyl substances (PFASs) became increasingly serious, the researches focused on removal of PFASs by adsorption-photocatalysis method has attracted considerable attention. To make the catalyst TiO₂ disperse uniformly as quantum dots onto hydrophobic surface which was liable to attract perfluorooctanoic acid (PFOA), the surfactant sodium dodecyl sulfate (SDS) were used in this work, which not only connected the hydrophilic TiCl₃ to the hydrophobic sulfonated graphene (SG) nanosheets, but also behaved as the molecular template for controlled nucleation and growth of the nanostructured TiO₂. After 3D SG-TiO₂ QD nanosheets were fabricated, a series of 3D SG-TiO₂ QD aerogels were self-assembled by ice-template. TiO₂ uniformly distributed on the surface of SG aerogel at QD size level (2-3 nm) and the size of TiO₂ could be effectively regulated by concentration of SDS. Compared with aggregated TiO₂ material, 3D SG-TiO₂ QD aerogels owned higher adsorption and photocatalytic performance. Benefiting from the hydrophobic surface of 3D SG as well as dispersed TiO₂ QDs, 3D SG-TiO₂ QD could enrich PFOA instantaneously (0.0381/s) and photocatalytic decomposed them effectively (1.898 E^-4/s). PFOA degradation by hole and hydroxyl radicals proceeded via a stepwise mechanism. The column made of 3D SG-TiO₂ QD could remove PFOA persistently in cycles of permeation. 3D SG-TiO₂ QD possessed powerful adsorption-photocatalytic decomposition capability of PFOA and steady reusability performance. The present work highlights the individual roles and synergistic effect of TiO₂ QD and 3D SG for effectively removing PFOA.

Research progress on the removal of hazardous perfluorochemicals: A review

Perfluorinated substances are global and ubiquitous pollutants. The persistent organic pollution of perfluorochemicals (PFCs) have drawn attentions worldwide. In view of the current need for sustainable development, many researchers began to study the remediation techniques for PFCs. Due to its unique hydrophobic and oil-phobic characteristics, the requirements for the PFCs removal process are different, so that their remediation techniques are still under continuous exploration. Hence, this review summarized the removal behaviors of various PFCs on different materials which supply a good foundation for future investigations in this field. It is evident from previous literature that every remediation techniques for PFCs has its own advantages. Among various currently evaluated removal methods, adsorption seems to be one of the most commonly used and recognized techniques for PFCs pollution control. Other innovative and promising techniques, such as physical and/or chemical methods, have also been tested for their effectiveness in removing perfluorinated compounds.

Electrochemical degradation of antibiotic levofloxacin by PbO2 electrode: Kinetics, energy demands and reaction pathways

In this work, the electrochemical degradation of antibiotic levofloxacin (LFX) has been studied using a novel rare earth La, Y co-doped PbO₂ electrode. The effect of applied current density, pH value and initial LFX concentration on the degradation performance were systematically evaluated. The results demonstrated that electrochemical oxidation of LFX over the La-Y-PbO₂ electrode was highly effective and the reaction followed an apparent first-order kinetic model. Considering the degradation efficiency and energy efficiency, the relative optimal conditions are identified as current density 30 mA cm^-2, pH 3 and initial LFX concentration 800 mg L^-1. According to the identified products, a reaction mechanism has been proposed and the products were further oxidized to CO₂, H₂O, NH₄⁺, NO₃^- and F^-. A total of four aromatic intermediate products of LFX degradation were identified and the different structural changes to the LFX molecule included pepiperazinyl hydroxylation, decarboxylation and defluorination.

Photocatalytic degradation and mineralization of perfluorooctanoic acid (PFOA) using a composite TiO2 -rGO catalyst

The inherent resistance of perfluoroalkyl substances (PFASs) to biological degradation makes necessary to develop advanced technologies for the abatement of this group of hazardous substances. The present work investigated the photocatalytic decomposition of perfluorooctanoic acid (PFOA) using a composite catalyst based on TiO₂ and reduced graphene oxide (95% TiO₂/5% rGO) that was synthesized using a facile hydrothermal method. The efficient photoactivity of the TiO₂-rGO (0.1gL^-1) composite was confirmed for PFOA (0.24mmolL^-1) degradation that reached 93±7% after 12h of UV-vis irradiation using a medium pressure mercury lamp, a great improvement compared to the TiO₂ photocatalysis (24±11% PFOA removal) and direct photolysis (58±9%). These findings indicate that rGO provided the suited properties of TiO₂-rGO, possibly as a result of acting as electron acceptor and avoiding the high recombination electron/hole pairs. The release of fluoride and the formation of shorter-chain perfluorocarboxilyc acids, that were progressively eliminated in a good match with the analysed reduction of total organic carbon, is consistent with a step-by-step PFOA decomposition via photogenerated hydroxyl radicals. Finally, the apparent first order rate constants of the TiO₂-rGO UV-vis PFOA decompositions, and the intermediate perfluorcarboxylic acids were found to increase as the length of the carbon chain was shorter.

Thermodynamics of aqueous perfluorooctanoic acid (PFOA) and 4,8-dioxa-3H-perfluorononanoic acid (DONA) from DFT calculations: Insights into degradation initiation

Modern fluorosurfactants introduced during and after perfluoroalkyl carboxylates/sulfonates phase-out present chemical features designed to facilitate abatement, hence reducing persistence. However, the implications of such features on environmental partitioning and stability are yet to be fully appreciated, partly due to experimental difficulties inherent to the handling of their (diluted) aqueous solutions. In this work, rigorous quantum chemistry calculations were carried out in order to provide theoretical insights into the thermodynamics of hydroperfluorosurfactants in aqueous medium. Estimates of acid dissociation constant (pK_a), standard reduction potential (E⁰), and bond dissociation enthalpy (BDE) and free energy (BDFE) were computed for perfluorooctanoic acid (PFOA), 4,8-dioxa-3H-perfluorononanoic acid (DONA) and their anionic forms via ensemble averaging at density functional theory level with implicit solvent models. A ‹pK_a› in the neighborhood of zero and a E⁰ of about 2.2 V were obtained for PFOA. Predictions for the acidic function of DONA compare well with PFOA's, with a pK_a of 0.8-1.5 and a E⁰ of 2.07-2.15 V. Deprotonation thus represents the dominant phenomenon at environmental conditions. Calculations indicate that H-abstraction of the aliphatic proton of DONA by a hydroxyl radical is the thermodynamically favored reaction path in oxidative media, whereas hydrolysis is not a realistic scenario due to the high dissociation constant. Short intramolecular interactions available to the peculiar hydrophobic tail of DONA were also reviewed, and the relevance of the full conformational space of the fluorinated side chain discussed.

Nitrogen dioxide radicals mediated mineralization of perfluorooctanoic acid in aqueous nitrate solution with UV irradiation

Effective decomposition of perfluorooctanoic acid (PFOA) has received increasing attention in recent years because of its global occurrence and resistance to most conventional treatment processes. In this study, the complete mineralization of PFOA was achieved by the UV-photolysis of nitrate aqueous solution (UV/Nitrate), where the in-situ generated nitrogen dioxide radicals (NO₂) efficiently mediated the degradation of PFOA. In particular, when the twinborn hydroxyl radicals were scavenged, the production of more NO₂ radicals realized the complete mineralization of PFOA. DFT calculations further confirm the feasibility of PFOA removal with NO₂. Near-stoichiometric equivalents of fluoride released rather than the related intermediates were detected in solution after decomposition of PEOA, further demonstrating the complete degradation of PFOA. Possible PFOA degradation pathways were proposed on the basis of experimental results. This work offers an efficient strategy for the complete mineralization of perfluorinated chemicals, and also sheds light on the indispensable roles of nitrogen dioxide radicals for environmental pollutants removal.

Combined sonochemical and short-wavelength UV degradation of hydrophobic perfluorinated compounds

Perfluorochemicals (PFCs), which are common in the aquatic environment, are toxic substances that have high chemical and heat resistance because of their strong C-F bonds. We investigated the effect of ultrasonication and short-wavelength UV irradiation on the degradation of perfluorooctane, perfluoropropionic acid, and perfluorooctanoic acid, which are examples of hydrophobic, hydrophilic, and intermediate PFCs, respectively. The results confirmed that ultrasonication was more effective for decomposing hydrophobic PFCs and UV irradiation was more effective for decomposing hydrophilic PFCs. Therefore, defluorination of the degradation intermediates was improved by a combination of ultrasonication and UV irradiation. Our results can be applied to the decomposition treatment of PFCs that have various levels of water solubility in the aquatic environment.

Factors controlling the rate of perfluorooctanoic acid degradation in laccase-mediator systems: The impact of metal ions

This study investigated the factors that regulated the degradation of perfluorooctanoic acid (PFOA) in laccase-catalyzed oxidative humification reactions with 1-hydroxybenzotriazole (HBT) as a mediator. The reaction rates were examined under conditions with key factors varied, including initial PFOA concentrations, laccase and HBT dosages, and the ionic contents of the reaction solutions. The PFOA degradation followed pseudo-first order kinetics, and the rate constants (k) were similar for the high (100 μmol L^-1) and low (1.00 μmol L^-1) initial PFOA concentrations, respectively at 0.0040 day^-1 (r² = 0.98) and 0.0042 day^-1 (r² = 0.86) under an optimum reaction condition tested in this study. The metal ions contained in the reaction solution appeared to have a strong impact on PFOA degradation. Differential UV-Vis spectrometry revealed that Cu²⁺ can complex with PFOA, which plays an essential role to enable PFOA degradation, probably by bridging the negatively charged PFOA and laccase, so that the free radicals of HBT that are released from laccase can reach and react with PFOA. It was also found that Fe³⁺ plays a similar role as Cu²⁺ to enable PFOA degradation in the laccase-HBT reaction system. In contrast, Mg²⁺ and Mn²⁺ cannot complex with PFOA under the investigated conditions, and do not enable PFOA degradation in the laccase-HBT system. Fluoride and partially fluorinated compounds were detected as PFOA degradation products using ion chromatography and high resolution mass spectrometry. The structures of the products suggest the reaction pathways involving free-radical initiated decarboxylation, rearrangement, and cross-coupling.

Temperature effect on photolysis decomposing of perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is recalcitrant to degrade and mineralize. Here, the effect of temperature on the photolytic decomposition of PFOA was investigated. The decomposition of PFOA was enhanced from 34% to 99% in 60 min of exposure when the temperature was increased from 25 to 85°C under UV light (201-600 nm). The limited degree of decomposition at 25°C was due to low quantum yield, which was increased by a factor of 12 at 85°C. Under the imposed conditions, the defluorination ratio increased from 8% at 25°C to 50% at 85°C in 60 min. Production of perfluorinated carboxylic acids (PFCAs, C7-C5), PFCAs (C4-C3) and TFA (trifluoroacetic acid, C2) accelerated and attained a maximum within 30 to 90 min at 85°C. However, these reactions did not occur at 25°C despite extended irradiation to 180 min. PFOA was decomposed in a step-wise process by surrendering one CF2 unit. In each cyclical process, increased temperature enhanced the quantum yields of irradiation and reactions between water molecules and intermediates radicals. The energy consumption for removing each μmol of PFOA was reduced from 82.5 kJ at 25°C to 10.9 kJ at 85°C using photolysis. Photolysis coupled with heat achieved high rates of PFOA degradation and defluorination.