Heat-activated Persulfate Research Articles

Oxidation of bromide by heat-activated persulfate – Effects of temperature and the organic matter surrogate phenol on kinetics and stoichiometry

• Oxidation of persulfate by sulfate radical affects persulfate decomposition kinetics. • Bromide oxidation to bromate was hindered by phenol. • Sulfate radicals reacting with Br-species decreased at higher temperature. • Insoluble phenol oxidation byproducts formation is favored at high temperature. Reaction mechanisms of sulfate radical with bromide and organic substances can be largely altered at elevated temperature in heat-activated persulfate process due to different activation energies. This study investigated kinetics and stoichiometry of bromide oxidation in the heat-activated persulfate process. We postulated that reaction of sulfate radical with persulfate, which has relatively low reaction rate (6.3 × 10 5 M −1 s −1 ), may become an important reaction at elevated temperatures. Persulfate decomposition was inhibited in the presence of sulfate radical scavenger phenol at low temperature (40 °C) whereas phenol affected persulfate decomposition only at < 50 °C but not at higher temperatures. This was because the second order reaction rate constant of sulfate radical with persulfate became higher (assumed as 10 10 M −1 s −1 ) than with phenol at a temperature > 50 °C, which can be explained by a high activation energy (estimated activation energy: 311 kJ/mol). Bromate formation was inhibited in the presence of phenol. However, phenol oxidation was not affected by the presence of Br − , even though Br − reacts faster with sulfate radicals than phenol and was present in excess. This indicated that formed reactive bromine species such as Br and Br 2 − oxidize phenol under reformation of bromide. Formation of insoluble products was also observed indicating polymerization of phenol. This can be explained by lack of dissolved oxygen under conditions of heat-activation.

Free radicals-triggered reductive and oxidative degradation of highly chlorinated compounds via regulation of heat-activated persulfate by low-molecular-weight organic acids

Heat/persulfate (PS)-based chemical oxidation for soil and groundwater remediation is limited in its ability to degrade highly chlorinated compounds (HCCs) due to their insensitivities to electrophilic radicals (e.g. SO4•- and O•H). Herein, we developed a universal system for reductive radicals formation with nucleophilic character through hydrogen atom transfer between low-molecular-weight organic acids (LMWOAs) and electrophilic radicals. Specifically, we found that oxalic acid could regulate heat/PS system to generate carbon dioxide radical anion (CO2•-) which initiated nucleophilic reduction of dichlorodiphenyltrichloroethane (DDT), followed by SO4•-/O•H-initiating electrophilic oxidization of dechlorination intermediates. The CO2•- was oxygen-dependent, resulting in higher DDT degradation performance in anaerobic environment, and corresponding degradation pathways were elucidated by theory calculations. Most importantly, compared to heat/PS system, appropriately distributing the amount of CO2•- and SO4•-/O•H by regulating additive concentration of oxalic acid significantly increased degradation efficiency (32.34%), degradation rate (174.20%), and mineralization efficiency (29.57%) on DDT, revealing great potentials of proposed system.

In Situ EPR Spin Trapping and Competition Kinetics Demonstrate Temperature-Dependent Mechanisms of Synergistic Radical Production by Ultrasonically Activated Persulfate.

Ultrasound coupled with activated persulfate can synergistically degrade aqueous organic contaminants. Here, in situ electron paramagnetic resonance spin trapping was used to compare radicals produced by ultrasonically activated persulfate (US-PS) and its individual technologies, ultrasound alone (US) and heat-activated persulfate (PS), with respect to temperature. Radicals were trapped using 5,5-dimethyl-1-pyrroline-N-oxide, DMPO, to form detectable nitroxide adducts. Using initial rates of radical adduct formation, and compared to US and PS, US-PS at 40 and 50 °C resulted in the largest synergistic production of radicals. Radicals generated from US were reasonably consistent from 40 to 70 °C, indicating that temperature had little effect on cavitational bubble collapse over this range. However, synergy indexes calculated from initial rates showed that ultrasonic activation of persulfate at the bubble interface changes with temperature. From these results, we speculate that higher temperatures enhance persulfate uptake into cavitation bubbles via nanodroplet injection. DMPO-OH was the predominant adduct detected for all conditions. However, competition modeling and spin trapping in the presence of nitrobenzene and atrazine probes showed that SO4•- predominated. Therefore, the DMPO-OH signal is derived from SO4•- trapping with subsequent DMPO-SO4- hydrolysis to DMPO-OH. Spin trapping is effective in quantifying total radical adduct formation but limited in measuring primary radical speciation in this case.

Feasibility study on produced water oxidation as a pretreatment at offshore platform

Produced water (PW) generated worldwide has lately become an issue of environmental concern. PW has a complex composition and a suitable treatment at offshore oil and gas platforms is required to achieve zero harmful discharge into the sea. The feasibility of electrochemical oxidation, heat-activated persulfate and ozonation was investigated as PW pretreatment. For comparison purposes, a common oxidant dosage level of 5% and 10% treatment equivalent chemical oxygen demand(COD) removal were established. Aiming to access PW biodegradability, an assay for biological oxygen demand(BOD) for high salinity matrix was also developed as a tool to characterize treatment efficiency. Electrochemical oxidation was largely independent on the anode materials, and controlled by the applied charge passed through the system. Heat-activated persulfate reaction was time-consuming and dependent on activation temperature, as well as initial oxidant concentration. Both methods reduced COD and BOD without significantly improving PW biodegradability, probably due to by-products generation. Ozonation had the most promising results applying doses ranging from 3.5 to 151mgO3/L. The benzene in PW after ozonation reduced up to 71% alongside with> 70% toxicity reduction for tested doses. Ozonation also showed to marginally improve PW biodegradability, which underline the potential of ozone to facilitate a subsequent biological treatment.

Modelling and optimizing Orange G removal by heat-activated persulfate using two-step statistical strategies: Plackett–Burman and Box–Behnken designs*

Modelling and optimizing Orange G removal by heat-activated persulfate using two-step statistical strategies: Plackett–Burman and Box–Behnken designs*

Advanced oxidation processes for removal of organics from cooling tower blowdown: Efficiencies and evaluation of chlorinated species

One of the major challenges in reusing cooling tower blowdown water (CTBD) utilizing membrane processes is its remaining organic compounds, e.g., humic substances leading to biofouling. Besides, the possible abundance of chloride in CTBD imposes the concern of the formation of chlorinated by-products. To choose a pre-treatment process for the studied CTBD composition, various advanced oxidation processes (AOPs), including electrooxidation (EO), photocatalytic degradation (PCD), heat-activated persulfate oxidation (PS), UVC/vacuum UV (UVC/VUV), and UVC processes, were evaluated and compared based on two main targets: i) highest removal and mineralization of the organics, especially humic substances; and ii) lowest formation of chlorinated by-products including adsorbable organic halides and oxychlorides. All the processes were conducted in the natural condition of the real CTBD, while solution pH was monitored. Based on results of chemical oxygen demand, total organic carbon, dissolved organic carbon, UV254 absorbance, liquid-chromatography–organic carbon detection (LC-OCD), and fluorescence excitation-emission matrices (FEEM), it is concluded that PS leads to complete removal of organic compounds along with the lowest formation of low molecular weight organic acids and organic neutrals. FEEM and LC-OCD data also indicated that EO, PCD, and UVC/VUV processes brought about substantial removal of organic compounds and broke down the humic substances into low molecular weight building blocks and organics. Besides, EO exhibited the highest AOX and oxychlorides formation, while these were limited when using the other AOPs. Summarizing, PS, PCD, and UVC/VUV were efficient processes for the degradation and mineralization of organics without generating significant amounts of chlorinated by-products.

Enhanced degradation of perfluorooctanoic acid by heat-activated persulfate in the presence of zeolites

The treatment of contaminations with perfluorooctanoic acid (PFOA) is a huge challenge due to its environmental persistence and global distribution. A combination of adsorption and degradation processes is considered as a promising approach for removing PFOA traces from water. In the present study, we developed a novel treatment strategy for PFOA using heat-activated persulfate in the presence of BEA35 - a BEA-structure type zeolite. Our experimental results show for the first time that BEA35 not only removes PFOA by adsorption, but also accelerates its degradation by means of heat-activated persulfate until complete mineralization. The presence of zeolite (50 g L-1) increases PFOA degradation up to 99.8% compared with 58% in homogeneous solution under the same reaction conditions (C0,persulfate = 100 mM, 90 min, 70 °C). The influence of reaction conditions such as pH value, zeolite dosage and type were investigated, and possible reaction mechanisms were considered. The applicability of the zeolite-based treatment system was verified with real groundwater samples. A first cost estimation was provided for the application case of a zeolite fixed-bed adsorber with intermittent regeneration by heat-activated persulfate. The presented approach has the potential to overcome several shortcomings of the existing PFOA degradation technologies, such as high energy demands, vulnerability in complex water matrices, and inefficiency at trace concentration levels. Our findings provide an effective and efficient strategy for treatment of water containing traces of PFOA, which can also inspire the development of remediation technologies for water contaminated by other micropollutants.

Recalcitrant pollutants removal from paper mill wastewater by ferrous ion- and heat- activated persulfate oxidation processes using response surface methodology: a comparison study

ABSTRACT In this study, the removal of UV254, phenol, and calcium from paper industry wastewater by persulfate oxidation was investigated. Fe2+ addition and heat application methods were used for persulfate activation. Response surface methodology and central composite design were applied for the optimization of effective parameters on processes. The statistical fit of the model was confirmed by the high R2 and adjusted R2 values. Based on the results obtained, response surface methodology models were developed. Estimated results calculated with model equations and experimental data were close to each other, and the models were confirmed to be significant. As a result of experimental studies conducted under the optimum conditions determined by the model, UV254, phenol, and calcium removal efficiencies from paper industry wastewater were 84.2%, 92.6%, and 85.7%, respectively by the Fe2+-activated persulfate process while they were 96.4%, 96.3%, and 81.8%, respectively by heat-activated persulfate process. The results of the study showed that persulfate oxidation is an effective advanced treatment process for recalcitrant pollutants removal from paper industry wastewater and response surface methodology is a useful tool for optimizing the treatment parameters.

Removal of drug losartan in environmental aquatic matrices by heat-activated persulfate: Kinetics, transformation products and synergistic effects

In this study, the oxidative degradation of losartan (LOS), a widely administered medicine for high blood pressure by heat-activated persulfate was investigated. Increased temperature and persulfate concentration, as well as acidic conditions enhance the degradation efficiency of LOS, whose rate follows pseudo-first order kinetics. From the respective apparent rate constants in the range 40–60 °C, an apparent activation energy of 112.70 kJ/mol was computed. Radical scavenging tests demonstrated that both HO• and SO4•− contribute towards LOS degradation. LOS degradation was suppressed in real water matrices including bottled water (BW) and secondary wastewater effluent (WW), while other experiments indicated that the presence of bicarbonates and humic acid negatively affected its oxidation. Instead, the addition of chloride ions at 250 mg/L resulted in a positive effect on LOS removal. The combination of heat-activated PS with low-frequency ultrasound exhibited a synergistic effect, with the ratio S being 2.29 in BW and 1.52 in WW. Five transformation products of LOS were identified through HRMS suspect and non-target screening approaches, among which two are reported for the first time. Using the in-house risk assessment program, ToxTrAMs was revealed that most of the identified TPs present higher toxicity than LOS against Daphnia magna.

Enhanced Recovery of Per- and Polyfluoroalkyl Substances (PFASs) from Impacted Soils Using Heat Activated Persulfate.

Varying transport potential of cationic, zwitterionic, and anionic per- and polyfluoroalkyl substances (PFASs) may pose challenges for remediation of aqueous film forming foam (AFFF) impacted sites, particularly during groundwater extraction. Slow desorption of stronger sorbing, zwitterionic, and cationic PFASs may cause extended remediation times and rebound in aqueous PFAS concentrations. Persulfate oxidation has the potential to convert a complex mixture of PFASs into a simpler and more recoverable mixture of perfluoroalkyl acids (PFAAs). AFFF-impacted soils were treated with heat-activated persulfate in batch reactors and subjected to 7-day leaching experiments. Soil and water were analyzed using a combination of targeted and high resolution liquid chromatography mass spectrometry techniques as well as the total oxidizable precursors assay. Following oxidation, total PFAS composition showed the expected shift to a higher fraction of PFAAs, and this led to higher total PFAS leaching in pretreated reactors (108-110%) vs control reactors (62-90%). In both pretreated and control soils, precursors that remained following leaching experiments were 61-100% cationic and zwitterionic. Results suggest that persulfate pretreatment of soils has promise as an enhanced recovery technique for remediation of total PFASs in impacted soils. They also demonstrate that PFAS distribution may have been altered at sites where in situ chemical oxidation was applied to treat co-occurring contaminants of concern.

Role of process parameters in the degradation of sulfamethoxazole by heat-activated peroxymonosulfate oxidation: Radical identification and elucidation of the degradation mechanism

The use of heat-activated peroxymonosulfate oxidation for the degradation of the antibiotic compound sulfamethoxazole (SMX) was studied in this paper. It was found that the degradation process follows a pseudo-first order kinetic model. Increasing the oxidant concentration and/or the activation temperature led to a higher sulfamethoxazole degradation efficiency. Increasing the pH from 3 to 9.5 resulted in a higher degradation efficiency as well, although the SMX degradation was significantly inhibited at a pH of 11. Through radical scavenging experiments, it was found that both •OH and •SO4− played a role in the SMX degradation mechanism. Seven transformation products were identified in the SMX degradation process. Both the radicals present and the initial pH value of the degradation process were found to influence the formation of several degradation products. Finally, the heat-activated peroxymonosulfate oxidation process was compared with the heat-activated persulfate process and the main intermediates formed in both processes were identified and compared with each other.

Effects of advanced oxidation processes on leachates and properties of microplastics

Microplastics (MPs) in natural environments undergo various aging processes. So far, little is known about the effects of chemical oxidation on leachates and properties of MPs. Here, we investigated the removal of pigment red from MPs by ozonation, Fenton, and heat-activated persulfate treatments, and further explored the nanoscale surface properties of treated MPs. Experimental results indicated that advanced oxidation processes effectively degraded pigment red released from MPs and the degradation rate was much faster than the leaching rate of pigments. Dominant reactive oxygen radicals in the ozone, Fenton, and heat-activated persulfate systems were identified as O2•−, HO•, and SO4•−, respectively. Height ranges of untreated, ozone-treated, Fenton-treated, and persulfate-treated MPs were 73 nm, 163 nm, 195 nm, and 206 nm, respectively. Oxidation of the -CH3 and -CH2 bonds occurred on the surface of treated MPs and the persulfate system achieved more serious oxidation degree than the ozone and Fenton systems. Addition of pigment red to the plastic polymer increased the glass transition temperature of MPs, which then showed a decline after advanced oxidation treatments except Fenton. The surface of persulfate-treated MPs was the stiffest, but the stiffness distribution of the ozone-treated and Fenton-treated MPs was more uneven. These research findings provide promising strategies to accelerate the aging process of MPs and contribute to a better understanding of the effects of aging on the environmental behavior of MPs.

Modelling and optimizing Orange G removal by heat-activated persulfate using two-step statistical strategies: Plackett–Burman and Box–Behnken designs

Modelling and optimizing Orange G removal by heat-activated persulfate using two-step statistical strategies: Plackett–Burman and Box–Behnken designs

Heat-activated potassium persulfate treatment of Sudan Black B dye: Degradation kinetic and thermodynamic studies

Water-soluble dyes are common persistent organic pollutants present in textile wastewater, which are associated with environmental pollution and health hazards. The conventional effluent treatment methods are not efficient to remove these dyes from textile wastewater. Heat activated persulfate based wastewater treatment is a promising advanced oxidation process (AOP) for the treatment of textile wastewater. Therefore, the main objective of the present work was to study the degradation of Sudan Black B (SBB) dye in aqueous solution by varying activation temperature (40–60 °C), KPS dosage (250–750 ppm), and initial dye concentration (20–50 ppm). The dye degradation was found in a range of 35%−100% for varied experimental conditions. Removal percentages were improved by the increase of temperature, time, and persulfate concentration but decreased with the increase of initial dye concentration. The kinetic study indicated that the degradation of SBB dye using KPS followed first order model with rate constants varied in a range of 0.15 × 10-2 − 40.5 × 10-2 min-1. Standard reaction enthalpies (ΔH˚), standard Gibbs free energies (ΔG˚), activation energies (Ea), standard entropies (ΔS˚) were found in a range of 190 − 505 kJ.mole-1, -33.0 − 0.6 kJ, 73 − 222 kJ.mole-1, 0.6–1.6 kJ/K for different sets of experimental conditions, respectively. Degradation reactions of SBB dye were endothermic (ΔH˚ +ve); non-spontaneous (ΔG˚ +ve) at 40 °C, but spontaneous (ΔG˚ −ve) at other temperatures (50 °C and 60 °C). Therefore, it can be predicted that heat-activated persulfate is an efficient method to achieve faster degradation of dye in the treatment of industrial wastewaters containing SBB dye.

Enhanced degradation of furfural by heat-activated persulfate/nZVI-rGO oxidation system: Degradation pathway and improving the biodegradability of oil refinery wastewater

Oil refinery wastewater is characterized by high values of temperature and furfural concentration. Furfural is a toxic and non-biodegradable substance in aqueous media that its absorption through the skin causes acute neurological and pulmonary effects. In this study, a heat-activated persulfate (HAP) system in combination with reduced graphene oxide-supported nano zero-valent iron catalyst (nZVI-rGO) was developed for oil refinery wastewater treatment. Five operational parameters regarding furfural removal were statistically modeled by an orthogonal central composite design (OCCD) and then optimized by genetic algorithm (GA) technique. The main characteristics of the nZVI-rGO as well as its reusability were investigated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy mapping (EDX-mapping), X-ray diffraction analysis (XRD) and vibrating sample magnetometer (VSM) analysis. The optimum values for the solution temperature, nZVI-rGO dosage, persulfate (PS) concentration, solution pH and reaction time were predicted to be 70 °C, 1.25 g L−1, 4.28 mmol L−1, 5.46 and 50 min, respectively. Under the optimized conditions, the experimental furfural removal efficiency in HAP/nZVI-rGO and HAP oxidation systems were obtained to be 97.80 and 68.20 %, respectively. Sulfate radical (SO4•-) has greater participation in furfural mineralization than hydroxyl radical (HO•). The major intermediates resulting from the furfural mineralization were short-chain acids including acetic acid and formic acid. Regardless, almost complete furfural mineralization was achieved after 100 min of the oxidation reaction. The optimized HAP/nZVI-rGO process was able to significantly improve the biodegradability of wastewater by more than 2 times.

Impact of application of heat-activated persulfate oxidation treated erythromycin fermentation residue as a soil amendment: Soil chemical properties and antibiotic resistance

Erythromycin fermentation residue (EFR) is the precipitation of fermentative biowaste used for extracting erythromycin (ERY) and may be disposed via land application after heat-activated persulfate (PS) oxidation treatment. However, the effects of the treated EFR as a soil amendment on soil chemical properties and the potential resistance risks caused by introduced ERY remain unclear. Here, a laboratory soil incubation experiment was performed to investigate the soil pH, salinity, introduced antibiotics, antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), as well as bacterial community structure in the treated EFR-amended soil. The results indicated that pH in treated EFR-amended soil decreased firstly and then increased. The salinity of soil increased but soil was still non-saline soil. In addition, the introduced ERY in the treated EFR-amended soil decreased with the half-life of 12.3 d. Moreover, the relative abundances of ERY resistance genes and MGEs in the treated EFR-amended soil were much lower than those in the control at the end of incubation. Bacterial community structure in the treated EFR-amended soil converged to similar structure in control soil after 49 d incubation. Our results showed that heat-activated PS oxidation treatment of EFR prior to application to soil might be in favor of limiting the spread of ERY resistance genes and MGEs.

Synergistic, aqueous PAH degradation by ultrasonically-activated persulfate depends on bulk temperature and physicochemical parameters.

Coupling ultrasound with other remediation technologies has potential to result in synergistic degradation of contaminants. In this work, we evaluated synergisms from adding high-power ultrasound (20kHz; 250W) to activated persulfate over a range of bulk temperatures (20-60°C). We studied the aqueous degradation kinetics of three polycyclic aromatic hydrocarbons (PAHs: naphthalene, phenanthrene, and fluoranthene) treated by ultrasound-alone, heat-activated persulfate, and combined ultrasonically-activated persulfate (US-PS). At 20°C, observed US-PS rate constants strongly correlated with Wilke-Chang diffusion coefficients. This correlation indicates PAH molecules diffuse to the bubble-water interface prior to reaction with sulfate radicals (SO4-) generated at the interface. At higher temperatures, observed US-PS rate constants appear to be a more complicated function of temperature and diffusion coefficients. Synergy indexes for PAHs with fast diffusion coefficients were greatest at 20°C. Fluoranthene, the largest and most hydrophobic PAH, had a maximum synergy index at 30°C; it benefited from additional thermal persulfate activation in bulk solution. Fluoranthene synergy indexes, however, decreased above 30°C and became antagonistic at 60°C. Electron paramagnetic resonance (EPR) spin trapping was used to quantify hydroxyl radical (OH) produced from acoustic cavitation in the absence of persulfate. These data showed consistent OH production from 20 to 60°C, indicating PAH antagonisms at 60°C were not due to lower bubble collapse temperatures. Instead, the results suggest that PAH antagonisms are caused by increased radical-radical recombination as bulk temperature increases. In effort to develop an efficient, combined remediation technology, this work suggests bulk temperatures between 20 and 40°C maximize US-PS synergisms.

The release of organic matter, nitrogen, phosphorus and heavy metals from erythromycin fermentation residue under heat-activated persulfate oxidation conditioning

Erythromycin fermentation residue (EFR) is one kind of biological waste with high organic matter content. The recycling of EFR is not only beneficial to the environmental protection, but also to the economic development. In this study, the release of organic matter, nitrogen (N), phosphorus (P) and heavy metals (HMs) from EFR under heat-activated persulfate (PS) oxidation conditioning was investigated. Results indicated that oxidation conditioning promoted the release of soluble chemical oxygen demand (SCOD). Heat-activated PS oxidation conditioning boosted the release of total nitrogen (TN), ammonia‑nitrogen (NH4+-N) and nitrate‑nitrogen (NO3−-N) into the supernatant, as well as the decomposition of organic nitrogen (ON). Concurrently, heat-activated PS oxidation conditioning facilitated the release of total phosphorus (TP), orthophosphate (PO43−-P) and organic phosphorus (OP) into the supernatant, and the decomposition of OP. Furthermore, heat-activated PS oxidation conditioning resulted in the increase of release efficiencies of HMs. Therefore, heat-activated PS oxidation conditioning was beneficial to the release of organic matter, nutrients and HMs.

A combo system consisting of simultaneous persulfate recirculation and alternating current electrical resistance heating for the implementation of heat activated persulfate ISCO

A combo system capable of simultaneous persulfate recirculation and low temperature electrical resistance heating (ERH) was developed for subsurface remediation of organic contaminants using heat-activated persulfate. First, dual-function injection/extraction-electrode wells were designed, and a laboratory-scale combo system was custom-build. Experiments in water tanks and sand tanks were then carried out to investigate the performance of the combo system, and study the impact of main operating parameters (persulfate dosage, recirculation rate, and phase voltage) on volumetric delivery and dispersion of heat and persulfate, and consequent volumetric oxidation of phenanthrene-spiked sand, a model compound of HOCs. The results indicate that the addition of persulfate salts could significantly improve volumetric heating rate, and application of recirculation brought more uniform elevation in temperature and enhanced volumetric degradation of phenanthrene in the recirculation-impacted zone. Overall, this study developed a promising combo system for the implementation of heat-activated persulfate ISCO.

FerrateVI oxidation of polycyclic aromatic compounds (PAHs and polar PACs) on DNAPL-spiked sand: degradation efficiency and oxygenated by-product formation compared to conventional oxidants.

In situ chemical oxidations are known to remediate PAH contaminations in groundwater and soils. In this study, batch-scale oxidations aim to compare the PAC (polycyclic aromatic compound) degradation of three oxidation processes traditionally applied for soil treatment: permanganate, heat-activated persulfate (60 °C) and Fenton-like activated by magnetite, to results obtained with ferrates (FeVI). Widely studied for water treatments, ferrates are efficient on a wide range of pollutants with the advantage of producing nontoxic ferric sludge after reaction. However, fewer works focus on their action on soil, especially on semi-industrial grade ferrates (compatible with field application). Oxidations were carried out on sand spiked with dense non-aqueous phase liquid (DNAPL) sampled in the groundwater of a former coking plant. Conventional 16 US-EPA PAHs and polar PACs were monitored, especially potential oxygenated by-products that can be more harmful than parent-PAHs. After seven reaction days, only the Fenton-like showed limited degradation. Highest efficiencies were obtained for heat-activated persulfate with no O-PAC ketones formed. Permanganate gave important degradation, but ketones were generated in large amount. The tested ferrates not only gave slightly lower yields due to their auto-decomposition but also induced O-PAC ketone production, suggesting a reactional pathway dominated by oxidoreductive electron transfer, rather than a radical one.