E-peroxone Process Research Articles

Degradation of the neonicotinoid insecticide imidacloprid by ozonation and the E-peroxone process: Mechanisms, transformation products, and toxicity

In this study, degradation of the neonicotinoid insecticide imidacloprid (IMI) by ozonation and the E-peroxone process was investigated. Results show that IMI is an O3-refractory compound with second-order rate constants for the reaction with O3 and •OH (kO3,IMI and k•OH,IMI) being 3.9 and 3.95 × 109 M−1 s−1 at pH 7, respectively. Due to its low O3 reactivity, IMI was only abated by < 20 % in a selected groundwater during ozonation with typical ozone doses applied in water treatment (1–5 mg/L). In comparison, the E-peroxone process considerably enhanced IMI removal efficiency to > 80 % under similar reaction conditions. During both ozonation and the E-peroxone process, IMI was mainly abated by •OH oxidation. The reaction mechanism of IMI with •OH was investigated with quantum computations, which show that H-abstraction at H23 site was the most favorable pathway. Sixteen transformation products (TPs) generated from IMI degradation were identified using various chromatographic and mass-spectrometric techniques. The acute and chronic toxicities of IMI and its TPs to different aquatic organisms were evaluated with Microtox bioassay and the ECOSAR program, which indicate that some TPs (e.g., TP2–TP5 and TP7–TP9) are even more toxic than IMI to aquatic organisms (e.g., daphnia). The results of this study suggest that IMI along with its TPs should be sufficiently abated during water treatment, and the E-peroxone process provides an efficient option to upgrade conventional ozonation for enhanced IMI abatement.

E-peroxone with a novel GDE decorated with hydrophobic membrane for the degradation of pyridine: Stability, byproducts and toxicity

E-peroxone process is an emerging electrochemical oxidation process, based on ozone and the in-situ cathodic generation of H2O2, but the stability of cathode is one of the key restraining factors. In this study, we designed a multilayer gas diffusion electrode (GDE) decorated with a commercial hydrophobic membrane for the degradation of pyridine. It was found that a proper control of membrane pore sizes and hot-pressing temperature can significantly promote the GDE stability. Subsequently, key operational parameters of the constructed E-peroxone system were investigated, including the ozone concentration, current density, pH value, electrolyte type and initial concentration of pyridine. The degradation pathways were proposed according to six identified transformation products. The toxicity variation along the degradation progress was evaluated with microbial respiration tests and Toxicity Estimation Software Tool (T.E.S.T.) calculation and an efficient detoxification capacity of E-peroxone was observed. This research provides a theoretical basis and technical support for the development of highly efficient and stable E-peroxone system for the elimination of toxic organic contaminants.

Revealing the characteristics of coagulant and ·OH generation in the electrocoagulation coupled with E-peroxone process and comparison of the synergistic effect for water purification

Electrocoagulation (EC) coupled with E-peroxone process (ECP) offers a promising approach for simultaneous coagulation and oxidation, enhancing contaminant removal efficiency and current efficiency within a single electrochemical system. However, understanding the production characteristics of active species and their synergistic effects remains limited. This study comprehensively investigated the production of active species (i.e., ·OH and coagulant) during the ECP process and explored their synergistic effect in real water purification. Increasing current density and O3 dosage led to significant enhancements in ·OH and Alb production. The synergistic factor (β) for ·OH production ranged from 1.68 to 1.73 for lower current density and from 1.19 to 1.32 for higher current density, while β for ·OH production in ECP increased from 0.77 to 1.16–1.19 with increased O3 dosage. Besides O3 decomposition and cathodically-induced H2O2 production, alternative pathways contributed to enhanced ·OH production and synergistic effects. The Al-based coagulant facilitated the reaction with O3, initiating a chain reaction for ·OH and Alb production. Furthermore, the feasibility and synergistic effects of ECP for two water matrices (surface water and shale gas produced water) were compared. ECP exhibited superior performance for both matrices, with TOC removal exceeding 63.2 % for surface water and 87.0 % for shale gas produced water. The study provides deeper insights into the ECP process, highlighting its potential for sustainable water treatment.

Pyridine N of N/Co-co-doped graphite gas diffusion electrode facilitating the efficient production of hydroxyl radicals in the electro-peroxone process

The electro-peroxone (E-peroxone) process combines ozone (O3) and hydrogen peroxide (H2O2) produced by an oxygen reduction reaction (ORR) pathway to generate super-active hydroxyl radical (·OH), which is considered to be a promising new advanced oxidation technology. Here, a N/Co-co-doped graphite gas diffusion electrode (Co-NG GDE) has been prepared by a simple mixed calcination method and applied in the E-peroxone system. Somewhat surprisingly, the Co-NG GDE exhibited the highest degradation efficiency for phenol and oxalate, though it performed the worst in the ORR to H2O2. The characterization test and experimental results have shown that Co-NG GDE produces abundant O2.– that can replace H2O2 to react with O3 to form super-active ·OH, which is due to the higher pyridine-N content of it. This work circumvents the limitation of H2O2 as the main intermediate in the traditional E-peroxone process by altering the main reaction pathway of the E-peroxone process and brings some new enlightenment to the research and development of this methodology.

The Use of E-Peroxone to Neutralize Wastewater from Medical Facilities at a Laboratory Scale

The treatment of medical wastewater by the peroxone (AOP) and electro-peroxone (E-peroxone) processes was analyzed. The E-peroxone process is based on the production of hydrogen peroxide electrochemically from an O2 and O3 gas mixture produced in sparged ozone generator effluent using graphite-polytetrafluorethylene cathodes. The electrogenerated H2O2 reacts with sparged ozone to produce hydroxyl radicals. All advanced oxidation processes presented in this study effectively removed chemical oxygen demand (COD) by up to 87%. The use of E-peroxone showed 15% better results in COD reduction than conventional peroxone. The research suggests that E-peroxone is more sufficient at removing pollutants in wastewater than peroxone. Hence, E-peroxone was found to be more cost-effective than AOP in this case.

Synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater by electro-peroxone process.

Herein, a highly efficient electro-peroxone (E-peroxone) process with graphite felt as ozone diffusion electrode (ODE) was developed for the synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater. Under optimal conditions, the total organic carbon (TOC) removal rate of real hospital wastewater could reach 93.9%. Importantly, 126 pharmaceutical compounds (antibiotics, antivirals, analgesics, antiepileptics, hormones, and others) were determined in hospital wastewater by using ultra performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS). 110 pharmaceutical compounds could be efficiently degraded in E-peroxone system. Concurrently, the microbial community analysis through high-throughput sequencing showed that E-peroxone process exhibited an excellent disinfection effect in real hospital wastewater. Escherichia coli as a bacterial indicator could be completely inactivated in E-peroxone process·H2O2 and hydroxyl radical (OH) were found in E-peroxone system based on the results of chemical probe experiments and electron paramagnetic resonance (EPR) analysis. The in-situ generation of H2O2 from cathodic oxygen reduction in ODE can react with ozone to produce OH, and realize high efficiencies for the elimination of pharmaceutical and sterilization. This work established a green and effective way without extra addition of chemical reagents for high-efficiency treatment of real hospital wastewater.

E-peroxone process of a chlorinated compound: Oxidant species, degradation pathway and phytotoxicity

An electro-peroxone (EP) process was conducted in an up-flow bubble column reactor with BDD electrodes. The efficiency of the process was tested in the 4-Chlorophenol (4-CPh) mineralization and compared with that attained by single treatments like ozonation (O3) and electro-oxidation (EO). At [TOC]o= 56 mg·L−1, pHo= 7.0, T = 293 K, j = 0.06 A·cm−2, t = 120 min, the oxidation power decreased in the following order EP>EO>O3, and the TOC removed was, in the same order, 100%> 93%> 40%. The calculated synergy coefficient was 0.31, while the mineralization current efficiency percentage (MCE%) and the energy consumption (EC) were 12.24% and 11.48%, 2.84 and 2.31 kW·h−1, for EP and EO, respectively. The germination percentage of Lactuca sativa, was 100%, 30% and 20%, at the end of EP, EO and O3, respectively. This indicates that phytotoxicity, was only eliminated with EP. Based on the by-products, e.g. aromatic compounds (4-chlorocatechol, catechol, phenol, p-benzoquinone, hydroquinone) and carboxylic acids (maleic, formic, fumaric, succinic, oxalic, malonic and acetic acids) identified by UHPLC-UV/DAD and the changes of the concentration of chloride ion (Cl-), hypochlorite, chlorite, chlorate and perchlorate, a reaction pathway was proposed for the 4-CPh mineralization by the E-peroxone process. It was demonstrated that under the studied conditions both, hydrogen peroxide and ozone, are produced during EO. At the end of EO, H2O2, carboxylic acids and perhaps persulfates, are responsible for the phytotoxicity of the solution.

Enhancement of E-Peroxone process with waste-tire carbon composite cathode for tinidazole degradation.

The cathode is the key component in the electro-peroxone process (E-Peroxone), which is popularly constructed with carbon materials. This study developed an innovative method to fabricate a cathode with waste-tire carbon (WTC) whose performance was evaluated for the degradation of tinidazole (TNZ), an antibiotic frequently detected in water. It was found that the addition of WTC in the cathode can significantly promote the yield of H2O2 and the current efficiency: around 2.7 times that of commercial carbon black at the same loading. The critical influencing factors were studied, including the current density, ozone concentration, initial pH value, chlorine ions and initial TNZ concentration. The scavenger tests demonstrated the possible involvement of •OH and O2•-. Some transformation products of TNZ were identified with UPLC-MS and the degradation pathway was proposed accordingly. These results demonstrated the potential of WTC for developing E-Peroxone cathodes.

Incineration of the antibiotic chloramphenicol by electro-peroxone using a smart electrolyzer that produces H2O2 through electrolytic O2

The experimental characterization of the electro-peroxone (E-peroxone) process during the elimination of the antibiotic chloramphenicol (CAP) was carried out in a flow plant using a novel flow-through electrolyzer equipped with two anodes and two cathodes in a cascade configuration, anode-cathode-anode-cathode. The H2O2 is formed at the graphite felt cathodes by reducing O2 provided from the oxygen evolution reaction (OER) performed at the Ti|IrO2-Ta2O5 anodes. This electrolyzer avoids employing an air compressor to supply the O2 for the electrosynthesis of H2O2 during the E-peroxone process. The characterization of E-peroxone was performed by using 2 L of a solution containing 0.05 M Na2SO4 at concentrations of CAP from 20 to 50 mg L−1 TOC (48.9–122.3 mg L−1 CAP), studying the influence of pH (3–9), applied current density (5 ≤ j ≤ 15 mA cm−2), and solution flow rate (0.4 ≤ Q ≤ 1.0 L min−1) on the oxidation of CAP. The best performance reached 100% CAP degradation, 63% TOC removal, at pH 3, j = 10 mA cm−2, Q = 0.4 L min−1 and FO3=17.5 mg min−1. The mineralization current efficiency (MCE) and electrolytic energy consumption (EC) were 19% and 0.202 kWh (g TOC)−1, respectively. The comparison of E-peroxone with anodic oxidation aided by H2O2 (AO-H2O2) and ozonation showed the oxidative power sequence E-peroxone > ozonation > AO-H2O2. The evolution of carboxylic acids and inorganic ions was performed by chromatographic and spectrophotometric techniques. Finally, a route of CAP degradation is proposed.

Role of in-situ electro-generated H2O2···bridge in tetracycline degradation governed by mechanochemical Si-O anchoring Cu2+ as electron shuttle during E-peroxone process

The efficient mineralization of tetracycline (TC) and reaction mechanism were investigated by designing heterogeneous H2O2···bridge linked with active sites in higher valency species. CuSi-BM60 was synthesized by anchoring Cu2+ on Si-O functional groups of MCM-48 by mechanochemical technology to assist electro-peroxone treatment (E-peroxone). Results suggested that catalysts as electron shuttle enhanced electron transfer and reactive oxygen species (ROSs) generation, showing a complete tetracycline (TC) degradation and excellent mineralization (73.2%, 60 min). Cu sites significantly raised the interaction with in-situ electro-generated H2O2, generating uneven electron cloud distribution by Si−O···Cu···HO−OH* bonding bridge, which enlarged H-O bonding length/angle near Cu and decreased orbital energy level gap. This work provided new insights into the complex of ball milling mediated Cu2+ with H2O2 accompanied by the cycle of H-O bonding cleavage and regeneration for efficient ROSs production during E-peroxone.

Removal of Aqueous Para-Aminobenzoic Acid Using a Compartmental Electro-Peroxone Process

The presence of emerging contaminant para-aminobenzoic acid (PABA) in the aquatic environment or drinking water has the potential to harm the aquatic ecosystem and human health. In this work, the removal of aqueous PABA by a compartmental electro-peroxone (E-peroxone) process was systematically investigated from the kinetic and mechanism viewpoints. The results suggest that single electrolysis or ozonation was inefficient in PABA elimination, and the combined E-peroxone yielded synergistic target pollutant degradation. Compared to the conventional E-peroxone oxidation, the sequential cathodic reactions, followed by anodic oxidations, improved the PABA removal efficiency from ~63.6% to ~89.5% at a 10-min treatment, and the corresponding pseudo first-order kinetic reaction rate constant increased from ~1.6 × 10−3 to ~3.6 × 10−3 s−1. Moreover, the response surface methodology (RSM) analysis indicated that the appropriate increase of inlet ozone concentration, applied current density, initial solution pH value, and solution temperature could accelerate the PABA degradation, while the excess of these operational parameters would have a negative effect on the treatment efficiency. The comparation tests revealed that the coupling of electrolysis and ozonation could synergistically produce hydroxyl radicals (HO•) and the separation of cathodic reactions and anodic oxidations further promoted the HO• generation, which was responsible for the enhancement of PABA elimination in the compartmental E-peroxone process. These observations imply that the compartmental E-peroxone process has the potential for aqueous micropollutants elimination, and the reaction conditions that favor the reactive oxygen species generation are critical for the treatment efficiency.

Onsite Graywater Treatment By Decoupled Electro-Peroxone Process with Recycled Effluent

This study investigates the efficacy of a decoupled electro-peroxone (E-peroxone) process for the lab-scale treatment of synthetic graywater. The E-peroxone process generally integrates conventional ozonation with in situ production of hydrogen peroxide (H2O2) in a single reactor for the transformation of ozone (O3) to hydroxyl radicals (*OH). In this study, however, the electrolysis of H2O2 generation via cathodic oxygen reduction was performed separately in order to finely control the H2O2 utilization for the E-peroxone process and to prevent the degradation of polytetrafluoroethylene (PTFE) coated carbon cathodes by highly reactive *OH. The dosage of the electro-generated H2O2 into a main reactor was optimized to enhance the performance of synthetic graywater treatment by facilitating the *OH formation. Under the optimal condition, the decoupled E-peroxone system treated synthetic graywater with initial chemical oxygen demand (COD) of 358 mg O2/L, total organic carbon (TOC) of 96.9 ppm, biochemical oxygen demand (BOD) of 162 mg O2/L, and turbidity of 11.2 NTU; the system consistently achieved removal of 89% COD, 86% TOC, 91% BOD, and 95% turbidity after 90-minute treatment, producing an effluent acceptable for discharge and non-potable applications such as toilet flushing. Part of the effluent was also recycled back into the system for H2O2 generation to minimize water consumption. This recycling process was successfully repeated consecutively for four cycles. Although the duration to reach the desirable concentration of H2O2 slightly increased from cycle to cycle, the system maintained comparable treatment performance with COD and TOC removal above 85% and 73%, respectively. Given these promising results in single-pass treatment and closed-loop recycling of graywater, the decoupled E-peroxone system can provide effective decentralized wastewater treatment for remote or water-sensitive areas. Figure 1

Onsite Graywater Treatment in a Two-Stage Electro-Peroxone Reactor with a Partial Recycle of Treated Effluent.

The efficacy of an uncoupled electro-peroxone (E-peroxone) prototype reactor system for the treatment of synthetic graywater is determined. The two-stage E-peroxone process integrates ozonation with the in situ production of hydrogen peroxide (H2O2) in a first stage reactor before ozone (O3) is converted via the peroxone reaction to a hydroxyl radical (•OH). The two-stage prototype reactor system allows for the generation of H2O2 via cathodic oxygen reduction in the first-stage reactor before mixing with O3 in the second-stage reactor. This approach prevents the degradation of polytetrafluoroethylene (PTFE) coated carbon cathodes by •OH that takes place in a single well-mixed reactor that combines electrochemical peroxide generation with O3. The dosage of H2O2 into the second-stage reactor is optimized to enhance graywater treatment. Under these conditions, the uncoupled E-peroxone system is capable of treating synthetic graywater with an initial chemical oxygen demand (COD0) of 358 mg O2/L, a total organic carbon (TOC0) of 96.9 mg/L, a biochemical oxygen demand (BOD0) of 162 mg O2/L, and a turbidity of 11.2 NTU. The two-stage electro-peroxone system can reduce the initial COD0 by 89%, the TOC0 by 91%, BOD0 by 86%, and the turbidity by 95% after 90 min of treatment. At this performance level, the reactor effluent is acceptable for discharge and for use in nonpotable applications such as toilet-water flushing. A portion of the effluent is recycled back into the first-stage reactor to minimize water consumption. Recycling can be repeated consecutively for four or more cycles, although the time required to achieve the desired H2O2 concentration increased slightly from one cycle to another. The two-stage E-peroxone system is shown to be potentially useful for onsite or decentralized graywater treatment suitable for arid water-sensitive areas.

Carbon felt modified with N-doped rGO for an efficient electro-peroxone process in diuron degradation and biodegradability improvement of wastewater from a pesticide manufacture: Optimization of process parameters, electrical energy consumption and degradation pathway

In this study, diuron abatement in aqueous medium and the remediation of wastewater from a pesticide manufacture were studied by the E-peroxone process, using carbon felt modified with N-doped rGO (N-rGO/CF) as cathode and Ti/PbO2 anode. Compared with the unmodified CF, the N-rGO/CF displayed a higher response current, improved oxygen reduction activity, and larger BET specific surface area. Also, the modified CF provided a higher H2O2 production rate. The influence of several effective parameters on the diuron degradation rate in aqueous medium by the E-peroxone process was systematically explored by central composite design-response surface methodology; the approach suggested the optimal operating condition at pH of 9, applied current of 500 mA, Na2SO4 of 0.05 M, ozone flow of 1 L min−1, and operating time of 15 min to attain the maximum removal of diuron. At the optimal condition, N-rGO/CF cathode increased diuron degradation rate and decreased electrical energy consumption rather than CF cathode, in the E-peroxone system. Radical quenching experiment and degradation pathway of diuron revealed that hydroxyl radicals were the dominant reactive oxidants. A possible degradation mechanism was proposed based on hydroxylated and demethylated products identified during diuron degradation. No significant difference of the electro-generated H2O2 after 10 successive recycles confirms the admirable reusability of N-rGO/CF. The application of the process for pesticide wastewater increased BOD5/COD ratio significantly from 0.041 (for non-treated wastewater) to 0.4 during 90 min treatment, showing a substantial improvement of the biodegradability of the wastewater. Accordingly, the E-peroxone system can be utilized as a promising pretreatment step before a biological process to facilitate and shorten the length of the biological treatment. The findings of this study could offer valuable information for practical applications of the E-peroxone system in the treatment of pesticide-manufacturing wastewater.

Electro-catalytic activity of CeOx modified graphite felt for carbamazepine degradation via E-peroxone process

Electro-catalytic activity of CeOx modified graphite felt for carbamazepine degradation via E-peroxone process

Identification of resistant pharmaceuticals in ozonation using QSAR modeling and their fate in electro-peroxone process

The abatements of 89 pharmaceuticals in secondary effluent by ozonation and the electro-peroxone (E-peroxone) process were investigated. Based on the results, a quantitative structure-activity relationship (QSAR) model was developed to explore relationship between chemical structure of pharmaceuticals and their oxidation rates by ozone. The orthogonal projection to latent structure (OPLS) method was used to identify relevant chemical descriptors of the pharmaceuticals, from large number of descriptors, for model development. The resulting QSAR model, based on 44 molecular descriptors related to the ozone reactivity of the pharmaceuticals, showed high goodness of fit(R2 = 0.963) and predictive power (Q2 = 0.84). After validation, the model was used to predict second-order rate constants of 491 pharmaceuticals of special concern ( $${k_{{{\rm{O}}_3}}}$$ ) including the 89 studied experimentally. The predicted $${k_{{{\rm{O}}_3}}}$$ values and experimentally determined pseudo-first order rate constants of the pharmaceuticals’ abatement during ozonation (kOZ) and the E-peroxone process (kEP) were then used to assess effects of switching from ozonation to the E-peroxone process on removal of these pharmaceuticals. The results indicate that the E-peroxone process could accelerate the abatement of pharmaceuticals with relatively low ozone reactivity ( $${k_{{{\rm{O}}_3}}} < \; \sim {10^2}{{\rm{M}}^{- 1}} \cdot {{\rm{s}}^{ - 1}}$$ ) than ozonation (3–10 min versus 5–20 min). The validated QSAR model predicted 66 pharmaceuticals to be highly O3-resistant. The developed QSAR model may be used to estimate the ozone reactivity of pharmaceuticals of diverse chemistry and thus predict their fate in ozone-based processes.

The performance of three typical single and two coupled electrochemical processes for drilling wastewater treatment: comparison and implication

The sequential process (EC–E-peroxone process) is the optimal solution for drilling wastewater treatment.

The synergistic effect of electrocoagulation coupled with E-peroxone process for shale gas fracturing flowback water treatment

Electrocoagulation (EC) coupled with E-peroxone process (ECP) was a promising and cost-effective integrated technology for shale gas fracturing flowback water (SGFFW) treatment. In this study, the ECP process was comprehensively compared with two sequential processes (EC followed by E-peroxone (EC-E-peroxone) and E-peroxone followed by EC (E-peroxone-EC)) to elucidate the synergistic effect of this coupled process. In EC-E-peroxone process, COD decreased by 89.2%, while COD decreased by 82.5% for 180 min in E-peroxone-EC process. However, COD removal efficiency was 82.4% in ECP for only 90 min. Average current efficiency of the ECP process was 29.9%, which was twice than that of the sequential processes. The enhancement factor was calculated to be 1.63, demonstrating the substantial significant synergistic effects for ECP. Only low MW components could be observed for the EC-E-peroxone (average MW = 533 Da with PD ≈ 1) and ECP process (MW = 538 Da with PD ≈ 1). These results suggested that EC-E-peroxone and ECP process had much stronger oxidation ability, demonstrating the enhancement of OH production induced by the Al-based coagulants might be responsible for the significant enhancement of COD removal. These results indicated there could be a synergistic effect between EC and ozone in addition to EC and E-peroxone reactions. Compared to the two sequential processes, ECP was a high efficiency and space-saving electrochemical system with simultaneous coagulation and enhanced OH generation by the products of anode and the cathode.

Evaluation of the stability of polyacrylonitrile-based carbon fiber electrode for hydrogen peroxide production and phenol mineralization during electro-peroxone process

This study evaluated the stability of polyacrylonitrile-based carbon fiber cathode for hydrogen peroxide (H2O2) production and phenol mineralization during multiple cycles of electro-peroxone (E-peroxone) process. Results show that the oxidation of bulk carbon fiber by electro-generated H2O2 and bubbled ozone (O3) is negligible during the E-peroxone process. Nevertheless, the carbon fiber surface was oxidized to some extent as the cathode was repeatedly used in the multi-cycle E-peroxone process. Due to the oxidation by H2O2 and O3, nitrogen-containing groups on the carbon fiber surface were converted from pyridinic-N to pyridonic-N during the E-peroxone process. These changes resulted in an increase in the activity of the cathode for oxygen reduction reaction (ORR), but a decrease in the selectivity of the cathode for two-electron ORR to H2O2. After the carbon fiber cathode was used for 30 cycles of the E-peroxone treatment of phenol solutions, the cathodic potentials for ORR shifted positively by ~450 mV, which is beneficial to reduce the energy consumption of electrochemical H2O2 production. Nevertheless, the apparent current efficiency (ACE) for H2O2 production decreased from ~91.5% for the virgin cathode to ~48.2% for the used cathode. Despite the decrease in the ACE for H2O2 production, sufficient amounts of H2O2 could still be produced during the E-peroxone process with the used cathode. Therefore, complete phenol mineralization was maintained during all 30 cycles of the E-peroxone treatment of phenol solutions. These results suggest that the polyacrylonitrile-based carbon fiber is a promising cathode material for long-term E-peroxone operations.

Paracetamol degradation and kinetics by advanced oxidation processes (AOPs): Electro-peroxone, ozonation, goethite catalyzed electro-fenton and electro-oxidation

The advanced oxidation of paracetamol (PCT), frequently used analgesic, promoted by electro-oxidation (EOX), goethite catalyzed electro-Fenton (GEF) with goethite, ozonation and electro-peroxone (E-peroxone) was investigated. The degradation efficiency of the processes was evaluated considering the decay of PCT versus time. All the processes showed pseudo-first order character for PCT degradation. kobs values, at optimum conditions for an individual process, were defined as 0.0022, 0.0029, 0.0870 and 0.1662 min-1 for EOX, GEF, ozonation and E-peroxone processes, respectively. Where EOX and GEF processes showed poor degradation efficiencies, novel E-peroxone process provided complete removal of PCT. The degradation of the PCT would mostly occur by OH• and molecular O3 due to the higher rate constants achieved at E-peroxone and ozonation. Conversely, with lower kobs values gained at EOX, hydroxyl radicals would not contribute noticeably to the PCT degradation. In GEF process, due to relatively lower OH• production rate, lower kobs values were obtained for the degradation of PCT. The formation of reaction intermediates, aromatics and carboxylic acids, was also determined in this study.