Hybrid Advanced Oxidation Process Research Articles

Enhanced Degradation of Ciprofloxacin Hydrochloride Using Hybrid Advanced Oxidation Process of Hydrodynamic Cavitation and Ozonation

Enhanced Degradation of Ciprofloxacin Hydrochloride Using Hybrid Advanced Oxidation Process of Hydrodynamic Cavitation and Ozonation

Constructing S-scheme Au/g-C3N4/BiVO4 heterojunction with peroxymonosulfate-enhanced photocatalytic activity and mechanism insight

Dissolved organic matter (DOM) in black-odorous water can cause excessive growth of plants and algae, leading to deterioration of water quality. Herein, an S-scheme Au/g-C3N4/BiVO4 heterojunction was constructed using a three-step method for DOM degradation in real black-odorous water in the presence of peroxymonosulfate (PMS). 4Au/g-C3N4/BiVO4/PMS exhibited highly efficient photocatalytic performance, and the DOM removal rate could reach 92.9 %, which was 19.1 and 9.9 times higher than that of g-C3N4/PMS and BiVO4/PMS, respectively. The changes of fluorescence components in DOM were detected using synchronous fluorescence spectra and two-dimensional correlated spectroscopy analysis, and the toxicity of catalytically treated black-odorous water was evaluated by growth inhibition of Escherichia coli. A reasonable S-scheme mechanism was suggested by theoretical calculations and photoelectrochemical tests. The S-scheme mechanism and the synergistic effect of photocatalysis and hybrid advanced oxidation process (HAOP) increased the catalytic activity of Au/g-C3N4/BiVO4/PMS.

Photocatalytic peroxydisulfate activation for dissolved organic matter degradation in eutrophic lake water using S-scheme BiVO4/g-C3N4 3D/2D heterojunction under visible light

Large amounts of carbon are stored primarily in dissolved organic matter (DOM), which plays an important indicator of lake eutrophication. However, removing DOM from eutrophic lakes remains a major challenge. Herein, a novel S-scheme flower-like microsphere BiVO4/nanosheet g-C3N4 3D/2D heterojunction was successfully constructed using a two-step method for DOM degradation of real eutrophic lake water in the presence of peroxydisulfate (PDS). 1.0-BiVO4/g-C3N4/PDS exhibited highly efficient photocatalytic performance with an 87.8 % removal rate of DOM for 60 min, which was 5.3 and 8.9 times higher than BiVO4/PDS and g-C3N4/PDS, respectively. Sulfate radical (·SO4−), hydroxyl radical (·OH) and singlet oxygen (1O2) were mainly responsible for DOM degradation in the 1.0-BiVO4/g-C3N4/PDS system, and the transformation pathway of 1O2 was emphatically analyzed. In addition, the changes of fluorescence components in DOM were detected using synchronous fluorescence spectra, second derivative spectra, and two-dimensional correlated spectroscopy analysis. Humic-like fluorescence, fulvic-like fluorescence, and protein-like substances were removed higher than 85.30 %, 73.02 %, and 67.23 % by the 1.0-BiVO4/g-C3N4 catalyst activating the PDS under visible light (VL), respectively. When the toxicity of catalytically treated eutrophic lake water was estimated by growth inhibition of Escherichia coli, the biotoxicity of DOM decreased continuously in the BiVO4/g-C3N4/PDS/VL coupling process. Theoretical calculations and photoelectrochemical tests suggested that the BiVO4/g-C3N4/PDS catalytic activity enhancement was attributed to the S-scheme mechanism and hybrid advanced oxidation process. It is expected that this work can provide new insight into DOM degradation in eutrophic lake water by the heterogeneous photocatalysis combined with the PDS activation system.

Intensified degradation of reactive blue 222 (RB222) textile dye by a hybrid AOP system of hydrodynamic cavitation coupled with inline UV and PMS oxidant

Treatment of textile wastewater poses a significant problem due to the recalcitrant nature of dyes. The present work aims to evaluate a hybrid advanced oxidation process (AOP) comprising hydrodynamic cavitation (HC), ultraviolet irradiation (UV) and different oxidants. Synthetic wastewater (SW) was prepared by dissolving 50 ppm of reactive blue 222 dye, salt, sodium carbonate and detergent. A venturi, a single-hole orifice plate and multiple-hole orifice plates were compared as cavitating devices for HC. Multiple-hole orifice plate 3 proved to be the most efficient cavitation device. Three different oxidants, namely Fenton, potassium peroxymonosulfate (PMS), and potassium persulfate (KPS), were compared in combination with HC + UV. PMS turned out to be the most effective oxidant at pH 6.5, and HC + UV + PMS was the most effective treatment process as compared to standalone methods. NaCl (salt) in wastewater promotes the degradation of RB222 dye, and sodium carbonate suppresses the degradation of RB222 by scavenging radicals. After 120 min, the TOC reduction for the HC-only, UV-only, HC + UV, UV + PMS (2 g/L), and HC + UV + PMS (2 g/L) process was 3.23 %, 4.17 %, 9.64 %, 32.48 %, 38.51 %, and 75.96 %, respectively. After 180 min of treatment with HC + UV + PMS (2 g/L), the maximum 85.66 % TOC reduction of SW was reached, and the complex intermediates formed are also reported.

Using KNbO3 catalyst produced from a simple solid-state synthesis method in a new piezophotocatalytic ozonation hybrid process

The present work reports the development and application of potassium niobate (KNbO3) as a catalyst in a novel hybrid piezophotocatalytic ozonation process aimed at wastewater remediation. Pure KNbO3 samples were produced through a simple solid-state synthesis using water-soluble ammonium niobate (V) oxalate hydrate (C4H4NNbO9·xH2O) as niobium source, employing different potassium precursors (KNO3, K2CO3, KOH, and C8H5KO4). The synthesis was also carried out using powdered niobium oxide as a precursor, aiming to evaluate the differences between the niobates obtained. The results achieved in this study show that all the niobates produced using ammonium niobate (V) oxalate hydrate were composed solely of the orthorhombic structure of KNbO3, while the materials synthesized using niobium oxide exhibited the rhombohedral structure of KNbO3 along with niobium-rich potassium niobates (K3Nb8O21, K2Nb4O21, and KNb3O8) and residual niobium oxide. This behavior was attributed to the enhanced chemical homogeneity derived from the synthesis using ammonium niobate (V) oxalate hydrate, which facilitated the reaction between the components during the thermal treatment step. Furthermore, the optical and morphological properties of the niobates were considerably influenced by the application of different potassium salts. Owing largely to its morphological and electrical properties, the material synthesized using potassium hydrogen phthalate displayed the highest photocatalytic activity in terms of methylene blue discoloration among the niobates produced using C4H4NNbO9·xH2O. Finally, the proposed piezophotocatalytic ozonation process was found to be a highly efficient strategy for the discoloration of methylene blue, as it successfully harnessed the synergy between the multiple mechanisms involving active radical generation toward the development of a highly promising hybrid advanced oxidation process.

Assessment of homogeneous hybrid advanced oxidation process for degradation of para‐nitrophenol

AbstractIn this work, degradation and mineralization of para‐nitrophenol in the aqueous medium by a mixture of two strong oxidants of persulfate and periodate have been studied. To this aim, a photo‐reactor with a volume of 1 L has been used. Optimization and modeling of the process was performed by the response surface methodology. According to the prediction of the model, the process has an ability to remove para‐nitrophenol up to 91.6% in the optimal conditions of para‐nitrophenol initial concentration of 15 mg/L, [KPS] = 50 mg/L, [KPI] = 49.7 mg/L, and pH = 5 after 40 min. Assessment of the mineralization of para‐nitrophenol under optimal conditions showed an efficiency of about 57%, while parallel processes alone (UV and UV/KPS and UV/KPI) showed lower mineralization efficiency. Also, the kinetic study showed that the results were fitted with a pseudo‐first‐order equation with a regression coefficient of 0.97 and rate constant of 0.052 (L/min). Moreover, the electrical energy consumption for the process was calculated as 110.77 (kWh/m3) in the optimum condition. In general, the results of this work showed that the use of the homogeneous hybrid AOP methods increases the efficiency of the mineralization.

Mineralization of Industrial Wastewater by a Hybrid Technique of Adsorption (Fe3O4@AC Nanocomposite) + Heterogeneous Fenton + Sonication and Discernment of Synergistic Effects

This paper reports investigations in the mineralization of industrial wastewater (COD = 3246 mg/L, TOC = 2500 mg/L) using a ternary (ultrasound + Fenton + adsorption) hybrid advanced oxidation process. Fe3O4 decorated activated charcoal (Fe3O4@AC) nanocomposites (surface area = 538.88 m2/g; adsorption capacity = 294.31 mg/g) were synthesized using coprecipitation. The wastewater treatment process was optimized using central composite statistical design. At optimum conditions, viz. pH = 4.2, H2O2 loading = 0.71 M, adsorbent dose = 0.34 g/L, reduction in COD and TOC of wastewater were 94.75% and 89%, respectively. These results are attributed to synergistic interactions between the adsorption of pollutants on Fe3O4@AC, surface Fenton reactions, and enhanced mass transfer due to sonication. This synergism boosted the interactions among •OH radicals and pollutant molecules, leading to effective degradation and mineralization. The Fe3O4@AC showed excellent recovery (>90 wt %) and reusability (>90% COD removal) in 5 successive cycles of treatment.

Photocatalytic-proxone process application in the degradation of toluene-diisocyante, and methylene diphenyl diisocyanate from polluted air

Isocyanates are one of the most widely used semi-volatile compounds in various industries, including the polyurethane industry. Applying a hybrid advanced oxidation process to the degradation of toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI) from polluted air were the main aims of the study. The BiOI@MOF/Zeolite nanocomposite was prepared by the solvothermal method. XRD, FT-IR, FESEM, EDAX, EDS element mapping, TEM, BET, XPS, and UV–vis spectra analysis were applied to indicate the nanocomposite characters. The effect of flow, ozone concentration, hydrogen peroxide concentration, initial isocyanates concentration, and relative humidity were investigated. The concentration of isocyanates measurement via NIOSH 5522 standard method. In the optimum conditions of the process, the supplementary studies were done. The results of the analysis of composite structure indicated that well synthesized had been done. Experimental results showed optimal operating conditions could degrade more than 90 % of isocyanates. The synergistic effect coefficient of the mechanisms was 2.03 and 2.34 for TDI and MDI, respectively. The stability of the process was observed in 6 consecutive steps. The residual ozone concentration in the system's outlet was negligible (0.047 mg/l). The CO2 and CO emissions proved that the mineralization of isocyanates occurred. The theoretical mineralization rate was 0.64 and 0.55 reported for TDI and MDI, respectively. The simultaneous presence of MDI and TDI in the reactor decreases the efficiency of the process. The pure oxygen gas, pure nitrogen gas, and atmospheric as a carrier gas showed different performances in the process of isocyanate removal (80.8, 35.4, and 61.7 % degradation in the simultaneous presence of MDI and TDI).

Solar-driven hybrid photo-Fenton degradation of persistent antibiotic ciprofloxacin by zinc ferrite-titania heterostructures: degradation pathway, intermediates, and toxicity analysis.

Present work puts forward an efficient strategy to degrade one of the persistent antibiotic contaminants, ciprofloxacin (CIP). Hybrid advanced oxidation process (HAOP) is tailored with a synergy effect between photocatalysis and photo-Fenton catalysis on zinc ferrite-titania heterostructured composite (ZFO-TiO2). The ZFO-TiO2 heterostructured composite enables heterogenous surfaces for enhanced charge separation where HAOP is implemented for CIP degradation with the aid of class AAA solar simulator. The results reveal an enhanced degradation rate of CIP (kobs = 0.255min-1), noticeably higher than the conventional TiO2-based photocatalysis. The HAOP system strongly enhances the reaction rates showing five times higher performance as compared to TiO2-based photocatalysis. The substitution reactions for degradation of CIP into its intermediates were analyzed by LC-MS/MS, and the plausible degradation pathways have been graphically modeled identifying 3-phenyl-1-propanol and phenol molecules as less toxic end products. Toxicity of the photodegraded samples reveal 18.1 ± 1.24% inhibition of V. fischeri at the end of 60-min treatment indicating reduced toxicity of CIP contaminated samples. Antimicrobial inhibition studies on E. coli also corroborate an effective CIP removal (~ 100%) in less than 90min. The study puts forward a novel ZFO-TiO2 composite HAOP system for efficient and rapid mineralization of an antibiotic pollutant, extendable towards wide range of pharmaceutical drug degradation studies.

Synthesis of BiOI@NH2-MIL125(Ti)/Zeolite as a novel MOF and advanced hybrid oxidation process application in benzene removal from polluted air stream.

One of the popular process in volatile organic compounds removal in gas phase is advanced oxidation process. We in this research, synthesized BiOI@NH2-MIL125(Ti)/Zeolite nanocomposite as a novel nanocomposite to degradation of benzene in hybrid advanced oxidation process. The nanocomposite synthesized via solvothermal method. The effect of airflow, ozone gas concentration, hydrogen peroxide concentration, relative humidity and initial benzene concentration are the main parameters in the UV/O3/H2O2/ nanocomposite hybrid process that were studied. The characterization by XRD, FT-IR, FESEM, EDS element mapping, TEM, BET, and UV-vis spectra indicated that nanocomposite were well synthesized. Optimal operating conditions of the process were determined at air flow of 0.1l/min, ozone concentration of 0.3mg/min, hydrogen peroxide concentration of 150ppm, relative humidity of 45 ± 3% and benzene concentration of 50 ppmv. Under these conditions, more than 99% of benzene was degraded. The synergistic effect coefficient of the mechanisms is 1.53. The nanocomposite had good stability in the hybrid process and remained above 99% efficiency up to 5 times. The ozone concentration residual the system was reported to be negligible (0.013mg/min). The CO and CO2 emissions in the hybrid process was higher than other processes, which indicates better mineralization in the hybrid process. Formaldehyde, octane, noonan, phenol, decanoic acid were reported as the main by-products. The results indicated that UV/O3/H2O2/ nanocomposite hybrid process has fantastic efficiency in the degradation of benzene as one of the indicators of VOCs.

Design and optimization of a sequential and hybrid advanced oxidation process system using response surface methodology

Of different approaches for refinery effluent treatment, the application of Advanced Oxidation Processes (AOPs) (e.g. electro-Fenton) and nano Zero-Valent Iron (nZVI) particles have been of great interest lately. Associated constraints with these methods inspired the design of a sequential hybrid system by which higher treatment efficiency and less energy consumption were acquired compared to a conventional system. The hybrid system consisted of an electro-Fenton and an nZVI slurry system working in sequence. Both sub-systems were first optimized using the Response Surface Methodology (RSM), and the hybrid system was then designed accordingly. 94.06% of COD removal was achieved by the hybrid system in only 47.5 min at its optimum condition (CODinitial = 500 mg/L, [nZVI] = 0.9 g/L, and H2O2/Fe2+ = 3.6). Whereas it took more than 75 min for the single electro-Fenton system to acquire similar efficiency. GC–MS analysis also supported the superiority of the hybrid system over the conventional one.

Laccase-coupled photoelectrocatalytic system for highly efficient degradation of bisphenol A

In the present work, a hybrid advanced oxidation process that combined laccase with photoelectrocatalysis (PEC) was explored for highly efficient degradation of bisphenol A (BPA). Visible light-responsive BiVO4 film electrode with good optical and photoelectrochemical properties was prepared via an electrodeposition method and employed as photoanode for PEC degradation of BPA. After laccase was facilely introduced into the PEC system, the BPA removal efficiency was significantly promoted, attributed to the synergistic effect of enzymatic catalysis and PEC processes. To obtain the optimum operation conditions, the effects of initial pH and applied bias potential were investigated systematically. Radicals trapping experiments revealed that •O2− dominated the biophotoelectrocatalytic degradation process, and the possible degradation pathway for BPA was proposed by identifying intermediates using liquid chromatography-mass spectrometry.

Degradation of 1,4-dioxane by sono-activated persulfates for water and wastewater treatment applications

This paper presents a hybrid advanced oxidation process (AOP) based on sonocavitational activation of persulfate (PS) for degradation of 1,4-dioxane during wastewater treatment. Application of sono-cavitation effectively convert PS to radical species demonstrating synergistic effect by increasing the reaction rate and reducing the required energy for activation. It is economically feasible and deployed alternative to the direct thermal activation method. A single and two-stage injection of PS were compared to eliminate self-scavenging effects related to excess of oxidant in system. A GC-MS analysis was used to determine the degradation products of dioxane and to propose the degradation mechanism. The studies revealed that the degradation was significantly enhanced by the addition of PS at molar ratio of oxidant to pollutant 4 with a two-stage injection. Under optimal conditions at US density of 105 W/cm2, dioxane with an initial concentration of 100 mg/L was completely degraded in 120 min.

Sulfadiazine degradation by combination of hydrodynamic cavitation and Fenton-persulfate: parametric optimization and deduction of chemical mechanism.

This paper reports the degradation of the sulfadiazine (SDZ) drug with a hybrid advanced oxidation process (AOP) of heterogeneous α-Fe2O3/persulfate coupled with hydrodynamic cavitation. The major objectives of the study are parametric optimization of the process and elucidation of the chemical mechanism of degradation. The optimum conditions for maximum SDZ degradation of 93.07 ± 1.67% were as follows: initial SDZ concentration = 20ppm, pH = 4, α-Fe2O3 = 181.82mg/L, Na2S2O8 = 348.49mg/L, H2O2 = 0.95mL/L, inlet pressure = 0.81MPa (8atm), orifice plate configuration: hole dia. = 2mm and number of holes = 4. Density functional theory (DFT) calculations revealed that the atoms of SDZ with a high Fukui index (f 0) were potentially active sites for the attack of •OH and [Formula: see text] radicals. Fukui index calculation revealed that atom 11N has a higher value of f 0 (0.1026) for oxidation at the α-amine group of the sulfadiazine molecule. Degradation intermediates detected through LC-MS/MS analysis corroborated the results of DFT simulations. Using these results, a chemical pathway has been proposed for SDZ degradation.

Recent progress in doped TiO2Photocatalysis and Hybrid Advanced Oxidation Processes for Organic Pollutant Removalfrom Wastewater

Hybrid advanced oxidation processes (HAPOs) for the removal of non-biodegradable organics from wastewater have been studied in recent literature. With the increase in industrial development, the quantity of wastewater generated from these industries also organic wastewater produced by industrial manufacturing has posed threats to the environment.AOP’s are one of the promising advanced technologies for mineralization of organics present in wastewater. Hybrid advanced oxidation process based on the ozonation, sonolysis, Photo-Fenton reagents and electrochemical method, has greater potential for complete mineralization of recalcitrantorganics. This review article includes recent progress in the research and application of TiO2 photocatalysis for the removal of nonbiodegradable organic pollutants present in water. It will provide a quick reference for various hybrid AOPs systems and their effectiveness. This review article provides quick insights into (1) hybrid AOP for treatment of various industrial effluents or model effluents, (2) work done on doped/co-doped photocatalyst as heterogeneous catalysts (3) study of parameters affecting the photocatalysis to enhance complete oxidation of organics present in wastewater. A mechanistic investigation of hybrid advanced oxidation processes with combinations of sonolysis and Fenton process coupled with UV, adsorption and addition of biochar has been discussed.

Evaluation of the performance of a hybrid advanced oxidation process for degradation of organic pollutants in aqueous media

ABSTRACT In this work, the performance of NMT/KPS process as a hybrid advanced oxidation process has been studied for degradation of organic compound. To this aim, nitrophenol has been used as a typical aromatic compound, which is widely used in industries as an organic toxic precursor. The NMT photo-catalyst was synthesised and characterised by TEM, EDS, XRD and VSM. The characterisation results showed that the catalyst had been synthesised with a particle size of 29 nm and paramagnetic properties. The process was performed in a bench scale glassware photoreactor with 1 l volume. In order to find the optimum condition of the process, the effects of various parameters such as pH, NMT dosage and KPS concentration were modelled and optimised by using design of experiment as a statistical method. The results showed that in the optimum condition by using the NMT dosage of 100 ppm, KPS concentration of 150 ppm, and pH 4, a degradation efficiency of about 89% was achieved for nitrophenol initial concentration of 20 ppm after 60 min. Also, electrical energy consumption was considered as an important industrial criterion that in the optimum condition with rate constant of 0.0479 (1/min), 150 W light source and 1 l of volume, the electrical energy consumption is calculated as 120.2 kWh/m3.

High removal efficiency of industrial toxic compounds through stable catalytic reactivity in water treatment system

We identified optimal conditions for the disposal of high concentration of organic contaminants within a short time using a hybrid advanced oxidation process (AOP) combining various oxidizing agents. Plasma-treated water (PTW) containing many active species, that play dominant roles in the degradation of organic substances like hydroxyl radicals, atomic oxygen, ozone, and hydrogen peroxide, was used in this study as a strategy to improve degradation performance without the use of expensive chemical reagents like hydrogen peroxide. In particular, the optimal decomposition conditions using PTW, which were combined with 10 mg/h ozone, 2 g/L iron oxide, and 4 W UV light, demonstrated excellent removal abilities of a high concentration of reactive black 5 (RB5; 100 mg/L, >99%, [k] = 4.15 h−1) and tetracycline (TC; 10 mg/L, >96.5%, [k] = 3.35 h−1) for 25 min, approximately 1.5 times higher than that without PTW (RB5; 100 mg/L, 94%, [k] = 2.80 h−1). These results confirmed that the production of strong reactive hydroxyl radicals from the decomposition process, as well as various reactive species included in PTW efficiently attacked pollutant substances, resulting in a higher removal rate. This suggests that a water treatment system with this optimal condition based on complex AOP systems using PTW could be useful in critical environmental and biomedical applications.

P–nitrophenol degradation by hybrid advanced oxidation process of heterogeneous Fenton assisted hydrodynamic cavitation: Discernment of synergistic interactions and chemical mechanism

The present study has investigated p-nitrophenol (PNP) degradation by hybrid advanced oxidation process (AOP) of hydrodynamic cavitation with heterogenous Fe3O4 nanoparticles. 78.8 ± 1.2% of PNP degradation was obtained at optimum operational conditions: inlet pressure = 8 atm, pH = 3, initial concentration of PNP = 20 mg L−1, Fe3O4:H2O2 = 1:100. PNP degradation profiles were analyzed using a kinetic model based on the reaction network. The closest match between the simulated and experimental degradation profiles was obtained for the initial concertation of [H2O2] = 0.6 M, which was far higher than concentration of externally added H2O2. This was attributed to in-situ generation of H2O2 through transient cavitation. Intense shear and turbulence generated in cavitating flow caused surface leaching of Fe3O4 particles that released Fe2+/Fe3+ ions. The synergy in the hybrid AOP was in-situ Fenton reactions between leached Fe2+/Fe3+ ions and H2O2 present in the reaction mixture. The mechanism in •OH mediated oxidative degradation of PNP was further explored with Density Functional Theory (DFT) simulations. Both •OH addition on benzene ring and H–abstraction reactions were simulated to identify the possible pathways for the degradation. On the basis of activation free energy analysis, degradation pathways initiating with both •OH addition and H abstraction were determined to be feasible. The ortho−C of benzene ring was the most favourable site for •OH addition, while H atom of phenolic hydroxyl group was more susceptible (or more reactive) for H-atom abstraction route.

Mechanistic analysis of carbamazepine degradation in hybrid advanced oxidation process of hydrodynamic cavitation/UV/persulfate in the presence of ZnO/ZnFe2O4

The present study has addressed carbamazepine (CBZ) degradation by hybrid advanced oxidation system of hydrodynamic cavitation (HC) assisted UV/persulfate with composite ZnO/ZnFe2O4 particles. This hybrid system is comprised of several parallel pathways for generation of both OH and SO4∙- radicals. 98.13 ± 1.03% CBZ degradation was obtained at optimum operational conditions: inlet pressure = 9 atm, pH = 4, initial concentration of CBZ = 15 mg/L, UV power = 18 W, Na2S2O8 = 500 mg/L, ZnO/ZnFe2O4 = 500 mg/L. HC alone resulted in 7.70% degradation of CBZ, while the binary HC + Na2S2O8 system resulted in markedly high degradation of 65.73%. Composite ZnO/ZnFe2O4 particles had dual characteristics, viz. photocatalytic activity and a source of Fe2+/Fe3+ ions released through surface leaching. Relative contributions of OH and SO4∙- radicals to CBZ degradation were identified through permutation-combination of different oxidation systems. Thermodynamic and kinetic behaviors of reactions of CBZ with OH and SO4∙- radicals were analyzed using density functional theory (DFT) at B3LYP/6-31 g(d) level. Single electron transfer (SET) between CBZ and SO4∙- was the primary (and thermodynamically favorable) reaction pathway in initiation of degradation. Degradation intermediates revealed ionization of CBZ through SET before hydroxylation and oxidation – which was corroboration of DFT simulations.

Mechanistic insight into ultrasound-induced enhancement of electrochemical oxidation of ofloxacin: Multi-response optimization and cost analysis

In this paper, a hybrid advanced oxidation process of sonoelectrochemical, in which ultrasound and electrochemical are applied simultaneously, has been used for the degradation of ofloxacin (bio-recalcitrant pharmaceutical pollutant). Response surface methodology based central composite design was applied to understand the parametric effects of ultrasonic power, current density, initial pH, and electrolyte dose. Enhanced ofloxacin degradation was obtained using sonoelectrochemical (≈95%) process in comparison to the electrochemical (≈60.6%) and sonolysis alone (≈7.2%) after 120 min treatment time. Multi-response optimization was used so as to maximize COD removal (70.12%) and minimize specific energy consumption (11.92 kWh (g COD removed)−1)at the optimized parametric condition of pH = 6.3 (natural pH), ultrasonic power = 54 W, current density = 213 A m−2, and Na2SO4 electrolyte dose = 2.0 g L−1. It was revealed that •OH radicals contribute major to the ofloxacin degradation reaction among the other oxidizing agents. Degradation of the ofloxacin followed pseudo-first-order kinetics with a higher reaction rate, which confirmed the synergistic effect of 34% between ultrasound and electrochemical approaches. The degradation pathway of ofloxacin removal was elucidated at optimum condition by the temporal evolution of the intermediate compounds and final products using gas chromatography coupled with mass spectroscopy (GC-MS), liquid chromatography-mass spectroscopy (LC-MS), high-resolution mass spectroscopy (HR-MS), and Fourier transform infrared spectroscopy (FTIR). Atomic force microscopy (AFM) and field emission scanning electron microscope (FE-SEM) coupled with energy dispersed X-ray (EDX) were used to determine the morphology of electrodes. Operational cost analysis was done based on the reactor employed in the present study.