Sonophotocatalytic Process Research Articles

Preparation of CuFe2O4/montmorillonite nanocomposite and explaining its performance in the sonophotocatalytic degradation process for ciprofloxacin

In the current study, a magnetic copper ferrite/montmorillonite (CuFe2O4/MMT) nanocomposite was successfully fabricated by a simple sol-gel combustion method which was used as a catalyst for ciprofloxacin (CIP) degradation in the sonophotocatalytic degradation process. The characterization properties were identified using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Brunner-Emmett-Teller (BET) method, vibrating sample magnetometer (VSM), and Fourier transform infrared (FTIR) spectroscopy. Results showed that the CIP degradation rate of the sonophotocatalytic method was higher than other methods like photocatalytic and sonocatalytic. Mineralization and biodegradability of CIP were determined by the TOC test and BOD5/COD ratio. The results showed that the mineralization rate of CIP rose to 92%, and biodegradability rose from 0.163 to 0.697 at the end of the sonophotocatalytic process. Rate of recyclability and reusability of the catalyst was also investigated in the 8 cycles, but no significant reduction in the removal rate was noted. Experiments using various scavengers revealed that SO4•- and •OH were the main radicals in the sonophotocatalytic degradation of CIP. In addition, the bioassay method using Daphnia magna was used to test toxicity. Results showed that the toxicity of the tested solutions was significantly reduced after sonophotocatalytic degradation. In conclusion, the combined sonophotocatalytic system with CuFe2O4/MMT catalyst could be a new and promising approach as a pretreatment technique to facilitate the biological treatment of pharmaceutical wastewater.

Efficient sonophotocatalytic degradation of acid blue 113 dye using a hybrid nanocomposite of CoFe2O4 nanoparticles loaded on multi-walled carbon nanotubes

Complete degradation of acid blue 113 (AB113) dye was successfully achieved by using the sonophotocatalytic process with CoFe2O4 nanoparticles loaded on multi-walled carbon nanotubes (MWCNTs/CoFe2O4), as a novel catalyst. The catalyst used was synthesized using the solvothermal co-precipitation method. First, the characteristic parameters of the synthesized catalyst were evaluated using advanced analyses of Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy-Dispersive X-Ray Spectroscopy (EDX), Thermogravimetric (TGA), Vibrating Sample Magnetometry (VSM), and Fourier Transform Infrared Spectroscopy (FTIR). The results of the sonophotocatalytic degradation experiments showed that the optimum parameters for 100% AB113 removal were: AB113 concentration = 25 mg/L, pH = 3, MWCNTs/CoFe2O4 dose = 0.4 g/L, reaction time = 40 min, intensity of UV light = 36 W, and intensity of ultrasonic waves = 50 kHz. To identify the utility of using MWCNTs/CoFe2O4 as a catalyst, the degradation efficiencies of AB113, resulting from the sonophotocatalytic process, were compared with those determined from other similar treatment processes, that is, adsorption, photolysis, sonolysis, and sonocatalytic and photocatalytic processes, where the sonophotocatalytic process was found to be the most efficient one. Catalyst recycling was performed in eight degradation–regeneration cycles, whereas, a total reduction of 9% was observed in removal efficiency after the 8th cycle. The results showed that the AB113 dye, which was a non-biodegradable contaminant, became almost a biodegradable compound after subjection to sonophotocatalytic treatment. The results also demonstrated a high mineralization rate of the applied treatment method. In addition, a toxicity test was performed using Daphna Magna, and the results indicated a low toxicity of the AB113 dye effluent. The results of this study clarified that the sonophotocatalytic process system using MWCNTs/CoFe2O4 could be a feasible and cost-effective system for degrading dyes, for example, AB113.

Synthesis and Characterization of Carbon and Carbon-Nitrogen Doped Black TiO2 Nanomaterials and Their Application in Sonophotocatalytic Remediation of Treated Agro-Industrial Wastewater.

The conventional open ponding system employed for palm oil mill agro-effluent (POME) treatment fails to lower the levels of organic pollutants to the mandatory standard discharge limits. In this work, carbon doped black TiO2 (CB-TiO2) and carbon-nitrogen co-doped black TiO2 (CNB-TiO2) were synthesized via glycerol assisted sol-gel techniques and employed for the remediation of treated palm oil mill effluent (TPOME). Both the samples were anatase phase, with a crystallite size of 11.09–22.18 nm, lower bandgap of 2.06–2.63 eV, superior visible light absorption ability, and a high surface area of 239.99–347.26 m2/g. The performance of CNB-TiO2 was higher (51.48%) compared to only (45.72%) CB-TiO2. Thus, the CNB-TiO2 is employed in sonophotocatalytic reactions. Sonophotocatalytic process based on CNB-TiO2, assisted by hydrogen peroxide (H2O2), and operated at an ultrasonication (US) frequency of 30 kHz and 40 W power under visible light irradiation proved to be the most efficient for chemical oxygen demand (COD) removal. More than 90% of COD was removed within 60 min of sonophotocatalytic reaction, producing the effluent with the COD concentration well below the stipulated permissible limit of 50 mg/L. The electrical energy required per order of magnitude was estimated to be only 177.59 kWh/m3, indicating extreme viability of the proposed process for the remediation of TPOME.

NiO nanoparticles with superior sonophotocatalytic performance in organic pollutant degradation

Herein, NiO nanoparticles were prepared by a facile solvothermal route. The as-synthesized nanoparticles were characterized using XRD, BET, TEM, HRTEM. The BET measurements prove the mesoporous nature of the NPs, having good specific surface area and pore volume. The synthesized NiO NPs were used for the first time in dye decomposition using methylene blue (MB) as a model pollutant in low frequency and low energy ultrasound at pH = 7 and room temperature in presence of UV light and H2O2 as an oxidant. The change of the pollutant concentration was estimated by UV–VIS spectrophotometry. Dye degradation performance investigated for sonocatalysis, photocatalysis, and sonophotocatalysis processes. The data showed that the decomposition performance was in the following order: sonophotocatalysis>photocatalysis>sonocatalysis. After about 30 min of dual (Sono + UV) irradiation in the presence of NiO NPs more than 90% of the pollutant degraded, achieving a rate constant of about 0.089 min−1. Sonophotocatalytic performance was compared with sonocatalysis and photocatalysis processes carried out in the same conditions. Interestingly, the combination of ultrasound and UV light irradiation in a sonophotocatalytic degradation process led to about 33% synergy effect, proving a positive synergy between the sonocatalytic and photocatalytic processes. Reusability data exhibited the excellent stability of sonophotocatalysts within four consecutive runs with negligible fading in their sonophotocatalytic performance. This feature improves the reusability potential of the sonophotocatalysts to be applied in the industrial directions. The obtained results proved that the performance of the sonophotocatalytic process was severely affected by the addition of different kinds of trapping agents, therefore based on these results the mechanism of the sonophotocatalysis was discussed. Finally, the presently combined system paved the way toward excellent efficiency and it could pose a good strategy, in terms of environmental impact and energy cost, in comparison to conventional sonophotocatalytic systems.

CeO2/TiO2/SiO2 nanocatalyst for the photocatalytic and sonophotocatalytic degradation of chlorpyrifos

AbstractA new nanohybrid photocatalyst named cerium (IV) oxide (CeO2)/TiO2 (titania)/silicon dioxide (SiO2) was firstly synthesized employing the co‐precipitation technique to elaborate the degradation efficiency of chlorpyrifos (CPS) as a relatively indelible organophosphorus pesticide in deionized water in photocatalytic and sonophotocatalytic processes. The influence of various parameters, including photocatalyst dosage, the CPS pesticide concentration, pH, and irradiation time, was investigated, and the optimal parameters for photodegradation and sonophotodegradation were determined. The activity and the electrical energy of this photocatalyst in the photodegradation and sonophotodegradation processes were compared, and it was revealed that the sonophotocatalytic process was superior to the photocatalytic one (about 15%). Results depicted that it can be employed four times for the photocatalytic reactions with the same yield of CPS degradation. Besides, the CPS degradation efficiency at the optimum conditions was found to be 81.1% and 90.8% for the photo‐degradation and sonophotodegradation, respectively. Pursuant to the kinetic studies, the kinetics models that govern these processes are leaner with acceptable accuracy.

Synergistic effect of sono-photocatalytic processes on sludge disintegration

Synergistic effect of sono-photocatalytic processes on sludge disintegration

Development of sonophotocatalytic process for degradation of acid orange 7 dye by using titanium dioxide nanoparticles/graphene oxide nanocomposite as a catalyst

In the present study, the sonophotocatalytic degradation of acid orange 7 (AO7) dye was evaluated. The catalyst used was the titanium dioxide nanoparticles/graphene oxide (TiO2/GO) nanocomposite, which was synthesized using the Hummers and Hoffman's method and the liquid phase deposition method. TiO2/GO nanocomposite was characterized through the analyses of transmission electron microscopy (TEM), X-ray diffraction (XRD), Energy Dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. In addition, properties of the surface area and pore size were determined by N2 adsorption–desorption and the Barrett-Joyner-Halenda methods. After modification, the nanocomposite properties showed successful stabilization of TiO2 on the graphene substrate and reduction of the recombinant carrier loads. By utilizing the proposed treatment, complete degradation of AO7 could be achieved under optimal operating parameters (pH = 5, initial concentration of AO7 dye = 50 mg/L, TiO2/GO nanocomposite dose = 0.5 g/L, UV light intensity = 36 W, ultrasonic wave intensity = 35 kHz, and reaction time = 30 min). Scavenging experiments confirmed that OH and h+ radicals were the predominant species in the sonophotocatalytic degradation reactions of the AO7 dye. The stability study confirmed the excellent shelf life of the TiO2/GO nanocomposite, with only a slight reduction in the degradation efficiency of the AO7 dye (<8.27%) detected, after six consecutive cycles of the sonophotocatalytic process. Studies related to the degradability of the AO7 dye and the biodegradability of the effluent from the process showed that the applied sonophotocatalytic system was able to remove the TOC concentration by 83% after a reaction time of 30 min. Moreover, the increase in the BOD5/COD ratio was also a confirmation for the increase in biodegradability of the treated AO7 dye effluent. Finally, the toxicity test showed that the growth inhibition rate of Escherichia coli (E. coli), as a viability index, decreased to about 7.34% after a reaction time of 180 min. This result indicated the formation of compounds with low toxicity and molecular weight over the reaction time of the sonophotocatalytic process of AO7 dye.

Enhanced methylene blue removal efficiency of SnO2 thin film using sono-photocatalytic processes

In order to improve the degradation of the methylene blue and to overcome the problem of the incapability of recyclability of the catalysts, we use in this work a thin film of tin oxide (SnO2) synthesized via ultrasonic spray pyrolysis technique in the inner wall of glass tube. The catalysts are characterized by XRD patterns, FTIR spectra, Raman spectra, UV–Visible spectra, XPS analysis, AFM images and SEM images with EDX analysis. The initial and degraded solutions of the methylene blue are analysed by UV–Vis absorption spectroscopy. Adsorption, photocatalysis, photolysis, sonocatalysis, sonolysis, sonophotocatalysis and sonophotolysis degradation of methylene blue in presence of tin oxide are studied. The results showed that the sonocatalysis process using the SnO2 thin film as a catalyst presents the best degradation efficiency compared to the other processes. A possible sonophotodegradation mechanism is proposed.

Sonochemical Synthesis, Characterization and Optical Properties of Tb-Doped CdSe Nanoparticles: Synergistic Effect between Photocatalysis and Sonocatalysis.

In this study, Tb-doped CdSe nanoparticles with variable Tb3+ content were synthesized by a simple sonochemical technique. The synthesized nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD). The sono-photocatalytic activities of the as-prepared specimens were assessed for the degradation of Reactive Black 5. The experimental results show that the sono-photocatalytic process (85.25%) produced a higher degradation percentage than the individual sono- (22%) and photocatalytic degradation (8%) processes for an initial dye concentration and Tb-doped CdSe dosage of 20 mg/L and 1 g/L, respectively. Response surface methodology (RSM) was utilized to assess model and optimize the impacts of the operational parameters, namely, the Tb3+ content, initial dye concentration, catalyst dosage, and time. The addition of benzoquinone results in remarkably inhibited degradation and the addition of ammonium oxalate reduced the removal percentage to 24%. Superoxide radicals and photogenerated holes were detected as the main oxidative species.

Understanding the origin of synergistic catalytic activities for ZnO based sonophotocatalytic degradation of methyl orange

Many studies have documented the existence of synergistic catalytic activities for ZnO based sonophotocatalysis, but the role of ultrasonic field during this sonophotocatalytic process is still unclear. In this work, ZnO samples with three different morphologies (rod-like, flower-like and sheet-like) have been synthesized for the sonophotocatalytic degradation of methyl orange (MO). The results indicate that MO degradation efficiency of ZnO based sonophotocatalysis is found to be higher than the sum of ZnO based photocalysis and sonocatalysis, which indicates the existence of synergy in the ZnO based sonophotocatalytic degradation of MO. The mechanistic investigation indicates that reactive oxygen species can be produced by ZnO in the presence of ultrasound. In addition, the presence of ultrasound in the ZnO based sonophotocatalysis is beneficial for the separation of electron-hole pairs of ZnO based photocatalysis, leading to the production of more reactive oxygen species in the ZnO based sonophotocatalysis. Overall, the origin of synergistic catalytic activities for ZnO based sonophotocatalytic degradation of MO has been revealed in this study.

Application of advanced materials in sonophotocatalytic processes for the remediation of environmental pollutants

Significant advances in various industrial processes have resulted in the discharge of toxic pollutants into the environment. Consequently, it is essential to develop efficient wastewater treatment processes to reduce water contamination and increase recycling/reuse. Photocatalytic degradation is considered as an efficient method for the degradation of toxic pollutants in industrial wastewater. However, the use of photocatalytic approaches is associated with numerous limitations, such as lengthy procedures and the necessity for large amounts of catalysts. Hence, it has been proposed that photocatalysis could be combined with other techniques, including sonolysis, electrochemical, photothermal, microwave, ultrafiltration, and biological reactor. The integration of photocatalysis with sonolysis could be remarkably beneficial for environmental remediation. The combination of these processes has the advantages of using uniformly dispersed catalysts, regeneration of the catalyst surface, improved mass transfer, enhanced surface area due to smaller catalyst particles, and production of more active radicals for the degradation of organic pollutants. In this review, an overview on employing sonophotocatalysis for the removal of toxic organic contaminants from aqueous environments is provided. Additionally, the limitations of photocatalysis alone and the fundamental sonophotocatalytic mechanistic pathways are discussed. The importance of utilizing advanced two-dimensional (2D) semiconductor materials in sonophotocatalysis and the common synthetic approaches for the preparation of 2D materials are also highlighted. Lastly, the review provides comprehensive insights into different materials based on metal oxides, chalcogenides, graphene, and metal organic frameworks (MOFs), which are involved in sonophotocatalytic processes employed for the remediation of environmental pollutants.

Facile hydrothermal synthesis and sonophotocatalytic performance of novel Bi2WO6 structure on the degradation of rhodamine B

Octahedral Bi2WO6 structure was prepared using facile hydrothermal synthesis. The prepared sample was characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and UV–visible spectroscopy. The XRD spectrum confirmed the crystallinity of the synthesized samples. The SEM images of the samples showed the novel octahedral morphology of Bi2WO6. The sonocatalytic activity of Bi2WO6 was investigated by studying the degradation of Rhodamine B (RhB) with or without the visible light. The sonophotocatalysis of Rhodamine B in presence of Bi2WO6 has achieved 99.6% degradation within 90 min. The kinetic studies of the degradation reactions exhibited and followed pseudo-first-order kinetics. In this work, the influence of ultrasound waves and the structure of Bi2WO6 on the photocatalytic degradation efficiency have been discussed. The degradation mechanism of Rhodamine B in the sonophotocatalysis process is also proposed.

Sonolytic, sonocatalytic and sonophotocatalytic degradation of a methyl violet 2B using iron-based catalyst

The degradation of methyl violet 2B was efficiently carried out using sonolytic and sonophotocatalytic processes, FePO4 is a heterogeneous catalyst which has already shown its efficiency for the photocatalytic degradation of the earlier mentioned dye was used as a catalyst for the sonolytic process under a constant frequency of 500 kHz, effect of the parameters: pH, catalyst concentration ultrasonic intensity and dye concentration were also studied. The results show that a better degradation occurred under acidic pH (pH 3) with 1 g/L of the catalyst and an ultrasonic power P = 80 W. To further optimize the degradation process, ultrasound was coupled with UV radiation (λ = 254 nm), the dye degradation was improved from 68% using the sonolysis process to 100% using the sonophotocatalytic process with FePO4 as heterogeneous catalyst. Finally, degradation byproducts formed under optimized conditions were identified.

Degradation of 2,6-dichlorophenol by Fe-doped TiO2 Sonophotocatalytic process: kinetic study, intermediate product, degradation pathway

ABSTRACT TiO2 and Fe-doped TiO2 nanoparticles were synthesised by sol-gel method. To determine the properties of nanoparticles, scanning electron microscopy, X-ray diffraction and diffuse reflectance spectroscopy were used. The results of the analysis showed that the synthesised nanoparticles are almost uniform and agglomerated as well as the Fe-TiO2 band gap has decreased from 3.1 to 2.84 and the absorption spectrum has changed towards the visible region. The final concentration of 2,6-dichlorophenol and degradation products were measured with gas chromatography-flame ionisation detector and gas chromatography-mass spectrometry. The maximum efficiency and reaction rate constant of 2,6-dichlorophenol were determined at pH 4 and k0 = 2.11 × 10−2, initial concentration of 2,6-dichlorophenol 20 mg L−1 and k0 = 8.01*10−2, and nanoparticles dosage of 500 mgL−1 and k0 = 5.07*10−2 at 90 min time. The degradation reaction followed the first-order kinetic model. The efficiency of degradation and mineralisation of 2,6-dichlorophenol were in order of sonophotocatalytic > photocatalytic > sonocatalytic.

Enhanced sonophotocatalytic degradation of paracetamol in the presence of Fe-doped TiO2 nanoparticles and H2O2

The presence of pharmaceutical compounds, particularly, paracetamol in water is of significant environmental concern due to their undesirable effects on aquatic organisms and poor biodegradability. The present work investigated the efficient degradation of paracetamol in water using sonophotocatalytic process in the presence of iron (Fe)-doped titanium dioxide (TiO2) nanoparticles. The effects of Fe doping into TiO2 and calcination temperatures were investigated using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, nitrogen adsorption–desorption analysis and X-ray photoelectron spectroscopy. It was discovered that 3 wt% Fe dopants into TiO2 nanoparticles with suitable calcination temperature at 600 °C could improve the sonophotocatalytic activity remarkably toward the degradation of paracetamol. The degradation efficiency of 100% was achieved under optimal experimental conditions, namely 5 mg/L initial paracetamol, 1 g/L 3 wt% Fe-doped TiO2-600, solution pH of 5, 0.5 mM of hydrogen peroxide (H2O2) after 30-min ultrasonic power of 296 W, ultrasonic frequency of 50 kHz and ultraviolet wavelength of 302 nm. These findings are crucial for designing Fe-doped TiO2 nanoparticles with high catalytic performance for the degradation of paracetamol and appeared as an alternative solution to treat pharmaceutical compounds effectively.

Synergistic Effect of Microwave Calcination and Sonophotocatalytic Activity of TiO2-Montmorillonite on The Degradation of Direct Yellow 106 and Disperse Violet 1

The TiO2-pillared montmorillonite nanoparticles (TiO2-Mt) were prepared by the sol-gel method, then applied for the elimination of dyes in solution: CI Direct Yellow 106 (DY106) (azo dye) and CI Disperse Violet 1 (DV1) (anthraquinone dye) by the sonocatalytic, photocatalytic and sonophotocatalytic processes, in order to test the efficiency of photocatalysts, while photolysis, sonolysis, and sonophotolysis tests have been done previously. The photocatalysts (TiO2-Mt) were characterized by X-ray Diffraction (XRD), X-ray Fluorescence analysis (XRF), Brunauer-Emmet-Teller (BET), Scanning Electron Microscopy (SEM) methods, thermal and thermogravimetric analysis (TG/DTA) and the zero load point (pHpzc). Aqueous solutions of dye of an initial concentration (50 mg/L), in the presence of 1 g/L of photocatalyst, were irradiated using a mercury lamp (Hg) of 40 Mw/cm2 and put in contact with an ultrasonic probe with a frequency of 20 kHz and a power of 750 W, providing the ultrasound. The results obtained indicate that a weak, good and better dye degradation rate has been observed successively by the application of the sonocatalytic, photocatalytic and sonophotocatalytic processes, where the latter has shown a synergistic effect, while the photocatalyst TiO2-Mt/MW showed significant efficiency during the degradation, due to the beneficial effect of the microwave calcination mode. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Synergistic Effect of Microwave Calcination and Sonophotocatalytic Activity of TiO2-Montmorillonite on The Degradation of Direct Yellow 106 and Disperse Violet 1

The TiO 2 -pillared montmorillonite nanoparticules (TiO 2 -Mt) were prepared by the sol-gel method, then applied for the elimination of dyes in solution: CI Direct Yellow 106 (DY106) (azo dye) and CI Disperse Violet 1 (DV1) (anthraquinone dye) by the sonocatalytic, photocatalytic and sonophotocatalytic processes, in order to test the efficiency of photocatalysts, while photolysis, sonolysis and sonophotolysis tests have been done previously. The photocatalysts (TiO 2 -Mt) were characterized by X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM) methods, thermal and thermogravimetric analysis (TG) / DTA) and the zero load point (pH pzc ). Aqueous solutions of dye of an initial concentration (50 mg.L -1 ), in the presence of 1 g.L -1 of photocatalyst, were irradiated using a mercury lamp (Hg) of 40 Mw / cm 2 and put in contact with an ultrasonic probe with a frequency of 20 kHz and a power of 750 W, providing the ultrasound. The results obtained indicate that a weak, good and better dye degradation rate has been observed successively by the application of the sonocatalytic, photocatalytic and sonophotocatalytic processes, where the latter has shown a synergistic effect, while the photocatalyst TiO 2 -Mt / MW showed significant efficiency during the degradation, due to the beneficial effect of the microwave calcination mode.

Photocatalytic and sonophotocatalytic degradation of rhodamine B by nano-sized La2Ti2O7 oxides synthesized with sol-gel method

Nano-sized La2Ti2O7 oxides were synthesized by sol-gel route. The photocatalytic properties of the Rhodamine B degradation on this photocatalyst were studied as a function of crystallite size, dye concentration, catalyst loading, temperature and intensity of UV light flux. The photocatalytic results as well as the microstructural analysis, carried out by X-ray Diffraction and Transmission Electron Microscopy, revealed a strong correlation between the apparent rate constant and the crystallite size/degree of crystallinity of the photocatalyst. Temperature studies have shown optimum photocatalysis at 40 °C. Measurements of the zeta potential as a function of pH made it possible to determine the point of zero charge of the photocatalyst at pH = 8 and to understand the influence of pH on the degradation of cationic or anionic pollutants. Finally, the sonophotocatalytic process was studied showing a noticeable improvement in the apparent rate constant, multiplied by a factor of ∼1.7 compared to photocatalysis alone. The synergistic effect was quantified via measurements in sonocatalysis alone and then coupled to UV irradiation. This synergistic effect is about 23 % in the case of degradation of Rhodamine B on La2Ti2O7 oxides synthesized at 1000 °C.

Effects of catalyst preparation method and reaction parameters on the ultrasound assisted Photocatalytic oxidation of reactive yellow 84 dye.

In this study, the Heterogeneous Sono-photocatalytic Process was used to degrade Reactive Yellow 84 (RY 84) dye dissolved in water over iron containing TiO2 and TiO2-Ce catalysts. The catalysts were prepared by sol-gel and incipient wetness impregnation methods and characterized using XRD, SEM, Nitrogen adsorption, UV-Vis DRS and ICP-AES measurements. The TiO2 catalyst containing 1% (in weight) iron, prepared by incipient wetness impregnation technique and calcined at 300°C (1%Fe/TiO2-300°C (IW)) was found to be the most effective catalyst. Parametric study was carried out over this catalyst and COD removal of 55% and TOC removal of 38% were achieved while the decolorization efficiency reached 100% after 45min of reaction at the optimum conditions of, (25mg/L of RY 84 solution, 0.5g/L of catalyst, 5mM of H2O2, a temperature of 25°C, pH = 6 and US at a power of 40W). Decolorization of RY 84 obeyed the first order kinetics with an activation energy of 20.7kJ/mol. Sonication increased the decolorization efficiency of the heterogeneous Fenton process (UV + Catalyst+H2O2) from 92.7% to 97.5% after 30min of reaction, with the COD and TOC reductions increasing from 87% to 90% and 48% to 57% after 120min of reaction, respectively. US also decreased the toxicity of the RY 84 dye. The results obtained from this study show that, iron containing TiO2 and TiO2-Ce catalysts could be efficiently used in the hybrid process of ultrasound assisted heterogeneous photocatalytic oxidation in a wide range of experimental conditions.

Degradation of ciprofloxacin using photo, sono, and sonophotocatalytic oxidation with visible light and low-frequency ultrasound: Degradation kinetics and pathways

Abstract This study investigates the degradation of an antibiotic ciprofloxacin (CPX) by the photocatalytic, sonocatalytic and sonophotocatalytic oxidation inside a novel multi-frequency reactor under low ultrasonic frequencies and visible light using N-doped TiO2 (N-TiO2) nanoparticles as the catalysts. The synthesized nanoparticles were characterized by XRD, FTIR, TEM, BET and UV–Vis reflectance spectroscopy. The average particle size of these nanoparticles was in the range of 12–18 nm. The effects of different operational parameters affecting the CPX degradation during these processes were studied. Maximum CPX degradation of 54.5%, 41.2%, and 44% was observed for photocatalysis, sonocatalysis and sonophotocatalysis under their individual optimum conditions after 210, 90, and 90 min respectively. The application of these doped catalysts improved the photocatalytic and sonocatalytic oxidation of CPX due to the improved visible light activity and extra nuclei for cavitation respectively. Further, a synergistic effect was observed by the simultaneous application of light and ultrasound in sonophotocatalytic oxidation in comparison to individual processes with a synergy index of 1.22. During the Sonophotocatalysis process, the simultaneous application of ultrasound and visible light was found more effective in comparison to their sequential or intermittent application. The degradation products in all three oxidation processes were identified, and potential degradation pathways are proposed. In addition, effect of real wastewater matrix on the process performance was also investigated.