Synergistic degradation of methyl orange in an ultrasound intensified photocatalytic reactor

Design of a new fountain reactor for contamination degradation using advanced oxidation processes with hybrid techniques and modeling evaluation

Due to the water and energy crises, wastewater treatment systems that are more energy efficient and capable of large volume degradation are a priority. Photochemical decomposition methods have a significant impact on pollutant treatment. The use of these methods in conjunction with a novel designed reactor and hybridization processes can result in considerable treatment results. This research used a fountain system in a UV/H2O2 process to generate a belt-type liquid film with a low thickness and high mixing to remove methyl orange as a model pollutant. The flow rate, H2O2 concentration, temperature, and UV intensity were the parameters evaluated in this series of tests. After 90 minutes under optimum conditions, the maximum degradation of methyl orange was 99.73 percent. The efficiency of the purification process was increased to 99 percent in 75 minutes by using the optimum state of hybridization of UV/US/H2O2 processes. Two deep neural network models and a pseudo-first-order kinetic model were created to fit the experimental data. The results reveal a good fit between the experimental data and the model prediction. The discovered synergistic factor (1.168) and energy yield (2.65 g/kWh) demonstrated the high efficiency of the hybridization process and the outstanding function of the designed system, respectively.

Capability of copper-nickel ferrite nanoparticles loaded onto multi-walled carbon nanotubes to degrade acid blue 113 dye in the sonophotocatalytic treatment process

In this study, copper-nickel ferrite (CuNiFe₂O₄) nanoparticles were successfully loaded onto multi-walled carbon nanotubes (MWCNTs) by using the coprecipitation method and used as new catalysts (MWCNT-CuNiFe₂O₄) in the sonophotocatalytic degradation process of the acid blue 113 (AB113) dye. The success of the MWCNT-CuNiFe₂O₄ synthesis and its properties were determined by analyzing it using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). A high efficiency of dye removal (100%), total organic carbon (93%), and chemical oxygen demand (95%) were achieved with the following conditions: pH of dye solution = 5, MWCNT-CuNiFe₂O₄ dosage = 0.6 g/L, AB113 dye concentration = 50 mg/L, UV light intensity = 36 W, ultrasonic wave frequency = 35 kHz, and treatment time = 30 min. The kinetic results revealed that the efficiency of the sonophotocatalytic process using MWCNT-CuNiFe₂O₄ was higher than that of the sonolysis, photolysis, photocatalysis, and sonocatalysis processes. Scavenging studies demonstrated that the holes (h⁺) and hydroxyl radical (•OH) were the main reactive species for the AB113 dye degradation. The stability and recyclability of MWCNT-CuNiFe₂O₄ were confirmed with eight consecutive cycles for a maximum efficiency of more than 92%. The high rate of BOD₅/COD indicated that the sonophotocatalytic process had the potential to degrade the dye into degradable compounds. The toxicity study with an Escherichia coli growth inhibition rate emphasized that MWCNT-CuNiFe₂O₄ in the sonophotocatalytic degradation process of the AB113 dye had a significant effect on reducing toxicity, when compared to processes of photolysis and photocatalysis. During the sonophotocatalytic process using MWCNT-CuNiFe₂O₄, the AB113 dye was mineralized into CO₂, H₂O, NH₄⁺, NO₃^-, and SO₄^2-. The results of the present study proved that the MWCNT-CuNiFe₂O₄-based sonophotocatalytic process was a promising dye degradation technology to protect the aquatic environment.

Recent Progress and Prospects in Catalytic Water Treatment

Presently, conventional technologies in water treatment are not efficient enough to completely mineralize refractory water contaminants. In this context, the implementation of catalytic processes could be an alternative. Despite the advantages provided in terms of kinetics of transformation, selectivity, and energy saving, numerous attempts have not yet led to implementation at an industrial scale. This review examines investigations at different scales for which controversies and limitations must be solved to bridge the gap between fundamentals and practical developments. Particular attention has been paid to the development of solar-driven catalytic technologies and some other emerging processes, such as microwave assisted catalysis, plasma-catalytic processes, or biocatalytic remediation, taking into account their specific advantages and the drawbacks. Challenges for which a better understanding related to the complexity of the systems and the coexistence of various solid-liquid-gas interfaces have been identified.

Degradation of amoxicillin with sono, photo, and sonophotocatalytic oxidation under low-frequency ultrasound and visible light

The presence of pharmaceutically active compounds in aquatic bodies is a global concern, and suitable treatment technologies are required. In this study, the efficacy of photocatalytic, sonocatalytic, and sonophotocatalytic oxidation processes for the degradation of amoxicillin (AMX) was investigated using visible light with N doped TiO₂ (N-TiO₂) nanoparticles as the catalyst and low-frequency ultrasound in a novel multifrequency reactor. The influence of different operational parameters on the extent of AMX degradation was studied. Sonophotocatalytic oxidation was found more efficient for AMX degradation when compared to photocatalysis or sonocatalysis alone, and may be due to the reduced bandgap of the catalyst, enhanced cavitation effect due to the presence of the solid catalyst, and improved mass transfer of pollutants. AMX degradation during sono, photo, and sonophotocatalytic oxidation processes was in good agreement with pseudo-first-order kinetics. Empirical kinetic models were also developed using multiple linear regression for predicting the degradation efficiency accounting for the operational parameters. Scavenger experiments suggested that ^•OH radicals largely contributed to AMX degradation, and a plausible mechanism for degradation was proposed. Further, possible degradation pathways for all three treatment processes are also proposed after identifying the degradation products.

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). 

Ultrasound and UV Stimulated Heterogeneous Catalytic Oxidation of an Azo Dye: A Synergistic Effect

This research deals with the decolourisation of direct azo dye, Direct Blue 71 (DB71), in aqueous solution by means of sonocatalytic, photocatalytic and sonophotocatalytic heterogeneous oxidation processes in the presence of a zinc oxide (ZnO) catalyst. The effect of these oxidation processes under visible light and 20 kHz ultrasound was investigated to study their influence on degradation rates by varying the initial dye concentration, pH and catalyst load and to understand the effect of synergy on the degradation process. The synergistic effect is quantified in terms of a synergy factor which has already been defined in the literature. The highest value of the factor was obtained for a low DB71 dye concentration at pH 5.5, 20 °C temperature and 400 mg L−1 optimum ZnO dosage. Pseudo first-order kinetics were followed for the removal of the azo dye according to the Langmuir–Hinshelwood model. For comparison, the Langmuir–Hinshelwood model was also used for experimental values obtained from the sonocatalytic process, the photocatalytic process and the combination of these processes. The Langmuir–Hinshelwood kinetic model demonstrated consistency in all calculations of the initial rates of degradation with the appropriate values for the reaction rate constant and DB71 dye absorption constant.

Titanium dioxide-based sonophotocatalytic mineralization of bisphenol A and its intermediates

In this study, bisphenol A (BPA) removal by sonophotocatalysis coupled with commercially available titanium dioxide (TiO₂, P25) was assessed in batch tests using energy-based advanced oxidation combining ultrasound (US) and ultraviolet (UV). The kinetics of BPA removal were systematically evaluated by changing operational parameters, such as US frequency and power, mechanical stirring speed, and temperature, but also comparison of single and coupled systems under the optimum US conditions (35 kHz, 50 W, 300 rpm stirring speed, and 20 °C). The combination of US/UV/P25 exhibited the highest BPA removal rate (28.0 × 10^-3 min^-1). In terms of the synergy index, the synergistic effect of sonophotocatalysis was found to be 2.2. This indicated that sonophotocatalysis has a considerably higher removal efficiency than sonocatalysis or photocatalysis. The removal of BPA was further investigated to identify BPA byproducts and intermediates using high-performance liquid chromatography-mass spectrometry. Five main intermediates were formed during sonophotocatalytic degradation, and complete removal of BPA and its intermediates was obtained after 3 h of operation. The degradation pathway of BPA by sonophotocatalysis was also elucidated.

Intensification of abamectin pesticide degradation using the combination of ultrasonic cavitation and visible-light driven photocatalytic process: Synergistic effect and optimization study

Degradation of abamectin pesticide was carried out using visible light driven Cu₂(OH)PO₄-HKUST-1 MOF photocatalyst through the sonophotocatalytic technique. Cu₂(OH)PO₄-HKUST-1 MOF as a visible-light driven photocatalyst, was synthesized and characterized by XRD, SEM, EDS and DRS. The direct bang gaps of HKUST-1 MOF and Cu₂(OH)PO₄-HKUST-1 MOF were estimated about 2.63 and 2.59eV, respectively, which reveals that these photocatalysts can be activated under blue light illumination. All sonophotodegradation experiments were performed using a continuous flow-loop reactor. The central composite design (CCD) methodology was applied for modeling, optimization and investigation of influence of operational parameters, i.e. irradiation time, pH, solution flow rate, oxygen flow rate, initial concentration and photocatalyst dosage on the sonophotocatalytic degradation of abamectin. The maximum degradation efficiency of 99.93% was found at optimal values as 20min, 4, 90mL/min, 0.2mL/min, 30mg/L and 0.4g/L, for irradiation time, pH, solution flow rate, oxygen flow rate, initial concentration and photocatalyst dosage, respectively. Evaluation of the synergism in the combination of ultrasonic and photocatalysis lead to a synergistic index of 2.19, which reveals that coupling of ultrasonic and photocatalysis has a greater efficiency than the sum of individual procedures for degradation of abamectin.

Sonophotocatalytic degradation of trypan blue and vesuvine dyes in the presence of blue light active photocatalyst of Ag3PO4/Bi2S3-HKUST-1-MOF: Central composite optimization and synergistic effect study

An efficient simultaneous sonophotocatalytic degradation of trypan blue (TB) and vesuvine (VS) using Ag3PO4/Bi2S3-HKUST-1-MOF as a novel visible light active photocatalyst was carried out successfully in a continuous flow-loop reactor equipped to blue LED light. Ag3PO4/Bi2S3-HKUST-1-MOF with activation ability under blue light illumination was synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), photoluminescence (PL) and diffuse reflectance spectra (DRS). The effect of operational parameters such as the initial TB and VS concentration (5-45mg/L), flow rate (30-110mL/min), irradiation and sonication time (10-30min), pH (3-11) and photocatalyst dosage (0.15-0.35g/L) has been investigated and optimized using central composite design (CCD) combined with desirability function (DF). Maximum sonophotodegradation percentage (98.44% and 99.36% for TB and VS, respectively) was found at optimum condition set as: 25mg/L of each dye, 70mL/min of solution flow rate, 25min of irradiation and sonication time, pH 6 and 0.25g/L of photocatalyst dosage. At optimum conditions, synergistic index value was obtained 2.53 that indicated the hybrid systems including ultrasound irradiation and photocatalysis have higher efficiency compared with sum of the individual processes.

HKUST-1-MOF–BiVO4 hybrid as a new sonophotocatalyst for simultaneous degradation of disulfine blue and rose bengal dyes: optimization and statistical modelling

A new hybrid material composed of BiVO₄ and HKUST-1 MOF (HKUST-1-MOF–BiVO₄), which is active under blue light irradiation, was synthesized and characterized by XRD, FE-SEM, BET, BJH, EDS and DRS analysis.

Sonophotocatalytic degradation of dye C.I. Acid Orange 7 by TiO2 and Ag nanoparticles immobilized on corona pretreated polypropylene non-woven fabric

This study discusses the possibility of using corona pre-treated polypropylene (PP) non-woven fabric as a support for immobilization of colloidal TiO2 and Ag nanoparticles in order to remove dye C.I. Acid Orange 7 from aqueous solution. Dye removal efficiency by sonocatalysis, photocatalysis and sonophotocatalysis was evaluated on corona pre-treated fabric loaded with TiO2 nanoparticles, corona pre-treated fabric double loaded with TiO2 nanoparticles and corona pre-treated fabrics loaded with TiO2 nanoparticles before and after deposition of Ag nanoparticles. In addition, the stability of PP non-woven fabric during these processes was investigated. The substrates were characterized by SEM, EDX and AAS analyses. The change of the dye concentration was evaluated by UV-VIS spectrophotometry. Unlike sonocatalysis and photocatalysis, complete dye removal from both solution and non-woven fabric was obtained already after 240-270 min of sonophotocatalysis. Corona pre-treated PP non-woven fabric loaded with Ag nanoparticles prior to deposition of TiO2 nanoparticles provided excellent degradation efficiency and superior reusability. Sonophotocatalytic degradation of dye in the presence of all investigated samples was the most prominent in acidic conditions. Although this nanocomposite system ensured fast discoloration of dye solution, TOC values of water measured after sonophotocatalysis were not satisfactory because of PP degradation. Therefore, it is suggested to include TOC evaluation in each case study where different supports for TiO2 nanoparticles are used since these nanoparticles may guarantee the dye removal from solution but the stability of support could be problematic causing even more serious environmental impact.

Phenol degradation under visible light irradiation in the continuous system of photocatalysis and sonolysis

The combination of photocatalysis under visible light irradiation and sonolysis in the continuous system has been used to degrade an aqueous solution of phenol. ZnFe(2)O(4)/TiO(2)-GAC was employed as the photocatalysts which were obtained by sol-gel process and characterized by spectroscopic X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray microanalyses (SEM-EDX) and Brunauer-Emmett-Teller sorptometer (BET). It was observed that the rates of phenol degradation were affected by the initial pH value of phenol solution, salt addition, gas supplying and the recycling times of the recovered photocatalyst. The kinetic law for the phenol degradation can be apparently expressed as the first-order with respect to the concentration of phenol. Degradation of phenol solution in the continuous system, i.e., photocatalysis and sonolysis has synergistic effect in comparison with the photocatalytic reaction and sonolysis, respectively.