Sonocatalytic Removal Research Articles

Trivacant Keggin-type polyoxometalate/TiO2 composite for enhanced sonocatalytic degradation of AR88 from aqueous solutions

Polyoxometalates (POMs) have been limited in their widespread use in catalysis in previous studies due to their strong carrier complexation and limited solubility. To overcome this limitation, in this study, Z-type heterojunction composites constructed with trivacant Keggin-type POMs K9SbW9O33·19.5H2O and TiO2 were synthesized by the sol–gel method and used for the sonocatalytic removal of the organic pollutant AR88. The results showed that, compared with pure K9SbW9O33·19.5H2O, the optimum K9SbW9O33·19.5H2O/TiO2 showed a significantly higher sonocatalytic degradation efficiency of 87.2 % for AR88, and the mineralization rate reached 51.8 %. Parameters such as dye pH and sonication power were optimized to determine the best conditions for sonocatalysis. In addition, the K9SbW9O33·19.5H2O/TiO2 Z-type heterojunction composites showed good stability and reusability. The excellent catalytic performance is attributed to the effective separation of charges and holes by the Z-type heterojunction, which enables them to produce active substances for AR88 decomposition. This study demonstrates the high potential of POMs for the application of sonocatalysis in the treatment of organic pollutants.

Synthesis of magnetic layered double hydroxide (Fe3O4@CuCr-LDH) decorated with ZIF-8 for efficient sonocatalytic degradation of tetracycline

A series of Fe3O4@CuCr-LDH hybrids decorated with different amount of ZIF-8 (FLZ, 10–40 wt%) was prepared using simple methods and characterized with different techniques. The activity of the synthesized nanocomposites was investigated in the sonocatalytic degradation of tetracycline (TC) antibiotic from wastewater. When the content of ZIF-8 in the nanocomposite structure was 20 wt%, the FLZ-20 sonocatalyst exhibited the high performance in the sonocatalytic removal of TC. At optimum conditions (0.7 g/L catalyst dosage, pH of 7, 50 mg/L initial concentration of antibiotic, and 15 min sonication time) of the sonocatalytic removal of TC approached to 91.4% under ultrasonic irradiation (USI) using FLZ-20. This efficiency was much higher than those of obtained results by Fe3O4@CuCr-LDH and pristine ZIF-8. The formed ●OH and ●O2− exhibited the major roles in the sonocatalytic TC degradation process. The excellent performance of FLZ-20 can be attributed to the heterojunctions created between composite components, which could improve the electron transfer ability and effectively separate e−/h+ pairs. In addition, FLZ-20 showed the superior reusability and stability during three successive recycling. Moreover, the facile magnetically separation of the sonocatalyst from the aqueous solution was another outstanding feature, which prevents the formation of secondary pollutants. It can be concluded that the fabrication of heterojunctions is an efficient procedure to promote the sonocatalytic acting of the catalyst.

Recyclable MXene-bridged Z-scheme NiFe2O4/MXene/Bi2WO6 heterojunction with enhanced charge separation for efficient sonocatalytic removal of ciprofloxacin

Sonocatalysis has emerged as a promising technology for addressing environmental pollution issues. However, the efficacy of sonocatalytic processes is primarily hindered by challenges related to the sluggish flow rate of photogenerated electrons. This study presents a novel approach to address this issue by developing an improved Z-scheme NiFe2O4/MXene/Bi2WO6 (NMB) composite that exhibits exceptional sonocatalytic activity for ciprofloxacin (CIP) degradation. In particular, the NiFe2O4/MXene (5 wt%)/Bi2WO6 composite could achieve high CIP (at 10 mg/L) degradation efficiency (97.39 %) after 60 min of ultrasonic irradiation. The exceptional sonocatalytic activity of the composite was attributed to the synergistic interaction of the Z-scheme heterojunction charge transfer route and the electron mediator of Ti3C2-MXene, which enhances light collection capacity, separates photogenerated carriers efficiently, and improves redox activity of the composite. The scavenging experiments reveal that the sonocatalytic degradation of CIP was driven by holes (h+), hydroxyl radicals (•OH), and superoxide anion radicals (•O2−), with the former playing a dominant role. The results of reuse experiments demonstrate the outstanding sonocatalytic stability of the catalyst, as well as its uncomplicated recovery. The developed NMB Z-scheme composite shows promise for sonocatalytic treatment of antibiotics in industrial wastewaters, particularly those with high turbidity and/or low transparency. The findings also open up avenues for developing efficient and cost-effective sonocatalysts with good recyclability and remarkable performance.

Sonocatalytic degradation of tetracycline by Cu2O/MgFe2O4 nanocomposites: Operational parameters, sonocatalytic mechanism, degradation pathways, and environmental toxicity

Cu2O/MgFe2O4 nanocomposites with an S-scheme heterojunction were synthesized successfully and the sonocatalytic degradation effect of tetracycline (TET) by Cu2O/MgFe2O4 nanocomposites was demonstrated. Using the combination of analytical characterization and theoretical estimates, the composition, microscopic shape, comparative surface area and catalysis properties of Cu2O/MgFe2O4 nanocomposite materials were investigated. The experiment results showed that Cu2O/MgFe2O4 had good sonocatalysis performance. Over 91.93±1.07% TET was removed within 90 min at the optimal conditions. The TET sonocatalytic degradation mechanism showed that reactive species such as holes (h+), hydroxyl free radicals (·OH), and superoxide anion radicals (·O2−) produced during the reaction played a vital role in the effective removal of TET. Finally, the possible degradation products of TET were investigated by MS Q-TOF. In conclusion, the sonocatalytic activity, reusability, and stability of the produced Cu2O/MgFe2O4 nanocomposites are excellent, demonstrating that Cu2O/MgFe2O4 nanocomposites will become the focus of research in the field of sonocatalytic removal of pollutants.

Heterogeneous Sono-Fenton like catalytic degradation of metronidazole by Fe3O4@HZSM-5 magnetite nanocomposite

In this research, Fe3O4@HZSM-5 magnetic nanocomposite was synthesized via a coprecipitation method for metronidazole (MNZ) degradation from aqueous solutions under ultrasonic irradiation which showed superb sonocatalytic activity. The synthesized magnetite nanocomposite was characterized by using field-emission scanning electron microscope-energy dispersive X-ray Spectroscopy, (FESEM-EDS), Line Scan, Dot Mapping, X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET). To investigate the sonocatalytic activity of the Fe3O4@HZSM-5 magnetite nanocomposite, the sonocatalytic removal conditions were optimized by evaluating the influences of operating parameters like the dosage of catalyst, reaction time, pH, the concentration of H2O2, MNZ concentration, and pH on the MNZ removal. The MNZ maximum removal efficiency and TOC at reaction time 40 min, catalyst dose 0.4 g/L, H2O2 concentration 1 mM, MNZ initial concentration 25 mg/L, and pH 7 were achieved at 98% and 81%, respectively. Additionally, the MNZ removal efficiency in the real wastewater sample under optimal conditions was obtained at 83%. The achieved results showed that using Langmuir-Hinshelwood kinetic model KL-H = 0.40 L mg−1, KC = 1.38 mg/L min) can describe the kinetic removal of the process. The radical scavenger tests indicated that the major reactive oxygen species were formed by hydroxyl radicals in the Sono-Fenton-like process. Evaluation of the nanocomposite reusability showed an 85% reduction in the MNZ removal efficiency after seven cycles. Based on the results, it can be concluded that Fe3O4@HZSM-5 were synthesized as magnetic heterogeneous nano-catalysts to effectively degrade MNZ, and the observed stability and recyclability demonstrated that Fe3O4@HZSM-5 was promising for the treatment of wastewater contaminated with antibiotics.

Sonocatalytic degradation of tetracycline by BiOBr/FeWO4 nanomaterials and enhancement of sonocatalytic effect

BiOBr/FeWO4 nanomaterials with S-scheme heterojunction were synthesized by a two-step hydrothermal method, and combined with K2S2O8 to perform sonocatalytic degradation of Tetracycline (TC). Under the optimum experimental conditions of initial concentration of TC = 45 mg/L, ultrasonic time = 120 min, ultrasonic power = 500 W, catalyst addition = 1 g/L, pH = 6.5, composite ratio of BiOBr and FeWO4 = 15%, the experiment results showed that BiOBr/FeWO4 sonocatalyst removed TC by 86.54 ± 4.26%. K2S2O8 was verified to enhance the sonocatalytic performance of BiOBr/FeWO4 efficiently, and the removal ratio of TC could reach 92.99 ± 0.24% within 30 min by using BiOBr/FeWO4 and K2S2O8. There was no difference between the diffraction peaks of the XPS of the sonocatalyst before and after four recycles. Inductively coupled plasma (ICP) result indicated that the sonocatalyst had excellent reusability. Finally, the mechanism of TC degradation was proposed, and the possible degradation intermediates and pathways of TC by MS Q-TOF were proposed. In conclusion, the synthesized BiOBr/FeWO4 sonocatalyst had excellent sonocatalytic activity, reusability and stability, which indicated good application potential for the sonocatalytic removal of organic pollutants.

Synthesis of Fe-TiO2@Fe3O4 magnetic nanoparticles as a recyclable sonocatalyst for the degradation of 2, 4-dichlorophenol.

2, 4-Dichlorophenol is a type of chlorophenol that, even at low concentrations, causes adverse effects such as anemia, coma, weakening of the nervous system, and cancer in humans and other organisms. Therefore, the aim of this study was to synthesize the Fe-TiO2@Fe3O4 sonocatalyst and to assess the removal efficiency of 2, 4-dichlorophenol using this sonocatalyst. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), value-stream mapping (VSM), Brunauer Emmett Teller (BET), and diffuse reflectance spectroscopy (DRS) analyses were performed for characterizing the synthesized nanoparticles. The effect of different factors, such as pH (3-9), initial concentration 2, 4-dichlorophenol (20-80mg/L), and level of nanoparticles (200-600mg/L) at different time points (15-90min), was assessed on sonocatalytic removal of 2, 4-dichlorophenol, and then the reaction kinetics, process mechanism, and stability of the synthesized nanoparticles were determined under optimal conditions. The highest removal efficiency of 2, 4-dichlorophenol and constant reaction rate was obtained at pH of 5, the initial concentration of 20mg/L, and the nanoparticles dose of 400mg/L under ultrasound with a frequency of 35kHz following the reaction time of 90min. The maximum mineralization efficiency (total organic carbon TOC) under optimal conditions was 81%. Analysis of the degradation kinetics indicated that the 2, 4-dichlorophenol degradation can follow a first-order reaction. The stability of the synthesized sonocatalyst decreased by 91% after 5 re-uses. This study confirmed the efficiency of the Fe-TiO2@Fe3O4 sonocatalytic process in the degradation and mineralization of 2, 4-dichlorophenol.

Sonocatalytic removal of tetracycline in the presence of S-scheme Cu2O/BiFeO3 heterojunction: Operating parameters, mechanisms, degradation pathways and toxicological evaluation

The development of efficient sonocatalysts is of great significance to the treatment of antibiotic wastewater. Herein, an S-scheme sonocatalyst Cu2O/BiFeO3 has been fabricated using a simple synthesis method, in which Cu2O nanoparticles grow on the surface of BiFeO3. Tetracycline (TET) was selected as a representative pharmaceutical model to systematically evaluate the sonocatalytic performance of the Cu2O/BiFeO3. The experimental results showed that optimized Cu2O/BiFeO3 (CBF-3) has superior sonocatalytic performance to TET (98.0 %, 0.02302 min−1), which is much higher than that of pure BiFeO3 (54.6 %, 0.00515 min−1). Combined with the experimental result and characterization analysis, the sonodegradation mechanism was discussed. The improved sonocatalytic performance can be ascribed to the S-scheme charge transfer mechanism between Cu2O and BiFeO3, which can simultaneously inhibit sonoelectron-hole recombination, promote carrier transfer, maintain high redox capacity, and generate more active substance. The possible intermediate products and degradation pathways of TET over CBF-3 were analyzed by ion chromatography and liquid chromatography-mass spectrometry. Furthermore, the results of the bacterial toxicity test indicated that the toxicity of the reaction solution decreased significantly after sonodegradation. This study provides a simple way for the rational design and successful preparation of S-scheme sonocatalyst with promising applications in the remediation of the water environment.

Synthesis of ZnO immobilized on recycled polyethylene terephtalate for sonocatalytic removal of Cr(VI) from synthetic, drinking waters and electroplating wastewater

In this study, Cr(VI) was removed sonocatalytically by the zinc oxide nanoparticle coated with polyethylene terephthalate (PET) fabricated through a facile co-precipitation method. The crystal structure, functional groups on the surface, morphology, surface composition and oxidation states of the nanomaterials were investigated by XRD, FTIR, SEM, EDX and XPS techniques. Environmental parameters including solution pH, catalyst dose, hexavalent chromium concentration, H2O2 content, purging gases, organic compounds and type and anions strength on the sonotocatalytic removal of Cr(VI) were also investigated. Additionally, the contribution of each process, reusability, Cr(VI) reduction from actual water and electroplating wastewater were evaluated. Under the optimal conditions, [Cr(VI)]0=20 mg/L, nanocomposite loading=1.6 g/L and pH=5, 99.92% of Cr(VI) was removed within 60 min. By increaing, Cr(VI) concentration (5–50 mg/L), kobs decreased to values between 0.1498 and 0.0063 min−1 and the calculated electrical energy per order (EEo) increased from 148.68 to 3535.24 kWh.m−3, respectively. The presence of purging gases, organic compounds and ionic strength negatively affected Cr(VI) reduction. Examination of radical scavengers showed that the most active radicals in Cr(VI) removal were O2•− and h+. The removal of the Cr(VI) using the US/ZnO-PET method (99.92%) was higher than that of the US/ZnO method (70.78%). The catalyst activity was well maintained up to eight consecutive cycles. In addition, the removal efficiency was approximately 72.23 and 68.55% for drinking water and real electroplating wastewater samples, respectively. The results of toxicity in the sonotocatalytic removal of Cr(VI) by Daphnia magna showed LC50 and toxicity unit (TU) 48 h, which was equal to 81.46 and 1.227 vol percent.

Sonocatalytic removal of naphthalene from an aqueous solution using ZnO nanoparticles

Abstract This research presents the sonocatalytic degradation of naphthalene from an aqueous medium using a zinc oxide (ZnO) catalyst synthesised by the thermal decomposition method. The present paper also aims to apply the response surface methodology for the evaluation of the effect of different parameters on the degradation rate. The optimum parameters were found to be 50 min of reaction time, 2.2 g/l of the ZnO catalyst mass, 30 °C, 280 V, and 80 mg/l of initial concentration under a constant ultrasonic treatment at 20 kHz and 260 W of power intensity. The elemental composition of the catalyst was as follows: Zn 25.18%, O 37.03%, Mg 3.20%, K 0.83%, Ca 4.05%, N 5.07%, Na 4.13%, Cl 3.43%, and Fe 0.32%. Fourier Transform Infra-Red (FTIR) confirmed the Zn–O bond stretching at 510 cm−1. The degradation efficiency of naphthalene was almost double when the ZnO catalyst was used. The naphthalene degradation rate was a first-order reaction. Analysis of variance (ANOVA) results show that the quadratic model is suitable for the obtained data (P-value = 0.0001) and in an optimal process, performance conditions were set equal to 100%. Regression analysis with a high correlation coefficient (R2 = 0.989) and the model F-value of 6.94 indicated the adequacy of the model. The reusability study revealed that ZnO as a catalyst sustained the catalytic activity over five cycles.

BiOBr/MgFe2O4 composite as a novel catalyst for the sonocatalytic removal of tetracycline in aqueous environment

A series of BiOBr/MgFe2O4 composites were synthesized and characterized. Tetracycline (TET) was used as a model antibiotic to verify the sonocatalytic activities of these BiOBr/MgFe2O4 composites. When the mass ratio of BiOBr to MgFe2O4 in the BiOBr/MgFe2O4 composites was 20%, the BiOBr/MgFe2O4 composite (BM-20) showed the best catalytic performance to the sonocatalytic removal of TET. Under the optimum conditions, such as the addition of catalyst 2.0 g/L, pH 7 and ultrasonic power 500 W, the initial concentration of TET 10 mg/L, the sonocatalytic removal rate of TET reached 91.10±2.36% in 30 min using BM-20 as a sonocatalyst, which was significantly better than that of MgFe2O4 (52.3±2.23%). The generated hydroxyl free radicals (•OH), holes (h+) and superoxide anion radical (•O2−) played major roles in the sonocatalytic removal process. The improved sonocatalytic performance of BM-20 was due to the S-scheme heterojunction formed between BiOBr and MgFe2O4, which could separate electron-hole (e−-h+) pairs effectively. Besides, BM-20 had great stability and reusability. To conclude, the fabrication of heterojunction was an effective method to improve the sonocatalytic performance of catalyst. The BiOBr/MgFe2O4 composites could be satisfactory utilized as a catalyst in the sonocatalytic elimination of organic contaminant.

A novel ZnWO4/MgWO4 n-n heterojunction with enhanced sonocatalytic performance for the removal of methylene blue: Characterizations and sonocatalytic mechanism

A novel ZnWO4/MgWO4 n-n heterojunction (0.9% ZnWO4/MgWO4) was fabricated successfully and characterized by different techniques. The methylene blue (MB) was removed to confirm the sonocatalytic activity by the 0.9% ZnWO4/MgWO4 composite. The sonocatalytic removal ratio of MB using MgWO4 was 40.04±4.34(%). It was significantly increased to 93.82±3.44(%) in the presence of 0.9% ZnWO4/MgWO4 composite. The significantly improved sonocatalytic performance was due to the form of n-n heterojunction, which could hinder the recombination of electron and hole (e−-h+) pairs effectively. The mechanism showed that hydroxyl radical (•OH) and h+ had important roles for the elimination of MB. Moreover, the 0.9% ZnWO4/MgWO4 composite had remarkable stability during the process of MB removal under the ultrasonic irradiation. The results suggested that the fabrication of heterojunction is a valid method to promote the sonocatalytic performance of catalyst. The results of this paper would provide valuable references for the development of new sonocatalysts used in environmental remediation.

Fabrication of CaWO4 microspheres with enhanced sonocatalytic performance for ciprofloxacin removal in aqueous solution

The calcium tungstate (CaWO 4 ) microspheres were prepared with citric acid as an adjuvant by a hydrothermal process and characterized. The removal ratio of ciprofloxacin (CIP) was 15.43% ± 3.31% under ultrasonic irradiation alone at 120 min. In the presence of CaWO 4 , the sonocatalytic removal ratio of CIP was 27.35% ± 2.81%. When the molar ratio of calcium ions to citric acid was 4 : 1 in the synthesis process, the prepared CaWO 4 -4 exhibited superior sonocatalytic performance, and the removal ratio of CIP was up to 74.75% ± 1.32%. The reaction rate constant k of the sonocatalytic removal of CIP in the presence of CaWO 4 -4 was 7.15 and 4.73 times than that of ultrasound alone and in the presence of CaWO 4 , respectively. The results indicated that citric acid had a great influence on the microstructure of CaWO 4 microspheres during the synthesis process, thus enhanced the sonocatalytic performance of the samples. The results of sonocatalytic mechanism suggested that the sonocatalytic decomposition of CIP was mainly due to the production of hydroxyl radicals and holes. In addition, CaWO 4 -4 had good stability and reusability within four recycles. These results suggested that CaWO 4 microspheres had the potential applied in the sonocatalytic removal organic pollutants in aqueous solution as a sonocatalyst. Sonocatalytic decomposition of CIP in the presence of CaWO 4 • Citric acid had a great influence on the microstructure of CaWO 4 microspheres. • Citric acid used in the synthesis enhanced the sonocatalytic performance of CaWO 4 . • CaWO 4 -4 had excellent sonocatalytic performance for ciprofloxacin removal.

Facile provision of CuO-Kaolin nanocomposite for boosted sonocatalytic removal of Cr(VI) from hydrous media

ABSTRACT Nowadays, nanoscale materials have been widely applied in the removal of contaminants from the water system. Reduction of Cr(VI) (as a poisonous species) to Cr(III) (as a slight toxic species) was performed using CuO-Kaolin with ultrasound (US) irradiation. The CuO-Kaolin nanocomposite was synthesized via a facile co-precipitation method. Then X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope and Energy dispersive X-ray spectroscopy analyses were performed to identify the structural features of CuO-Kaolin. The role of influential parameters for the reduction of Cr(VI) was investigated in sonocatalytic advanced oxidation system. About 89.35% of Cr(VI) was removed via US/CuO-Kaolin process after 90 min at optimum conditions (pH = 3, sonocatalyst dosage = 1 g L−1 and [Cr (VI)]0 = 20 mg L−1). This outstanding result was due to the synergistic effect of the increased electron delivery to conduction band on CuO-Kaolin nanocomposite and the increased reactive surface region of nanoparticles by sonication. The presence of H2O2 as an amplifier improved the removal efficiency of Cr(VI) from 89.35% to 100% after 20 min. Kinetic experimental results were well described by a pseudo-first-order kinetic model. Desorption experiments showed excellent stability of sonocatalyst during the reaction and maintenance of the catalytic activity up to 10 sequential cycles.

Synthesis of CaMoO4 microspheres with enhanced sonocatalytic performance for the removal of Acid Orange 7 in the aqueous environment

Herein, a series of CaMoO4 microspheres were prepared at different pH values by the hydrothermal method. The sonocatalytic performances of the prepared CaMoO4 microspheres were estimated by the removal of Acid Orange 7 (AO7) as a model of organic pollutants. The results showed that the synthesis pH had a great influence on the morphology and the sonocatalytic performance of CaMoO4. The CaMoO4 microspheres prepared at pH = 7 (CaMoO4-7) exhibited superior sonocatalytic performance. The removal ratio of AO7 using CaMoO4-7 as a sonocatalyst was 97.02 ± 0.65%. The sonocatalytic removal of AO7 in the presence of CaMoO4-7 was mainly attributed to the generation of hydroxyl radical (•OH), superoxide anion radical (•O2−) and holes (h+). The optimized operational conditions, such as CaMoO4-7 dose, initial concentration of AO7, initial pH of AO7, ultrasonic power and ultrasonic time were 1.0 g/L, 5 mg/L, pH = 5, 200 W and 120 min, respectively. In addition, CaMoO4-7 had excellent reusability and stability in the sonocatalytic removal process. These results indicated that CaMoO4-7 had the potential as the sonocatalyst to apply in the environmental remediation.

Improvement of Ultrasound‐Assisted Removal of Rifampin in the Presence of N: ZnO/GO Nanocomposite as Sonocatalyst

AbstractThe sonocatalytic Removal of Rifampin by Nitrogen‐doped Zinc oxide/Graphene oxide hybrid nanocomposite (N: ZnO/GO) is reported in this study. The structural properties of the nanocomposites were confirmed by the X‐ray diffraction (XRD), the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), the X‐ray energy spectroscopy (EDX) and the diffraction reflectance spectroscopy (DRS). The experiments were investigated by applying the Response Surface Methodology (RSM) using the Design of Experiments software. Analysis of variance (ANOVA) confirmed that the quadratic model has good reliability for predicting the sonocatalytic efficiency with different operational factors (R2=0.9958 and Adjusted R2=0.9920). According to the RSM data, the optimized nanocomposite (N: ZnO (0.2 M)/GO (0.1 g)) demonstrated a reasonable catalytic activity for sonocatalytic degradation of RIF at the initial concentration (30 mg L−1), the ultrasonic irradiation time (60 min), natural pH and under the ultrasonic irradiation power of 400 W with a reaction rate constant of 0.0466 min−1which was higher compared with the other ones. The residual RIF amount has determined by the spectrophotometric method. The percentage of the RIF minerals was 80.8 % after 60 min of RIF degradation over N: ZnO (0.2 M)/GO.

Ultrasonically Induced Sulfur-Doped Carbon Nitride/Cobalt Ferrite Nanocomposite for Efficient Sonocatalytic Removal of Organic Dyes

The sulfur-doped carbon nitride/cobalt ferrite nanocomposite (SCN/CoFe2O4) was prepared via ultrasonication and studied for the sonocatalytic degradation of wastewater organic dye pollutants including methylene blue, rhodamine B, and Congo red. The X-ray photoelectron spectroscopy confirmed the presence and atomic ratios of S, C, N, Co, Fe, and O elements and their corresponding bonds with Co2+ and Fe3+ cations. The nanocomposite was found to have aggregated nanoparticles on a sheet-like structure. The bandgap energy was estimated to be 1.85 eV. For the sonocatalytic degradation of 25-ppm methylene blue at 20 kHz, 1 W and 50% amplitude, the best operating condition was determined to be 1 g/L of catalyst dosage and 4 vol % of hydrogen peroxide loading. Under this condition, the sonocatalytic removal efficiency was the highest at 96% within a reaction period of 20 min. SCN/CoFe2O4 outperformed SCN and CoFe2O4 by 2.2 and 6.8 times, respectively. The SCN/CoFe2O4 nanocomposite was also found to have good reusability with a drop of only 7% after the fifth cycle. However, the degradation efficiencies were low when tested with rhodamine B and Congo red due to difference in dye sizes, structural compositions, and electric charges.

Application of ZnO nanorods doped with Cu for enhanced sonocatalytic removal of Cr(VI) from aqueous solutions.

The aim of this research was to develop a simple and inexpensive process for reduction of Cr(VI) to Cr(III). Zinc oxide nanoparticles were synthesized with an easy co-precipitation procedure, and the addition of Cu2+ doping agent effectively enhanced the Cr(VI) reduction in the presence of ultrasound (US). XRD, FT-IR, FE-SEM, EDX, VSM, and XPS were used to determine the structural specifications of the zinc oxide nanoparticles. Under optimal conditions such as pH 3, initial Cr(VI) content of 20 mg/L, and catalyst dosage of 0.8 g/L, the ultrasonic/Cu-ZnO process showed a higher sonocatalytic activity (96.83%) than ultrasonic/ZnO (67.36%) after 60 min. By increasing pH and Cr(VI) concentration, the removal efficacy of Cr(VI) declined. The experimental data was well described with the first-order kinetic model. When initial Cr(VI) concentration increased from 10 to 50 mg/L, the first-order rate constant declined from 0.2326 to 0.0019 min-1 and electrical energy per order (EEO) enhanced from 19.81 to 2425.26 kWh/m3. Also, the ultrasonic/Cu-ZnO system exhibited considerable sonocatalytic performance in Cr(VI) reduction in the presence of hydrogen peroxide and citric acid, and complete removal was achieved within 60 min. The presence of anions negatively affected Cr(VI) reduction. Complete reduction was attained when ultrasound was applied at a power of 100 W. The catalyst activity was well maintained up to six consecutive cycles. In addition, the removal efficiency was approximately 62 and 65% for field water and real electroplating wastewater samples, respectively.

Sonocatalytic removal of ampicillin by Zn(OH)F: Effect of operating parameters, toxicological evaluation and by-products identification.

Zinc hydroxyfluoride (Zn(OH)F) sonocatalyst was prepared by using solvothermal method and was characterized by using various techniques. The sonocatalytic degradation of ampicillin (AMP) in water by sonolysis, bare ZnO and Zn(OH)F was investigated in terms of AMP removal, mineralization, detoxification of solution, and remaining by-products at the end of process. Results revealed that the sonocatalytic performance of Zn(OH)F was significantly greater than that of bare ZnO. Under the optimum conditions, the removal percentage of AMP by Zn(OH)F was ∼97% after 90 min reaction, while 51% and 36% COD and TOC removal were achieved after 120 min reaction, respectively. The study of Zn(OH)F stability revealed that the degradation efficiency of AMP was reduced by only 5% even after being reused for four experiments. The toxicity of initial and treated solutions was assessed by using agar-well diffusion method and ToxTrak™ toxicity assay, and the results indicated a substantial reduction in the toxicity of solution after the treatment. The formation of some by-products during the sonolysis and sonocatalysis was evaluated by LC-HR-MS/MS method. LC-HR-MS/MS results showed that the concentration of most by-products, which were produced after 90 min treatment by US/Zn(OH)F process, was considerably lower than those obtained during sonolysis and US/ZnO processes.

Oxygen-rich bismuth oxychloride Bi12O17Cl2 materials: construction, characterization, and sonocatalytic degradation performance

In this study, a series of oxygen-rich bismuth oxychloride Bi12O17Cl2 samples were prepared at different calcination temperatures and characterized by X-ray diffraction patterns, UV–Vis diffuse reflectance spectra, scanning electron microscope, X-ray energy dispersion spectroscope, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The calcination temperature greatly affected microstructures and band structures of as-prepared samples, further influencing sonocatalytic degradation efficiencies over dye Rhodamine B. Some dependant factors such as ultrasonic power, catalyst dosage, pH value, initial concentration of Rhodamine B, and reaction temperature were systematically investigated and the robust sample Bi12O17Cl2-550 with a favorable microstructure and band structure provided the best sonocatalytic removal efficiency around 90% at the optimal condition. Based upon reactive species entrapping and hydroxyl radical detection experiments, a primary sonocatalysis mechanism was eventually speculated.