Sonocatalytic Degradation Research Articles

Cerium-substituted magnetite: Fabrication, characterization and sonocatalytic activity assessment

The present paper reports the sonocatalytic activity of cerium-substituted-magnetite for removal of oxytetracycline (OTC). The catalyst was prepared through a chemical route (co-precipitation, Fe3-xCexO4) and a mechanical procedure (CeO2/Fe3O4). Subsequently, the physico-chemical characteristics of both samples were determined using XRD, BET, SEM, EDX, TEM, Dot-mapping, FT-IR, DRS, and VSM analysis and compared to pristine magnetite and ceria. Afterwards, the effects of various operational conditions were assessed on sonocatalytic performance of Fe2.8Ce0.2O4 for OTC removal and the obtained optimal conditions were applied to compare the resulted DE with so-synthesized Fe3O4, CeO2, and CeO2/Fe3O4 samples. Fe2.8Ce0.2O4 (0.75 g/L) exhibited great catalytic performance for sono-degradation of OTC under its unchanged pH and US power of 300 W, wherein about 88% and 64% of OTC was removed at its initial concentrations of 20 and 50 mg/L. Moreover, the effects of the addition of a number of oxidants, organic and inorganic compounds and gases on the sonocatalytic degradation of OTC were evaluated under the identical condition. The obtained results presented an effective sonocatalytic system based on the synergistic action of Fe2.8Ce0.2O4 under ultrasonic irradiation.

Preparation of novel CeO2-biochar nanocomposite for sonocatalytic degradation of a textile dye

The sonocatalytic performance of CeO2 nanoparticles synthesized by a hydrothermal method (CeO2-H) and CeO2@biochar (CeO2-H@BC) nanocomposite, were evaluated for the degradation of Reactive Red 84 (RR84) under ultrasonic irradiation. For comparison purposes the corresponding performance of bare biochar (BC) and commercial CeO2 (CeO2-C) samples were also assessed. A complementary characterization study, involving scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), N2 adsorption at −196°C (Brunauer–Emmett–Teller (BET) method) and Fourier transform infrared spectroscopy (FT-IR) was undertaken to gain insight into the structure-performance relationships. The effect of various parameters such as initial RR84 concentration, solution pH, catalyst amount and ultrasonic power on the sonodegradation of RR84 was studied in detail. The results indicated that the CeO2-H@BC nanocomposite exhibited the best RR84 degradation efficiency, which is enhanced with the increase of CeO2-H@BC amount and ultrasonic power but diminished with the increment in RR84 concentration and pH value. A 98.5% degradation was obtained with a CeO2-H@BC amount of 1g/L, ultrasonic power of 450 W, pH of 6.5 and initial RR84 concentration of 10mg/L. The quenching effects of various scavengers proposed that OH radical plays the key role in the process. Analyses of intermediates by Gas chromatography-Mass spectroscopy (GC–MS) identified several by-products and accordingly the main pathway was proposed.

Enhanced sonocatalytic degradation of organic dyes from aqueous solutions by novel synthesis of mesoporous Fe3O4-graphene/ZnO@SiO2 nanocomposites

Fe3O4-graphene/ZnO@mesoporous-SiO2 (MGZ@SiO2) nanocomposites was synthesized via a simple one pot hydrothermal method. The as-obtained samples were investigated using various techniques, as follows: scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and specific surface area (BET) vibrating sample magnetometer (VSM), among others. The sonocatalytic activities of the catalysts were tested according to the oxidation for the removal of methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) under ultrasonic irradiation. The optimal conditions including the irradiation time, pH, dye concentration, catalyst dosage, and ultrasonic intensity are 60min, 11, 50mg/L, 1.00g/L, and 40W/m2, respectively. The MGZ@SiO2 showed the higher enhanced sonocatalytic degradation from among the three dyes; furthermore, the sonocatalytic-degradation mechanism is discussed. This study shows that the MGZ@SiO2 can be applied asa novel-design catalyst for the removal of organic pollutants from aqueous solutions.

ZnFe-Cl nanolayered double hydroxide as a novel catalyst for sonocatalytic degradation of an organic dye

ZnFe nanolayered double hydroxide (NLDH) with anions of Cl− in its interlayer space was synthesized using a facile co-precipitation method. The synthesized ZnFe-Cl NLDH was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), N2 adsorption/desorption, diffuse reflectance spectroscopy (DRS) and point of zero charge pH (pHpzc) analyses. In this research, the sonocatalytic activity of the as-prepared NLDH was investigated for removal of acid red 17 as model pollutant. The effects of the operating parameters including sonocatalyst concentration, pH, initial dye concentration, intensity of ultrasonic irradiation and the presence of radical scavengers and process enhancers were studied on the sonocatalytic degradation of acid red 17. The decreased decolorization efficiency in the presence of the radical scavengers confirmed that the free radicals play the basic roll in the degradation of acid red 17 molecules. In addition a probable mechanism for degradation of acid red 17 through the sonocatalytic process was proposed according to the identified intermediates detected using gas chromatography–mass (GC–MS) spectroscopy.

The degradation of landfill leachate in the presence of different catalysts by sonolytic and sonocatalytic processes

ABSTRACTIn the study, the degradation of landfill leachate by single ultrasound (sonolytic) and sonolytic combined with Fe2+ and TiO2 catalysts was carried out in laboratory conditions. The effect of pH and ultrasonic wave amplitude was also investigated in terms of color removal, total organic carbon (TOC) and chemical oxygen demand (COD) from leachate by the sonolytic degradation process. In this process, the color removal efficiency was recorded as 81.81% at 620 nm, pH = 2.0 and 70% wave amplitude. The sonocatalytic degradation of landfill leachate accompanied by different catalysts was studied by using the 70% wave amplitude at pH = 2.0 and room temperature for 20 min. The sonocatalytic degradation of leachate by using Fe2+ and TiO2 was found to be significantly higher than sonolytic degradation (p < 0.05). As the Fe2+ concentration increased from 1.0 to 3.0 mg/L, the COD and color removal of leachate significantly decreased (p < 0.05) from 50 to 35.7% and from 95.5 to 90.9%, respectively. The experimental data obtained from sonocatalytic degradation was analyzed using the Behnajady–Modirshahla–Ghanbery (BMG) kinetic models and found to be compatible. The results showed that the combination of catalyst and sonolysis was a highly effective way to remove color, COD and TOC from landfill leachate.

Structural investigation and sonocatalytic efficiency of Ce0.9Nd0.1O1.95 and Ce0.9Pr0.1O1.95 nanocatalysts

The cost-effective low-frequency ultrasound (42 kHz) producing bath type sonicator was utilized to demonstrate the synthesis of sequential (SP) and co-precipitated (CP) Ce0.9Pr0.1O1.95, Ce0.9Nd0.1O1.95 and their bare catalysts. The analytical characterizations of the catalysts showed that the 42 kHz ultrasound fetches the interesting physicochemical properties with unusual sonocatalytic efficiency in the resulting catalysts. In addition, the ultrasound introduced the nanoporous structure in the CeO2, Ce0.9Pr0.1O1.95 (SP, CP) and Ce0.9Nd0.1O1.95 (SP, CP) catalysts, however, the nanoporous structure was not observed for the bare praseodymium and neodymium oxides. The sonocatalytic efficiency of the catalysts was evaluated by studying the degradation kinetics of Acid Blue 113 (AB113) dye. The sonocatalytic degradation of AB113 followed the first-order kinetic rate law and the r2 (linear regression coefficient) was >0.92. The extended ultrasound irradiation of AB113 was studied for 7 h in the presence of various nanocatalysts in order to evaluate the total organic carbon (TOC) removal from the sonocatalytic microenvironment. The rapid development of cost-effective technology based on 42 kHz ultrasound assisted degradation of various environmental pollutants significantly contributes to reducing the cost required for the commercialization of advanced oxidation processes.

Heterogeneous sonocatalytic degradation of anazolene sodium by synthesized dysprosium doped CdSe nanostructures

Undoped and Dy–doped CdSe nanoparticles are synthesized and then characterized by the SEM, XRD, FT–IR, XPS and BET methods, which verify successful preparation of the doped catalyst. The sonocatalytic degradation of anazolene sodium as a model azo dye is higher than sonolysis process and the 2% Dy–doped CdSe with band gap of 1.42eV exhibits the greatest sonocatalytic performance. The decolorization efficiency (DE%) of sonocatalysis with 2% Dy–doped CdSe, undoped CdSe and sonolysis after 90min of the process is 91.32%, 56.13% and 39.14%, respectively. In addition, the sonocatalytic degradation of anazolene sodium increases with enhancement of the dopant, catalyst dosage, ultrasonic power, dissolved gasses and decreasing of initial anazolene sodium concentration. Furthermore, with addition of chloroform, sulfate, chloride and ethanol as the radical scavengers, the DE% decreases indicating the controlling mechanism of free radicals for the dye degradation. Besides, the results reveal the appropriate reusability of the catalyst and various degradation by–products are identified using the GC–MS technique. Eventually, the empirical kinetic model is expanded by nonlinear regression analysis for prediction of pseudo first–order constants in various operational conditions.

In Ukrainian

We have studied mechanochemical, microwave, and ultrasonic treatments of niobium pentoxide of different origin and specific surface area ( 0.1-474 m 2 / g). The aims of work were: examination of crystal, porous, and electronic structure of obtained products, evaluation of their photocatalytic activity under visible light as well as mechano- and sonocatalytic degradation of dyes. We used XRD and DTA-TG analysis, UV-Vis spectroscopy, adsorption-desorption of nitrogen for characterization of initial and modified samples. We have found that high-dispersed X-ray amorphous powders and xerogel are crystallized only under microwave treatment. Simultaneously, the reducing in the specific surface area of powders, but increasing it for xerogel as well as the formation of meso-macroporous structure with uniform mesoporous fraction takes place. The narrowing of band gap and increase of adsorption of visible light occurs after modification, as a rule. As a result, photocatalytic activity of modified Nb 2 O 5 under visible irradiation significantly increases. All Nb 2 O 5 samples show sono- and mechanocatalytic activity in the degradation of Safranin T. The rate of degradation is directly proportional to the specific surface area of the catalyst in the first case and reverse proportional - in the second.

Sonocatalytic degradation of methylene blue by a novel graphene quantum dots anchored CdSe nanocatalyst

Cadmium selenide/graphene quantum dots (CdSe/GQDs) nanocatalyst with small band gap energy and a large specific surface area was produced via a facile three-step sonochemical-hydrothermal process. The features of the as-prepared CdSe, GQDs and CdSe/GQDs samples were characterized by photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), diffuse-reflectance spectrophotometer (DRS), and Brunauer–Emmett–Teller (BET) analysis. The sonocatalytic activity of the synthesized CdSe/GQDs was effectively accelerated compared with that of pure CdSe nanoparticles in degradation of methylene blue (MB). The influence of the CdSe/GQDs dosage (0.25–1.25g/L), initial MB concentration (20–30mg/L), initial solution pH (3–12), and ultrasonic output power (200–600W/L) were examined on the sonocatalytic treatment of MB aqueous solutions. The degradation efficiency (DE%) of 99% attained at 1g/L of CdSe/GQDs, 20mg/L of MB, pH of 9, and an output power of 200W/L at 90min of ultrasonic irradiation. Furthermore, DE% increased with addition of K2S2O8 and H2O2 as the enhancers via producing more free radicals. However, addition of sulfate, carbonate, and chloride as radical sweeper decreased DE%. Furthermore, well-reusability of the CdSe/GQDs sonocatalyst was demonstrated for 5 successive runs and some of the sonocatalytic generated intermediates were indicated by GC–MS analysis.

Sonocatalytic degradation of Reactive Yellow 39 using synthesized ZrO2 nanoparticles on biochar

ZrO2-biochar (ZrO2-BC) nanocomposite was prepared by a modified sonochemical/sol–gel method. The physicochemical properties of the prepared nanocomposite were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray fluorescence, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller model. The sonocatalytic performance of ZrO2-BC was investigated in sonochemical degradation of Reactive Yellow 39 (RY39). The high observed sonocatalytic activity of the ZrO2-BC sample could be interpreted by the mechanisms of sonoluminescence and hot spots. Parameters including ZrO2-BC dosage, solution pH, initial RY39 concentration and ultrasonic power were selected as the main operational parameters and their influence on RY39 degradation efficiency was examined. A 96.8% degradation efficiency was achieved with a ZrO2-BC dosage of 1.5g/L, pH of 6, initial RY39 concentration of 20mg/L and ultrasonic power of 300W. In the presence of OH radical scavengers, RY39 degradation was significantly inhibited, providing evidence for the key role of hydroxyl radicals in the process. The sonodegradation intermediates were identified using gas chromatography-mass spectroscopy and the possible decomposition route was proposed.

Sonocatalytic degradation of organic pollutant by SnO2/MWCNT nanocomposite

Developing highly active catalysts is central to sonocatalytic degradation of organic pollutants. In this work, efficient sonocatalytic degradation of organic pollutants is achieved using a novel sonocatalyst SnO2/multiwall carbon nanotube (MWCNT) nanocomposite. By taking methylene blue (MB) as a model pollutant, almost complete degradation is obtained over the SnO2/MWCNT nanocomposite with high rate constant, while the bared SnO2 and the mechanical mixture of SnO2 and MWCNT show inferior sonocatalytic performance. The results indicate that the SnO2/MWCNT nanocomposite can efficiently utilize the light emitted during bubble collapse, promote separation of electron-hole pairs as well as transfer of electrons from SnO2 to MWCNT, due to the synergistic effect of SnO2 and MWCNT, thus leading to much higher sonocatalytic activity. The current work paves a way for preparing highly efficient sonocatalysts with carbon nanotube as an excellent electron sink.

Optimisation of chemical oxygen demand removal from landfill leachate by sonocatalytic degradation in the presence of cupric oxide nanoparticles.

Leachate is the liquid formed when waste breaks down in the landfill and water filters through that waste. This liquid is very toxic and can pollute the land, ground water, and water resources. In most countries, it is mandatory for landfills to be protected against leachate. In addition to all other harms to the environment, disposal of raw landfill leachate can be a major source of hazard to closed water bodies. Hence, treatment of landfill leachate is considered an essential step prior to its discharge from source. This article describes the sonocatalytic degradation of chemical oxygen demand in landfill leachate using cupric oxide nanoparticles as sonocatalyst (cupric oxide/ultrasonic) and aims to establish this method as an effective alternative to currently used approaches. An ideal experimental design was carried out based on a central composite design with response surface methodology. The response surface methodology was used to evaluate the effect of process variables including pH values (3, 7, 11), cupric oxide nanoparticles dose (0.02, 0.035, 0.05 g), reaction time (10, 35, 60 minutes), ultrasonic frequency (35, 37, 130 KHz), and their interaction towards the attainment of their optimum conditions. The derived second-order model, including both significant linear and quadratic terms, seemed to be adequate in predicting responses (R2 = 0.9684 and prediction R2 = 0.9581). The optimum conditions for the maximum chemical oxygen demand sonocatalytic degradation of 85.82% were found to be pH 6.9, cupric oxide nanoparticles dosage of 0.05 gr L-1, and the ultrasonic frequency of 130 kHz at a contact time of 10 min.

Sonocatalytic removal of ibuprofen and sulfamethoxazole in the presence of different fly ash sources

We examined the feasibility of using two types of fly ash (an industrial waste from thermal power plants) as a low-cost catalyst to enhance the ultrasonic (US) degradation of ibuprofen (IBP) and sulfamethoxazole (SMX). Two fly ashes, Belews Creek fly ash (BFA), from a power station in North Carolina, and Wateree Station fly ash (WFA), from a power station in South Carolina, were used. The results showed that >99% removal of IBP and SMX was achieved within 30 and 60min of sonication, respectively, at 580kHz and pH 3.5. Furthermore, the removal of IBP and SMX achieved, in terms of frequency, was in the order 580kHz>1000kHz>28kHz, and in terms of pH, was in the order of pH 3.5>pH 7>pH 9.5. WFA showed significant enhancement in the removal of IBP and SMX, which reached >99% removal within 20 and 50min, respectively, at 580kHz and pH 3.5. This was presumably because WFA contains more silicon dioxide than BFA, which can enhance the formation of OH radicals during sonication. Additionally, WFA has finer particles than BFA, which can increase the adsorption capacity in removing IBP and SMX. The sonocatalytic degradation of IBP and SMX fitted pseudo first-order rate kinetics and the synergistic indices of all the reactions were determined to compare the efficiency of the fly ashes. Overall, the findings have showed that WFA combined with US has potential for treating organic pollutants, such as IBP and SMX, in water and wastewater.

Sonocatalytic Degradation of Methylene Blue with LaMnO3 Supported by Different Surface Area of Graphene

The present study compared the sonocatalytic degradation ability of LaMnO3 supported by different surface area of graphene on methylene blue (MB) as a model of the organic pollutant under ultrasonic irradiation. Both sonocatalysts were synthesized by using co-precipitation method and characterized by using X-Ray Diffraction (XRD), Fourier Transform Infrared, and Brunauer-Emmet-Teller (BET) surface area analysis. The orthorhombic structure of LaMnO3 was detected on the composites, while the existence of graphene was also confirmed. The present of graphene in the samples could improve the magnetic properties and surface area of composites as well as the sonocatalytic performance. LaMnO3 supported by different surface area of graphene (SA-1 and SA-2) showed the significant improvement of sonocatalytic activity compared to LaMnO3. LaMnO3/SA-2 composites with the largest surface area showed the highest degradation efficiency. To detect the possible reactive species involved in the degradation of MB, control experiments with introducing scavenger into the solution of MB were carried out. The results indicated that photo-generated hole played an important role in the degradation of MB.

Sonocatalytic degradation of an anthraquinone dye using TiO2-biochar nanocomposite

TiO2-biochar (TiO2-BC) nanocomposite was synthesized by sol-gel method. The characteristics of the prepared nanocomposite were examined using X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption analysis. The performance of synthesized TiO2-BC nanocomposite as efficient sonocatalyst was studied for the degradation of Reactive Blue 69 (RB69). Sonocatalytic degradation of RB69 in the presence of TiO2-BC nanocomposite could be explained by the mechanisms of hot spots and sonoluminescence. The optimized values for main operational parameters were determined as pH of 7, TiO2-BC dosage of 1.5g/L, RB69 initial concentration of 20mg/L and ultrasonic power of 300W. Furthermore, the effect of OH, h+ and O2− scavengers on the RB69 degradation efficiency was studied. Gas chromatography-mass spectroscopy analysis was used to identify intermediate compounds formed during the RB69 degradation. The results of repeated applications of TiO2-BC in the sonocatalytic process verified its stability in long-term usage.

Aqueous norfloxacin sonocatalytic degradation with multilayer flower-like ZnO in the presence of peroxydisulfate

Multilayer ZnO nanoflowers were synthesized through a simple precipitation method and characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and nitrogen absorption-desorption techniques. The FE-SEM images show the integrated morphology of an individual flower-like ZnO nanostructure, which is made of nano-platelets with uniform thickness (20–30nm). The average pore size and Brunauer-Emmet-Teller (BET) surface area of the as-synthesized ZnO were 27.25nm and 13.53m2/g. The sonocatalytic ability of the prepared samples was evaluated through norfloxacin (NF) degradation in an aqueous system using ultrasound (US) irradiation. To improve degradation efficiency, peroxydisulfate (Na2S2O8) was introduced to develop a US/ZnO/peroxydisulfate system, which exhibited an excellent synergistic effect. The effects of ZnO dosage, Na2S2O8 concentration, pH, and initial NF concentration were studied to determine the performances of the US/ZnO/peroxydisulfate process. Corresponding results showed that NF degradation rate increased with the increase of ZnO dosage but decreased with the increase of initial NF concentration. Under the optimal Na2S2O8 concentration of 0.1gL−1 at pH 9, the best degradation efficiency can be achieved. Moreover, based on the scavenging experiment results and literatures, NF degradation through US/ZnO/peroxydisulfate system is majorly induced by OH and SO4− radicals.

Preparation of a novel sonocatalyst, Au/NiGa2O4-Au-Bi2O3 nanocomposite, and application in sonocatalytic degradation of organic pollutants

A novel nanocomposite, Au/NiGa2O4-Au-Bi2O3, as an effective sonocatalyst was prepared through hydrothermal process and high-temperature calcination methods, and then characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The sonocatalytic activity of Au/NiGa2O4-Au-Bi2O3 nanocomposite was detected through the degradation of some organic pollutants under ultrasonic irradiation. Furthermore, the influences of mass ratio of NiGa2O4 and Bi2O3, ultrasonic irradiation time and used times on the sonocatalytic degradation efficiency were investigated by using Total Organic Carbon (TOC) and UV–vis spectroscopy. The experimental results showed that, because of the existence of Au nanoparticles (AuNPs) served as both conductive passageway and co-catalyst, the nanocomposite sonocatalyst (Au/NiGa2O4-Au-Bi2O3) displayed an excellent sonocatalytic activity in degradation of some organic pollutants under ultrasonic irradiation.

Contaminant salts as enhancers of sonocatalytic degradation of organic water pollutants: Effect of concentration, reaction time and adsorption on the efficiency of enhancement and the fate of concurrently formed H2O2

The effect of salts/anions on ZnO-mediated sonocatalytic degradation of phenol in water is investigated. Anions such as CH3COO−, SO42−, CO32−, HCO3−, NO3−, F−, Cl− and PO43− enhance the degradation. However, the effect is dependent on concentration of the anion and duration of reaction. The enhancing effect in sonocatalysis is different from and contradictory to the inhibiting effect of anions in photo- and sonophoto- catalysis. The enhancement is maximum in the presence of F−, SO42− and CH3COO− and the least in the presence of HCO3− and PO43− though minor exceptions are there depending on the experimental conditions. The basic mechanism of enhancement involves the formation of reactive radical anions by interaction of the anions with the highly reactive .OH radicals and their reaction with phenol. The lower reactivity of the radical anions compared to OH is compensated by the relatively higher concentration. Moreover, they interact exclusively with the substrate whereas the .OH participates in many reactions simultaneously including recombination and self- deactivation. Other effects of dissolved salts/anions such as increasing the ionic strength of the medium, modification in the partition coefficient, decreasing vapor pressure, increase in hydrophilicity etc. also favor sonocatalytic degradation of phenol. The concentration of concurrently formed H2O2 does not increase corresponding to the degradation of phenol and varies in a wave-like fashion (oscillation) due to the simultaneous formation and decomposition with either of them dominating periodically. The anions also influence the nature of the oscillation curve. Possible reasons for the anion effect and potential practical application are discussed.

Sonocatalytic rapid degradation of Congo red dye from aqueous solution using magnetic Fe0/polyaniline nanofibers

Nano-sized magnetic Fe0/polyaniline (Fe0/PANI) nanofibers were used as an effective material for sonocatalytic degradation of organic anionic Congo red (CR) dye. Fe0/PANI, was synthesized via reductive deposition of nano-Fe0 onto the PANI nanofibers at room temperature. Prepared catalyst was characterized using HR-TEM, FE-SEM, XRD, FTIR instruments. The efficacy of catalyst in removing CR was assessed colorimetrically using UV–visible spectroscopy under different experimental conditions such as % of Fe0 loading into the composite material, solution pH, initial concentration of dye, catalyst dosage, temperature and ultrasonic power. The optimum conditions for sonocatalytic degradation of CR were obtained at catalyst concentrations=500mg.L−1, concentration of CR=200ppm, solution pH=neutral (7.0), temperature=30°C, % of Fe0 loading=30% and 500W ultrasonic power. The experimental results showed that ultrasonic process could remove 98% of Congo red within 30min with higher Qmax value (Qmax=446.4 at 25°C). The rate of degradation of CR dye was much faster in this ultrasonic technique rather than conventional adsorption process. The degradation efficiency declined with the addition of common inorganic salts (NaCl, Na2CO3, Na2SO4 and Na3PO4). The rate of degradation suppressed more with increasing salt concentration. Kinetic and isotherm studies indicated that the degradation of CR provides pseudo-second order rate kinetic and Langmuir isotherm model compared to all other models tested. The excellent high degradation capacity of Fe0/PANI under ultrasonic irradiation can be explained on the basis of the formation of active hydroxyl radicals (OH) and subsequently a series of free radical reactions.

Hydrothermal-precipitation preparation of CdS@(Er3+:Y3Al5O12/ZrO2) coated composite and sonocatalytic degradation of caffeine

Here, we reported a novel method to dispose caffeine by means of ultrasound irradiation combinated with CdS@(Er3+:Y3Al5O12/ZrO2) coated composite as sonocatalyst. The CdS@(Er3+:Y3Al5O12/ZrO2) was synthesized via hydrothermal-precipitation method and then characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and UV–vis diffuse reflectance spectra (DRS). After that, the sonocatalytic degradation of caffeine in aqueous solution was conducted adopting CdS@(Er3+:Y3Al5O12/ZrO2) and CdS@ZrO2 coated composites as sonocatalysts. In addition, some influencing factors such as CdS and ZrO2 molar proportion, caffeine concentration, ultrasonic irradiation time, sonocatalyst dosage and addition of several inorganic oxidants on sonocatalytic degradation of caffeine were investigated by using UV–vis spectra and gas chromatograph. The experimental results showed that the presence of Er3+:Y3Al5O12 could effectively improve the sonocatalytic degradation activity of CdS@ZrO2. To a certain extent some inorganic oxidants can also enhance sonocatalytic degradation of caffeine in the presence of CdS@(Er3+:Y3Al5O12/ZrO2). The best sonocatalytic degradation ratio (94.00%) of caffeine could be obtained when the conditions of 5.00mg/L caffeine, 1.00g/L prepared CdS@(Er3+:Y3Al5O12/ZrO2), 10.00mmol/LK2S2O8, 180min ultrasonic irradiation (40kHz frequency and 50W output power), 100mL total volume and 25–28°C temperature were adopted. It seems that the method of sonocatalytic degradation caused by CdS@(Er3+:Y3Al5O12/ZrO2) displayspotentialadvantages in disposing caffeine.