Shan Chong

Sonocatalytic degradation of diclofenac with FeCeOx particles in water

This paper studies the sonocatalytic degradation of diclofenac in water using FeCeOx-catalyzed ultrasound. The effects of pre-adsorption and gas addition were investigated. Nitrogen adsorption/desorption, SEM, XRD, Raman and XPS analyses of FeCeOx before and after sonication were characterized. The proposed mechanism was based on the microstructure changes of FeCeOx and reactive-species-scavenging performances. The results show that FeCeOx has excellent performance in catalyzing an ultrasonic system in water, and 80% of diclofenac was removed in 30min ([Diclofenac]=20mg/L, FeCeOx amount=0.5g/L, pH=6, ultrasonic density=3.0W/cm3, ultrasonic frequency=20kHz, temperature=298K). The Fe, Ce, and O elements remained highly dispersed in the structure of FeCeOx, and the solid solution structure of FeCeOx remained stable after the reaction. Ce (III) was gradually oxidized to Ce (IV) and Fe (III) was gradually reduced to Fe (II) after the reaction, which indicates that Fe and Ce ions with different valences coexisted in dynamic equilibrium. The amount of oxygen vacancies in FeCeOx significantly decreased after the reaction, which indicates that oxygen vacancy participated in the ultrasonic process. Singlet oxygen 1O2 was the primary reactive species in the degradation process, and the hydroxyl radicals OH and superoxide radical anion O2- also participated in the reaction. FeCeOx had excellent chemical stability with negligible leaching ions in the ultrasonic process.

Diclofenac degradation in water by FeCeOx catalyzed H2O2: Influencing factors, mechanism and pathways

The degradation of diclofenac in a like Fenton system, FeCeOx-H2O2, was studied in details. The influencing factors, reaction kinetics, reaction mechanism and degradation pathways of diclofenac were investigated. The optimum conditions were at a solution pH of 5.0, H2O2 concentration of 3.0mmol/L, diclofenac initial concentration of 0.07mmol/L, FeCeOx dosage of 0.5g/L, and 84% degradation of diclofenac was achieved within 40min. The kinetics of FeCeOx catalyzed H2O2 process involved adsorption-dominating and degradation-dominating stages and fitted pseudo-second order model and pseudo-first order model, respectively. Singlet oxygen 1O2 was the primary intermediate oxidative species in the degradation process; superoxide radical anion O2- also participated in the reaction. The surface cerium and iron sites and the oxygen vacancies in the FeCeOx catalyst were proposed to play an important role in H2O2 decomposition and active species generation. The detected intermediates were identified as hydroxylated derivatives (m/z of 310, 326 and 298), quinone imine compounds (m/z of 308, 278 and 264) and hydroxyl phenylamine (m/z of 178). The majority intermediates were hydroxylated derivatives and the minority was hydroxyl phenylamine. The degradation pathways were proposed to involve hydroxylation, decarboxylation, dehydrogenation and CN bond cleavage.

Rapid degradation of dyes in water by magnetic Fe(0)/Fe3O4/graphene composites.

Magnetic Fe(0)/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption-desorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating-sample magnetometer (VSM) measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that Fe(0)/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe(0)/Fe3O4/graphene and pollutants. Fe(0)/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe(0)/Fe3O4/graphene rapidly. After 20min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe(0)/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe(0)/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water.

Preparation of FeCeOx by ultrasonic impregnation method for heterogeneous Fenton degradation of diclofenac.

FeCeOx has been successfully synthesized by ultrasonic impregnation method and applied in diclofenac removal in heterogeneous Fenton process. The effects of ultrasonic density, impregnation time, mole ratio of Fe and Ce and calcination temperature were investigated. Nitrogen adsorption/desorption, SEM, XRD, HRTEM, Raman and XPS analyses were characterized. Stability and reusability of FeCeOx were evaluated. The results indicated that 83% degradation efficiency of diclofenac was achieved by FeCeOx under the optimum preparation conditions. Fe ions were distributed uniformly in crystal structure and the solid solution structure of FeCeOx with a lattice constriction was formed. Exposed crystalline plane (200) with a relatively high surface energy may be the main reason to provide high catalytic activity of FeCeOx. Oxygen vacancies took part in catalytic process and a portion of them were oxidized after reaction. FeCeOx showed an excellent chemical stability and reusability in heterogeneous Fenton process.

MnO2/CeO2 for catalytic ultrasonic decolorization of methyl orange: Process parameters and mechanisms.

MnO2/CeO2 catalyst was prepared and characterized by means of Brunauer-Emmet-Teller (BET) method, X-ray diffraction (XRD) and scanning electron microscope (SEM). The characterization showed that MnO2/CeO2 had big specific surface area and MnO2 was dispersed homogeneously on the surface of CeO2. Excellent degradation efficiency of methyl orange was achieved by MnO2/CeO2 catalytic ultrasonic process. Operating parameters were studied and optimized. The optimal conditions were 10 min of ultrasonic irradiation, 1.0 g/L of catalyst dose, 2.6 of pH value and 1.3 W/ml of ultrasonic density. Under the optimal conditions, nearly 90% of methyl orange was removed. The mechanism of methyl orange degradation was further studied. The decolorization mechanism in the ultrasound-MnO2/CeO2 system was quite different with that in the ultrasound-MnO2 system. Effects of manganese and cerium in catalytic ultrasonic process were clarified. Manganese ions in solution contributed to generating hydroxyl free radical. MnO2/CeO2 catalyst strengthened the oxidation ability of ultrasound and realized complete decolorization of methyl orange.

NiFe(C2O4)x as a heterogeneous Fenton catalyst for removal of methyl orange

This paper studies a heterogeneous Fenton catalyst NiFe(C2O4)x, which showed better catalytic activity than Ni(C2O4)x and better re-usability than Fe(C2O4)x. The methyl orange removal efficiency was 98% in heterogeneous Fenton system using NiFe(C2O4)x. The prepared NiFe(C2O4)x had a laminated shape and the size was in the range of 2-4xa0μm, and Ni was doped into catalysts structure successfully. The NiFe(C2O4)x had a synergistic effect of catalyst of 24.7 for methyl orange removal, and the dope of Ni significantly reduced the leaching of Fe by 77%. The reaction factors and kinetics were investigated. Under the optimal conditions, 0.4xa0g/L of catalyst dose and 10xa0mmol/L of hydrogen peroxide concentration, 98% of methyl orange was removed within 20xa0min. Analysis showed that hydroxyl radicals and superoxide radicals participated in the reaction. With NiFe(C2O4)x catalyst, the suitable pH range for heterogeneous Fenton system was wide from 3 to 10. The catalyst showed good efficiency after five times re-use. NiFe(C2O4)x provided great potential in treatment of refractory wastewater with excellent property.

Effects and mechanism of diclofenac degradation in aqueous solution by US/Zn0

A system of ultrasound radiation coupled with Zn0 was applied to degrade diclofenac. The effects of initial pH, dosage of Zn0 and ultrasound density were investigated. To further explore the mechanism of the microcosmic reaction, the fresh and used Zn0 powders were characterized by SEM, XRD and XPS. Radical scavengers were used to determine the oxidation performance of strong oxidizing free radicals on diclofenac, including hydroxyl radicals and superoxide radicals. The results showed that the optimum removal of diclofenac reached to over 85% at pH of 2.0 in 15min, with Zn0 dosage of 0.1g/L and ultrasound density of 0.6W/cm3. TOC removal of 72.6% in 15min and dechlorination efficiency of diclofenac reached 70% in 30min. Characterization results showed that a ZnO membrane was generated on the surface of Zn particles after use. According to the mass spectrometry results, several possible pathways of diclofenac degradation were proposed, and most diclofenac was turned into micro-molecules or CO2 finally. The synergistic effect of US/Zn0 in the reactions led to a proposed degradation mechanism in which zinc could directly attack the target contaminant diclofenac because of its good reducibility with the auxiliary functions of ultrasonic irradiation, mechanical shearing and free radical oxidation.

Enhanced degradation of nitrobenzene by combined ultrasonic irradiation and a zero-valent zinc catalyst

AbstractEnhanced ultrasonic catalytic activity in nitrobenzene degradation was found by combining ultrasonic irradiation and a zero-valent zinc (Zn0) catalyst. In this system, the influence of the reaction parameters, reaction kinetics, intermediates, and mechanism was investigated. Under the optimum conditions (initial nitrobenzene concentration of 0.01xa0mmol/L, Zn0 dosage of 0.4xa0g/L, initial pH 7, ultrasonic intensity 4.0xa0W/cm2), approximately 91.2% of nitrobenzene could be removed within 30xa0min. The degradation process followed the pseudo-first-order kinetics model, and the reaction rate constant was 0.0670xa0min−1. The mechanism of the synergetic effect of ultrasound and Zn0 was proposed. Three intermediates of nitrophenol, phenylhydroxylamine, and aniline were identified by liquid chromatography–mass spectrometry (LC-MS). The degradation pathways of hydroxyl radical oxidation and Zn0 reduction were deduced. This combined system is promising for the removal of nitrobenzene pollutants from water.

Ultrasonic impregnation of MnO2/CeO2 and its application in catalytic sono-degradation of methyl orange

MnO2/CeO2 catalyst was prepared by ultrasonic impregnation method. The traditional and stirring impregnation methods were used as control. Results showed that ultrasonic impregnation was the best synthesis method. The impregnation time was shortened from 120xa0min (traditional method) to 20xa0min, the specific surface area of catalyst was three times larger, and the catalytic activity of catalyst was also the highest. Furthermore, MnO2 had crystalline structure and distributed uniformly on the support, CeO2. The preparing conditions were further examined and the optimal conditions were found to be: 20xa0min of ultrasonic impregnation, 4.3xa0mol/L of manganese nitrate concentration and 450xa0°C of calcination temperature. The so prepared catalyst removed 94% of methyl orange in 30xa0min with a dosage of 0.5xa0g/L. The efficiency was 77.7% and 85.9% for traditional and stirring impregnation method under the same experimental conditions. The reaction process involved two stages: adsorption-dominated and degradation-dominated stages. The reaction rate constant of adsorption-dominated stage had little difference. However, compared with traditional impregnation, the reaction rate constant of degradation-dominated stage improved from 0.01 to 0.14 min-1 by ultrasonic impregnation. Mechanism analysis showed that the activity of ultrasonic impregnation MnO2/CeO2 was improved by the effects of acoustic cavitation and ultrasound oscillation on solid-liquid transport and distribution status.

Preparation of a magnetic N-Fe/AC catalyst for aqueous pharmaceutical treatment in heterogeneous sonication system

High efficiency and facile separation are desirable for catalysts used in water treatment. In this study, a magnetic catalyst (nitrogen doped iron/activated carbon) was prepared and used for pharmaceutical wastewater treatment. The catalyst was characterized using BET, SEM, XRD, VSM and XPS. Results showed that iron and nitrogen were successfully loaded and doped, magnetic Fe2N was formed, large amount of active surface oxygen and Fe(II) were detected, and the catalyst could be easily separated from water. Diclofenac was then degraded using the catalyst in ultrasound system. The catalyst showed high catalytic activity with 95% diclofenac removal. Analysis showed that ·OH attack of diclofenac was a main pathway, and then ·OH generation mechanism was clarified. The effects of catalyst dosage, sonication time, ultrasonic density, initial pH, and inorganic anions on diclofenac degradation were studied. Sulfate anion enhanced the degradation of diclofenac. Mechanism in the catalytic ultrasonic process was analyzed and reactions were clarified. Large quantity of oxidants was generated on the catalyst surface, including ·OH, O2-, O- and HO2·, which degraded diclofenac efficiently. In the solution and interior of cavitation bubbles, ·OH and hot spot effects contributed to the degradation of diclofenac. Reuse of the catalyst was further investigated to enhance its economy, and the catalyst maintained activity after seven uses.