Weilin Guo

Heterogeneous activation of Oxone by CoxFe3−xO4 nanocatalysts for degradation of rhodamine B

The removal of Rhodamine B (RhB) by Co(x)Fe(3-x)O(4) magnetic nanoparticles activated Oxone has been performed in this study. A series of Co(x)Fe(3-x)O(4) nanoparticles was synthesized using a hydrothermal method. The synthetic Co(x)Fe(3-x)O(4) nanoparticles were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that they were spinel structures and Co was introduced into their structures. The performances of Co(x)Fe(3-x)O(4) nanocatalysts on the activation of Oxone for removal of RhB were investigated and we found that the higher cobalt content in the catalyst, the better removal performance was resulted. A series experiments of reaction conditions were also performed, which confirmed that weak acidic, higher temperature, higher dosages of Co(x)Fe(3-x)O(4) nanocatalyst and Oxone and lower concentration of RhB were favored for the degradation of RhB. The pseudo-first order kinetics was observed to fit the Co(x)Fe(3-x)O(4)/Oxone process. Furthermore, the reaction mechanism was discussed and the scavenging effect was examined by using phenol and tert-butyl alcohol which indicated that sulfate radicals were the dominating reactive species responsible for the degradation process. Finally, the stability of Co(x)Fe(3-x)O(4) nanocatalyst was studied.

Degradation of amoxicillin in aqueous solution using sulphate radicals under ultrasound irradiation.

Degradation of the antibiotics amoxicillin in aqueous solution using sulphate radicals under ultrasound irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with only oxone (2KHSO(5) · KHSO(4) · K(2)SO(4)), cobalt activated oxone (oxone/Co(2+)), oxone+ultrasonication (oxone/US) and cobalt activated oxone+ultrasonication (oxone/Co(2+)/US). The chemical oxygen demand (COD) removal efficiency were in the order of oxone<oxone/Co(2+) < oxone/US < oxone/Co(2+)/US for the amoxicillin solution. The variables considered for the effect of degradation were the temperature, the power of ultrasound, the concentration of oxone, as well as catalyst and the initial amoxicillin concentration. More than 98% of COD removal was achieved within 60 min under optimum operational conditions. Comparative analysis revealed that the sulfate radicals had the high oxidation potential and the use of ultrasound irradiation reduced the energy barrier of the reaction and increased the COD removal efficiency of organic pollutants. The degradation of amoxicillin follows the first-order kinetics.

Degradation of rhodamine B in aqueous solution by using swirling jet-induced cavitation combined with H2O2.

The degradation of rhodamine B in aqueous solution by using swirling jet-induced cavitation combined with H(2)O(2) was investigated. It was found that there is an obvious synergetic effect between hydrodynamic cavitation and H(2)O(2) for the degradation of rhodamine B. The effects of various operating parameters such as H(2)O(2) dosage, medium pH, solution temperature, fluid pressure and the dye initial concentration on the degradation of rhodamine B have been studied. It was found that the removal of rhodamine B in aqueous solution was increased with increasing the addition of H(2)O(2) and the fluid pressure, and the removal of rhodamine B was decreased with increasing the medium pH and dye initial concentration. It was also found that the degradation of rhodamine B is dependent on the solution temperature. The removal of rhodamine B increased with increase of temperature from 30 to 50 degrees C, but less degradation ratio is observed at 60 degrees C. The degradation kinetics of rhodamine B in aqueous solution using swirling jet-induced cavitation combined with H(2)O(2) under various operational conditions was also investigated. It was found that the degradation of rhodamine B follows a pseudo-first-order kinetics.

Sonochemical synthesis of silver nanorods by reduction of sliver nitrate in aqueous solution

The sonochemical synthesis of silver nanorods has been achieved by ultrasonic irradiation of the aqueous solution of silver nitrate, methenamine (HMTA) and poly (vinyl pyrrolidone) (PVP) for 60 min. The silver nanorods obtained have lengths of 4-7 microm and mean diameters of about 100 nm. The structures of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and X-ray powder diffraction (XRD), and the chemical composition of the sample was examined by energy-dispersive X-ray spectrum (EDS). The effects of the irradiation time, the concentration of PVP and the reaction temperature on the morphology of silver nanorods were discussed, and the mechanism of the silver nanorods formation was tentatively inferred.

Intensification of sonochemical degradation of antibiotics levofloxacin using carbon tetrachloride

Sonochemical degradation of levofloxacin was investigated to assess the operational parameters and the impacts of rate enhancers (CCl(4)) and rate inhibitors (t-butanol). Different dosages of CCl(4), pH value of solutions, ultrasonic power, and initial concentration of levofloxacin which affected the degradation of levofloxacin were studied. The degradation rate of levofloxacin was accelerated with increased concentrations of CCl(4) via the accumulation of reactive chlorine species and the hindrance of ()OH radical combination reactions with atomic hydrogen. The addition of t-butanol at all test concentrations inhibited the degradation of levofloxacin regardless of the quantity of ()OH radicals in solution. It was also found that 5-day biochemical oxygen demand (BOD(5)) of the solution increased evidently after sonochemical treatment, and the ratio of BOD(5)/COD that was a good measure for biodegradability increased from 0 to 0.41, which indicated that biodegradability of the solution was obviously enhanced. Based on the results, it is feasible that sonochemical oxidation can be used for pretreatment of levofloxacin effluent before biological treatment processes.

Synthesis of dendritic silver nanostructures by means of ultrasonic irradiation.

In this paper, a simple and effective route for the synthesis of silver dendritic nanostructures by means of ultrasonic irradiation has been developed. Well-defined silver dendritic nanostructures were obtained by sonicating the aqueous solution of 0.04mol/L silver nitrate with 4.0mol/L isopropanol as reducing agent and 0.01mol/L PEG400 as disperser for 2h. The effects of the irradiation time, the concentration of Ag(+) and the molar ratio of PEG to AgNO(3) on the morphology of silver nanostructures were discussed. The structures of the obtained samples were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray powder diffraction (XRD), and the chemical composition of the dendrites was examined by energy-dispersive X-ray spectrum (EDS).

The kinetics and mechanism of ultrasonic degradation of p-nitrophenol in aqueous solution with CCl4 enhancement.

The ultrasonic degradation of p-nitrophenol (p-NP) in aqueous solution with CCl4 enhancement was studied. The effects of operating parameters such as CCl4 dosage, ultrasonic power, media temperature, the initial concentration of p-NP and initial pH value of the aqueous solution on the degradation of p-NP were investigated, and the enhancement mechanism of CCl4 for p-NP sonolysis was also discussed. The results showed that the sonochemical degradation of p-NP was obviously enhanced by adding CCl4. It attributed to the increase ·OH radicals concentration in the presence of CCl4 as a hydrogen atom scavenger, and the formation of some oxidizing agents such as free chlorine and chlorine-containing radicals. The degradation of p-NP follows a pseudo-first-order kinetics. The degradation rate of p-NP increased with decreasing the temperature, the initial pH value of the solution and decreasing the initial concentration of p-NP. It was also found that p-NP can be mineralized in this process.

Sonochemical decomposition of levofloxacin in aqueous solution.

The decomposition of levofloxacin was performed in an aqueous solution under ultrasound irradiation. The effect of operating conditions, including pH value, reaction time, initial concentration, and ultrasound power on the chemical oxygen demand (COD) removal rate was examined at room temperature (23 +/- 2 degrees C). Under a given condition (initial levofloxacin concentration = 20 mg/L, ultrasonic power = 400 W, and pH = 5.86), a 56.6% COD removal rate was obtained after 120 minutes of reaction time. It also was found that 5-day biochemical oxygen demand (BOD5) of the solution increased evidently after sonochemical treatment, and the ratio of BOD5/COD, which was a good measure for biodegradability, increased from 0 to 0.40, indicating that the biodegradability of the solution was enhanced. Based on the results, it is feasible that sonochemical oxidation can be used for the pretreatment of levofloxacin effluent before biological treatment processes.

Determination of triclocarban in aquatic plants by using SPE combined with HPLC-ESI-MS/MS

A specific, sensitive, and reliable analytical method involving homogenate extraction, solid phase extraction (SPE), and detection by high-performance liquid phase chromatography-electrospray ionization tandem mass spectrometry was developed in this study for the determination of triclocarban (TCC) in aquatic plants. Key factors that could affect the extraction and clean-up performance, including the extraction solvent and its volume, the homogenate extraction time, the SPE cartridge used, and the eluents and their volume, were examined and optimised. Under optimum conditions, the linearity of the method ranged from 0.2 ng g−1 to 200 ng g−1, with correlation coefficients (r2) >0.999. The limit of detection was 0.05 ng g−1, based on the ratio of the chromatographic signal to baseline noise (S/N = 3). Spiked recoveries of TCC in real aquatic plant samples ranged from 91.8% to 106.1%. The matrix effect value was 101.90%, with a relative standard deviation of 5.1%. The proposed method was successfully applied to analyse TCC in aquatic plant samples collected from a natural water environment.