Xikui Wang

Temperature-controlled ionic liquid dispersive liquid-phase microextraction for the sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC-ESI-MS/MS.

A novel dispersive liquid-phase microextraction method without dispersive solvents has been developed for the enrichment and sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC-ESI-MS/MS. This method used only green solvent 1-hexyl-3-methylimidazolium hexafluorophosphate as extraction solvent and overcame the demerits of the use of toxic solvents and the instability of the suspending drop in single drop liquid-phase microextraction. Important factors that may influence the enrichment efficiencies, such as volume of ionic liquid, pH of solutions, extraction time, centrifuging time and temperature, were systematically investigated and optimized. Under optimum conditions, linearity of the method was observed in the range of 0.1-20 microg/L for triclocarban and 0.5-100 microg/L for triclosan, respectively, with adequate correlation coefficients (R>0.9990). The proposed method has been found to have excellent detection sensitivity with LODs of 0.04 and 0.3 microg/L, and precisions of 4.7 and 6.0% (RSDs, n=5) for triclocarban and triclosan, respectively. This method has been successfully applied to analyze real water samples and satisfactory results were achieved.

Degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron

The degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron (US-Fe(0))was investigated and an evident synergistic effect was observed. The synergetic effect is mainly due to the increase of ()OH radical concentration from Fentons reaction. The ()OH radical concentrations in sole sonication and US-Fe(0) process were detected by using terephthalic acid as a fluorescent probe and found that ()OH radicals were generated continuously during sonication and the production of ()OH radicals in US-Fe(0) process was much higher than that in sole sonication. The degradation of direct sky blue 5B followed a pseudo-first-order kinetics and the degradation rate constants were found to be 0.0206 and 0.169 min(-1) with sole sonication and US-Fe(0) process respectively. It was also found that the degradation ratio of direct sky blue 5B increased with the increase of zero-valent iron dosage and decrease of pH value of the dye aqueous solution. The degradation mechanism of direct sky blue 5B with US-Fe(0) process was discussed by the changes of UV-Vis spectrogram of the dye during degradation. The dramatic changes of UV spectra showed a disappearance of both azo and aromatic groups during the degradation.

Photodegradation of the antimicrobial triclocarban in aqueous systems under ultraviolet radiation

This work aimed to investigate the effectiveness of ultraviolet (UV) radiation on the degradation of the antimicrobial triclocarban (TCC). We investigated the effects of several operational parameters, including solution pH, initial TCC concentration, photocatalyst TiO2 loading, presence of natural organic matter, and most common anions in surface waters (e.g., bicarbonate, nitrate, and sulfate). The results showed that UV radiation was very effective for TCC photodegradation and that the photolysis followed pseudo-first-order kinetics. The TCC photolysis rate was pH dependent and favored at high pH. A higher TCC photolysis rate was observed by direct photolysis than TiO2 photocatalysis. The presence of the inorganic ions bicarbonate, nitrate, and sulfate hindered TCC photolysis. Negative effects on TCC photolysis were also observed by the addition of humic acid due to competitive UV absorbance. The main degradation products of TCC were tentatively identified by gas chromatograph with mass spectrometer, and a possible degradation pathway of TCC was also proposed.

Rapid removal of caffeine in aqueous solutions by peroxymonosulfate oxidant activated with cobalt ion

The removal of caffeine (CAF) in aqueous solution by peroxymonosulfate oxidant activated with cobalt ion was investigated under a variety of operating conditions. The effects of various operating parameters, such as oxone and Co²⁺ concentrations, pH value, and the coexistence of dissolved organic matter and inorganic anions on the removal of CAF have been investigated. The removal efficiency increased with the increase in the concentrations of oxone and Co²⁺ ion added. The additions of chloride, bicarbonate, and sodium humate have negative effects on the removal of CAF. Near-neutral condition (5.0 < pH < 7.0) is favorable for the removal of CAF. Based on our experiments, 100% degradation of 50 mg/L CAF can be achieved within 4 minutes under the conditions of 1.00 mM oxone and 0.10 mM Co²⁺ ion at pH 5.0-7.0.

A TiO2 modified abiotic–biotic process for the degradation of the azo dye methyl orange

To investigate the feasibility of titanium dioxide (TiO2) employed as a modifier in the sodium alginate immobilization system, the degradation of methyl orange with the strain Delftia sp. A2(2011) (STT01) was carried out using a TiO2 modified sodium alginate system (TiO2/SA) and a non-TiO2 modified sodium alginate system (SA). It was found that the decolorization of methyl orange was enhanced from 76.5% to 100%, and the chemical oxygen demand (COD) removal was increased from 35.6% to 52.7%. The results further revealed that the TiO2 played a crucial role in the cell immobilization system, and the potential modification mechanisms of dye sensitization and TiO2–SA complex-mediated photocatalysis were investigated. Additionally, the intrinsic bright color of the bacterial strain STT01 could be ingeniously employed as an indicator for the degradation efficiency. This work not only presents a promising opportunity for developing novel cell immobilization techniques but also affords a direct and visually observed treatment for azo dye wastewater.

Determination of trace triclosan in environmental water by microporous bamboo-activated charcoal solid-phase extraction combined with HPLC-ESI-MS.

A sensitive and efficient analytical method for triclosan (TCS) determination in water, which involves enrichment with bamboo-activated charcoal and detection with HPLC-ESI-MS, was developed. The influence of several operational parameters, including the eluant and its volume, the flow rate, the volume andacidity of the sample, and the amount of bamboo-activated charcoal, were investigated and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.02-20 μg/L, with correlation coefficients (r(2) ) >0.9990. The limit of detection was 0.002 μg/L based on the ratio of chromatographic signal to baseline noise (S/N = 3). The spiked recoveries of TCS in real water samples were achieved in the range of 97.6-112.5%. The proposed method was applied to analyze TCS in real aqueous samples. All the surface water samples collected in Xiaoqing River had detectable levels of TCS with concentrations of 42-197 ng/L.

Influence of pH, inorganic anions, and dissolved organic matter on the photolysis of antimicrobial triclocarban in aqueous systems under simulated sunlight irradiation

The photolysis of the antimicrobial triclocarban (TCC) in aqueous systems under simulated sunlight irradiation was studied. The effects of several abiotic parameters, including solution pH, initial TCC concentration, presence of natural organic matter, and most common inorganic anions in surface waters, were investigated. The results show that the photolysis of TCC followed pseudo-first-order kinetics. The TCC photolysis rate constant increased with increasing solution pH and decreasing the initial TCC concentration. Compared with the TCC photolysis in pure water, the presence of aqueous bicarbonate, nitrate, humic acids, and its sodium salt decreased the TCC photolysis rate, but fulvic acid increased the TCC photolysis rate. The electron spin resonance and reactive oxygen species scavenging experiments indicated that TCC may undergo two different types of phototransformation reactions: direct photolysis and energy transfer to generate 1O2. The main degradation products were tentatively identified by gas chromatography interfaced with mass spectrometry (GC-MS), and a possible degradation pathway was also proposed.

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.

Preparation and characterization of polymer-coated Fe3O4 magnetic flocculant

ABSTRACT The ordinary flocculants rely on gravity settling for solid-liquid separation, it is difficult to meet the requirements of wastewater treatment in short flocculation settling time, few sludge production and low moisture content. A new type of flocculant is required to solve these difficulties. Magnetic materials are given more attention because of the magnetism in magnetic field. It is significant to prepare magnetic composite flocculant to realize solid-liquid separation with the combined effects of both gravity and external magnetic field. The gelatin-based magnetic flocculant consisted of poly (acrylamide-co-acryloyloxyethyl thimethylammonium chloride) grafted gelatin-coated Fe3O4 [magnetic poly (AM-co-DAC)-g-gelatin] was prepared in this article. A Box-Behnken design for determination of optimal plan with three-level and three-variable was designed. The best conditions of preparing magnetic poly (AM-co-DAC)-g-gelatin were determined. The structure of magnetic poly (AM-co-DAC)-g-gelatin was studied by infrared spectrum and its magnetic properties were characterized by magnetic hysteresis loop. The flocculation of magnetic poly (AM-co-DAC)-g-gelatin was compared with conventional flocculant. The flocculation experiment results showed that the magnetic poly (AM-co-DAC)-g-gelatin was effective for removal of turbidity and significantly reduced the settling time of flocs, compared to conventional flocculants.

Investigations on the Synthesis and Properties of Fe2O3/Bi2O2CO3 in the Photocatalytic and Fenton-like Process

Catalyst of Bi2O2CO3 and Fe2O3 modified Bi2O2CO3 (Fe2O3/Bi2O2CO3) were prepared by hydrothermal method and characterized by X-ray diffractions (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and UV-vis DRS. The catalytic activity of Bi2O2CO3 and Fe2O3/Bi2O2CO3 were comparatively investigated in the photodegradation and Fento-like process. Rhodamine B(RhB) was selected as the target pollutant under the irradiation of 300 W xenon lamp. The results indicated that Fe2O3 plays a great role in the enhancing the treatment efficiency and the and the maximum reaction rate was achieved at the Fe2O3 loading of 1.5%. The Fenton-like degradation rate constant of RhB with bare Bi2O2CO3 in dark is 0.4 min-1, while that with 1.5 Fe2O3/Bi2O2CO3 increases to 28.4 min-1 under visible light irradiation, a 71-fold improvement. It is expected to shed a new light for the constructing novel composite photocatalyst and also provide a potential method for the removal of dyes in the aqueous system.