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Liu Q.,Guangxi University | Yu Z.-B.,Guangxi University | Yu Z.-B.,Guangxi Hualan Design and Consulting Group Co. | Zhang R.-H.,Guangxi University | And 6 more authors.
Huanjing Kexue/Environmental Science | Year: 2015

Perfluorooctanoic acid (PFOA) is a new persistent organic pollutant which has got global concern for its wide distribution, high bioaccumulation and strong biological toxicity. In present study, the photocatalytic degradation of PFOA using palladium doped TiO2(Pd-TiO2) prepared by chemical reduction method was investigated. The photocatalysts were characterized by XRD, FESEM and UV-vis DRS and were used for PFOA degradation under 365 nm UV irradiation. The results indicated that the grain size of TiO2 was smaller while the specific surface area increased and the absorption of ultraviolet light also enhanced after using chemical reduction method, but all these changes had no influence on PFOA degradation. However, the degradation was significantly enhanced because of the deposition of Pd, the fluoride concentration of PFOA was 6.62 mg·L-1 after 7 h irradiation which was 7.3 times higher than that of TiO2(P25). Experiments with the addition of trapping agent and nitrogen indicated that ·OH played an important role in PFOA degradation while the presence of O2 accelerated the degradation. The main intermediate products of photocatalytic degradation of PFOA were authenticated by an ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry systems (UPLC-QTOF-MS). The probable photocatalytic degradation mechanism involves h+ attacking the carboxyl of PFOA and resulting in decarboxylation. The produced ·CnF2n+1 was oxidized by ·OH underwent defluorinetion to form shorter-chain perfluorinated carboxylic acids. The significant enhancement of PFOA degradation can be ascribed to the palladium deposits, acting as electron traps on the Pd-TiO2 surface, which facilitated the transfer of photogenerated electrons and retarded the accumulation of electrons. ©, 2015, Science Press. All right reserved. Source


Chen Y.,Guangxi University | Yu Z.,Guangxi University | Yu Z.,Guangxi Hualan Design and Consulting Group Co. | Wang Y.,Guangxi University | And 6 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2015

The application of titanium dioxide-loaded granular activated carbon (TiO2-GAC) in a dielectric barrier discharge (DBD) reactor for degradation of methyl orange (MO) was investigated. Several factors, such as peak voltage, pH, solution conductivity, MO concentration and TiO2-GAC content, and the effect of TiO2-GAC in the combined treatment of DBD and TiO2-GAC were considered to explore the applicability, and a reaction kinetics model was established. Experimental results indicated that a synergistic effect appeared in the combined treatment, where degradation efficiency and chemical oxygen demand (COD) removal rate were 96.2% and 90% after a 25 minutes reaction. Compared to DBD, the degradation efficiency and COD removal rate increased 53.7% and 50.4% in DBD combined with TiO2-GAC. The empirical kinetic equation of MO degradation fit well with the experimental data, with an overall reaction order of 2.352. The experimental data showed that with the addition of TiO2-GAC, concentration of H2O2 increased while O3 decreased in DBD reactor, which suggested that TiO2-GAC catalyst induced a well catalytic effect in the combined treatment. The regeneration efficiency of TiO2-GAC was about 80% after five times DBD regeneration cycles, which confirmed the reuse feasibility of the regenerated GAC. ©, 2015, Science Press. All right reserved. Source


Chen Y.,Guangxi University | Yu Z.,Guangxi University | Yu Z.,Guangxi Hualan Design and Consulting Group Co. | Sun L.,Guangxi University | And 3 more authors.
Chinese Journal of Environmental Engineering | Year: 2013

According to landfill leachate's characteristics of high concentration of pollutants, poor biochemical degradability, etc, semi-aerobic aged refuse bioreactor and ultrasound/Fenton process were applied to treat landfill leachate. The removal rates of chemical oxygen demand(COD), ammonia nitrogen(NH3-N), total phosphorus(TP) and colorimetry treated by semi-aerobic aged refuse bioreactor were 80%, 85%, 92%, 85%, respectively. The optimal technical conditions of ultrasound/Fenton process were discovered by single factor and orthogonal experiments. Satisfying treatment effect of the total removal rate of landfill leachate by combined semi-aerobic aged refuse bioreactor and ultrasound/Fenton process could be achieved. The highest removal rates of COD, NH3-N, TP and colorimetry were 96%, 86%, 94% and 95%, respectively. The final effluent was inodorous with color of pale yellow. Its BOD5/CODi increased from 0.16 to 0.35, which met follow-up biological treatment. The effluent of COD, TP could meet the Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB 16889-2008). Source


Peng Z.,Guangxi University | Yu Z.,Guangxi University | Yu Z.,Guangxi Hualan Design and Consulting Group Co. | Sun L.,Guangxi University | And 4 more authors.
Chinese Journal of Environmental Engineering | Year: 2014

In this study, the treatment of rhodamine B simulated wastewater using photoelectro-Fenton system under visible light was investigated. The effects of the electrolyte, anodizing time, annealing temperature and annealing time on preparation of the anode material-TiO2 thin film electrode were explored. Then, the photoelectric effect and synergy of the application of such anodes materials in photoelectro-Fenton system under visible light in degradation of rhodamine B were analyzed. Based on the parameters ranges of the single factor experiments, preparation conditions were obtained using the response surface optimization methodology to anode material: electrolyte of 0.5%NH4F glycerol solution, anodic oxidation time of 93.26 min, annealing temperature of 602.89℃ and annealing time of 127.49 min. The simulated removal rate to rhodamine B under the conditions of application of the anode material of the photoelectro-Fenton system was 70.78%, and synergistic factor showed in photocatalysis and electro-Fenton in this condition was 1.92, which means that the photoelectric synergistic effect is remarkable. The sequence of key factors of preparation TiO2 thin film electrode influencing the photoelectron-Fenton removal efficiency are anodic oxidation time, annealing time, annealing temperature, respectively. Three experimental surface model validation errors were less than 5%, which indicats that the model is valid. Source


Xiang G.,Guangxi University | Yu Z.,Guangxi University | Yu Z.,Guangxi Hualan Design and Consulting Group Co. | Chen Y.,Guangxi University | Yang O.,Guangxi University
Chinese Journal of Environmental Engineering | Year: 2014

Sugarcane bagasse was added into sludge to prepare compositional activated carbons(CACs), and Plackett-Burman combining with response suraface methodology was employed to sieve and optimize the conditions affecting the iodine adsorption value of CACs. The Plackett-Burman results show that pyrolysis temperature, pyrolysis time and dried weight ratio of sugarcane bagasse to sludge are the main influencing factors. Using these three factors as variables, a second order model of the iodine adsorption value of CACs was obtained by Box-Behnken design and response surface methodology analysis. The model shows that the interactions of pyrolysis temperature and pyrolysis time, pyrolysis temperature and dried weight ratio are significant, and determines that the optimal pyrolysis temperature is 550℃, pyrolysis time is 30 min and dried weight ratio is 50%. The iodine adsorption value of CAC prepared under this condition is 814 mg/g, being higher than other CACs'. The effects of sugarcane bagasse addition on the physicochemical properties of CACs were investigated by analyzing surface area, pore structure, iodine adsorption value and carbon content, which indicate that the addition of sugarcane bagasse increases the surface area, micro-pore volume, iodine adsorption value and carbon content. The results indicate that addition of sugarcane bagasse and optimization of preparation conditions are effective methods to improve the adsorption properties of sludge based activated carbon. ©, 2014, Science Press. All right reserved. Source

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