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Perfluorooctanoic acid (PFOA) is widespread in the environment, which causes serious health and safety concerns. A mechanistic study on reductive defluorination of PFOA by titanium(III) citrate in the presence of catalysts was conducted. Vitamin B 12 was used to catalyze reduction reactions by shuttling electrons from a reducing agent (electron donor) to PFOA to produce a Co-carbon bond intermediates. In the presence of copper nanoparticles, a precursor complex, B 12 -C 7 F 14 COOH, adsorbed on the metal surface, followed by a hydrogenolytic reaction to form less-fluorinated products. The synergistic effect between vitamin B 12 and copper nanoparticles enhances the reductive activities by electron-transfer reactions and hydrogenolysis. The efficient reduction of PFOA to less-noxious compounds was demonstrated with a copper dose of 2 g L −1 , titanium(III) citrate (45 mM), and vitamin B 12 (0.2 mM) with an initial pH of 9.0 and 70 °C. In this anoxic aqueous solution, the biomimetic reductive system effectively removed 65% of PFOA. The mass balance on fluoride matched the observed degradation of PFOA, while no short-chain intermediates were detected. [ABSTRACT FROM AUTHOR]

Abstract: The removal of dimethyl phthalate (DMP), which is a pollutant of concern in water environments, was carried out by catalytic ozonation with TiO2/Al2O3 catalysts. The heterogeneous catalytic ozonation was an ozonation process combined with the catalytic and adsorptive properties of the TiO2/Al2O3 catalysts to significantly accelerate the mineralization efficiency. Semi-batch ozonation was performed under various experimental conditions including the fed ozone concentration, catalyst type, catalyst dosage, and ultraviolet radiation on the degradation of DMP. The complete removal of DMP was efficiently achieved by both sole and catalytic ozonation; meanwhile, the presence of the catalysts slightly accelerated the elimination rate of DMP. On the other hand, the mineralization efficiency, in terms of total organic carbon (TOC) removal, was substantially enhanced by employing the TiO2/Al2O3 catalyst. The mineralization efficiency using the TiO2/Al2O3 catalyst was the highest, followed in decreasing order by the Al2O3 catalyst, the TiO2 catalyst, and sole ozonation. In addition, the use of the TiO2/Al2O3 catalyst would increase the utilization efficiency of the fed ozone, especially in the late ozonation period. Furthermore, the decrease in the catalytic activity of the TiO2/Al2O3 catalyst after multi-run experiments can be mostly recovered by an incineration process at a high temperature. [Copyright &y& Elsevier]

Abstract: This study investigates the photocatalytic degradation of dimethyl phthalate (DMP) with both the titanium dioxide-coated magnetic poly(methyl methacrylate) (TiO2/mPMMA) and platinum-doped TiO2/mPMMA (Pt–TiO2/mPMMA) microspheres. The TiO2/mPMMA and Pt–TiO2/mPMMA microspheres are employed as novel photocatalysts that offer high photocatalytic activity, magnetic separability and good durability. The photocatalytic experiments of DMP under various conditions are conducted to examine the effects of the initial DMP concentration, photocatalyst dosage, UV radiation intensity and Pt doping content on the degradation of DMP. In addition, the correlations of the photocatalytic kinetics and quantum yield for DMP removal are proposed associated with the system parameters. According to the experimental results, there exists a distinct relationship between the reduction percentages of total organic carbons and DMP. Furthermore, the photodegradation mechanism of DMP in the photocatalytic process is established based on the identification of the intermediates. Moreover, the good repeatability of the photocatalytic performance with the use of the Pt–TiO2/mPMMA microspheres has also been demonstrated in the multi-run experiments. Therefore the Pt–TiO2/mPMMA microspheres are considered as a practical and promising photocatalyst in a suspension reaction system and they can be effectively recovered after use. This study provides useful information about the applications of the TiO2/mPMMA and Pt–TiO2/mPMMA microspheres for the photodegradation of DMP. [Copyright &y& Elsevier]

Abstract: This study investigates the enhanced ozonation of dimethyl phthalate (DMP), which is a pollutant of concern in water environments, with high silica zeolites and ultraviolet (UV) radiation. Semibatch ozonation experiments are performed under various reaction conditions to examine the effects of inlet gas ozone concentration, high silica zeolite dosage, and UV radiation intensity on the decomposition of DMP. The complete removal of DMP can be efficiently achieved via both O3 and O3/UV treatments. Note that the presence of high silica zeolites accelerates the decomposition rate of DMP in the O3 process. On the other hand, the removal efficiencies of both chemical oxygen demand (COD) and total organic carbons (TOC) are significantly enhanced by employing the ozonation combined with UV radiation. The O3/UV process is also advantageous for the utilization efficiency of fed ozone especially in the late ozonation period. Furthermore, the correlation between the COD removal percentage (%) and the mole ratio of ozone consumed to the DMP treated (molmol−1) is obtained. The clear-cut removal relationship of the TOC with COD during the ozonation of DMP has also been presented. Consequently, the results evaluate the flexibility of ozonation system associated with high silica zeolites and UV radiation for the removal of DMP and provide the useful information in engineering application. [Copyright &y& Elsevier]

Abstract: The removal efficiency of polycyclic aromatic hydrocarbons (PAHs) by ozonation using a rotating packed bed (RPB) in the surfactant-containing solution is studied. As an ozonation process starts, the ozone-containing gas is introduced and transferred into to the solution. The target PAHs in the solution would be then eliminated via both the gas stripping and ozonation decomposition. The RPB, which provides high gravitational force by adjusting the rotational speed, is employed as a novel ozone contactor. The naphthalene (NAP) and Brij 30 are chosen as the model pollutant and surfactant. Note that the experiments with different concentrations of NAP, Brij 30, and inlet gas ozone are performed for the further investigation. The residual NAP, effluent dissolved oxygen and ozone, and off-gas ozone concentrations are simultaneously monitored. As a result, the removal of NAP in the RPB is remarkably efficient compared with the convectional contactors because of its greater mass transfer coefficient. Moreover, the removal efficiency of NAP is found significantly dependent on the concentrations of NAP, Brij 30, and inlet gas ozone. It takes about several minutes to reach the steady state under the conditions of this study. In addition, it suggests employing RPBs as ozone contacting devices for the high removal efficiency of NAP. Consequently, the present study is useful for the practicable understanding of application of RPBs for the ozonation of PAHs in surfactant-containing solution. [Copyright &y& Elsevier]

This study investigated the oxidation of methyl methacrylate (MMA) by sole ozonation and ozone/UV treatments. The semi-batch ozonation experiments were proceeded under different reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of MMA. The experimental results indicated that both the oxidation of MMA by the sole ozonation and O3/UV processes can completely decompose MMA to form the following intermediates within 30min reaction time. To increase the applied ozone dosage can significantly raise the removal efficiency of MMA. However, the mineralization of MMA via the direct oxidation reaction of molecular ozone was slow, while introducing the UV radiation can promote the mineralization rate of MMA. In addition, the pH value of the oxidized solution in the O3/UV treatment decreased lower than that in the sole ozonation treatment of about 1unit. The possible scheme of the decomposition pathway of MMA under the ozonation process is proposed in this study. Formic acid and acetic acid were found to be the main ozonated intermediates. [Copyright &y& Elsevier]

Fenton process was employed to treat synthetic dye wastewater with supply of Fe(II) electrolytically generated from iron-containing sludge which was recycled and reused throughout the study. Treated water quality and properties of iron sludge after being repeatedly used were reported and discussed. Experimental results showed that COD was mainly removed by oxidation other than coagulation. Although, the process was quite effective for COD and color removal, conductivity of treated water was enormously high. Meanwhile, repeated use of iron-containing sludge results in accumulation of organic materials embedded in the sludge as indicated by increasing volatile suspended solid (VSS)/TSS ratio and decreasing zeta potential. [Copyright &y& Elsevier]

Abstract: This study evaluated the performance of photo-Fenton reaction initiated by the UV irradiation with H2O2/Fe3+, denoted as UV/H2O2/Fe3+, to decompose di-n-butyl phthalate (DBP) in the aqueous solution. The concentration of total organic carbon (TOC) was chosen as a mineralization index of the decomposition of DBP by the UV/H2O2/Fe3+ process. A second-order kinetic model with respect to TOC was adequately adopted to represent the mineralization of DBP by the UV/H2O2/Fe3+ process. The experimental results of this study suggested that the dosages with 4.74×10−5 molmin−1 L−1 H2O2 and initial Fe3+ loading concentration of 4.50×10−4 molL−1 in the solution at pH 3.0 with 120μWcm−2 UV (312nm) provided the optimal operation conditions for the mineralization of DBP (5mgL−1) yielding a 92.4% mineralization efficiency at 90min reaction time. [Copyright &y& Elsevier]