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This article reports on the synthesis of TiO2 nanotubes (NTs) with tunable morphologies by adjusting the reaction conditions during anodization to balance electrochemical reaction and chemical etching. Nanoporous and free-standing NTs with different lengths and diameters are thus obtained in a controlled manner, solving the bundling, sealing, and etching pit issues in the conventional anodization. The high growth speed (60 μm/h) of TiO2 NT arrays with the pore diameter of 120 nm was achieved. The photoelectrochemical response of the NT photoelectrodes is studied under both UV and visible illumination from 250 to 600 nm, showing that the photoresponse occurred between 300−400 nm with the maximum value at 355 nm. The nanoporous TiO2 film has the higher photocurrent density than the nonporous NTs array because of fewer defects and perfect alignment. However, the photocatalytic performance to degrade methylene blue showed an inverse trend: the free-standing TiO2 NTs have better photocatalytic degradation than the nanoporous TiO2 NT film probably due to the larger effective contact area.

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Mixed-phase Fe 2 O 3 was prepared from Fe(NO 3 ) 3 and (C 2 H 5 ) 3 NHCl via solution combustion. Photocatalytic oxidative desulfurization of dibenzothiophene (DBT) under simulated sunlight irradiation using mixed-phases of a-and b-Fe 2 O 3 as catalysts was investigated. The DBT in the oil phase was extracted into water phase and then photooxidized to CO 2 and SO 4 2À by Fe 2 O 3 and O 2 dissolved in water. The Fe 2 O 3 containing 36.6% b-Fe 2 O 3 and 63.4% a-Fe 2 O 3 exhibited the highest photocatalytic activity. Sulfur removal of DBT in n-octane was 92.3% for 90 min irradiation under the conditions of V(water) : V(n-octane) = 1 : 1, air flow rate at 150 mL min À1 , and Fe 2 O 3 addition at 0.05 g. The kinetics of photooxidative desulfurization of DBT was a pseudo-first-order with an apparent rate constant of 0.0287 min À1 and half-time of 24.15 min. The sulfur content of the actual diesel could be reduced from 478 mg mL À1 to 44.5 mg mL À1 after 90 min. The radical scavengers experiments and terephthalic acid fluorescence technique indicated that OH and O 2 À were the main reactive species in the DBT photocatalytic degradation.

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In this study, the water-soluble products formed during the hydrothermal carbonization of glucose were analyzed by liquid chromatography (LC)–mass spectrometry (MS) and LC–MS2 to determine the formulas and the possible structures of the main compounds. In addition to the well-known compounds of 3-deoxyglucosone, 5-hydroxymethylfurfural, and levulinic acid, the furanic compounds and the carbocyclic oxy-organics containing hydroxy group and carbonyl group with a molecular mass range between 170 and 260 Da were also identified. Both C–C coupling reaction and C–C cleavage reaction were proved to be involved during the formation of these carbocyclic oxy-organics, so they were proposed to be released via C–C cleavage of the primary polymers, which were formed by aldol condensation of the primary precursors formed during the degradation of glucose. The identification of these carbocyclic oxy-organics was indirect evidence that aldol condensation played a crucial role during the formation of hydrochar from carbonization of glucose.

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a b s t r a c tThe influences of solvent system on the hydrodechlorination (HDC) of transformer oil-contained PCBs with H 2 over Pd/C catalyst were studied. The addition of water in solvent system significantly accelerated the HDC reaction, which suggested its critical role for enabling Pd/C catalyst to keep high activity and stability. The mechanism of this phenomenon was studied through catalyst characterization (TEM, XRD and XPS), and the change of surface composition of Pd/C catalyst in different solvent in the HDC reaction was raveled. Above results indicated that water in isopropanol-water prevented NaCl accumulating on the surface of catalyst, which avoided the decline in activity and stability of the catalyst. On the basis of these studies, isopropanol-water (60/40, v/v) solvent system was developed to dispose high concentration transformer oil-contained PCBs, where the chloride atom removal ratio of transformer oil-contained PCBs at 2% (w/w) and 5% (w/w) concentration could reach 95.2% and 88.0% for 10 h under mild conditions respectively, and the Pd/C could be recovered and reused at least 10 times without any loss of catalytic activity.