Visible-light driven degradation of ibuprofen using abundant metal-loaded BiVO4 photocatalysts.

An efficient method for the degradation of ibuprofen as an aqueous contaminant was developed under visible-light irradiation with as-prepared bismuth vanadate (BiVO4) catalysts. The metal-loaded catalysts Cu-BiVO4 and Ag-BiVO4 were synthesized using a hydrothermal process and then a wet-impregnation method. All of the materials were fully characterized by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and BET surface area. The results indicated that all of the prepared samples had monoclinic scheelite structures. In the metal-loaded catalysts, silver existed as a mixture of Ag and Ag2O on the surface of the catalysts. However, copper existed as Cu2O and CuO. Additionally, the band gap values of BiVO4, Ag-BiVO4, and Cu-BiVO4 were 2.38, 2.31, and 2.30eV, respectively. Compared to the BiVO4 catalyst, the metal-loaded BiVO4 catalysts showed superior photocatalytic properties for the degradation of ibuprofen.

Electrocatalytic reduction of CO2 to formic acid on palladium-graphene nanocomposites gas-diffusion electrode.

Palladium-graphene nanocomposites catalysts for the conversion of CO2 to formic acid were prepared by means of sodium borohydride reduction of K2PdCl4 in a graphite oxide suspension, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) technologies. The characterization results showed that graphene with a d-spacing of 3.82 Å was fabricated, and palladium nanoparticles with an average size of 3.8 nm were highly dispersed in the graphene sheets with amorphous structure. The cyclic voltammogram analyses indicated palladium-graphene nanocomposites catalysts posed high catalytic activity for the CO2 reduction and the rate-determining step was the CO2 diffusion process from bulk solution to electrode surface. Then the electrocatalytic reduction of CO2 was investigated in a diaphragm electrolysis device, using Pd/graphene gas-diffusion electrode as a cathode and a Ti/RuO2 net anode. The reduction process was optimized by the application of factorial design 2(3) (voltage, reaction time and electrolyte concentration) and response surface methodology (RSM). Optimum conditions for the production of formic acid were given as following: voltage: 5.1 V, reaction time: 50.4 min and electrolyte concentration: 0.5 mol L(-1). The yield of formic acid formation was 3157.7 mg L(-1) and Faraday efficiency was 86.9% under the optimum operation condition.

[Degradation mechanism of phenol with electrogenerated hydrogen peroxide on a Pd/C gas-diffusion electrode].

Using a self-made Pd/C gas-diffusion electrode as the cathode and Ti/IrO2/RuO2 as the anode, the degradation of phenol was investigated in an undivided electrolysis device by the electrochemical oxidation process. Hydroxyl radical (*OH) was determined in the reaction mixture by the electron spin resonance spectrum (ESR). The result indicated that the Pd/C catalyst in Pd/C gas-diffusion electrode system accelerated the two-electron reduction of O2 to H2O2 when feeding air, which is in favor of producing *OH. After 120 min electrolysis in Pd/C gas-diffusion electrode system, the steady concentration of H2O2 was 7.5 mg/L. The removal efficiency of phenol and COD reached about 97.2% and 50% after 120 min electrolysis, respectively, which suggested that most of phenol were oxidized to intermediates using the Pd/C gas-diffusion electrode. Furthermore, the ratio of BOD5/COD of the solutions was 9.1 times larger than the initial ones. Hence the electrochemical oxidation can enhance the biodegradation character of the phenol solution. The degradation of phenol was supposed to be cooperative oxidation by direct and/or indirect electrochemical oxidation at the anode and H2O2, *OH produced by oxygen reduction at the cathode. UV-Vis and GC-MS identified catechol, hydroquinone, and benzoquinone as the main aromatic intermediates, and adipic, maleic, fumaric, succinic, malonic, and oxalic acids as the main aliphatic carboxylic intermediates. A reaction scheme involving all these intermediates was proposed.

Degradation mechanism of diethyl phthalate with electrogenerated hydroxyl radical on a Pd/C gas-diffusion electrode.

Using a self-made Pd/C gas-diffusion electrode as the cathode and a Ti/IrO(2)/RuO(2) anode, the degradation of diethyl phthalate (DEP) has been investigated in an undivided electrolysis device by electrochemical oxidation processes. Hydroxyl radical (HO) was determined in the reaction mixture by the electron spin resonance spectrum (ESR). The result indicated that the Pd/C catalyst in Pd/C gas-diffusion electrode system accelerated the two-electron reduction of fed O(2) to H(2)O(2), which is in favor of producing HO. Additionally, the percentage removal of DEP and COD reached about 80.9 and 40.2% after 9h electrolysis, respectively. It suggested that most of DEP were oxidized to intermediates using the Pd/C gas-diffusion electrode. Furthermore, the ratio of BOD(5)/COD of resulted solutions was three times larger than the initial ones. Hence, the electrochemical oxidation enhanced the biodegradation character of the DEP solution. Finally, main aromatic intermediates (e.g., monoethyl phthalate (MEP) and phthalic acid (PA)) and main aliphatic carboxylic intermediates (e.g., formic, mesoxalic, oxalic, malonic, succinic, maleic, dodecanoic, and hexadecanoic acids) were identified by GC-MS. Moreover, a reaction scheme involving all these intermediates was proposed.