•OH + ONO2* was predominant channel of HO2NO2 photolysis in aqueous phase at 266 nm.•The quantum yield of OH radicals of HO2NO2 photolysis was to be 0.14 ± 0.01.•OH react with HO2NO2 with a rate constant of (1.58 ± 0.03) × 109 L mol−1 s−1.The photodissociation of peroxynitric acid (HO2NO2) aqueous solution both in nitrogen-saturated and oxygen-saturated were studied by using 266 nm laser flash photolysis techniques. Hydroxyl radical and NO3 radical was observed in the time resolved spectra from the photolysis of HO2NO2. The yield of NO3 at 266 nm of 0.12 ± 0.02 was consistent with OH quantum yield of (0.14 ± 0.01) A small OH yield indicated that OH was mainly from the direct photodissociation of peroxynitric acid and OH + NO3 was predominant photolysis channel (if not the only photolysis pathway) from the HO2NO2 photolysis in the aqueous phase. The pKa of HO2NO2 was calculated to be 5.93. OH radical would sequentially react with HO2NO2 to form OHHO2NO2 adduct with a second-order rate constant of (1.58 ± 0.03) × 109 L mol−1 s−1.Download high-res image (99KB)Download full-size image

•The rate constants of biphenyl with H2ONO+, HONO and NO2− were determined.•OH reacts with biphenyl with a rate constant of 9.4 × 109 L mol−1 s−1.•Nitro-compounds was generated from the reaction between biphenyl with N(III).The photochemical reaction between biphenyl (Bp) and N(III) under irradiation at 365 nm UV light was investigated. The results showed that Bp conversion efficiency was strongly influenced by N (III) concentration, Bp initial concentration and pH. Species-specific rate constants determined by reaction of Bp with H2ONO+ (k1), HONO (k2) and NO2− (k3) were k1 = (0.058 ± 0.005 L mol−1 s−1), k2 = (0.12 ± 0.06 L mol−1 s−1) and k3 = (0.0019 ± 0.0003 L mol−1 s−1), respectively. Laser flash photolysis studies confirmed that OH radical deriving from the photolysis of N(III) attacked aromatic ring to form Bp-OH adduct with a rate constant of 9.4 × 109 L mol−1 s−1. The products analysis suggested that Bp-OH adduct could be nitrated by N (III) and NO2 to generate nitro-compounds.Download high-res image (173KB)Download full-size image

•The photo-induced interfacial charge transfer of goethite was determined.•Excitation of goethite generated conduction-band electron (ecb−) and hole (h+).•ecb− reacted with MV2+ with a rate constant of 2.6 × 109 L mol−1 s−1.•Efb (goethite, pH = 7) = 0.24 V (vs NHE).The photochemical behavior of goethite has been one of the most important topics in the field of environmental science due to it plays a significant role in the removal and transformation process of numerous pollutants. However, the interfacial electron transfer process of goethite is not clear. Using a nanosecond laser flash photolysis spectrometer, we report the transient spectroscopic observations of interfacial electron-transfer reactions in goethite dispersion under UV irradiation. Excitation of goethite generated conduction-band electron (ecb−) and hole (h+). The conduction band electron (ecb−) reacted with an electron acceptor, methylviologen dichloride hydrate (MV2+), forming reduced methylviologen (MV+) with a second-order rate constant of (2.6 ± 0.3) × 109 L mol−1 s−1. The concentration of MV+ was strongly influenced by MV2+ initial concentration and pH values. The flat band potential of goethite was calculated to be Efb (goethite, pH = 7) = 0.24 V (vs NHE). Oxygen did not react with conduction band electron of goethite. The present study provides a reliable method to investigate the photo-induced interfacial charge transfer of goethite.Download high-res image (184KB)Download full-size image

•The TiO2/goethite/palygorskite photocatalytic composite was prepared and analyzed.•TiO2/goethite/palygorskite composite exhibited good photocatalytic synergistic effect.•Electron–holes and oxygen synergy effect were responsible for benzene degradation.The nano-TiO2/goethite/palygorskite catalysts were prepared by sol–gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV–Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N2 adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m3, the degradation efficiency, over TiO2/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO2 composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron–holes and oxygen synergy effect.

•p-NP was the predominant product of the photochemical reaction of HNO3 and benzene.•p-NP produced from α-Fe2O3 surface was much higher than that in the gas phase.•Photochemical reaction on particle surface was an important source to form SOA.The 308 nm photochemical reactions of nitric acid (HNO3) and benzene in the gas phase and on α-Fe2O3 surface at 298 K was investigated by using Fourier transform infrared spectroscopy (FT-IR) combined with high performance liquid chromatography (HPLC). The concentration and yield of HONO and p-nitrophenol (p-NP) had been examined as a function of reaction time, benzene initial concentration and relative humidity on photochemical reaction. The results showed that gaseous HNO3 did not directly react with benzene in the dark, and p-NP was formed irradiation under 308 nm UV light. When HNO3 initial concentration was 400 Pa and benzene was 300 Pa, the illumination time was 100 min, the concentration of p-NP produced from the photochemical reaction of HNO3 and benzene on α-Fe2O3 surface was about 3.08 times higher than that in the gas phase. In the meantime, while reaction time was 40 min and relative humidity was 70%, the concentration of HONO and p-NP formed on α-Fe2O3 surface were about 3.55 and 2.51 times higher than those in the gas phase, and the yield of p-NP was 3.74% and 2.99%, respectively. Surfaces effect played a leading role in photochemical reaction of HNO3 and benzene on α-Fe2O3 surface.

•Co3O4/β-PbO2 electrode was prepared and an excellent electrocatalytic property.•Co3O4/β-PbO2 electrode had good corrosion resistance characterization and lifetime.•BPA electrocatalytic degradation followed pseudo-first-order reaction process.Ti-base Co3O4/β-PbO2 composite electrodes were prepared using electro-deposition and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry and the accelerated life testing, it indicated that the self-made electrode had high activity in electrolysis as well as excellent corrosion resistance and excellent catalytic performance. The results showed that the removal efficiency of CODCr could be reached up to 92.2% after 1.5 h electrolysis at NaCl concentration of 0.020 mol·L−1, bisphenol A initial concentration of 20 mg·L−1, applied voltage of 20 V, electrode spacing of 7 cm and electrolyte pH of 5. The reaction mechanism and kinetics of Co3O4/β-PbO2/Ti composite electrodes electro-catalytic degradation bisphenol A mainly caused by the OH radical attacking parent molecules and the degradation followed pseudo-first-order kinetics.

H3PW12O40/TiO2/palygorskite composite photocatalysts were prepared by the sol–gel method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and N2 adsorption–desorption measurement. These results indicated that the self-made composite photocatalysts had excellent catalytic performance of degradation of gaseous benzene. In the case of the benzene concentration at 100 mg/m3, over the composite catalysts H3PW12O40/TiO2/palygorskite with mass ratio of 1:5:5 calcined at 350 °C, reached 96.3% after 210 min UV irradiation. The gaseous benzene photo-catalytic degradation was mainly caused by strong oxidizing property of HPW, the TiO2 electron–holes and oxygen synergy effect. The degradation followed pseudo-first-order reaction process and the main products were CO2 and H2O.