Photocatalytic Degradation Of Phenanthrene Research Articles

Low-temperature synthesis and characterization of porous chromium terephthalate MIL-101(Cr) and its photocatalytic degradation of phenanthrene

Low-temperature synthesis and characterization of porous chromium terephthalate MIL-101(Cr) and its photocatalytic degradation of phenanthrene

Experimental evidences and theoretical calculations on phenanthrene degradation in a solar-light-driven photocatalysis system using silica aerogel supported TiO2 nanoparticles: Insights into reactive sites and energy evolution

Quantitative identification on reactive sites of target organic molecule during photocatalysis can help to get deep insight into the pollutant degradation pathway and energy evolution process. In this study, a new class of silica aerogel supported TiO2 (TiO2/SiO2) photocatalysts were fabricated via a two-step approach, and applied for adsorption and photocatalytic degradation of phenanthrene. Anatase crystalline structure was formed upon calcination at 400 and 600 °C, while mixed crystal interphases of anatase and rutile were generated at 800 °C (anatase:rutile = 0.67:0.33). The higher calcination temperature resulted in better crystallinity of TiO2, higher photocatalytic activity, and reduced adsorption affinity toward phenanthrene. TiO2/SiO2-800 (TiO2/SiO2 calcined at 800 °C) showed minimal phenanthrene uptake (~5.2%) but the strongest photocatalytic activity, and it was able to completely degrade phenanthrene within 3 h. The SiO2 aerogel component in the composite enabled the pre-concentration of phenanthrene on the photoactive sites, while the nanoscale mixed-phases of anatase and rutile of TiO2/SiO2-800 act as an efficient transfer medium for photo-induced charge carriers. Moreover, the formed Ti–O–Si linkage in TiO2/SiO2-800 induced formation of Ti3+ under solar light irradiation, promoting photoexcited electron trap and separation of electron-hole pairs. Based on the degraded phenanthrene intermediates/products, theoretical calculations according to the density functional theory (DFT) reveal that the atoms of phenanthrene with high electrophilic Fukui index (f-) are the most reactive sites towards the radicals. Potential energy surface profile for phenanthrene degradation further reveals the intermediates energy evaluation via radicals attack.

Photocatalytic degradation of phenanthrene by graphite oxide-TiO2-Sr(OH)2/SrCO3 nanocomposite under solar irradiation: Effects of water quality parameters and predictive modeling

Polycyclic aromatic hydrocarbons (PAHs) are persistent and harmful pollutants with high priority concern in the environment. To efficiently and energy-savingly remove PAHs from water, this work prepared a novel graphite oxide-TiO2-Sr(OH)2/SrCO3 nanocomposite and evaluated its photocatalytic activity for degradation of phenanthrene (a model PAH) under simulated solar irradiation. The presence of 50 mg/L of the photocatalyst enhanced the pseudo-first-order photodegradation rate constant of phenanthrene by 11.6 times from 0.0005 ± 0.0000 min−1 (control) to 0.0058 ± 0.0004 min−1. Superoxide radicals (O2−) and hydroxyl radicals (OH) were found to be the key reactive species in the photocatalytic process. Based on analysis of intermediates and established photocatalysis chemistry, the degradation pathway was elucidated. The effects of various water quality parameters were investigated, including temperature, pH, ionic strength, humic acid and two surfactants (Tween 80 and sodium dodecyl sulfate (SDS)), and the underlying mechanisms were illustrated. Based on the effects of individual water quality parameters, two predictive models were established by addition or multiplication to predict the photocatalytic degradation rate under complex water matrices. Based on experimental results with seawater and in the presence of three model oil dispersants, the multiplicative model was shown to present a robust and accurate prediction of the phenanthrene photodegradation rate with a predicted correlation coefficient (r2pred.) of 0.9483. This study not only developed a new photocatalyst of high activity under solar light, but also provided useful information for its practical application under various water quality conditions.

Photocatalytic degradation of phenanthrene in the presence of akaganeite nano-rods and the identification of degradation products

The spiked samples of phenanthrene on the soil surfaces were irradiated in presence of akaganeite nano-rods.

Photocatalytic degradation of phenanthrene on soil surfaces in the presence of nanometer anatase TiO2 under UV-light

The effect of nanometer anatase TiO2 was investigated on the photocatalytic degradation of phenanthrene on soil surfaces under a variety of conditions. After being spiked with phenanthrene, soil samples loaded with different amounts of TiO2 (0 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, and 4 wt.%) were exposed to UV-light irradiation for 25 hr. The results indicated that the photocatalytic degradation of phenanthrene followed the pseudo first-order kinetics. TiO2 significantly accelerated the degradation of phenanthrene with the half-life reduced from 45.90 to 31.36 hr for TiO2 loading of 0 wt.% and 4 wt.%, respectively. In addition, the effects of H2O2, light intensity and humic acid on the degradation of phenanthrene were investigated. The degradation of phenanthrene increased with the concentration of H2O2, light intensity and the concentration of humic acids. It has been demonstrated that the photocatalytic method in the presence of nanometer anatase TiO2 was a very promising technology for the treatments of soil polluted with organic substances in the future.

Photodegradation of phenanthrene on cation-modified clays under visible light

Transformation and fate of polycyclic aromatic hydrocarbons (PAHs) are critically influenced by natural conditions, especially their interactions with various components of soils and sediments. In the present study, phenanthrene was employed as a model to explore the potential photocatalysis effect of various cation-modified clay minerals in the soil under visible-light irradiation. For five types of cation-modified smectite clays, the photodegradation rates of phenanthrene follow the order: Fe3+>Cu2+>>Ca2+>K+>Na+, which is explained in terms of photo-Fenton-like catalysis. To further inspect the effect of clay type, additional two types of clays were paralleled. Among three types of Fe(III)-modified clays, Fe(III)-smectite shows the highest photodegradation rate followed by Fe(III)-vermiculite and Fe(III)-kaolinite. The photoactivity order is consistent with the iron content contained in the three clays, suggesting that Fe(III) content plays an important role in photocatalytic degradation of phenanthrene. The reactivity of iron species greatly depends on the interlayer microenvironment of smectite such as pH and water content. Moreover, phthalates, 9,10-phenanthrenequinone and alkanoic acids were identified by GC/MS analyses as the main intermediate compounds, and the organic compounds were mineralized finally. The overall results provide valuable insights on the transformation and fate of PAHs in the natural soil environment.

Photocatalytic Degradation of Polycyclic Aromatic Hydrocarbons on Soil Surfaces Using Fe<sub>2</sub>O<sub>3</sub> under UV Light

The photocatalytic degradation of phenanthrene (PHE), pyrene (PYRE) and benzo[a]pyrene (BaP) on soil surfaces in the presence of Fe2O3 using ultraviolet (UV) light source was investigated. The effects of various factors, namely Fe2O3, soil pH, and humic acid, on the degradation performance of polycyclic aromatic hydrocarbons (PAHs) were studied. The results show that photocatalytic degradation of PAHs follows the pseudo-first-order kinetics. Catalyst Fe2O3 accelerated the photodegradation of PHE, PYRE and BaP significantly. In acidic or alkaline conditions, the photocatalytic degradation rates of the PAHs were greater than those in neutral conditions. Humic acid significantly enhanced the PAH photocatalytic degradation by sensitizing radicals capable of oxidizing PAHs.

Photocatalytic degradation of phenanthrene and pyrene on soil surfaces in the presence of nanometer rutile TiO 2 under UV-irradiation

Photocatalytic degradation of phenanthrene and pyrene on soil surfaces in the presence of nanometer rutile TiO 2 was investigated. After being spiked with phenanthrene and pyrene, soil samples loaded with different dosages of nanometer rutile TiO 2 (0, 1, 2, 3, and 4 wt%) were exposed to UV-irradiation for 25 h. The results indicated that the photocatalytic degradation of phenanthrene and pyrene followed the pseudo-first-order kinetics. The catalyst dosage of 2 wt% was chosen as the optimal one for further studies. According to the half-life, the degradation rate of the phenanthrene and pyrene on soil surfaces was related to their absorption spectra in soil and oxidation-half-wave-potential. In addition, the degradation of phenanthrene and pyrene increased along with increasing H 2O 2, light intensity and humic acids. All results indicated that the photocatalytic method in the presence of nanometer rutile TiO 2 was an advisable choice for the treatments of PAHs polluted soil in the future.

Photocatalytic degradation of polycyclic aromatic hydrocarbons on soil surfaces using TiO 2 under UV light

The photocatalytic degradation of phenanthrene (PHE), pyrene (PYRE) and benzo[ a]pyrene (BaP) on soil surfaces in the presence of TiO 2 using ultraviolet (UV) light source was investigated in a photo chamber, in which the temperature was maintained 30 °C. The effects of various factors, namely TiO 2, soil pH, humic acid, and UV wavelength, on the degradation performance of polycyclic aromatic hydrocarbons (PAHs) were studied. The results show that photocatalytic degradation of PAHs follows the pseudo-first-order kinetics. Catalyst TiO 2 accelerated the photodegradation of PHE, PYRE and BaP significantly, with their half-lives being reduced from 533.15 to 130.77 h, 630.09 to 192.53 h and 363.22 to 103.26 h, respectively, when the TiO 2 content was 0.5%. In acidic or alkaline conditions, the photocatalytic degradation rates of the PAHs were greater than those in neutral conditions. Humic acid significantly enhanced the PAH photocatalytic degradation by sensitizing radicals capable of oxidizing PAHs. Photocatalytic degradation rates of PYRE and BaP on soil surfaces with 2% TiO 2 were different at UV irradiation wavelengths of 254, 310 and 365 nm, respectively. The synergistic effect of UV irradiation and TiO 2 catalysis was efficient for degradation of PAHs in contaminated soil.