Photodecomposition of H_2S to H_2 over Cd_xZn_(1-x)S composite photocatalysts

A series of CdxZn1-xS (x = 0.1-0.9) photocatalysts were prepared by coprecipitation. They could form solid solution semiconductors with hexagonal phase in agreement with pure CdS by characterization of XRD. The photophysical properties of CdxZn1-xS photocatalysts were measured by UV-Vis diffuse reflectance spectrum and surface photovoltage spectroscopy (SPS). The band gap energy gradually reduced with the increasing of x value in CdxZn1-xS,and when x = 0.7,the Cd0.7Zn0.3S photocatalyst had the strongest sur...

Yeast-TiO₂Biotemplate for Oxytetracycline Solar Photodecomposition

The detection of the pharmaceutical compounds used in human and veterinary medicine is in several environmental matrices (surface waters, effluents, groundwater, soils, and sediments), and such presence promotes the resistance bacteria development, making them ineffective in some diseases treatment. The research project promotes the TiO2 synthesis using yeast culture as biotemplate, the step followed by the microstructure characterization with surface area enhancement;such properties are responsible for the improvement of solar photodecomposition processes of the veterinary antibiotic oxytetracycline. In such simple and standard process conditions the system reaches about 84% of removal percentage with a better agreement with the pseudo-first-order with the Pearson coefficient in the range from 0.82 to 0.94 and K1 = 0.035 M−1∙s−1. The degradation rate constant increased with the increasing initial Yeast-TiO2 dosage until the maximum mass of 0.1 g or with the decreasing of initial oxytetracycline concentration. The solar light used as a sustainable irradiation source is abundant and low cost in tropical countries, perfect to be applied in water treatment to decompose the pharmaceuticals pollutants, as the veterinarian antibiotics. The study demonstrates that solar photodecomposition is an efficient treatment technology for the removal of antibiotics from polluted water and provides insightful information on the potential practical application of this technology to treat contaminated water, possibly also in rural, distant areas.

Oxytetracycline Water Contamination Treated with Biocarbon TiO2 and Solar Photodecomposition

Reliable data of antibiotic use and environmental discharge as veterinary medicine are essential to help countries raise awareness of the appropriate use, control, and correct water release. The first approach is to change the regulatory framework based on consuming information, use policy, and discharge laws. The important research contribution is a novel water treatment process to treat, remove, and reduce antibiotic concentration in discharged water, mainly those used in the animal protein industry. The low particle biochar added during the titanium isopropoxide hydrolysis reduces the titanium dioxide (TiO2) agglomerates and promotes the adsorption surface process. Such improved catalyst material enhances the solar decomposition efficiency to 93% from original oxytetracycline with better correspondence with the Elovich kinetics, intraparticle diffusion, R-P isotherm, and Langmuir-Hinshelwood model.

Plasmon-mediated photodecomposition of NH3 via intramolecular charge transfer

As an excellent clean medium for hydrogen storage and fuel cell applications,the photolysis of ammonia via localized surface plasmon could be invoked as a promising route towards significantly reducing the temperature for conventional thermolysis.Here,we explore the underlying microscopic mechanism of ultrafast carrier dynamics in plasmon-mediated NH3 photodecomposition at the single-molecular level using real-time time-dependent density functional theory.The NH_(3)molecule adsorbed on the tip of archetypal magic metal clusters represented by tetrahedral Ag_(2)0 and icosahedral Ag147,splits within a hundred femtoseconds upon laser pulse illumination.We found that the splitting of the first N-H bond is dominated by the intramolecular charge transfer driven by localized surface plasmon.Surprisingly,the phase of laser pulse could modulate the dynamics of charge transfer and thus affect the plasmon-induced bond breaking.These findings offer a new avenue for NH3 decomposition and provide in-depth insights in designing highly efficient plasmon-mediated photocatalysts.

Microstructure and Photocatalytic Decomposition of Methylene Blue by TiO2-Mounted Halloysite, a Natural Tubular Mineral

On the basis of analysis of structure and properties, halloysite, a natural tubular mineral, was developed for an environmental treatment. TiO2 was mounted into halloysite by using hydrolysis of tetrabutyl titanate at room temperature. The adsorption and photocatalytic performance of halloysite and TiO2-mounted halloysite have been examined in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Their performance of adsorption and photodecomposition was evaluated from the adsorbed and degraded amounts of methylene blue （MB）. Due to the mixture of adsorption and photodecomposition, the concentration of MB, organic pollution, in water decreased rapidly with TiO2-mounted halloysite powder, which is a faster reaction than that with halloysite-only adsorption. This new use of halloysite is leading to many interesting applications in the decomposition and elimination of various pollutants in air and water.

Generation of Hydrogen from Photolysis of Organic Acids by Photosynthetic Bacteria

Photodecomposition of ten kinds of organic acids by Rhodopseudomonas palustris for producing hydrogen has been investigated. By using acetate as hydrogen donor, dynamics of hydrogen production and cell growth has been determined; the influences of acetate concentration, temperature, light intensity and the effects of the interaction among metal ions (Fe3+, Ni2+), acetate and glutamate in aqueous solution on hydrogen production have been examined for optimizing the conditions of H2 generation. The results show that H2 production is partially correlated with cell growth; Ni2+ inhibits hydrogen production, but enhances cell growth; Fe3+ promotes hydrogen production evidently. The highest rate of H2 production is 22.1 mL L-1 h-1 under the conditions of 35 ~ 37℃, 6000 ~ 8000 lx, 30 mmolL-1 of acetate, 9 mmolL-1 of glutamate, and 50 mmolL-1 of Fe3+.

Absorption and Emission Spectra of p-Phenylbenzoyl Methanthiol: Methanol Effect Based on M06-2X Calculations

The absorption and emission spectra, as well as the photolysis mechanism of p-phenylbenzoyl methanthiol in methanol and in gas phase were elucidated in detail based on the molecular structures of the ground states, excited states and their spectroscopic characters. The TD-M062 X calculations demonstrate that the S_1 state in gas phase will decompose into SH and p-phenylbenzoyl radical via a barrierless process, but the T_1 and T_2 do not photolyze. By adding 1 and 2 methanol molecules onto p-phenylbenzoyl methanthiol, the CPCM model can perfectly describe the solvation effects of methanol. Methanol may stabilize the excitation states, but also protects the resulting radical products from recombination.

Synthesis and Property of H_2La_2Ti_3O_(10)/CdS Layered Nanocomposite Photocatalyst

H2La2Ti3O10/CdS nanocomposite with er photoactivity was synthesized by a stepwise exchange process from H2La2Ti3O10, which was obtained by H^＋ -exchanging reaction of H2La2Ti3O10 with HCl other than the normally used HNO3. The pillaring process was investigated by XRD, TEM, FT-IR and BET methods. The photocatalytic decomposition of aniline was used as the model system to evaluate the photochemical properties of H2La2Ti3O10/CdS,H2La2Ti3O10 and K2La2Ti3O10. It is found that the photoactivity of layered H2La2Ti3O10 is greatly improved by the intercalation of CdS in the interlayer. In general, the excellent photoactivity of the H2La2Ti3O10/CdS nanocomposite might be attributing to the extremely small particle size of incorporated CdS and good contact between CdS and La2Ti3O10^2- layers. On the other hand, the coupling of two semiconductor particles with different energy gap is useful to achieve effective charge separation. In H2La2Ti3O10/CdS, a photo-generated electron can transfer from CdS to the La2Ti3O10^2- layer, while the holes remain in the CdS particles. This helps to diffuse the electrons and holes before reaching the interface, and the holes and electrons can be effectively captured by the electrolyte in the solution. Simuhaneously, the optimal operating condition of photodecomposition aniline was investigated.

Effect of transition metaldoping under reducing calcination atmosphere on photocatalytic property of TiO_2 immobilized on SiO_2 beads

TiO2 immobilized on SiO2 （TiO2 /SiO2 ） have been prepared by sol-gel method and various ions of transition metals （Cr3＋ , Co2＋ , Ni2＋ , Cu2＋ , and Zn2＋ ）weredoped on the photocatalyst usingwet impregnation method under reducing calcination atmosphere. The photocatalytic activity of metaldoped TiO2 /SiO2 towards phenoldegradation under black light irradiationwere investigated and comparedwith undoped TiO2 /SiO2 . The results showed that the photoresponse of Cu2＋ and Zn2＋doped TiO2 /SiO2were larger than undoped TiO2 /SiO2 , indicating that the photogenerated carrierswere separated more efficiently in Cu2＋ and Zn2＋doped TiO2 /SiO2 . The reactivitywas in the order of Cu2＋ 〉 Zn2＋ 〉 Ni2＋ 〉 Cr3＋ 〉 Co2＋ . Thedifferent photoreactivitywas ascribed to combine effect of thedifferent ionic radii and photocorrison tendency of thedopants. The samplewas also characterized by surface analytical methods such as X-raydiffraction, scanning electron micrograph/electrondispersive X-ray analyzer and UV-Vis absorption spectrum.

Photochemical decomposition of 1H,1H,2H,2H-perfluorooctane sulfonate(6:2FTS)induced by ferric ions

Perfluorooctane sulfonate（PFOS） had wide applications,such as in the electroplating industry,but its use was restricted in 2009 by the Stockholm Convention,due to its environmental persistence and potential hazards.As the most common PFOS alternative,lH,lH,2H,2H-perfluorooctane sulfonic acid（6：2FTS） and its salts have been increasingly used.However,little is known about its photochemical decomposition.This paper reports the ferric ion-induced efficient decomposition and defluorination of 6：2FTS under 254 nm ultraviolet（UV） irradiation;the underlying mechanisms were also investigated.In the presence of 100 ｜imol/L ferric ion and at pH 3.0,the first-order decomposition rate constant of 6：2FTS（10 mg/L） was 1.59/hr,which was 6 times higher than for direct UV photolysis.The effects of the ferric ion concentration and the solution pH on the 6：2FTS photodecomposition were investigated and the optimal reaction conditions were determined.In addition to fluoride and sulfate ions,shorter-chain PFCAs（C2-C7） were detected as major intermediates.The addition of hydrogen peroxide or oxalic acid accelerated the decomposition of 6：2FTS under UV irradiation,but not its defluorination,indicating that hydroxyl radicals can directly react with 6：2FTS but not with the shorter-chain PFCAs.Accordingly,a mechanism for 6：2FTS photochemical decomposition in the presence of ferric ion was proposed,which comprises two reaction pathways.First,hydroxyl radicals can directly attack 6：2FTS,leading to C- C bond cleavage.Alternatively,6：2FTS coordinates with ferric ion to form Fe（III）-6：2FTS complexes,which can undergo ligand-to-metal charge transfer under UV irradiation,causing C-S bond cleavage.