Rate Of Oxygen Formation Research Articles

Combustion synthesis and photoelectrochemical characterization of gallium zinc oxynitrides

Abstract

Oxygen Production from Halate Aqueous Solutions by UV Photoinduced Oxidation

Oxygen generation from halate solution under ultraviolet irradiation was studied. The results show that with regard to KBrO3, KIO3, and KClO3 solution containing 9mmol of halate ions, and the average rates of oxygen formation were 14.1, 10.2 and 2.5 mmol, respectively in the first 3 hours. The rates and amount of oxygen formation increased with increasing halate concentration. The oxygen evolved from the oxidation of water by the excited radical (XO3 ) formed from UV absorption of XO3− ions, resulting in the reduction of halate ions to halide ions

Sustainable Zero-Valent Metal (ZVM) Water Treatment Associated with Diffusion, Infiltration, Abstraction, and Recirculation

Socio-economic, climate and agricultural stress on water resources have resulted in increased global demand for water while at the same time the proportion of potential water resources which are adversely affected by sodification/salinisation, metals, nitrates, and organic chemicals has increased. Nano-zero-valent metal (n-ZVM) injection or placement in aquifers offers a potential partial solution. However, n-ZVM application results in a substantial reduction in aquifer permeability, which in turn can reduce the amount of water that can be abstracted from the aquifer. This study using static diffusion and continuous flow reactors containing n-ZVM and m-ZVM (ZVM filaments, filings and punchings) has established that the use of m-ZVM does not result in a reduction in aquifer permeability. The experimental results are used to design and model m-ZVM treatment programs for an aquifer (using recirculation or static diffusion). They also provide a predictive model for water quality associated with specific abstraction rates and infiltration/injection into an aquifer. The study demonstrates that m-ZVM treatment requires 1% of the weight required for n-ZVM treatment for a specific flow rate. It is observed that 1 t Fe0 will process 23,500 m3 of abstracted or infiltrating water. m-ZVM is able to remove >80% of nitrates from flowing water and adjust the water composition (by reduction) in an aquifer to optimize removal of nitrates, metals and organic compounds. The experiments demonstrate that ZVM treatment of an aquifer can be used to reduce groundwater salinity by 20 –> 45% and that an aquifer remediation program can be designed to desalinate an aquifer. Modeling indicates that widespread application of m-ZVM water treatment may reduce global socio-economic, climate and agricultural stress on water resources. The rate of oxygen formation during water reduction [by ZVM (Fe0, Al0 and Cu0)] controls aquifer permeability, the associated aquifer pH, aquifer Eh and the degree of water treatment that occurs.

Photo-oxidation of water sensitized by WO3 powder

WO3 powder photosensitized the oxidation of water by Fe3+ ions with blue light (400–450 nm). The formal quantum efficiency for oxygen production at 405 nm was (3.1 ± 0.1)× 10–3 mol ein–1. Oxygen production was partially inhibited by Fe2+, oxygen and high concentrations of Fe3+(> 10–2 mol dm–3). Depositing RuO2 on to the semiconductor powder produced a moderate increase in the rate of oxygen production, while deposits of Pt, Rh and Ru lead to a decrease in the rate of oxygen formation. Unlike most of the artificial systems which have been described for the photo-oxidation of water with visible light, this system operates with an electron acceptor (Fe3+) which is part of a reversible redox couple (Fe3+/Fe2+).

Photo(Electro)Chemical Oxidation of Water by the Persulfate Ion Over Aqueous Suspensions of Strontium Titanate SrTiO3 Containing Lanthanum Chromite LaCrO3

AbstractThe photodecomposition of the S2O2‐8 ion to the SO2‐4 ion with concomitant oxidation of water to molecular oxygen over n‐type SrTiO3 powders mixed with LaCrO3 (mole fraction x = 0–1), using UV light (λ > 300 nm), is considerably faster than the photochemical (UV) decomposition of S2O2‐8 in water or the thermal reaction with or without the powder under the same conditions. The rate of oxygen formation is dependent on the temperature (Eact = 61 kJ/mol), the persulfate concentration in first order and x. At 64°C and constant [S2O2‐8] a maximum rate is found at x = 0.25. The rate determining step, i.e. the transfer of an energy‐rich electron from the conduction band to the S2O2‐8 ion, is expected to proceed faster in the case of p‐type semiconductors. In view of the reported p‐type conductivity of LaCrO3, which has previously been doped with the charge‐compensating Sr11 ion, our results with the SrTiO3‐x LaCrO3 powders are in agreement with these expectations. The sensitivity of these materials towards visible irradiation is much lower than their UV response (about 1–2%) which has also been found by determining i/V and i/λ characteristics of SrTiO3‐x LaCrO3 single crystals under illumination in a photoelectrochemical cell.