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The role of dissolved oxygen (DO) in a visible Fenton-like degradation of atrazine driven by Ta(O)N was examined in detail. First, Ta(O)N samples were prepared by the nitridation of Ta 2 O 5 nanoparticles, which showed strong absorption in the range of 300–600 nm. Second, the degradation of atrazine, the decomposition of H 2 O 2 , and the formation of intermediates in the visible Ta(O)N-Fenton-like system in the presence of DO were compared with those in the absence of DO. In the visible Ta(O)N–Fenton-like system, atrazine degradation was based on the attack of • OH and the atrazine degradation pathways were similar in the presence and absence of DO. Notably, however, the presence of DO suppressed atrazine degradation. An investigation into the effects of DO on the photoreduction of Fe 3+ and the photodecomposition of H 2 O 2 catalyzed by Ta(O)N showed that the presence of DO suppressed the formation of Fe 2+ but did not affect the decomposition of H 2 O 2 . Therefore, the presence of DO slowed the generation of • OH. The role of DO in atrazine degradation by a visible Ta(O)N-Fenton-like system was proposed on the basis of the experimental results. [ABSTRACT FROM AUTHOR]

Highlights: [•] TaON exhibited higher photocatalytic activity than Ta3N5. [•] eCB is captured by either Fe3+ or H2O2 and hVB could not oxidize atrazine. [•] OH, from the reduction of H2O2 by Fe2+ or by eCB, is the active species. [•] By capturing eCB, H2O2 was preferred to be reduced to H2O than to OH. [•] TaON showed the higher separation efficiency of electrons and holes than Ta3N5. [ABSTRACT FROM AUTHOR]

In order to obtain TiO2 with high photocatalytic activity, a cathode reduction was used to dope I7+ and I5+ into TiO2 nanotubes of anodized Ti in C2H2O4⋅2H2O + NH4F electrolyte. SEM images show that the anodization method integrated the preparation with the doping process, which for nonmetals-doping is advantageous to maintain the morphological integrity of TiO2 nanotubes. I7-I5+-doping enhances the UV response of TiO2 and result in a red-shift. Under UV/visible irradiation, a I7+-I5+-doped sample (400°C) showed the highest Iph and photocatalytic efficiency. A part of I- in the I7+-I5+-doped sample is involved in the UV response, the red-shift and the higher Iph. [ABSTRACT FROM AUTHOR]

A kinetic model of the degradation of 4-CP by Fenton/O2 system was established, in which particular attention was paid to the role of oxygen in the process because many former researches suggested that the presence of oxygen could decrease the input of H2O2. The proposed model well predicted 4-CP degradation and H2O2 consumption by Fenton/O2 and Fenton/N2 systems at varying levels of Fe2+, H2O2, and 4-CP input. Most correlation coefficients between experimental and predicted data of 4-CP and H2O2 concentration were above 0.95. The model could predict the enhancement of 4-CP degradation by oxygen and the difference in the evolution of aromatic intermediates between Fenton/O2 and Fenton/N2 system. The predicted and experimental data both showed the degree of benzene ring cleavage in Fenton/O2 system was higher than that in Fenton/N2 system. Understanding the role of oxygen is very important to improve the decomposition performance. [Copyright &y& Elsevier]

This paper reported the degradation of 4-CP wastewater by a novel photocatalysis oxidation system—UV/Fe2+/air system, in which air was used as a cheap oxidant that reacted with the excitation state of organics to form H2O2 under the UV light. The formed H2O2 reacted with the added ferrous ion to form Fenton reaction and led to the quick degradation of organic pollutants. It was found that 4-CP could be completely removed within 40 min. The degradation of 4-CP in the UV/Fe2+/air system was superior to the conventional UV/Fenton system (the initial concentration of H2O2 was 22 mg·L-1). UV/Fe2+/air is an effective and cheap method for treatment of the organics that can be excited by UV light. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 nanotubes showed high photocatalytic activity for microcystin-LR degradation. [•] Conjugated system and methoxy group in Adda chain are liable to be attacked by OH. [•] Conjugated system in Mdha amino acid is susceptible to be attacked by OH. [•] Carboxyl and amino groups of the peptides are inferred to be hydrolyzed. [•] Adda is proposed to be separated from heptapeptides, leaving alkyl derivatives. [Copyright &y& Elsevier]

Abstract: Fe–N-codoped TiO2 powder prepared by sol–gel method is loaded on low-density polyethylene film to obtain immobilized photocatalyst. The obvious agglomeration phenomena exist in the annealed samples with nanometer size, as observed in SEM images. XRD results suggest that the adding amount of impurities has a great effect on the crystallinity and particle size of TiO2. Compared with undoped and Fe/N-doped TiO2, Fe–N-codoped TiO2 shows an obviously higher catalytic activity under visible irradiation. The DFT calculations indicate that the doping of nitrogen and Fe induced the formation of new states between the valence band and conduction band. The codoping of TiO2 with nitrogen and Fe leads to the much narrowing of the band gap and greatly improves the photocatalytic activity under visible irradiation. Moreover, the Fe–N-codoping can promote the separation of the photogenerated electrons and holes to accelerate the transmission of photocurrent carrier. [Copyright &y& Elsevier]

Abstract: The increasing atmospheric CO2 level causes global warming and may pose catastrophic effects to the humanity. Among the various options to reduce the CO2 atmospheric loading, hydrothermal reactions may have a high potential for rapidly and effectively converting CO2 into useful chemicals. In this study, the hydrothermal conversion of CO2 into formic acid was carried out by using Fe as a reductant and Ni as a catalyst. The effect of various experimental parameters, e.g., amount of Fe (Ni), Fe/Ni ratio, temperature, reaction time, alkalinity etc. was investigated. Results showed that Ni played a catalytic role in the hydrothermal conversion of CO2 into formic acid. The highest yield of formic acid of 15.6% was achieved under optimal conditions, i.e., Fe/Ni ratio of 1:1, temperature of 300°C, reaction time of 120min, filling rate of 35% and NaHCO3: Fe of 1:6. Additionally, the selectivity of formic acid was more than 98%. It was also found that the hydrothermal conversion could not occur without either the addition of catalyst or the existence of CO2 when Fe was used as a reductant. The role of CO2 in the hydrogen production was discussed. [Copyright &y& Elsevier]

The photodegradation of p-cholorophenol in a hydrogen peroxide-aided photolysis process was investigated. The reaction was influenced by the original concentration of p-chlorophenol and H2O2 addition and carrier gas. With the aid of dioxygen, the removal of phenol and CODCr were reached about 96% and 50% respectively if the original concentration of H2O2 added was only half of stoichiometric calculation. A pseudo-first order kinetic model was adopted to represent the reaction.