Treatment of spent caustic by three kinds of photocatalyticoxidation processes

The investigation of the performance of UV/H2O2, UV/O3 and UV/H2O2/O3 oxidation systems treating spent caustic from an ethylene plant shows that in UV/H2O2 system, with the increase of H2O2dosage, removal efficiencies of COD and the ratio of biochemical oxygen demand （BOD） to chemical oxygen demand （COD） of the effluent were increased and a better performance was obtained than the H2O2system alone. In UV/H2O2 system, removal efficiency of COD reached 68% under the optimum condition, and BOD/COD ratio was significantly increased from 0.22 to 0.52. In UV/O3 system, with the increase of O3dosage, removal efficiency of COD and BOD/COD ratio were increased, and a better performance was obtained than the O3system alone. Under the optimum condition, removal efficiency of COD was 54%, and BOD/COD ratio was significantly increased from 0.22 to 0.48. In UV/H2O2/O3 system, COD removal efficiency was found to be 22.0% higher than UV/O3 system.

Importance, features and uses of metal oxide catalysts in heterogeneous catalysis

This short review paper aims at assembling the present state of the art of the multiuses of metal oxides in heterogeneous catalysis, concerning liquid and gaseous phases of the reactant mixtures on solid catalysts. It includes the description of the main types of metal oxide catalysts, of their various preparation procedures and of the main reactions catalysed by them (acid-base type, selective and total oxidations, bi-functional catalysis, photocatalysis, biomass treatments, environmental catalysis and some of the numerous industrial applications). Challenges and prospectives are also discussed.

Solar-driven H_(2)O_(2)synthesis from H_(2)O and O_(2)over molecular engineered organic framework photocatalysts

H_(2)O_(2)is an environmentally friendly oxidant and a promising energy-containing molecule widely applied in industrial production,environmental remediation,and as a potential carrier for energy storage.Solar-driven conversion of earth-abundant H_(2)O and O_(2)is the most ideal method for producing H_(2)O_(2).Due to poor separation of photogenerated charge carriers in semiconductors,sacrificial reagents such as ethanol are typically added to consume photogenerated holes,but this is not an energy storage process.Therefore,developing efficient photocatalysts for direct H_(2)O_(2)production from H_(2)O and O_(2)without sacrificial agents is crucial for sustainable energy conversion.Organic framework materials,due to their customizable structures,have gained traction in the photosynthesis of H_(2)O_(2)from pure H_(2)O and O_(2).A series of functionalized molecules have been introduced as building blocks into organic frameworks to enhance the H_(2)O_(2)production performance,but their key roles in performance and reaction pathways have not been summarized in detail so far.This review aims to address this gap and elucidate the relationship between the structure and performance of organic framework photocatalysts,providing insights and guidance for the development of efficient photocatalysts.

Photoreduction of C02 on BiOCI nanoplates with the assistance of photoinduced oxygen vacancies

CO2 photoreduction by semiconductors is of growing interest. Fabrication of oxygen-deficient surfaces is an important strategy for enhancing CO2 photoreduction activity. However, regeneration of the oxygen vacancies in photocatalysts is still a problem since an oxygen vacancy will be filled up by the O atom from CO2 after the dissociation process. Herein, we have fabricated highly efficient BiOC1 nanoplates with photoinduced oxygen vacancies. Oxygen vacancies were easily regenerated by light irradiation due to the high oxygen atom density and low Bi~） bond energy even when the oxygen vacancies had been filled up by the O atom in the photocatalytic reactions. These oxygen vacancies not only enhanced the trapping capability for CO2, but also enhanced the efficiency of separation of electron-hole pairs, which resulted in the photocatalytic CO2 reduction under simulated solar light. Furthermore, the generation and recovery of the defects in the BiOC1 could be realized during the photocatalytic reduction of CO2 in water. The existence of photoinduced defects in thin BiOC1 nanoplates undoubtedly leads to new possibilities for the design of solar-driven bismuth based photocatalysts.

In situ FT-IR investigation on the reaction mechanism of visible light photocatalytic NO oxidation with defective g-C_3N_4

The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-C_3N_4. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance(EPR) radical scavenging. It was revealed that(1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products;(2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction;(3) the hydroxyl radicals(-OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.