Reaction Of Reactive Species Research Articles

Chloride-enhanced ammonia removal in heat/peroxymonosulfate system: Production and contribution of chlorine

Heat-activated peroxymonosulfate (PMS) has been widely accepted as an attractive approach in degrading organic contaminants. Nevertheless, heat/PMS process possesses poor performance on the removal of ammonia (NH4+−N). In this study, the commonly existing anion of chloride ion (Cl−) was employed to augment the removal of NH4+−N in the heat/PMS process. Heat/PMS/Cl− process possesses well performance on the removal of NH4+−N over the wide pH range of 3–11. The removal of NH4+−N in the heat/PMS/Cl− process adhered to the pseudo-zero order kinetic model, and kobs rose from 0.294 mg/L min−1 to 1.61 mg/L min−1 with the addition of 30 mM Cl− at pH 7. Chlorine (HClO), instead of HO, SO4−, Cl and 1O2, was identified as the primary oxidant responsible for NH4+−N removal according to the quenching experiments. The formation of HClO was proved to be mostly through the direct reaction between PMS and Cl−, rather than the reactions of reactive species with Cl−. The environmentally friendly gas of N2 predominated as the primary degradation product during the removal of NH4+−N with heat/PMS/Cl− process, although nitrite and nitrate nitrogen were also detected. Increasing Cl− concentration, PMS dosage and reaction temperature facilitated the removal of NH4+−N. Br− could significantly accelerate the removal of NH4+−N in heat/PMS/Cl− process. The other anions of SO42−, CO32− and NO3−, the cations of Cu2+ and Fe3+, humic acid and landfill leachate had negligible effects on the removal of NH4+−N. Overall, this study offered an efficient approach to boost the oxidation capacity of heat/PMS process towards the removal of NH4+−N, and these findings had significant implications for the utilization of heat/PMS process in Cl−-containing water.

Plasmonic silver nanoparticle-deposited n-Bi2S3/p-MnOS diode-type catalyst for enhanced photocatalytic nitrogen fixation: Introducing the defective p-MnOS

Photocatalytic nitrogen reduction reaction (PNRR) is clean and sustainable, considered an ideal synthesis technology for ammonia (NH3). In this study, we in situ developed the n-Bi2S3 nanorod/p-MnOS cubic composite catalyst for the first time using a one-step hydrothermal method, as MnOS, listed in the X-ray diffraction standard data file as an uncharacterized compound, has not been reported since 1965. Then, using a photodeposition technique, Ag nanoparticles (NPs) were added to the surface of the Bi2S3/MnOS to enhance PNRR via the surface plasmon resonance. After different characterization techniques for evaluation, Ag-Bi2S3/MnOS is found to be highly effective in the spatial separation of photogenerated electron-hole pairs due to the charge transfer at the composite interface. Photodeposited Ag is applied as an electron trapper to enhance the spatial separation of charge carriers. Based on their ability to reduce nitrogen under simulated solar light irradiation, the PNRR activities of Bi2S3, MnOS, Bi2S3/MnOS, and 0.5 to 2 % Ag-Bi2S3/MnOS were evaluated. After two hours, the PNRR activity of 1 % Ag-Bi2S3/MnOS produced ammonia 5.9 mmol/g, double the amount of Bi2S3/MnOS composite and approximately 5 times the amounts of Bi2S3 and MnOS materials. PNRR enhancement involves the internal static electron field created at the n-type Bi2S3/p-type MnOS interface and the improved electron conductivity with the photodeposition of Ag NPs, to speed up the reaction of reactive species. The importance of solid solution engineering in material design is demonstrated in this work.

Influence of reactive oxygen species concentration and ambient temperature on the evolution of chemical bonds during plasma cleaning: a molecular dynamics simulation.

The research on plasma chemistry involved in the formation and dissociation of abundant chemical bonds is fundamental to developing plasma cleaning. To understand the influence of reactive oxygen species' concentration and ambient temperature on the evolution behavior of the chemical bond during plasma cleaning, microscopic reaction models between organic contaminants and reactive oxygen species were established and performed by reactive molecular dynamics. Dibutyl phthalate, as a representative organic contaminant, was selected as the research object. The simulation results suggested that hydrogen bonds between hydroxyl radicals reduced the mobility of reactive species, resulting in the cleaning ability of hydroxyl radicals being much lower than atomic oxygen and ozone radicals. The concentration of reactive species dominated the efficiency of plasma cleaning, and the increase in ambient temperature further improved the cleaning ability. C-H, C-C and C-O bonds were gradually oxidized to C[double bond, length as m-dash]C, C-O, C[double bond, length as m-dash]O and O-H bonds by hydrogen abstraction reaction during the reaction of reactive species with organic contaminants. An increase in ambient temperature induced the possibility of benzene ring destruction under the action of reactive species, which was considered a method of complete dissociation of aromatic hydrocarbons.

Penetration of plasma surface modification into porous media. III. Multiple samples exposed to CF4 and C2F4 low temperature cascade arc torch

AbstractThe depth and possible mechanisms of the penetration of surface modification into porous media by a low temperature cascade are torch are investigated. Two different modes of such penetration (“flow controlled” and “diffusion controlled”) are evaluated. Three porous samples [stacks of 10 sheets of nonwoven fabrics of poly(ethylene terephthalate)each], placed at an axial distance of 24, 28, and 32 cm from the cascade are anode, are exposed to a low temperature cascade arc torch containing argon and CF4 or C2F4, and surface properties of each of the sheets within treated porous samples are examined by ESCA. It is shown that interaction of chemically reactive species, created in the low temperature cascade arc torch, with the surface is not limited to the surface directly contacted by the torch. The flow controlled penetration is more pronounced for the outer layers, while diffusion controlled penetration is within the inner layers of the porous structure. Substantial differences in the fluorination effect of CF4 (nonpolymer forming gas) and C2F4 (polymer forming gas) discharges for the second and third stacks are observed, that can be explained by the fact that the major effect of the CF4 cascade arc torch treatment is based on the reaction of reactive species with the surface polymer molecules. The effect of C2F4 cascade arc torch treatment is based on the reactions of reactive species with polymers as well as reactions of reactive species themselves at the surface (plasma polymerization). Reactivity of the species created in C2F4 discharge is much higher compared to that created in CF4 discharge, which is one of the major factors influencing penetration trends of low temperature cascade arc treatment into porous media. © 1995 John Wiley & Sons, Inc.