[Investigation of the oxidation reaction of O3 with bromide ion in aqueous solution].

The reaction mechanism of O3 with bromide ion in aqueous solution was studied by ion chromatography and UV-Vis spectrometry instruments. Ion chromatography analysis showed that only 10% of Br- which was oxidized by ozone was formed into bromate ion. The results demonstrated that the final products of the oxidation reaction were identified as Br2 and Br3- except for BrO3-. The formation of Br3- which was yielded from the reaction of Br2 with Br- was the major process in the reaction of Br attacked by O3. The characteristic absorption spectrum of Br3- with an absorption peak at 260 nm was also investigated. The results may provide helpful information about the mechanism of the oxidation reaction of Br- with O3 and fate of Br- or its derivatives in the environment by the oxidation processes.

Photolysis of low concentration H2S under UV/VUV irradiation emitted from microwave discharge electrodeless lamps.

The photolysis of simulating low concentration of hydrogen sulfide malodorous gas was studied under UV irradiation emitted by self-made microwave discharge electrodeless lamps (i.e. microwave UV electrodeless mercury lamp (185/253.7 nm) and iodine lamp (178.3/180.1/183/184.4/187.6/206.2 nm)). Experiments results showed that the removal efficiency (eta H2S) of hydrogen sulfide was decreased with increasing initial H2S concentration and increased slightly with gas residence time; H2S removal efficiency was decreased dramatically with enlarged pipe diameter. Under the experimental conditions with pipe diameter of 36 mm, gas flow rate of 0.42 standard l s(-1), eta H2S was 52% with initial H2S concentration of 19.5 mg m(-3) by microwave mercury lamp, the absolute removal amount (ARA) was 4.30 microg s(-1), and energy yield (EY) was 77.3 mg kW h(-1); eta H2S was 56% with initial H2S concentration of 18.9 mg m(-3) by microwave iodine lamp, the ARA was 4.48 microg s(-1), and the EY was 80.5mg kW h(-1). The main photolysis product was confirmed to be SO4(2-) with IC.

[Photolysis of simulating CS2 malodorous gas using microwave electrodeless lamps].

The photolysis of simulating carbon disulfide malodorous gas was studied under UV irradiation emitted by microwave electrodeless lamps. Experiments results show that the photolysis of carbon disulfide is determined by the initial concentration, residence time and gas humidity. When air velocity is 0.2 m/s, initial concentration is about 100 mg/m3, and gas humidity is about 40%, the conversion ratio of carbon disulfide can reach to 75% with microwave electrodeless mercury lamp and 50% with microwave electrodeless iodine lamp. The mechanism of carbon disulfide photolysis was further studied. It is concluded that the photolysis of carbon disulfide is probably a collective action of direct photolysis and *OH radical oxidation.

A combined plasma photolysis (CPP) method for removal of CS2 from gas streams at atmospheric pressure.

A combined plasma photolysis (CPP) reactor that utilizes a dielectric barrier discharge (DBD) plasma and 207 nm UV radiation from discharge-driven KrBr* excimers was designed and constructed. Gas streams containing CS2 were treated with stand-alone DBD and CPP at atmospheric pressure. In comparison to DBD, CPP greatly enhanced the removal efficiency at the same applied voltage, waste gas concentration and gas residence time. Thus the applied voltage could be reduced to a certain extent in the plasma processing of industrial wastes. Influences of the KrBr* radiation, inlet CS2 concentration and gas residence time on CS2 removal by CPP were also studied. In addition, the likely reaction mechanisms for the removal of CS2 by CPP are suggested based on the byproducts analysis. The enhanced removal efficiency and reaction mechanisms implied that the CPP process would probably be suitable for the removal of a large number of gaseous pollutants.

Photochemistry in the mixed aqueous solution of nitrobenzene and nitrous acid as initiated by the 355 nm UV light.

The 355 nm photon-initiated microscopic reaction mechanisms of the mixed aqueous solution of nitrobenzene and nitrous acid in the presence or absence of O(2) were studied by the laser flash photolysis technique. The main transient absorption peaks in the recorded spectra were assigned and the growth/decay trends of several transient species were investigated. It was found that the OH radical formed from the photolysis of nitrous acid triggered most of the subsequent radical reactions. The rate constant of the reaction between OH radical and nitrobenzene was measured to be (3.4 +/- 0.1) x 10(9) l mol(-1) s(-1). The product from this reaction, namely C(6)H(5)NO(2)-OH adduct, was found to react with O(2) to yield C(6)H(5)NO(2)-OHO(2) adduct with a rate constant of (1.6 +/- 0.2) x 10(9) l mol(-1) s(-1). Final steady-state products were identified by GC/MS analysis and were in accordance with the transient spectroscopic results. The possible reaction pathways were proposed.

[Photocatalytic degradation of hexafluorobenzene by tungstophosphoric acid].

We verified that C6F6, a typical perfluorine compound, could be photocatalytic degraded by H3PW12O40. The defluorination of C6F6 was determined as a function of irradiation time, pH, initial concentration of H3PW12O40, and additives as well. The defluorination of C6F6 increased with the irradiation time. Acid condition, especially pH = 1.0 is preferred. 3 mL solution of 2.0 x 10(-4) mol/L C6F6 and 5.0 x 10(-6) mol/L H3PW12O40 was irradiated for 20 min and the defluorination of C6F6 was equal to 208.1%. O2, KMnO4 and K2S2O8 added in the solution were able to increase the defluorination of C6F6 via oxidating [PW12O40](4-). The defluorination of C6F6 would decline in the presence of alcohol and aromatic compounds.

Reactions between the SO4*(-) radical and some common anions in atmospheric aqueous droplets.

The rate constants of reactions between the SO4*(-) radical and some common anions in atmospheric aqueous droplets e.g. Cl-, NO3-, HSO3- and HCO3- were determined using the laser flash photolysis technique. Absorption spectra of SO4*(-) and the product radicals were also reported. The chloride ion was evaluated among all the anions to be the most efficient scavenger of SO4*(-). The results may supply useful information for a better understanding of the vigorous radical-initiated reactions in atmospheric aqueous droplets such as clouds, rains or fogs.

[Dissociation of SF5CF3 under discharge].

SF5CF3 was identified recently as a potent greenhouse gas with strong radiative force and long atmosphere residential life. Spark discharge method was used to take simulative investigation on the elimination of SF5CF3 from atmosphere under discharge here. The results show that SF5CF3 was dissociated under discharge and formed some compounds containing S, F, O and C. The dissociation of SF5CF3 was reduced if the system existed H2O, but it was independent of the amount of H2O. The rate coefficients were estimated to be 0.011s(-1) under moisture circumstance when the system total pressure was about 31 kPa. And the increase of the system pressure would cause exponential decrease of SF5CF3 dissociation. The reactive mechanism was argued based on the experiment results and the sinks of SF5CF3 under lightning (one of the discharge in the atmosphere) was estimated to be 53.6 kg x a(-1).

Reaction mechanism of 3-chlorophenol with OH, H in aqueous solution.

The reaction mechanism of 3-chlorophenol with OH, H in aqueous solution was studied by transient technology. The 3-chlorophenol aqueous solutions have been saturated with air or N2 previously. Under alkaline condition, the reaction of OH radical with 3-chlorophenol produces 3-chlorinated phenoxyl radical, with the absorption peaks at 400 nm and 417 nm. Under neutral condition, the reaction of OH radical with 3-chlorophenol produces OH-adduct with the maximal absorption at about 340 nm. And in acid solution, the reaction of H with 3-chlorophenol produces H-adduct with the maximal absorption at about 320 nm. 3-chlorophenol is compared with 4-and 2-chlorophenols from the free radical pathways. The results show that the positions of chlorine on the aromatic ring strongly influence the dehalogenation and degradation process.