The influence of metal ions, such as Fe2+ , Fe3+ , Cu2+ and Mn2+ , on 4-CP degrada- tion was investigated in an aqueous pulsed discharge plasma system with or without the addition of a TiO 2 photo-catalyst. From an analysis of the pseudo first-order rate constant (k CP ) and energy efficiency (G 50% ) for 4-CP degradation, the experimental results show that the degradation of 4-CP is much enhanced in the presence of ferrous ions at the optimal concentration of 0.2～0.8 mmol/L or 0.2 mmol/L in an aqueous pulsed discharge plasma without or with the TiO2 system, respectively, and the enhancement is ascribed to plasma induced Fenton and photo-Fenton reactions. Meanwhile, the rank of such metal ions for catalytic effect on 4-CP degradation was Fe2+ > Fe3+ > Cu2+ > Mn2+ and Fe2+ > Fe3+ > Mn2+ > Cu2+ for the former and the latter systems, respectively, and the reasons behind this were discussed through the analysis of active species, especially hydrogen peroxide.
Atmospheric air discharge above the surface of water is an effective method for water treatment.The leakage current and Joule heating of water are reduced by the air gap,which raises the energy efficiency of the water treatment.However,the application of this kind of discharge is limited by a pair of conflicting factors:the chemical efficiency grows as the discharge gap distance decreases,while the spark breakdown voltage decreases as the gap distance decreases.To raise the spark breakdown voltage and the chemical efficiency of atmospheric pressure water surface discharge,both the high-voltage electrode and the ground electrode are suspended above the water surface to form an electrode-water-electrode discharge system.For this system,there are two potential discharge directions:from one electrode to another directly,and from the electrodes to the water surface.The first step in utilizing the electrode-water-electrode discharge is to find out the discharge direction transition criterion.In this paper,the discharge direction transition criterions of spark discharge and streamer discharge are presented.By comparing the discharge characteristics and the chemical efficiencies,the discharge propagating from the electrodes to the water surface is proved to be more suitable for water treatment than that propagating directly between the electrodes.
Hydrogenation of carbazole and N-ethylcarbazole over Raney-Ni catalyst were realized in the temperature range of 393-503 K. 4[H] adduct dominated the hydrogenation products and the formation of 2[H] adduct was the rate-limiting step during the period, in which the conversion of carbazole was less than 40%. The hydrogenation process followed pseudo-first-order kinetics and the hydrogenation activation energies of carbazole and N-ethylcarbazole were 90 k J/mol and 115 k J/mol, respectively. The reaction starting position as well as the pathway of the hydrogenation of(N-ethyl)carbazole were investigated by comparing the kinetic characteristics of hydrogen uptake of carbazole and Nethylcarbazole. The results showed that the reaction was a stepwise hydrogenation process and the first H2 was added to the C1 = C10 double bond in the hydrogenation.
Although electrohydraulic discharge is effective for wastewater treatment,its application is restricted by water conductivity and limited to the treatment of low conductivity water. For high conductivity water treatment,water-surface discharge is the preferred choice.However. the metallic electrodes are easily corroded because of the high temperature and strong oxidative environment caused by gas phase discharge and the electrochemical reaction in water.As a result. the efficiency of the water treatment might be affected and the service life of the reactor might be shortened.In order to avoid the corrosion problem,nonmetallic electrode water-surface discharge is introduced into high conductivity water treatment in the present study.Carbon-felt and water were used as the high voltage electrode and ground electrode,respectively.A comparison of the electrical and chemical characteristics showed that nonmetallic electrode discharge maintained the discharge characteristics and enhanced the energy efficiency,and furthermore,the corrosion of metal electrodes was avoided.
Titanium dioxide (TiO2 ) thin films were grown onto Indium tin oxide (ITO) glass under atmospheric pressure by chemical vapor deposition (AP-MOCVD) using titanium tetraisopropoxide astitanium precursor. The as-prepared TiO2 /ITO films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photoelectrochemical measurements. Their photocatalytic (PC) and photoelectrocatalytic (PEC) activities were evaluated based on the results of methyl orange dye (MO) degradation experiments in aqueous solution. The difference between the front side (EE, electrolyte/electrode interface) and the back side (SE, substrate/electrode interface) illumination was evaluated in both photocurrent and MO degradation experiments. The effect of the film thickness on degradation rate by PEC under the two illumination directions was also studied. Stability of TiO2 /ITO film electrode was investigated in repetitive degradation experiments. Overall, the TiO2 /ITO film with thickness ranging from 321 to1440 nm deposited by MOCVD method is an effective photoelectrode for MO degradation under SE illumination in PEC reaction system.
Oxidation of S(Ⅳ)to S(Ⅵ)in the effluent of a flue gas desulfurization(FGD)system.is very critical for industrial applications of seawater FGD.This paper reports a pulsed corona discharge oxidation process combined with a TjO_2 photocatalyst to convert S(Ⅳ)to S(Ⅵ)in artificial seawater.Experimental results show that the oxidation of S(Ⅳ)in artificial seawater is enhanced in the pulsed discharge plasma process through the application of Ti02coating electrodes.The oxidation rate of S(IV)using Ti metal as a ground electrode is about2.0x10^(-4)mol·L^(-1)·min^(-1),the oxidation rate using TiO_2/Ti electrode prepared by annealing at500℃in air is 4.5x10^(-4)mol·L^(-1)·min^(-1),an increase with a factor 2.25.The annealing temperature for preparing TiO_2/Ti electrode has a strong effect on the oxidation of S(Ⅳ)in artificial seawater.The results of in-situ emission spectroscopic analysis show that chemically active species(i.e.hydroxyl radicals and oxygen radicals)are produced in the pulsed discharge plasma process.Compared with the traditional air oxidation process and the sole plasma-induced oxidation process,the combined application of TiO_2 photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(Ⅳ)for the seawater FGD
