The degradation of an azo dye, acid orange 7 (AO7), caused by different high voltage pulsed electrical discharge modes (spark, streamer and corona discharge) induced by the various initial conductivities was investigated. A new type of pulsed high voltage source with thyratron switch and Blumlein pulse forming net (BPFN) was used. The typical discharge waveforms of voltage, current, power, pulse en-ergy and the pictures of spark, streamer and corona discharge modes were presented. The results in-dicated that pulsed electrical discharges led to complete decolorization and substantial decrease of the chemical oxygen demand (COD) of the dye solution. The main intermediate products were monitored by GC-MS. The discharge modes changed from spark to streamer and to corona discharge, and the streamer length decreased with the liquid conductivity increasing. At a constant input power, the peak voltage, peak current, peak power and energy per pulse of the three discharge modes ranked in the following order: spark > streamer > corona. The effective energy transfer efficiency of AO7 removal was higher for spark discharge (57.2%) than for streamer discharge (40.4%) and corona discharge (27.6%). Moreover, the energy utilization efficiency of AO7 removal for spark discharge was 1.035×10^(-9) mol/J, and for streamer and corona discharge they were 0.646×10^(-9) and 0.589×10^(-9) mol/J. Both the energy transfer efficiency and the energy utilization efficiency of spark discharge were the highest.
In order to realize hydrogen generation under visible light, novel CdS/TiO_2 nanotubes arrays are de- veloped by electrochemical anodization of Ti in 0.15 mol/L NH_4F + 0.08mol/L H_2C_2O_4 electrolyte. The diameter of the nanotube is 80―100nm and the length is approximately 550 nm. The CdS nano-particles are deposited on the TiO_2 nanotubes arrays by chemical bath deposition (CBD) in the ammonia-thiourea system. A 300W Xe lamp is used as the light source, CdS/TiO_2 nanotube arrays are used as the photoanode with the application of 1.0V bath voltage, and 0.1 mol/L Na_2S + 0.04 mol/L Na_2SO_3 solution is used as the electrolyte, then the rate of photoelectrocatalytic hydrogen generation is 245.4 μL/(h·cm^2). This opens new perspectives for photoelectrocatalytic hydrogen generation by using CdS/TiO_2 nanotubes arrays.
In order to simulate the behavior of gas hydrate formation and decomposition,a 3-Dimension experimental device was built,consisting of a high-pressure reactor with an inner diameter of 300 mm,effective height of 100 mm,and operation pressure of 16 MPa.Eight thermal resistances were mounted in the porous media at different depthes and radiuses to detect the temperature distribution during the hydrate formation/decomposition.To collect the pressure,temperature,and flux of gas production data,the Monitor and Control Generated System(MCGS) was used.Using this device,the formation and decomposition behavior of methane hydrate in the 20 ～ 40 mesh natural sand with salinity of 3.35 wt% was examined.It was found that the front of formation or decomposition of hydrate can be judged by the temperature distribution.The amount of hydrate formation can also be evaluated by the temperature change.During the hydrate decomposition process,the temperature curves indicated that the hydrate in the top and bottom of reactor dissociated earlier than in the inner.The hydrate decomposition front gradually moved from porous media surface to inner and kept a shape of column form,with different moving speed at different surface position.The proper decomposition pressure was also determined.
Kehua SuChangyu SunXin YangGuangjin ChenShuanshi Fan
Fabrication and S-F-codoping of TiO2 nanotubes were carried out by a one-step electrochemical ano-dization process to extend the photoresponse of TiO2 to the visible-light region. The prepared samples were annealed in air and detected by SEM,XRD,XPS and UV-vis DRS spectrophotometer. The results showed that the average tube diameter of the nanotubes was 150 nm and the average tube length was 400 nm. The doped TiO2 nanotubes exhibited strong absorption in visible-light region. Photoelectro-catalytic degradation efficiency of 4-CP over S-F-codoped TiO2 nanotubes was 39.7% higher than that of only-F-doped sample. Moreover,sulfur and fluorine codoped into substitutional sites of TiO2 had been proven to be indispensable for strong response and high photocatalytic activity under visible light,as assessed by XPS.
Methane partial oxidation to methanol (MPOM) using dielectric barrier discharge over a Fe2O3-CuO/γ-Al2O3 catalyst was performed.The multicomponent catalyst was combined with plasma in two different configurations,i.e.,in-plasma catalysis (IPC) and post-plasma catalysis (PPC).It was found that the catalytic performance of the catalysts for MPOM was strongly dependent on the hybrid configuration.A better synergistic performance of plasma and catalysis was achieved in the IPC configuration,but the catalysts packed in the discharge zone showed lower stability than those connected to the discharge zone in sequence.Active species,such as ozone,atomic oxygen and methyl radicals,were produced from the plasma-catalysis process,and made a major contribution to methanol synthesis.These active species were identified by the means of in situ optical emission spectra,ozone measurement and FT-IR spectra.It was confirmed that the amount of active species in the IPC system was greater than that in the PPC system.The results of TG,XRD,and N2 adsorption-desorption revealed that carbon deposition on the spent catalyst surface was responsible for the catalyst deactivation in the IPC configuration.
