Meifen Wu

Electrosorption-promoted Photodegradation of Opaque Wastewater on A Novel TiO2/Carbon Aerogel Electrode

A novel electrosorption-photocatalysis synergistic electrode of TiO(2)/carbon aerogel (TiO(2)/CA) is prepared. The thermal stability and dispersion of the anatase TiO(2) particles are well facilitated by the porous and discontinuous microstructure of CA. The degradation experiments show that the TiO(2)/CA material is not only a good photocatalyst but also an excellent electrosorptive electrode. The TiO(2)/CA is easily molded to an agglomerate electrode. The opaque wastewater with dyestuff is degraded effectively by the electrosorption-promoted photocatalytic process on this electrode. For the simulated methylene blue (MB) wastewater (150 mg L(-1)), the rate constant of MB degradation in the electro-assisted photocatalytic process with the conventional ITO-supported TiO(2) (TiO(2)/ITO) is 0.55 x 10(-3) min(-1) and that the electrosorption-promoted photocatalysis with TiO(2)/CA is 10.27 x 10(-3) min(-1), which is 18 times the former. In the electrosorption-promoted photocatalytic process with TiO(2)/CA, the energy consumption removing per unit TOC is only 15% of that in the electro-assisted photocatalysis with TiO(2)/ITO, because the electrosorption is a nonfaradic process irrelative to any electron transfer and requires very low consumption. This study provides a new method for exploring highly efficient electrosorption-promoted photocatalytics technology in the treatment of opaque wastewater.

Electrochemical degradation of chlorobenzene on boron-doped diamond and platinum electrodes

In this paper the electrochemical degradation of chlorobenzene (CB) was investigated on boron-doped diamond (BDD) and platinum (Pt) anodes, and the degradation kinetics on these two electrodes was compared. Compared with the total mineralization with a total organic carbon (TOC) removal of 85.2% in 6h on Pt electrode, the TOC removal reached 94.3% on BDD electrode under the same operate condition. Accordingly, the mineralization current efficiency (MCE) during the mineralization on BDD electrode was higher than that on the Pt electrode. Besides TOC, the conversion of CB, the productions and decay of intermediates were also monitored. Kinetic study indicated that the decay of CB on BDD and Pt electrodes were both pseudo-first-order reactions, and the reaction rate constant (k(s)) on BDD electrode was higher than that on Pt electrode. The different reaction mechanisms on the two electrodes were investigated by the variation of intermediates concentrations. Two different reaction pathways for the degradation of CB on BDD electrode and Pt electrode involving all these intermediates were proposed.

Applicability of boron-doped diamond electrode to the degradation of chloride-mediated and chloride-free wastewaters

The electrochemical degradation of chloride-mediated and chloride-free dye wastewaters was investigated on a boron-doped diamond (BDD) electrode in comparison with that on a dimensionally stable anode (DSA), and the applicability of BDD electrode to the degradation of these two kinds of wastewaters was explored. In chloride-free wastewater, the electrochemical degradation efficiency of dye on BDD electrode was much higher than that on DSA, with a chemical oxygen demand (COD) removal of 100% and 26% for BDD and DSA, respectively. In chloride-mediated dye wastewater, COD removal was faster than that in chloride-free wastewater on both BDD and DSA electrodes with COD removal efficiencies higher than 95%, whereas the rate of COD removal on DSA was faster than that on BDD electrode. The investigation indicates that DSA is more suitable than BDD electrode in degradation of originally chloride contained dye wastewaters for the sake of energy and time saving. However, for chloride-free dye wastewaters, with the aim of environmental protection, BDD electrode is more appropriate to realize complete mineralization. At the same time, the secondary pollution can be avoided.

The mechanism and kinetics of ultrasound-enhanced electrochemical oxidation of phenol on boron-doped diamond and Pt electrodes.

The research on ultrasound (US) enhanced electrochemical oxidation of Phenol (Ph) on boron-doped diamond (BDD) and Pt electrodes is studied. The enhancement by US on BDD is much greater than for Pt. With the assistance of US, the degradation rate and current efficiency on BDD are increased by 301% and 100%, respectively, while those on Pt are 51% and 49%. The difference of the enhancement on these two electrodes is caused by the fact that mass transport, adsorption amount and electrode reaction affected by US on BDD are different from those of Pt. The kinetics investigation on intermediates formed during electrochemical degradation show that the variety of intermediates produced on BDD is less than for Pt. In the presence of US, on both electrodes, no change occurred to the amounts of the intermediate species. However, time for intermediates to reach the highest concentration is cut down. This effect for degradation of Ph on BDD is more obvious than for Pt. The present research indicates that BDD is suitable for degradation of Ph by US assisted electrochemical oxidation.

Ultrasound enhanced electrochemical oxidation of phenol and phthalic acid on boron-doped diamond electrode.

The enhancement on degradation of two typical organic pollutants, phenol (Ph) and phthalic acid (PA) on boron-doped diamond (BDD) electrode is particularly investigated in this study. Results show that ultrasound (US) has remarkable influence on electrochemical (EC) oxidation of the two pollutants including degradation efficiency, EC oxidation energy consumption, mass transport and electrochemical reaction. With US, the enhancement on degradation efficiency and decreasing of EC oxidation energy consumption of Ph are more obvious. US can also efficiently reduce the average electrochemical oxidation energy consumption (AE), decreasing by 74 and 69% for Ph and PA, respectively. Mass transport process can be greatly accelerated by US. The mass transport coefficients of Ph and PA both reach 2.0 x 10(-5)ms(-1) in ultrasound-assisted electrochemical (US-EC) process, from 5.4 x 10(-6) and 6.7 x 10(-6) ms(-1) in EC, increasing by 270 and 199%, respectively. The reaction amount of Ph decreases by 79% with US, from 6.49 x 10(-10) to 1.39 x 10(-10) mol cm(-2). For PA, the reaction amount decreases from 1.25x10(-11) to 3.11 x 10(-12) mol cm(-2) with US. The oxidation peak current increases by 32% for Ph. While for PA, there is no direct oxidation happened in US-EC process.

Photoelectrocatalytic properties of a vertically aligned Ti-W alloy oxide nanotubes array and its applications in dye wastewater degradation

A highly ordered and vertically oriented array of nanotubes (NTs) of mixed oxide was prepared in situ by Ti-W alloy anodization. Compared with the traditional TiO2 NTs, the photoelectrocatalytic activity of the resulting Ti-W-O NTs was greatly enhanced. Results indicated a narrowing of the band gap from 3.2 eV for pristine TiO2 to 2.7 eV for Ti-W-O NTs. Under irradiation with 254 and 365 nm UV lights, Ti-W-O NTs showed much higher photoelectroconversion efficiency (η) than TiO2 NTs and TiO2-WO3 coating. The η254 and η365 on Ti-W-O NTs reached as high as 51.8% and 57.0% respectively, four to five times those on TiO2 NTs and TiO2-WO3 coating. As a result of its narrow band gap energy and fast electron–hole separation, Ti-W-O NTs presented outstanding photoelectrocatalytic features. The electrochemically assisted photocatalytic degradation of highly concentrated Rhodamine 6G wastewaters was studied. The results showed that the rates of colour and TOC removal were much higher on Ti-W-O NTs than on TiO2 NTs and TiO2-WO3 coating. The photocatalytic material obtained by alloy anodization is of significance in the advanced oxidation of environmental pollutants.