Dahui Wang

Hg0 oxidative absorption by K2S2O8 solution catalyzed by Ag+ and Cu2+

The aqueous phase oxidation of gaseous elemental mercury (Hg(0)) by potassium persulfate (K(2)S(2)O(8), KPS) catalyzed by Ag(+) and Cu(2+) was investigated using a glass bubble column reactor. Concentrations of gaseous Hg(0) and aqueous Hg(2+) were measured by cold vapor generation atomic absorption spectrometry (CVAAS). The effects of several experimental parameters on the oxidation were studied; these include different types of catalysts, pHs and concentrations of potassium persulfate, temperatures, Hg(0) inlet concentrations and tertiary butanol (TBA). The results showed that the removal efficiency of Hg(0) increased with increasing concentration of potassium persulfate and catalysts Ag(+), Cu(2+) and Ag(+) provided better catalytic effect than Cu(2+). For example, in the presence of 5.0 mmol l(-1) KPS, the mercury removal efficiency could reach 75.4 and 97.0% for an Ag(+) concentration of 0.1 and 0.3 mmol l(-1), respectively, and 69.8 and 81.9% for 0.1 and 0.3 mmol l(-1) Cu(2+). On the other hand, high temperature and the introduction of TBA negatively affect the oxidation. Furthermore, the removal efficiency of Hg(0) was much greater in neutral solution than in either acidic or alkaline solution. But the influence of pH was almost eliminated upon the addition of Ag(+) and Cu(2+), and high Hg(0) inlet concentration also has positive impact on the removal efficiency of Hg(0). The possible catalytic oxidation mechanism of gaseous mercury by KPS was also proposed.

A novel fluidized electrochemical reactor for organic pollutant abatement

To promote organic pollutant treatment efficiency by improving mass transfer, a novel fluidized electrochemical reactor that integrated advanced electrochemical oxidation process (AEOP) with activated carbon (AC) fluidization in a single cell was developed for model pollutant p-nitrophenol (PNP) abatement. Synergetic effect on COD removal was found in such a combined process and the COD removal efficiency was enhanced to be 97.8%. The combined process has been proved to be a promising abatement process for biorefractory organic pollutants degradation, which is advantageous over using either AEOP or adsorption alone. The roles of the location of AC in the cell, liquid flowrate, AC mass and initial PNP concentrations on COD removal were investigated to optimize the performance. A lumped kinetic model based on adsorption/electrocatalysis/oxidation mechanism for COD removal was proposed to predict the role of adsorption, electrocatalysis and oxidation in the combined process. The output of the kinetic model was found to be in good agreement with the experimental data obtained at various initial PNP concentrations and AC mass.

ELECTROCATALYTIC DEGRADATION OF PHENOL IN ACIDIC AND SALINE WASTEWATER

ABSTRACT The electrocatalytic degradation of low concentration of phenol (100–800 mg L−1) as a model contaminant for wastewater treatment was studied on modified β-PbO2 anode. Various affected factors such as current density (7.5–30 mA cm−2), reaction temperature (5–60°C), pH (2–6), salinity of the electrolyte (0.5–10 g L−1 K2SO4), and circulation rate (100–2400 mL min−1) were investigated. Phenol at a concentration level of 100 mg L−1 could be completely degraded within 30 min under the current density of 7.5 mA cm−2 with the addition of K2SO4 (1.0 g L−1) at pH 5.6 and temperature 60°C. The method showed promising application for treating phenolic wastewater of high salinity and acidity. Analysis of the intermediates of the phenol degradation products indicated good catalytic characteristics of the anode for breaking down the aromatic compounds to organic acids. The overall degradation of phenol was considered a controlled process of mass-transfer. According to the proposed model and Arrheniuss Law, the activation energy was calculated 23.8 kJ mol−1.

Synergetic effects of anodic–cathodic electrocatalysis for phenol degradation in the presence of iron(II)

A novel electrocatalysis method for phenol degradation was described using a beta-PbO2 anode modified with fluorine resin and a Ni-Cr-Ti alloy cathode. In case of air sparging at the cathodic zone, the techniques of anodic-cathodic electrocatalysis (ACEC) and ferrous ion catalyzed anodic-cathodic electrocatalysis (FACEC) in the presence of iron(II) were developed. Both of ACEC and FACEC were more effective than anodic electrocatalysis (AEC). The percentage of phenol eliminated by FACEC could increase by nearly 30% compared with that of AEC, and the current efficiency could reach to 70%. Important operating factors such as ferrous ion concentration, air-sparging rate and applied current were investigated and it was found that such beneficial effects could be achieved at a suitable current and ratio of the concentration of ferrous ion to the air sparged. The mechanism of phenol degradation is proposed to be the generation of hydroxyl radicals concerned with the two electrodes. Results also indicated that the process provided an efficient way to regenerate ferrous ion compared with the conventional Fentons system.

Electrocatalysis method for wastewater treatment using a novel beta-lead dioxide anode

A novel β-PbO2 anode modified with fluorine resin was developed for typical pollutant electrocatalytic degradation and wastewater treatment. Various operating parameters such as applied voltage (3.5–10.5 V), pH (2–6), salinity of the electrolyte (0.5–2 g/L K2SO4) and initial phenol concentration (100–400 mg/L) were investigated to explore the electrocatalytic ability of the anode by taking phenol as sample. A preliminary study on dyeing wastewater treatment by this method indicated that the biodegradability could be increased to suit subsequent biological treatment. The stability of the anode has been proved to be high against acidity. The anode showed promising application for treatment of wastewater, especially of high salinity and high acidity wastewater.

Ti / SnO2 – Sb Electrodes for Pollutant Degradation Prepared Using Ultrasonic Spray Pyrolysis

Antimony-doped tin oxide Ti/SnO 2 -Sb films were successfully deposited on Ti substrates by ultrasonic spray pyrolysis at 600°C. The physicochemical and electrochemical properties as well as the electrocatalytic activity of Ti/SnO 2 -Sb electrodes were investigated. It was found that the Ti/SnO 2 -Sb electrodes prepared had compact microstructure, high overpotential for O 2 evolution, and superior activity for pollutant degradation. Over 95% chemical oxygen demand removal was achieved for degradation of phenol, with current efficiency of 53% obtained.