Photo-assisted electrochemical degradation of the commercial herbicide atrazine.

This paper presents a degradation study of the pesticide atrazine using photo-assisted electrochemical methods at a dimensionally stable anode (DSA(®)) of nominal composition Ti/Ru(0.3)Ti(0.7)O(2) in a prototype reactor. The effects of current density, electrolyte flow-rate, as well as the use of different atrazine concentrations are reported. The results indicate that the energy consumption is substantially reduced for the combined photochemical and electrochemical processes when compared to the isolated systems. It is observed that complete atrazine removal is achieved at low current densities when using the combined method, thus reducing the energy required to operate the electrochemical system. The results also include the investigation of the phytotoxicity of the treated solutions.

Photoassisted electrochemical degradation of organic pollutants on a DSA type oxide electrode: process test for a phenol synthetic solution and its application for the E1 bleach Kraft mill effluent.

In this paper, the performance of a photoassisted electrolysis process, for the degradation of organic pollutants, is investigated. Results obtained in this work have shown that the thermally prepared anode of titanium, coated with 70TiO2/30RuO2, exhibits photoactivity and may be used for the treatment of effluents. A synthetic phenol aqueous solution and a real paper mill industry effluent were treated. Kinetic analysis showed a synergetic effect of electrolysis and photocatalysis and degradation rates are an order of magnitude greater than the sum of the results reached by using both processes individually. Using a 125 W mercury bulb and 20 mA cm-2, the phenol concentration decayed 85% in 90 min and 70% reduction of TOC was obtained. In the application of the treatment process for the degradation of the E1 bleach Kraft mill effluent, total phenols were practically eliminated in a short period of processing time, and color, usually resistant to biological treatment, was reduced to 10% from its initial value measured in terms of absorbance. Reductions of AOX, COD, and BOD by 25%, 30%, and 35%, respectively, were also observed.

Preconcentration and Voltammetric Determination of Mercury(II) at a Chemically Modified Glassy Carbon Electrode.

In this work, the organic compound 2-mercaptobenzimidazole was covalently bound on the surface of a glassy carbon rod, via silanization, yielding a material capable of selectively complexing Hg(2+) ions. This material was applied as an electrode for voltammetric determination of mercury(II) following its nonelectrolytic preconcentration. After exchanging the medium, the voltammetric measurements were carried out by anodic stripping in the differential pulse mode (pulse amplitude, 50 mV; scan rate, 1.25 mV s(-)(1)) using 10(-)(2) mol L(-)(1) NaSCN solution as supporting electrolyte. An anodic stripping peak was obtained at 0.06 V (vs SCE) by scanning the potential from -0.3 to +0.3 V. After a 5 min preconcentration period in a pH 4.0 Hg(2+) solution, this electrode shows increasing voltammetric response in the range 0.1-2.2 µg mL(-)(1), with a relative standard deviation of 5% and a practical detection limit of 0.1 µg mL(-)(1) (5.0 × 10(-)(7) mol dm(-)(3)). Compared with the conventional stripping approach, this chemically modified glassy carbon electrode procedure presented good discrimination against interference from Cu(II) in up to 10-fold molar excess.