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ABSTRACT:
A highly active electrocatalytic electrode for nitrate reduction was prepared by the electro-deposition of palladium onto a copper electrode. The capacity of nitrate reduction by a palladium-modified copper electrode has been studied using cyclic voltammetry (CV). The existence of a reduction peak at -0.605 V versus saturated calomel electrode in 0.1-M sodium nitrate + 0.1-M perchloric acid solution (pH = 0.86) can be found in the CV measurement. The influence of solution properties, such as pH, nitrate concentration, and other anions in solution, on nitrate reduction was determined in detail. Results showed that nitrate reduction was suppressed in alkaline solution, while it was beneficial to nitrate reduction in acid or neutral solution. At low nitrate concentrations (0.01 to 0.5 M), nitrate reduction current increased with increasing nitrate concentration, but was hindered by sulfate. At high nitrate concentrations (1 to 5 M), no significant difference on nitrate reduction was observed. Compared with other different electrodes prepared in our work (copper, titanium, and palladium-modified titanium electrodes), the palladium-modified copper electrode showed the highest electrocatalytic capacity and stability in the nitrate-reduction process. Water Environ. Res., 78, 724 (2006).
KEYWORDS: nitrate reduction, electrocatalysis, palladium-modified copper electrode, water treatment.
doi:10.2175/106143006X110665
(ProQuest Information and Learning: ... denotes formulae omitted.)
Introduction
Increasing nitrate pollution in water has stimulated intensive research on the denitrification of drinking water, because nitrate causes serious health risks (Super et al., 1981). The toxicity of nitrate for human beings is a result of the body's reduction of nitrate to nitrite, responsible for Blue Baby Syndrome and a precursor to carcinogenic nitrosamines and other N-nitroso compounds (Pintar, 2003).
In this respect, there are many useful methods for the reduction of nitrate. Available physical-chemical processes for nitrate separation include ion-exchange, reverse osmosis, and electrodialysis (Kapoor and Viraraghavan, 1997). In these processes, nitrate ions are concentrated in secondary waste streams that must be treated and, thus, result in high process costs. Biodenitrification (Flere et al., 1999; Rittmann and Huck, 1989) is currently the most promising technique to solve the nitrate problem. The main reasons for the slow transfer of technology to drinking water purification are possible bacterial contamination, the presence of residual organics, and the possible increase in chlorine demand in purified water (Kapoor and Viraraghavan, 1997). Chemical reduction...