Abstract
We modified and evaluated the performance of a CuO/Cu electrochemical electrode for chemical oxygen demand (COD) determination by covering it with a Nafion (Nf) film. The resulting modified CuONf/Cu electrode sensor was used for the electrochemical determination of COD in river, slaughterhouse and estuarine water samples in order to evaluate its performance for this particular task. It was compared with the CuO/Cu sensor with no Nafion. The main electrochemical characteristics of interest, resistance, sensitivity, accuracy and reproducibility, were assessed by means of Linear Sweep Voltammetry using glucose as a standard. Results of these essays indicate that the procedure used produced smooth and firmly attached Nf films covering the whole copper surface. This sensor was shown to be resistant to interferences and effective in electro-oxidation of a wide range of organic compounds and therefore very useful for COD determination. Using the newly developed CuONf/Cu electrode an analytical linear range of 50 to 1000 mg·L−1 COD, with a detection limit of 2.11 mg·L−1 (n = 6) COD was achieved. The comparison shows that the CuONf/Cu sensor is more appropriate for COD determination than its counterpart with no Nafion.
Highlights
Oxygen, even though it is barely soluble in water, is an essential element for preserving aquatic life
A number of metals in alkaline media can electrocatalytically oxidize a wide range of organic compounds
We chose Cu as the substrate of our electrodes due to its demonstrated capability as an electrocatalyst for oxidation of the major organic contaminants contributing to chemical oxygen demand (COD) in water systems, as already mentioned [9]
Summary
Even though it is barely soluble in water, is an essential element for preserving aquatic life. Organic contaminants which consume oxygen during their decomposition could affect, in a fast and direct way, the survival of these ecosystems. The extent of organic contamination which could consume oxygen in aqueous systems could be evaluated by measuring their chemical oxygen demand, COD. This is one of the most important parameters to take into consideration when monitoring surface water quality in lakes, rivers or wastewater. COD values represent the amount of oxygen, mg·L−1 , consumed in the oxidation process of organic contaminants by oxidant reagents such as O2 , Cr2 O7 −2 , MnO4 − and Ce4+ [1,2]
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