Abstract
The electrochemical degradation of the Reactive Red 141 dye using a filter-press reactor with a β-PbO2 anode was investigated through the application of the response surface methodology. The charge required for 90% decolorization (Q90) and the chemical oxygen demand removal percentage after 30 min electrolysis (COD30) were used to model the system. The investigated independent variables were the current density, pH, NaCl concentration, and temperature. Low values of Q90 (0.2-0.3 A h L-1) were obtained at acidic conditions (pH 1-3) and high concentrations of NaCl (1.0-2.0 g L-1), when Cl2 and HOCl are the predominant oxidant species. The best values of COD30 were obtained at high current densities and acidic to neutral conditions (pH 5-7); however, the consequent energy consumption makes the process not economically feasible under these conditions. For strongly acidic solutions, specific energy consumptions associated to Q90 as low as 0.79 kW h m-3 were attained.
Highlights
The contamination of water is one of the greatest current challenges, as it is becoming a scarce natural resource
Non-significant coefficients were excluded based on the results for each model analysis of variance (ANOVA) and the student t test
Application of Response Surface Methodology (RSM) allowed investigating a high number of variables that affect the electrochemical degradation of the Red 141 (RR 141) dye, leading to knowledge of their effects and interactions
Summary
The contamination of water is one of the greatest current challenges, as it is becoming a scarce natural resource. The textile industry, in particular, stands in a delicate position due to the large volumes of water used and wastewater produced during dyeing process steps.[1] Among the dyes used by this industry, the azo (-N=N-) ones are the most produced and consumed.[2,3] It should be noticed that a considerable amount of synthetic dyes are discharged in the environment during production. As summarized by Martinez-Huitle and Brillas,[3] biological, physico-chemical, and chemical methods, among others, are commonly used for the treatment of industrial wastewaters. All these methods have advantages and disadvantages, no current technology has universal application.[3,6,7] The biological treatment is commonly the most efficient and economic for wastewater chemical oxygen demand (COD) abatement, but is
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