Study of the Influence of the Operational Parameters on the Photo-Electro-Fenton Performance of an Industrial Waste-Water Treatment Prototype

Abstract

A design of experiments (DOE) was used to characterize the influence of the operational parameters of an industrial prototype for waste-water treatment that was designed and built to operate using the Photo-Electro-Fenton technology. Since the approach under study is based on the photo-assisted Fenton reaction, which in turn is based on the production of hydroxyl radical species via electro-generated hydrogen peroxide (H2O2) and iron ions (Fe2+), the reaction was carried out in a prototype conceived in two reactor chambers. While in the first chamber hydrogen peroxide (H2O2) is produced via oxygen reduction using carbon cloth electrodes, the aqueous solution passes to a second chamber containing an iron-loaded resin in which a UV lamp promotes not only the oxidant species production but also iron reduction. The performance of the industrial prototype was followed by the absorbance decrease of a commercial dye aqueous solution ( (4-(2-Hydroxy-1-naphthylazo) benzene sulfonic acid, sodium salt, ≥98.0%) considering the applied current, the amount of iron-loaded resin, the flow rate and the pH as the operational variables to be characterized and eventually optimized for the operation of the prototype. In this way, a 24 factorial design was considered with two levels for each variable, central points and duplicate and randomized experiments. Variable interactions from the DOE were assessed using variance analysis and parameter estimation (ANOVA) using the statistical software JMP 7.0.2, SAS Institute Incorporated. The results revealed that the interactions for which the Prob >ltl being 0.05 or less are those corresponding to pH, resin and the pH-current-resin interaction parameters. From this information and the corresponding analysis it was possible to obtain an empirical equation that describes the reactor´s performance, along with a series of surface response curves that provide information on the relationship of the different operational variables that control the generation of oxidant species and the performance of the prototype under study.