Influência de íons cloreto na degradação eletroquímica de efluente têxtil

Abstract

The advanced oxidation processes stand out amongst other methods of degradation through the process of photoelectrocatalysis. The present study aimed to evaluate the influence of chloride ions on photoassisted electrochemical degradation of reactive dyes, byproducts and simulated effluents of textile industry, the evaluation of the efficiency of the process through the analysis of chemical oxygen demand (COD) and total organic carbon (TOC) and of the presence of organochlorine products which could have eventually been generated during the treatment employed. Materials used included an electrochemical cell with a Ti/Ru0,3Ti0,7O2 anode (De Nora Brazil), two Ti counter electrodes, standard hydrogen electrode and ultraviolet PenRay® (UVP LLC). It was evaluated the effect of electric current and concentration of supporting electrolyte on the generation of free chlorine species (FCS) in 90 minutes of experiment. Concentrations of 0.2 and 0.3 M NaCl produced similar concentrations of FCS. The behavior of production could be divided in two definite moments. In the first moment, until 30 minutes of electrolysis, production tends to grow. After 30 minutes, the behavior varied according to concentration of salts (descending or slightly ascending behavior). Under UV irradiation, it was obtained a lower production of FCS. Photo-assisted electrochemical degradation was more efficient to remove COD and COT than the one not photo-assisted. It was observed during and after the degradation experiment, absorbance peaks on 290 nm. Such peaks were higher on the irradiated treatment of 90 minutes, decreasing notably after 300 minutes of irradiated treatment. This peak could refer to the absorbance of hypochlorite or chlorinated products.