Comparação entre Fenton e processos eletroquímicos no tratamento de efluentes contaminados com verde de malaquita

The development of fish farming is an example of technology developed to increase food production; however, this activity can cause environmental degradation.1 Fish farmers use several chemical products to pests and diseases. Although these substances do not interfere in the development of fish, many of these substances are refractory to conventional treatment of wastewater and might accumulate in receiving bodies. In the present work, we evaluated the efficiency of the Fenton reactions and electrochemical process to treat effluents from fish farming, using as model effluent a solution containing malachite green (MG). Experimental conditions: Fenton – 100 mmol L -1 H2O2 and 0.5 mmol L-1 Fe2+; electrochemical: Ti/Ru0,3Ti0,7O2 as anode, current density of 10 mA cm-2 , and 0.1 mol L-1 Na2SO4 as supporting electrolyte. Figure 1 shows the reduction of absorbance of the solutions (λmax 616 nm) under all the methods studied. The Fenton, photoFenton and sono-Fenton reactions showed excellent results, reaching 100% reduction of absorbance in 60 minutes of reaction. Using the degradation process, we observed the reduction of 62.7%, 78.4% and 85.2% of COD to Fenton, sono-Fenton and photoFenton reactions, respectively. The effluent containing MG showed high toxicity to lactuca sativa germination (GRI =0.55 and GI = 42.7%). The Fenton reaction reduced the effluent toxicity. The electrochemical process increased the effluent toxicity, probably due to the presence of the supporting electrolyte. Results indicate the following order of efficiency: Fenton < sono-Fenton < photo-Fenton.