Abstract
In this work, the Fenton technology was applied to decolorize methylene blue (MB) and to inactivate Escherichia coli K12, used as recalcitrant compound and bacteria models respectively, in order to provide an approach into single and combinative effects of the main process variables influencing the Fenton technology. First, Box–Behnken design (BBD) was applied to evaluate and optimize the individual and interactive effects of three process parameters, namely Fe2+ concentration (6.0 × 10−4, 8.0 × 10−4 and 1.0 × 10−3 mol/L), molar ratio between H2O2 and Fe2+ (1:1, 2:1 and 3:1) and pH (3.0, 4.0 and 5.0) for Fenton technology. The responses studied in these models were the degree of MB decolorization (D%MB), rate constant of MB decolorization (kappMB) and E. coli K12 inactivation in uLog units (IuLogEC). According to the results of analysis of variances all of the proposed models were adequate with a high regression coefficient (R2 from 0.9911 to 0.9994). BBD results suggest that [H2O2]/[Fe2+] values had a significant effect only on D%MB response, [Fe2+] had a significant effect on all the responses, whereas pH had a significant effect on D%MB and IuLogEC. The optimum conditions obtained from response surface methodology for D%MB ([H2O2]/[Fe2+] = 2.9, [Fe2+] = 1.0 × 10−3 mol/L and pH = 3.2), kappMB ([H2O2]/[Fe2+] = 1.7, [Fe2+] = 1.0 × 10−3 mol/L and PH = 3.7) and IuLogEC ([H2O2]/[Fe2+] = 2.9, [Fe2+] = 7.6 × 10−4 mol/L and pH= 3.2) were in good agreement with the values predicted by the model.
Highlights
Some of the effluents produced by industries such as textiles, dyes, tanneries, cosmetics and pulp are colored [1]
The optimal conditions obtained for methylene blue (MB) decolorization and E. coli K12 inactivation are different for each of the responses studied. These results indicate that some authors have suggested that it is possible to analyze the bacteria inactivation of advanced oxidation processes (AOP) by extrapolating from dye decolorization [42], these processes have differences
The present study provided a comprehensive description regarding the application of the Fenton technology as a process for MB decolorization and E. coli K12 inactivation in aqueous solutions at different [H2 O2 ]/[Fe2+ ] values (1.0, 2.0 and 3.0), [Fe2+ ] values (6.0 × 10−4, 8.0 × 10−4 and 1.0 × 10−3 mol/L)
Summary
Some of the effluents produced by industries such as textiles, dyes, tanneries, cosmetics and pulp are colored [1]. Effluents are colored due to the presence of lignin byproducts and other phenolic compounds formed [2]. These compounds are considered dangerous and recalcitrant because of their low biodegradability and resistant to chemical degradation [1,3]. Recalcitrant compounds with biological activity contained in treated effluent discharges are generating a loss of biodiversity in ecosystems. In addition to the presence of recalcitrant compounds, the bacteria in the effluents of the pulp industry must be seriously considered. The presence of bacteria in effluents discharged to water bodies are generating humans and animals diseases
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