Uso do resíduo siderúrgico na adsorção e peroxidação catalítica de surfactante aniônico

Abstract

The purpose of this study is to evaluate the application of a siderurgical waste in adsorption and catalytic wet peroxide oxidation of an anionic surfactant used in textile industry. The waste tested in this research was a fine powder from blast furnace unit, which presents high carbon and iron content. The mechanism of adsorption of the surfactant onto the waste was investigated and the experimental data were analyzed by the Langmuir and Freundlich adsorption isotherms. The capacity adsorption of the siderurgical waste at the equilibrium followed the Freundlich model of adsorption. The rates of adsorption showed a good correlation with the pseudo-second order kinetics. In this research four alternative processes were discussed: Fenton homogenous using ferrous sulfate and the iron leached from siderurgical waste to the liquid phase, Fenton heterogeneous and the combination of treatments: Fenton - adsorption. The evaluation of the treatments effects was based on factorial experiment design, in which the response variables were the maximum reduction in the chemical oxygen demand (COD), the total organic carbon (TOC) and the minimum concentration of residual hydrogen peroxide in the surfactant treated by these different processes. Results indicated as the best alternative to degrade of surfactant, the combination of treatments Fenton - adsorption, with reduction of COD and TOC of 80% and 75% respectively. The optimal conditions were: [H2O2] = 750 mg/L, [Fe2+] = 500 mg/L. The pH did not affect the reaction. Results obtained with Fenton homogeneous of iron leached, reached a maximum reduction of 46% of COD e 31% of TOC. A application of waste as heterogeneous catalysis for Fenton reaction was not possible. The Fenton reaction followed the pseudo-second order kinetic model. The practical use of the siderurgical waste was promising, as adsorbent and was not as catalysis in catalytic wet oxidation.