Dark-Fenton oxidative degradation of methylene blue and acid blue 29 dyes using sulfuric acid-activated slag of the steel-making process

Abstract

The pollution of water by effluents from dye industries is a widely established environmental and health problem that requires new insights and urgent attention. In this study, methylene blue (MB) and acid blue 29 (AB29) dyes were oxidatively degraded under the dark-Fenton process conditions using abundant electric arc furnace steel slag activated by sulfuric acid (S-EAF). The severity of the oxidative degradation conditions was screened under conditions at 50–150 mg/l dyes solution initial concentration, the H2O2 concentration range of 2–12 mM, and pH from 2 to 7. The results show that predominant crystalline ferrous ions on the S-EAF catalyst stimulated the decomposition of the H2O2, to enhance the generation of •OH radicals, which promoted oxidation of the dyes to realize 95% and 82% removal under 6 mM (AB29), and 8 mM (MB) H2O2 concentration at 30 °C. The pseudo-first-order kinetic sufficiently described the experimental data and application of the Langmuir-Hinshelwood model validated the dominant role of surface reaction, which was collaborated by the activation energy. The S-EAF catalyst sustained the oxidative degradation for seven cycles with minor leaching of irons (Fe).