Fluidized-bed Fenton-like oxidation of a textile dye using natural magnetite

Degradation of Acid Orange 7 (AO7) as a model azo dye was investigated in a recirculating pilot fluidized-bed reactor by a Fenton-like process using natural magnetite (NM) and potassium persulfate (K2S2O8). Scanning electron microscopy was performed to characterize the magnetite sample. The heterogeneous Fenton-like process (NM/S2O82-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{S}}_{2} {\text{O}}_{8}^{2 - }$$\end{document}) is a modified method owing to its enhanced mass transfer. It can be operated reliably and simply by reducing the produced iron oxide sludge in the conventional Fenton process. Degradation efficiency (DE %) of AO7 by NM/ S2O82-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{S}}_{2} {\text{O}}_{8}^{2 - }$$\end{document} process was affected by operational parameters. The DE % of 75 % was obtained for the AO7 treatment (15 mg/L) at the desired conditions, such as pH 5, 0.2 mM S2O82-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{S}}_{2} {\text{O}}_{8}^{2 - }$$\end{document}, and 0.5 g/L NM after 120 min of reaction time. The dye degradation rate in all the experiments followed the pseudo-second-order kinetic with high correlation coefficients (R2 ≥ 0.98). The low released iron concentration, successive reusability at milder pH and the recirculation mode with the proper mixing are the significant advantages of the NM/S2O82-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{S}}_{2} {\text{O}}_{8}^{2 - }$$\end{document} process.