Electro-enhanced goethite activation of peroxydisulfate for the decolorization of Orange II at neutral pH: Efficiency, stability and mechanism

The decolorization of Orange II by an electro-enhanced goethite (α-FeOOH) activating peroxydisulfate (PDS) process (EC/α-FeOOH/PDS process) is reported in this study. Sulfate radicals was produced by activating PDS with Fe(II), which was generated continuously from the cathodic reduction of Fe(III) on α-FeOOH surface. The decolorization of Orange II showed little dependence on the initial pH. The comparison of Orange II decolorization under different systems was investigated. The surface properties of α-FeOOH before and after reaction were investigated by X-ray Photoelectron Spectroscopy (XPS). The radical species generated in EC/α-FeOOH/PDS process were determined by Electron Paramagnetic Resonance (EPR). On the basis of the results, the mechanism of Orange II decolorization in EC/α-FeOOH /PDS process was proposed. The catalyst α-FeOOH maintained its high activity during repeated batch experiments. Response surface methodology (RSM) based on Box–Behnken statistical experiment design (BBD) was applied to analyze the experimental variables. The response surface methodology models were derived from the experimental results and the response surface plots of the pseudo-first-order decolorization rate constant were developed accordingly.