Acceleration of Persulfate Activation by MIL-101(Fe) with Vacuum Thermal Activation: Effect of FeII/FeIII Mixed-Valence Center

Jieyang Yang,Yan Cui,Zhanggen Huang,Zequan Zeng

doi:10.3390/catal9110906

Abstract

In this work, the activation effect of vacuum thermal treatment on MIL-101(Fe) (MIL: Materials of Institute Lavoisier) was investigated for the first time. It demonstrated that vacuum thermal activation could accelerate the activation of persulfate (PS) by MIL-101(Fe), and the enhancement of the catalytic capacity of MIL-101(Fe) was mainly attributed to the change in the FeII/FeIII mixed-valence center. The results of the SEM and XRD showed that vacuum thermal activation had a negligible effect on the crystal structure and particle morphology of MIL-101(Fe). Meanwhile, the higher temperature of vacuum thermal activation caused a higher relative content ratio of FeII/FeIII. A widely used azo dye, X-3B, was chosen as the probe molecule to investigate the catalytic performance of all samples. The results showed that the activated samples could remove X-3B more effectively, and the sample activated at 150 °C without regeneration could effectively activate PS to remove X-3B for at least 5 runs and approximately 900 min. This work highlights the often-overlooked activation effect of vacuum thermal treatment and provides a simple way to improve the catalytic capacity and reusability of MIL-101(Fe) which is beneficial for the application of MIL-101(Fe)/PS systems in azo dye wastewater treatment.

Highlights

Effluents of textile industries, pulp mills, and dyestuff manufacturing are known to contain considerable colors which are caused by dyes
The as-prepared MIL-101(Fe) and the samples activated at different temperatures of vacuum thermal activation were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron photoelectron spectroscopy spectroscopy (XPS)
The catalytic capacity for PS activation was investigated through X-3B removal experiments

Summary

Introduction

Pulp mills, and dyestuff manufacturing are known to contain considerable colors which are caused by dyes. Among these dyes, azo dyes constitute the largest and the most important class of commercial dyes [1,2]. Advanced oxidation processes (AOPs) have proved to be economical and efficient in treating dye effluents and producing high-quality water [6,7]. Sulfate radical-based AOPs have been regarded as effective technologies for degradation of recalcitrant organic contaminants and received considerable attention for destruction of azo dye compounds [8,9,10]. The Fe/PS system has some intrinsic drawbacks, such as strict pH range limits and accumulation of ferric oxide sludge, which limit its widespread application [16,17,18]

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