Synthesis of Rectorite/Fe3O4/ZnO Composites and Their Application for the Removal of Methylene Blue Dye

Huanhuan Wang,Yunfei Yuan,Yifei Wang,Rui Guo,Hongju Zhan,Peijiang Zhou

doi:10.3390/catal8030107

Abstract

A novel series of rectorite-based magnetic zinc oxide (ZnO) photocatalysts (REC/Fe3O4/ZnO) was synthesized and characterized in the present work. The fabricated REC/Fe3O4/ZnO composite possessed a high specific surface area and high capacity of adsorption and photocatalysis toward methylene blue (MB) dye. The adsorption isotherm of the dye on the composite fitted well to the Langmuir model, with a maximum adsorption of 35.1 mg/g. The high adsorption capacity increased the interactions between the dye and the REC/Fe3O4/ZnO, which enabled efficient decomposition of the dye under simulated solar radiation using REC/Fe3O4/ZnO as the photocatalyst. The degradation kinetics of MB dye followed the Langmuir–Hinshelwood model. More importantly, the degradation of MB dye and the mass loss of REC/Fe3O4/ZnO after three repetitive experiments were quite small. This suggests that the magnetic composite has great potential as an effective, stable, and easily recovered catalyst. Four major intermediates were detected during the degradation of MB dye and the degradation pathway was proposed.

Highlights

Synthetic dyes are used in a wide range of industries, including textiles, cosmetics, printing, pharmaceuticals, and food
The morphologies of the various REC/Fe3 O4 /zinc oxide (ZnO) composites were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) (Figure 1)
The rate constant kobs increased from 0.011 to 0.019 min−1 as the solution pH increased from 5.0 to 6.0, and decreased to 0.0076 min−1 at pH 8.0. These findings demonstrated that the solution pH had variable effect on the adsorption and degradation process of methylene blue (MB) dye on REC/Fe3O4/ZnO

Summary

Introduction

Synthetic dyes are used in a wide range of industries, including textiles, cosmetics, printing, pharmaceuticals, and food. Of these dyes, approximately 1–2% and 1–10%, are discharged into the environment by manufacturing processes and end-users, respectively [1,2,3,4,5], which poses a serious threat to human health and the environment. Chemical and biological techniques have been used to treat dyestuff waste, but the high cost, formation of hazardous coproducts, and intensive energy requirements have limited their extensive application [6]. Traditional wastewater treatment processes are inefficient in handling dye pollutants because of their biological resistance and chemical stability [7,8,9]. Direct reaction between valence-band holes and organic pollutants could induce oxidation or decomposition of these target

Methods

Results

Conclusion