Activation of bisulfite by LaFeO3 loaded on red mud for degradation of organic dye

Abstract

In this study, red mud (RM) was used as a support for LaFeO3 to prepare LaFeO3-RM via the ultrasonic-assisted sol–gel method for the removal of methylene blue (MB) assisted with bisulfite (BS) in the aqueous solution. Characterization by scanning electron microscopy and the Brunauer–Emmett–Teller method indicated that LaFeO3-RM exhibited a large surface area and porous structure with a higher pore volume (i.e. 10 times) compared with the bulk LaFeO3. The XRD, XPS and FTIR results revealed that the support of porous RM not only dispersed LaFeO3 particles but also increased Fe oxidation capability, oxygen-containing functional groups and chemically adsorbed oxygen (from 44.3% to 90.3%) of LaFeO3-RM, which improved the catalytic performance in structure and chemical composition. MB was removed through the synergistic effect of adsorption and catalysis, with MB molecules first absorbed on the surface and then degraded. The removal efficiency was 88.19% in the LaFeO3-RM/BS system under neutral conditions but only 27.09% in the LaFeO3/BS system. The pseudo-first-order kinetic constant of LaFeO3-RM was six times higher than that of LaFeO3. Fe(III) in LaFeO3-RM played a key role in the activation of BS to produce [Formula: see text] by the redox cycle of Fe(III)/Fe(II). Dissolved oxygen was an essential factor for the generation of [Formula: see text]. This work provides both a new approach for using porous industrial waste to improve the catalytic performance of LaFeO3 and guidance for resource utilization of RM in wastewater treatment.

Keywords

• red mud
• perovskite
• sulfate radical
• fenton-like
• dyes
• waste utilization