Activation of bisulfite by LaFeO 3 loaded on red mud for degradation of organic dye

Abstract

In this study, red mud (RM) was used as a support for LaFeO 3 to prepare LaFeO 3 -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 LaFeO 3 -RM exhibited a large surface area and porous structure with a higher pore volume (i.e. 10 times) compared with the bulk LaFeO 3 . The XRD, XPS and FTIR results revealed that the support of porous RM not only dispersed LaFeO 3 particles but also increased Fe oxidation capability, oxygen-containing functional groups and chemically adsorbed oxygen (from 44.3% to 90.3%) of LaFeO 3 -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 LaFeO 3 -RM/BS system under neutral conditions but only 27.09% in the LaFeO 3 /BS system. The pseudo-first-order kinetic constant of LaFeO 3 -RM was six times higher than that of LaFeO 3 . Fe(III) in LaFeO 3 -RM played a key role in the activation of BS to produce SO 4 ⋅ − by the redox cycle of Fe(III)/Fe(II). Dissolved oxygen was an essential factor for the generation of SO 4 ⋅ − . This work provides both a new approach for using porous industrial waste to improve the catalytic performance of LaFeO 3 and guidance for resource utilization of RM in wastewater treatment.