In this study, red mud was used as a support for LaFeO3 to prepare a synergistic catalyst (LaFeO3-RM) via ultrasonic-assisted sol-gel method for the enhanced removal of methylene blue (MB) assisted with bisulfite (BS) in an aqueous solution. The Characterization of SEM and BET indicated that comparing with the non-porous structure of bulk LaFeO3, LaFeO3-RM exhibited high surface area and obvious porous structure with a higher pore volume (i.e. 10 times). XRD, XPS and FTIR revealed that in addition to dispersing LaFeO3 particles, the support of porous RM also increased Fe oxidation activity, oxygen-containing functional groups and chemically adsorbed oxygen (from 44.3% to 90.3%) of LaFeO3-RM which enhanced the catalytic performance in structure and chemical composition. MB was removed through the synergistic effect of adsorption and catalysis with MB molecule was first absorbed on the surface and then degraded. The pseudo-first-order kinetic constant of LaFeO3-RM was 6 times than that of LaFeO3. Fe(III) in LaFeO3-RM played a key role in the activation of BS to produce SO4·- by the redox cycle of Fe(III)/Fe(II). With the application of LaFeO3-RM as a promising low-cost synergistic catalyst for the activation of BS under neutral condition, this work provides a new approach of using porous industrial waste to improve the catalytic performance of LaFeO3.

All experiments were repeated three times, and the data of repeated times were averaged for use in figures and tables. The corresponding experimental errors are shown by error bars, which were within ±5%.

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