Green synthesis of red mud based ZnO-Fe2O3 composite used for photo-Fenton reaction under visible light

In this work, using solid waste red mud (RM) as main raw material and without addition of chemical reagents of alkali and ferric salt, a new method of flocculation-calcination was introduced as a green and facile process to produce RM based ZnO-Fe2O3 composite (RM-C) which can be used as a catalyst for photo-Fenton reaction under visible light. The prepared catalyst was characterized by SEM, EDS, XRD, BET, UV-Vis DRS and XPS. The characterization results showed the iron phase in RM-C was mainly alpha-Fe2O3, and ZnO formed in RM-C was amorphous and highly dispersed. RM-C showed a good response to the visible light, and the order of absorbance in 373-542 nm was RM-C > RM > ZnO. RM-C had an excellent long-term stability in the photo-Fenton process. The possible mechanisms in photo-Fenton system catalyzed by RM-C under visible light were presented. Using RM-C as catalyst, the toxicity of Orange II was greatly weakened by the photon-Fenton system under visible light. The method of flocculation-calcination was a green and feasible process for the preparation of RM-C, and the prepared RM-C was an effective composite catalyst for the photon-Fenton reaction under visible light. (C) 2018 Elsevier Ltd. All rights reserved.