Novel red mud-based FeS2 composite used as an effective heterogeneous catalyst for the degradation of levofloxacin: Preparation, application and degradation mechanism

•A novel red mud-based catalyst of RM-FeS2 is prepared by simple one-step calcination.•Internal cause for the strong activation of PMS by RM-FeS2 has been revealed.•RM-FeS2/PMS system has a wide working pH range for efficient degradation of LVF.•The LVF degradation in RM-FeS2/PMS system follows non-radical oxidation mechanism.•The primary ROS including Fe(Ⅳ) and 1O2 for LVF degradation are confirmed. Red mud (RM), as industrial waste, was considered as the base material in this study. A heterogeneous catalyst of RM based-FeS2 (RM-FeS2) was prepared using a simple one-step calcination method. RM-FeS2, as an effective activator of peroxymonosulfate (PMS), was utilized in the levofloxacin (LVF) degradation progress. The effect of the preparation conditions on crystal structure and catalytic activity of RM-FeS2 was investigated. The systematic characterizations indicated that the surface area, electrical conductivity and the number of Fe(II) sites of RM were improved after compounding with FeS2. According to the investigation of catalytic performance of RM-FeS2, approximately 87 % of LVF (10 mg/L) was degraded in 60 min with the reaction conditions: [RM-FeS2] = 0.2 g/L, [PMS] = 1 mmol/L and initial pH of 6.2. The RM-FeS2 possessed excellent stability and reusability. ·OH, SO4•−, 1O2 and Fe(Ⅳ) were the dominant active species in RM-FeS2/PMS system. Several possible degradation pathways of LVF were proposed. The toxicity of the treated LVF solution was effectively reduced in the RM-FeS2/PMS system. In a word, this study not only realized the resource utilization of RM, but also presented a novel perspective for the effective degradation of organic pollutants in wastewater. [Display omitted]