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

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.