Simultaneous reduction of Cr(VI) and degradation of tetracycline hydrochloride by a novel iron-modified rectorite composite through heterogeneous photo-Fenton processes

To develop a low-cost, efficient and environmentally benign technique for the simultaneous removal of heavy metals and organic contaminants is a great challenge in practical wastewater treatment. In this work, a novel iron-modified rectorite (Fe-R) composite was prepared via the degradation of Rhodamine B (RhB) in a Fenton-like process and used for the simultaneous degradation of tetracycline hydrochloride (TC) and reduction of Cr(VI) through heterogeneous photo-Fenton processes. The results reveal that the introduction of RhB to the rectorite could induce more iron ions into its interlayers which accelerates the decomposition of H2O2, inhibits iron leaching and enhances its electrical conductivity. The presence of TC increased the Cr(VI) reduction rate 47.4-fold in the Fe-R-2/H2O2/LED system owing to the generation of reductive intermediates which effectively reduce Cr(VI) to Cr(III), while consuming hydroxyl radicals and suppressing the reoxidation of Cr(III). The effects of various operating parameters, as well as the adaptability, reusability, stability of the catalyst and the identities of the intermediates were comprehensively investigated. This work may shed light on the design of green, efficient and recyclable heterogeneous catalysts, and advance the practical utility of heterogeneous Fenton-like process for mixed contaminants remediation.