Red mud-derived functional materials for sustainable water treatment applications

Abstract

Red mud (RM), a major byproduct of the Bayer process in alumina production, poses significant environmental challenges due to its large volume, high alkalinity, and potential contamination risks. Nevertheless, its abundant iron content provides an attractive opportunity for the synthesis of value-added functional materials. In this study, RM was valorized as an iron source for the preparation of Prussian Blue (PB), which was subsequently immobilized within a carboxymethyl cellulose (CMC) hydrogel matrix to fabricate a sustainable PB/CMC composite for norfloxacin (NFX) removal from aqueous solutions. The synthesized material was comprehensively characterized using SEM–EDS, XRD, FTIR, and BET analyses. The results confirmed the successful formation of PB with a well-defined crystalline structure, uniform elemental distribution, and mesoporous characteristics. Batch experiments demonstrated that the PB/CMC hydrogel achieved more than 90% NFX removal at initial concentrations of 10–30 mg L−1 under optimized conditions (2 wt% PB, 120 min). Compared with raw red mud, the PB-based composite exhibited enhanced catalytic performance owing to the highly ordered Fe(II)/Fe(III) redox framework, which facilitated H2O2 activation and heterogeneous Fenton-like degradation. Furthermore, immobilization within the CMC hydrogel improved catalyst stability and handling. This work demonstrates a sustainable waste-to-resource strategy for transforming red mud into functional hydrogel catalysts, providing a promising approach for antibiotic wastewater treatment and circular economy applications.