Highly Dispersed Magnetite Nanoparticles on Biochar with Sulfonation Modification for Simultaneous Removal of Arsenite and Tetracycline from Aqueous Solutions: Performance and Mechanistic Insight

The remediation of combined pollution of heavy metals and antibiotics in an aqueous environment remains challenging. Through magnetite (Fe3O4) dispersion followed by sulfonation modification, we report a novel bifunctional biochar-based composite (labeled Fe3O4@BC-SO3H) for simultaneous removal of arsenite (As(III)) and tetracycline (TC) in aqueous solutions. Batch experiments in single-solute systems show that Fe3O4@BC-SO3H exhibits faster kinetic and higher adsorption capacity than raw biochar, Fe3O4, and magnetite-dispersed biochar (Fe3O4@BC), thus leading to enhanced removal efficiency for either As(III) or TC. More notably, Fe3O4@BC-SO3H can simultaneously remove above 85% of As(III) and TC compared with less than 50% removal of As(III) and TC by biochar, Fe3O4, and Fe3O4@BC. Combining the spectroscopic analyses, the co-removal process of As(III) and TC indicates a unique mechanism with two-stage reactions, which involves As(III) redox transformation in the first stage and TC adsorption in the second stage. This study proposes a new strategy to design biochar-based composites for the decontamination of As(III) and TC. Overall, the excellent performance and stability of Fe3O4@BC-SO3H show its substantial potential as a low-cost, highly efficient, and eco-friendly material for the remediation of combined pollution in water.

Automated summary

We report a novel bifunctional biochar-based composite (labeled Fe3O4@BC-SO3H) for simultaneous removal of arsenite (As(III)) and tetracycline (TC) in aqueous solutions. The composite exhibit faster kinetic and higher adsorption capacity, leading to enhanced removal efficiency. The co-removal process involves two-stage reactions, including As(III) redox transformation and TC adsorption. This study proposes a new strategy for designing biochar-based composites for the decontamination of As(III) and TC.