Ambient aqueous remediation for methyl orange-Cr(VI) hybrid wastewater using zero-valent iron loaded biochar

Water pollution caused by the coexistence of organic dyes and heavy metals remains a critical environmental challenge, calling for sustainable and cost-effective remediation strategies. In this work, nZVI/BC composites were prepared by a one-step in situ reduction method utilizing luffa sponge biochar as a carrier for the treatment of blended wastewater with methyl orange (MO) and Cr(VI). The results indicated that the carrier biochar effectively mitigated the agglomeration of nZVI and improved the removal performance of the material. Under the optimal conditions of 1 g L^-1 and pH = 5, the removal rates of MO and Cr(VI) by nZVI/BC could reach 96.9% and 91.4%. XPS analysis revealed that the removal mechanism of MO and Cr(VI) by nZVI/BC included adsorption, reduction, and co-precipitation. Molecular dynamics simulations further elucidated the stable interactions between pollutant molecules and the nZVI/BC surface. The adsorption behavior was well described by the pseudo-second order adsorption kinetic model and the Freundlich adsorption model. The nZVI/BC exhibits acceptable recyclability and moderate operational stability. Furthermore, life cycle assessment further highlights the environmental performance of nZVI/BC, underscoring its promise as a scalable and sustainable solution for hybrid wastewater remediation.