Bifunctional Co0.75Fe0.25@C nanocomposite towards zero waste approach: Organic pollutants removal and OER electrocatalysis

Abstract

Bagasse-derived value-added products have received immense importance recently due to their eco-friendly nature. Here, we report the synthesis of magnetic nanocomposites with a zero-waste approach for organic pollutant removal and oxygen evolution reaction. The nanocomposite was synthesized by carbonization of Co2+ -Fe3+ metal ions soaked bagasse at optimized conditions. The nanocomposite was characterized using FE-SEM, HR-TEM, PXRD, Zeta-potential, and VSM techniques. For dye adsorption, the kinetic study is carried out at pH=3 using Pseudo-first order (PFO), Pseudo-second order (PSO), Elovich, and intraparticle-diffusion models, and an isotherm study is carried out using Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin adsorption isotherm models. The nanocomposite exhibited an impressive adsorbent property for organic dyes (90-96% removal), pharmaceutical drug (paracetamol, 84% removal), and 'hair dye' (95% removal). Maximum adsorption capacities (q<inf>m</inf>) for Methyl Orange, Congo Red, and Amido Black dye are 1103.0mg/g, 1254.0, and 877.2mg/g, respectively. Thermodynamic data gives negative ΔG, showing a spontaneous adsorption process. The nanocomposite recyclability demonstrates the practical benefits of the material for water remediation. Interestingly, after the adsorption, the generated secondary waste (exhausted dye adsorbed nanocomposite) was employed as an electrocatalyst for the oxygen evolution reaction (OER). The dye-adsorbed nanocomposite shows good OER activity in an alkaline medium (0.1M, KOH) with an overpotential of 268mV at 10mA/cm2. Tafel slope value observed for CFC is 83mV/dec, and CFC-dye ads is 90mV/dec. The nanocomposite exhibited operational stability up to 30h. The study shed light on a zero-waste approach for developing efficient OER electrocatalysts by reusing spent nanocomposites after adsorption. © 2025 Elsevier B.V., All rights reserved.