Dynamic adsorption of toxic indigo carmine dye on bio-inspired synthesised Fe₃O₄ nanoparticles: kinetic and thermodynamic study

The bio-inspired synthesis of Fe₃O₄ nanoparticles using a common kitchen waste, Bengal gram bean (Cicer arietinum L.) extract (BGBE) for enhanced adsorption of toxic indigo carmine dye is reported. Synthesised adsorbent was characterised by FTIR, FE-SEM, XRD, BET and XPS to understand its meticulous properties. The Fe₃O₄ adsorbent shows fascinating surface area of 78.61 m² g⁻¹ with a pore volume of 0.25 cc g⁻¹ at P/P₀ = 0.98 and displayed nanograin like morphology. The efficiency towards adsorption of toxic IC dye was found up to 99.71 ± 0.35% within 40 min at pH 7 with 0.25 g of Fe₃O₄ nanomaterials having the 299 ± 2 K surrounding temperature. The Langmuir monolayer adsorption capacity was found to 393.7 mg g⁻¹ at the stroke speed 150 rpm. The experimental data follows the Freundlich adsorption isotherm. Kinetically the uptake rate of IC dye follows pseudo-second-order kinetic model. The thermodynamic study reveals that IC dye adsorption process is spontaneous and endothermic in nature.