Valorization of Brassica juncea waste into iron oxide nanoparticles for efficient hexavalent chromium [Cr(VI)]...

Hexavalent chromium [Cr(VI)] has emerged as a significant environmental pollutant because of its toxicity and long-term persistence. As a result, remediation of Cr(VI) is urgently needed to save the ecosystem and human health. There are several traditional remediation methods that are not sustainable. Therefore, the current work explores the green synthesis of iron oxide nanoparticles (BJ-IONPs) derived from Mustard (Brassica juncea) waste. The synthesized BJ-IONPs were characterized using X-ray Diffraction (XRD), Differential Scanning Calorimetry - Thermogravimetric Analysis (DSC-TGA), Fourier Transform Infrared Spectroscopy (FTIR), Zeta Potential, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM) techniques for the surface morphology, physical charge, and particle size. Additionally, batch studies were conducted to evaluate the efficiency of synthesized nanoparticles for Cr(VI) remediation by varying the pH, temperature, initial Cr(VI) concentration, adsorbent dose, and contact time. Following the experiments, maximum adsorption i.e. 99.66% (3.83 mg g⁻¹) was achieved at a pH of 4.24 and a temperature of 40 °C with an adsorbent dose of 2.6 g L⁻¹ for 10 mg L⁻¹ Cr(VI). The process of adsorption was best reported by the Elovich and Intraparticle Diffusion (IPD) models and showed good agreement with the Freundlich isotherm. Apart from this, this study also developed an Artificial Neural Network (ANN) model to validate the experimental data and predict the rate of adsorption beyond the environment of lab setting. With a correlation coefficient (R²) of 0.9564, the model showed a remarkable prediction capacity, verifying the accuracy of the adsorption process simulation.