Comparative Performance of Bio-Derived Nanomaterials for Chromium Removal From Contaminated Water

This study evaluated the efficiency of biosynthesized nanoparticles (NPs) derived from moringa seed waste (MSW-NPs), pomegranate peel (PP-NPs), sawdust (SD-NPs), and their combinations for the removal of hexavalent chromium from contaminated water. The NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX) analyses, revealing predominantly amorphous structures, highly porous morphologies, nanoscale particle sizes, and abundant surface functional groups favorable for adsorption. Batch adsorption experiments demonstrated that Cr sorption followed the Langmuir model, with MSW-NPs exhibiting the highest maximum adsorption capacity (q_max = 88.22 mg/g). Fourier-transform infrared spectroscopy (FTIR) analyses confirmed biomass-specific binding mechanisms, where MSW-NPs interacted mainly through amino and carboxyl groups, while PP- and SD-based NPs relied on oxygen-containing functional groups for surface complexation. Column experiments further verified the strong performance of these materials under continuous-flow conditions, with removal efficiencies ranging from 96% to 100%. MSW-NPs achieved complete Cr removal with minimal effluent chromium concentration, while combinations of NPs (MSW/PP, MSW/SD, and PP/SD) provided enhanced structural stability and synergistic adsorption behavior. The findings highlight that these green-synthesized NPs are low-cost, environmentally sustainable, and highly effective nano-biosorbents for Cr remediation. Their strong adsorption performance and operational stability make them promising candidates for practical wastewater treatment applications and scalable environmental remediation technologies.