Eichhornia crassipes Biochar Support Nano‐Zero‐Valent Iron for Cr (VI) Removal by Adsorption and Reduction From Real and Synthetic Wastewater

Eichhornia crassipes , an invasive aquatic plant, disrupts ecosystems by promoting eutrophication and damaging waterbodies. In this study, E. crassipes biomass was utilized for the synthesis of nano‐sized zerovalent iron (ZVI) biochar for hexavalent chromium (Cr(VI)) removal from wastewater through a reduction–adsorption mechanism. The modified biochar (MB) was synthesized through a one‐step carbothermal process by mixing biomass with FeCl 3 during pyrolysis. The ZVI‐MB behaves as a strong reductant, donating electrons to reduce Cr(VI) to Cr(III) under acidic conditions, with pH levels of 3.5 for MB and 2 for PB. Furthermore, the MB porous structure and functional groups facilitate Cr(III) adsorption through electrostatic attraction and complexation. Langmuir and Temkin isotherms better fit MB, indicating monolayer adsorption with chemical interactions, while PB followed the Freundlich isotherm, suggesting multilayer adsorption. Both showed pseudo‐second‐order kinetics, confirming chemisorption. This ZVI biochar using E. crassipes offers a cost‐effective and sustainable solution, with its nanoscale structure and dual reduction–adsorption reduction‐adsorption mechanism enabling efficient Cr (VI) reduction and removal.