Synthesis and evaluation of a highly reusable MIL-101(Fe)/biochar adsorbent for efficient ammonium removal: Kinetic, isotherm, and thermodynamic insights

The remediation of ammonium contaminated water demands the development of high-performance and cost-effective adsorbents. Herein, we report the successful synthesis of a novel composite material, MIL-101(Fe)/biochar, produced through a simple, environmentally friendly combination of hydrothermal treatment and pyrolysis, and evaluate its efficacy for NH 4 + removal. Characterization confirmed the successful synthesis of the composite, featuring MIL-101(Fe) octahedral particles uniformly distributed onto the biochar’s honeycomb-like structure. The resulting MIL-101(Fe)/biochar adsorbent possessed a favorable mesoporous structure, with a specific surface area of 66.54 m 2 /g and a mean pore diameter of 3.35 nm. NH 4 + adsorptive removal process was impacted by operating parameters (reaction time, temperature, pH value, adsorbent dose, and initial NH 4 + content). Under optimal conditions (pH 7.0, 4 g/L adsorbent, 100 mg/L NH 4 + , and 6 h), the material showed a maximum NH 4 + uptake of 16.47 mg/g, surpassing several existing adsorbents. Kinetic, isotherm, and thermodynamic studies suggest that NH 4 + adsorption process was spontaneous, endothermic, and governed by a combination of both physisorption and chemisorption. The adsorbent demonstrated very good stability and reusability, maintaining its high adsorption capacity after four treatment cycles, confirming its long-term viability. This research highlights MIL-101(Fe)/biochar adsorbent as a promising, effective, and sustainable alternative for practical removal of NH 4 + from wastewater. • MIL-101 (Fe)/biochar composites were successfully synthesized using hydrothermal treatment and pyrolysis • MIL-101 (Fe) dispersed onto biochar led to an improvement in surface areas and ease of recovery • MIL-101 (Fe) dispersed onto biochar led to an improvement in NH 4 + adsorption efficiency • NH 4 + removal impacted by operating factors, with a maximum uptake of 16.47 mg/g • NH 4 + adsorption was spontaneous, endothermic, and governed by both physical and chemical adsorption • MIL-101 (Fe)/biochar composites showed high stability and durability during NH 4 + removal