Crown Ether‐Functionalized Mesoporous Silica Derived from Sorghum bicolor Roots for Efficient Cr(VI) Removal: Synthesis, Characterization, and Adsorption Studies

Chromium in its hexavalent form, Cr(VI), is a highly carcinogenic pollutant commonly found in industrial wastewater, requiring efficient and sustainable removal strategies. In the present work, a new adsorbent, crown ether‐functionalized mesoporous silica, DFDB18C6@MSN‐NH 2 , was synthesized using biomass‐derived silica obtained from root ash of Sorghum bicolor . Covalent anchoring of 4,4′‐diformyldibenzo‐18‐crown‐6 onto aminated mesoporous silica produced a stable tethered adsorbent containing functionalized adsorption sites suitable for Cr(VI) uptake. The resulting adsorbent was characterized using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), Bernauer–Emmett–Teller (BET) surface analysis, Field emission scanning electron microscopy (FESEM), and Transmission electron microscopy (TEM). Batch adsorption studies demonstrated efficient Cr(VI) removal under acidic conditions, with optimum adsorption achieved at short contact time and moderate adsorbent dosage. The adsorbent exhibited a maximum Cr(VI) removal efficiency of 89.05% and an adsorption capacity of 71.21 mg g − 1 . Adsorption behavior was analyzed using Langmuir, Freundlich, and Temkin isotherm models, with the Langmuir model showing the best fit, indicating monolayer adsorption. Kinetic and thermodynamic studies suggested favorable, spontaneous, and exothermic adsorption. Overall, the study demonstrates the potential of biomass‐derived crown ether‐functionalized mesoporous silica as a cost‐effective and reusable adsorbent for Cr(VI) removal from aqueous systems.