Development and Analysis of Glycine-Modified Silica Gel for Efficient Fe3+ Ion Capture: Exploring Synchrotron XAFS Insights

A glycine-functionalized silica gel material (SG-Gly-Na⁺) was synthesized via a sol–gel approach for efficient Fe³⁺ ion removal from aqueous solutions. Characterization by ATR-FTIR, SEM, elemental analysis, and synchrotron-based X-ray absorption spectroscopy confirmed the successful incorporation of glycine and the structural integrity of the silica matrix. FTIR and thermal analysis validated the presence of carboxylate and secondary amine groups and demonstrated thermal stability up to 350°C. XANES analysis revealed that iron remains in the +3 oxidation state upon sorption, while EXAFS indicated coordination of Fe³⁺ to oxygen atoms at ~1.95 Å, with longer-range interactions involving the silica framework. Notably, the glycine moiety does not reduce Fe(III) within the matrix. Batch sorption tests showed that SG-Gly-Na⁺ achieved 70% Fe³⁺ removal efficiency, a significant improvement over unmodified silica gel (10%), demonstrating its potential as a selective and thermally stable sorbent for iron remediation.