Silica-Sulfonated Iron Oxide Hybrid for Superior Methylene Blue Degradation

Chemistry Education Study Program, Faculty of Teacher Training and Education, Sebelas Maret University, Jl. Ir. Sutami 36A, Surakarta 57126, Indonesia

^* Corresponding author: mariaulfa@staff.uns.ac.id

Abstract

This study presents the synthesis and photocatalytic performance of SSIO (silica-sulfonated iron oxide) for the degradation of methylene blue, directly comparing it with pure iron oxide (IO). The SSIO catalyst was prepared via a soft-template approach using gelatin and P123, followed by sulfonation and Fe₂O₃ incorporation through wet impregnation, resulting in a pale-yellow, fine powder.XRD analysis confirmed Fe₂O₃ crystallites in SSIO with an average size of 2.08 nm and crystallinity of 89.2%, while FTIR spectra indicated –COOH, Si–OH, and Si–O–Si groups. Sulfonic acid- related signals were not clearly observed in the XRD, suggesting a predominantly amorphous or low-crystallinity nature. SEM imaging showed short rod- and platelet-like structures, providing a high surface area for catalytic reactions.Photocatalytic tests revealed that SSIO degraded methylene blue with an efficiency of 88.7% within 90 minutes, significantly higher than IO, which achieved 72.5% under the same conditions. Kinetic analysis followed a pseudo-first-order model with a rate constant of 0.0135 min⁻¹ for SSIO. These results demonstrate that incorporating sulfonated silica into SSIO substantially enhances photocatalytic activity compared to IO alone, offering a low-cost and efficient solution for treating dye- contaminated wastewater.