Rice husk silica as a platform for iron biocatalysts via silanol group confinement

In this study, isolated Fe atoms were incorporated into rice husk silica to obtain bio-SACs, which are then used in a Fenton process. As a synthesis strategy, the silica structure is modified by incorporating a template (pluronic P123) to encapsulate the silanol groups, followed by a pyrolysis process to obtain bio-SACs ( x Fe@SiO 2 ). XRD analysis reveals good dispersion of the metallic phase, as well as H 2 -TPR profiles, which show shifts in the Fe(III) signals to lower temperatures compared to the conventional catalyst. N 2 adsorption-desorption analysis reveals the change in the textural properties of the silica after incorporation of the template, and IR and TG-MS and DTG analyses confirm the incorporation of the polymer into the silica surface to ensure the isolation of the Fe atoms, as well as their elimination and the formation of ≡Si-O-Fe bonds after calcination. The formation of Fe sites associated with isolated Fe(III) on the silica surface was confirmed by UV–vis DR analysis. The catalytic activity was evaluated in the wet oxidation of phenol with H 2 O 2 . The 2.5Fe@SiO 2 and 5Fe@SiO 2 catalysts achieved phenol conversions greater than 96–98 % in 30 min and high CO 2 selectivity (58–63 %) in just 60 min, demonstrating superiority over the conventional catalyst and revealing the potential of rice husk silica as a support for obtaining bio-SACs. • Silica obtained from rice husk in the production of Fe biocatalysts. • Pyrolysis by polymer encapsulation allows for control of Fe species dispersion. • Biomass-derived single-atom catalyst for environmental remediation. • High mineralization in the catalytic oxidation of phenol. • Catalysts with amounts of 2.5–5 % Fe achieves conversions above 96 % in 30 min.