Influence of Functionalization on the Textural Properties and Photocatalytic Performance of ZnO-Modified Metakaolin...

Metakaolin-based geopolymers modified with ZnO and surface-functionalized ZnO were developed and investigated in terms of structure, morphology, textural properties, and photocatalytic performance. ZnO, ZnO@AS(zinc oxide functionalized with steric acid), and ZnO@PEG(zinc oxide functionalized with polyethylene glycol) were incorporated into the geopolymer matrix and characterized by XRD(X-ray diffraction), ATR-FTIR(Fourier transform infrared spectroscopy in attenuated total reflectance, SEM-EDS (scanning electron microscopy coupled with spectroscopy with energy-dispersive X-ray spectroscopy), and BET(Brunauer-Emmett-Teller) analysis. The results showed that ZnO incorporation did not significantly modify the amorphous aluminosilicate network but affected the morphology and porosity depending on the functionalization method. ZnO@AS induced matrix densification and reduced accessible porosity, while ZnO@PEG improved particle dispersion and preserved the porous structure. Among the ZnO-modified metakaolin-based geopolymers, GP/ZnO@PEG(geopolymer with ZnO@PEG particles) exhibited the highest photocatalytic performance, characterized by a BET surface area of 17.22 m²/g, an apparent kinetic constant of 0.01668 min^-1, and a half-life of approximately 41 min, achieving approximately 90% methylene blue removal after 120 min of UV-A irradiation. The study demonstrates that ZnO surface functionalization controls the interfacial interaction with the geopolymer matrix and plays a key role in the performance of geopolymer-based photocatalytic materials.