Engineering TiO2-phosphate glass networks: A paradigm shift toward self-optimizing photocatalytic materials

Abstract

This study presents the synthesis and characterization of TiO 2 -doped phosphate glass-ceramics with composition (1–2x) ZnO Na 2 O-P 2 O 5 -xTiO 2 (0 ≤ x ≤ 0.05 mol%) for photocatalytic wastewater treatment. Materials were prepared via melt-quenching at 1000 °C, followed by a controlled two-step heat treatment to induce crystallization. Structural characterization by XRD, FTIR, SEM, and UV–Vis spectroscopy confirmed progressive formation of NaZn(PO 3 ) 3 and anatase TiO 2 crystalline phases. Thermal analysis revealed a systematic increase in glass transition temperature from 335 to 340 °C, indicating enhanced network rigidity through P-O-Ti bonding. FTIR spectra evidenced structural evolution from mixed Q 1 -Q 2 phosphate environments to predominantly Q 2 metaphosphate units after crystallization, consistent with the P/O ratio 3. Density increased from 2.75 to 2.82 g·cm -3 in glassy samples, while glass-ceramics exhibited slightly lower densities (2.60–2.69 g·cm -3 ) due to crystallization-induced porosity. Optical bandgap decreased from 3.27 to 3.20 eV, improving visible-light absorption. Photocatalytic tests using MB under UV–visible irradiation demonstrated that ZNPT 0.04 glass-ceramic exhibited optimal activity with a degradation rate constant of 0.0149 min⁻¹, exceeding undoped glass by twofold. Optimum conditions were 0.4 g·L⁻¹ catalyst dose and pH 6. Scavenger experiments identified hydroxyl radicals and photogenerated holes as dominant reactive species. The material retained over 90% efficiency after seven consecutive cycles, demonstrating excellent reusability. These findings establish TiO 2 -modified phosphate glass-ceramics as promising durable photocatalysts for sustainable environmental remediation.