Dual-platform Photocatalysts: Evaluation of the Catalytic Properties of α-MoO₃ and ZnMoO₄ Nanosystems for Visible-light MB Degradation
J. Environ. Nanotechnol., Volume 14, No 4 (December 2025) pp. 100-112
Abstract
Textile effluents enriched with recalcitrant dyes demand robust, solar‐assisted treatments. Here, we evaluate undoped molybdenum trioxide (MoO₃) and zinc molybdate (ZnMoO₄) as photocatalysts for methylene blue (MB) abatement and correlate performance with structure. X-ray diffraction confirms phase-pure orthorhombic α-MoO₃ (ICDD 00-005-0508) and monoclinic ZnMoO₄; Raman spectroscopy resolves the terminal Mo═O and Mo–O–Mo modes of α-MoO₃ and the ν₁/ν₃ vibrations of isolated [MoO₄]²⁻ tetrahedra in ZnMoO₄. FTIR further confirms α-MoO₃ holds Mo═O (~995 cm⁻¹), bridging Mo–O–Mo (820–870 cm⁻¹), and the ZnMoO₄ MoO₄ manifold (∼1170/920/742/606 cm⁻¹), along with surface –OH/H₂O, beneficial for radical generation. FESEM shows micron-scale platelet aggregates that furnish step edges and mesovoids, while EDS verifies the intended Zn–Mo–O or Mo–O compositions without extraneous elements. Photoluminescence in the 400–520 nm window is vacancy-mediated for MoO₃ and arises from intrinsic [MoO₄]²⁻ charge-transfer emission in ZnMoO₄. Under irradiation, MB (λmax ≈ 664 nm) decolorizes steadily: after 150 min, degradation efficiencies are ~64% (MoO₃) and ~67% (ZnMoO₄). The time profiles obey the Langmuir–Hinshelwood, pseudo-first-order model with apparent rate constants (kapp) of approximately 6.9 × 10⁻³ min⁻¹ for MoO₃ and 7.3 × 10⁻³ min⁻¹ for ZnMoO₄. Adsorption behavior can be described by Langmuir/Freundlich/Temkin isotherms with intraparticle-diffusion contributions. These results validate α-MoO₃ and ZnMoO₄ as credible, structurally well-defined platforms for dye-laden wastewater remediation and motivate heterojunction/defect engineering for further activity gains.
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