Solid-Phase Synthesis of Mesoporous ZnO Using Lignin-Amine Template and Its Photocatalytic Properties

Nanoparticles of zinc oxide (ZnO) with high sunlight photocatalytic activity were synthesized by a solid-phase method using lignin-amine (LA) template. The prepared ZnO was characterized using UV–visible diffuse reflectance spectroscopy (UV–vis/DRS), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), Brunauer–Emmett–Teller (BET) analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. XRD confirmed the formation of hexagonal wurtzite structural ZnO, and the SEM results indicated the porous surface characteristic of the products. The average ZnO crystallite size determined by XRD was 15–44 nm. Room-temperature PL spectra exhibited a strong ultraviolet emission band centered at about 383 nm. The BET isotherms were of type IV with a type H3 hysteresis loop, suggesting the presence of abundant mesoporous structures in the architectures of the as-prepared ZnO. The sample calcined at 400 °C (ZL4) showed a PL emission peak of weaker intensity, higher specific surface areas, and better photocatalytic activity than those calcined at other temperatures. The degradation rate of methyl orange (MO) in the presence ZL4 catalyst reached up to 99.26% under UV light irradiation for 1 h and 96.48% under solar radiation for 6 h.