Green synthesis of ZnO@SiO₂ nanoparticles using Calligonum comosum L. extract: an efficient approach for organic pollutant degradation in wastewater

A novel core-shell nanomaterial, ZnO nanoparticles (NPs), and a shell-core ZnO@SiO₂ using extracts from Calligonum comosum L. leaves successfully fabricated. The investigation focuses on evaluating the photocatalytic efficiency of the produced catalyst against organic pollutants. SiO₂ NPs, ZnO NPs, and shell-core ZnO@SiO₂ structures exhibit spherical morphologies with average diameters of approximately 25–50 nm, 50–100 nm, and 35–65 nm, respectively. SiO₂ NPs possess an amorphous structure, while ZnO NPs, SiO₂ NPs, and the ZnO shell exhibit crystalline arrangements, featuring average crystallite sizes of 32.8 nm, 62.3, and 13.5 nm, respectively. Band gap energies are determined to be 3.6 eV, 2.3 eV, and 2.15 eV for SiO₂ NPs, ZnO NPs, and ZnO@SiO₂ nanocomposite, respectively. Catalytic performance is evaluated using Methylene Blue (MB) as a cationic dye and Rose Bengal (RB) as an anionic dye. Remarkably, the shell-core ZnO@SiO₂ nanocomposite achieves degradation efficiencies of 99.3% for MB and 98.0% for RB, surpassing ZnO NPs with degradation coefficients of 86.6% for MB and 91.7% for RB. These degradation processes occur under solar light irradiation, at a contact time of 120 min, pH 7, and temperature of 25 °C. The study underscores the potential of the ZnO@SiO₂ nanocomposite as an effective, cost-efficient, and environmentally friendly solution for water treatment.