Removal of Cr(VI) by silica-titania core-shell nanocomposites: In vivo toxicity assessment of the adsorbent by Drosophila melanogaster

Silica-titania core-shell nanocomposite (SiO₂–TiO₂) was successfully synthesized via nanoparticle encapsulation route. The morphology and the chemical properties of the prepared nanocomposite were evaluated by different instrumental techniques before and after adsorption of Cr(VI) as required to check the existence of Cr and its oxides on the surface of the adsorbent. Subsequently, the efficiency of the nanocomposite to adsorb Cr(VI) from synthetic solution was studied in different experimental conditions like solution temperature (30–80 °C), pH (2–10), initial Cr(VI) concentration (10–100 mg L⁻¹), reaction time (10–120 min), and, amount of the adsorbent (0.1–1 g). The maximum adsorption reached 98% by utilizing 0.5 g L⁻¹ of the nanocomposite at pH 5, with 30 mg L⁻¹ initial Cr(VI) concentration, while the temperature was maintained 50 °C and the equilibrium time was 70 min. Besides, the process of Cr(VI) adsorption is well fitted with the Langmuir adsorption isotherm model and pseudo-second-order kinetic model. On the other hand, endothermic and spontaneous nature of the adsorption process was revealed by the negative ΔG and the positive ΔH values. The cytotoxicity of the nanocomposite was examined by using Drosophila as a model organism. The effects of oral ingestion of the nanocomposite (10, 40, 60, 80, and 100 μg mL⁻¹) were observed on the growth, development, and behavior of Drosophila and the result showed there are no major phenotypic defect on Drosophila. The above outcomes suggested that the SiO₂–TiO₂ core-shell nanocomposite could be a promising nontoxic material for Cr(VI) removal from contaminated water.