Mesoporous hierarchical ZrO2@rice straw-derived SiO2 nanocomposite for rapid adsorption and sunlight-driven photocatalytic degradation of methylene blue

Abstract

Herein, novel mesoporous hierarchical ZrO2@rice straw-derived SiO2 nanocomposite was synthesized through a well-distributed combination of ZrO2 with rice straw-derived SiO2. ZrO2 was used to enhance the functionality of rice straw-derived SiO2 toward methylene blue-photocatalytic degradation. The rice straw-derived SiO2 was used as a platform to (i) reduce the overall cost of material preparation, and (ii) recycling of agricultural waste for environment protection. Our characterization results indicated that the ZrO2 nanoparticles were well dispersed along with the rice straw-derived SiO2 matrix, leading to enhance both the adsorption and sunlight-driven photocatalytic efficiency of the ZrO2@rice straw-derived SiO2 nanocomposites for methylene blue decolorization. Computational density function theory of charge distributions, band structure, and density of state were investigated to estimate the optical property, bandgap, and recombination of photogenerated charge carriers. Up to 75 and 85 % of the initial methylene blue concentration could be removed within 30 min at pH 10. The mechanism of methylene blue adsorption and the sunlight-driven photocatalytic degradation were explained mathematically through kinetic and isotherm models. Moreover, ZrO2@rice straw-derived SiO2 could be simply regenerated and reused at least five times with acceptable efficiency. In conclusion, our manuscript offers some advantages such as (i) recycling of agricultural waste, (ii) ease of preparation, (iii) cost-effective process, (iv) fast and efficient removal operation, and (v) recycling and reusing the spent adsorbent/photocatalyst.