Fe2O3-decorated hollow porous silica spheres assisted by waste gelatin template for efficient purification of synthetic wastewater containing As(V)

Abstract

Purification of As(V)-contaminated water through adsorption by Fe₂O₃-based materials is a promising technology due to its low-cost and high efficiency. Dispersing the Fe₂O₃ phase on silica supports can improve both the adsorption rate and capacity due to the reduction in Fe₂O₃ particle sizes and the prevention of clumping of the Fe₂O₃ particles. However, the clusters in conventional silica materials largely impede the diffusion of As(V) to reach the Fe₂O₃ sites dispersed inside the clusters. Here, by applying a gelatin template strategy, the structure of silica materials was tailored by changing the gelatin-to-silica ratio (0, 0.6, 1.2 and 1.8) and hydrothermal temperature (60 °C, 100 °C and 140 °C). The silica cluster size could be reduced using either a low gelatin-to-silica ratio (0.6) or a low hydrothermal temperature (60 °C). Increasing the gelatin-to-silica ratio to 1.2 created porous silica spheres with a hollow structure. The Fe₂O₃-loaded hollow porous silica spheres with a shell thickness of 280 nm had twice the maximum As(V) adsorption capacity (7.66 mg g^-1) compared to the Fe₂O₃-loaded silica product prepared in the absence of gelatin (3.82 mg g^-1). The maximum As(V) adsorption capacity could be further enhanced to 9.94 mg g^-1 by reducing the shell thickness to 80 nm through increasing the gelatin-to-silica ratio to 1.8 and the hydrothermal temperature to 140 °C. In addition, the best Fe₂O₃-loaded hollow porous silica spheres had rapid As(V) adsorption and showed excellent durability as the As(V) removal efficiency slightly decreased to 98.9% subsequent to five adsorption-regeneration cycles.

Keywords: Arsenic removal; Contaminated water; Fe(2)O(3) nanoparticles; Gelatin template; Hollow porous silica.