Evaluation of arsenic sorption performance using dendritic anatase and polycrystalline rutile nano-TiO2 for environmental applications

Abstract

Two synthetic nano-TiO2-based materials, aggregated dendritic anatase nano-TiO2 and polycrystalline rutile nano-TiO2 attached to the surface of SiO2, were analyzed and compared for geo-environmental engineering applications. Characterization of crystal structure, purity, and morphologic, microscopic features of the materials were examined by X-ray powder diffraction, X-ray fluorescence, and scanning electron microscope, respectively. Arsenic removal rates/efficiencies were compared between the two materials in different settings for laboratory batch experiment. The adsorption curve on arsenic was obtained. Subsequently, different concentrations of arsenic solutions were injected in batches at different flow rates 0.67, 0.83, 1.00, 1.25, 1.67, 2.50, 5.00, and 10.00 ml/min to simulate field conditions. Results show that both of TiO2-based materials demonstrate outstanding capabilities for arsenic removal. Removal rates are 83% (± 0.025) and 95% (± 0.024) for aggregated TiO2, while 82% (± 0.031) for 93% (± 0.013) for attached TiO2. Results suggest that attached form of TiO2 is more effective for arsenic removal under fast groundwater flow condition, while aggregated form TiO2 can be suitable for high arsenic concentration and low water flow rate. Both materials are considered cost-effective as both can be recovered and reused after regeneration process.