Enhanced surface hydroxyl groups by using hydrogen peroxide on hollow tubular alumina for removing fluoride

Abstract

Abstract A novel modified method of hollow tubular alumina was investigated for improving the ability to remove fluoride. In this paper, we designed two parts to improve the adsorption capacity of fluoride: (1) increased the exposed surface area by compounding hollow tubular structure; (2) hydroxylated with different concentrations of H2O2 from 0 to 10 wt%. The modified alumina had uniform hollow tubular and crystal form of γ-Al2O3. Modified hollow tubular alumina exhibited a good performance of 74.25% with 1% H2O2. The kinetic and thermodynamic were thoroughly explained to fit different models. It demonstrated that the pseudo-second-order model and Freundlich model, indicating that chemical and heterogeneous adsorption. The adsorptive velocities of 1% H2O2/Al2O3 were 8.07 × 10−8 and 1.39 × 10−6 m/s when the initial concentrations were 10 ppm and 100 ppm, respectively. The adsorption mechanism was discussed and the adsorbent was stable after adsorbing fluoride. The addition of hydrogen peroxide promoted the more hydroxyl groups, and the exchange hydroxyl groups with fluoride were the main mechanism of adsorption. The ratio of hydroxyl groups with the form of Al–O–OH and Al–OH descended from 80%, 29.3%–30.4%, 20.1%, respectively. These results show hollow structure and modified with H2O2 are the economic and environmental methods for enhancing to remove fluoride.