Arsenic(III) removal from low-arsenic water by adsorption with amorphous mesoporous TiO₂

Abstract

The present study investigated the removal of As(III) from low-arsenic water through adsorption on amorphous mesoporous TiO₂. The mesoporous TiO₂ adsorbent size was 3.92 nm as calculated by adsorption average pore width. The Brunauer–Emmett–Teller surface area was 205 m²/g. A 0.2 g adsorbent treatment during five hours resulted in less than 4 μg/L remaining As(III) in the water, and nearly 84% of As(III) in the solution were removed in only 20 min. The As(III) adsorption kinetics data were well described by the pseudo-second-order model. The maximum adsorption pH value of 9.3 coincided with the first pK ₁ dissociation constant of H₃AsO₃ of 9.22. The Dubinin-Radushkevich and Langmuir isotherms provided maximum adsorption capacity of 4.57 and 4.79 mg/g, respectively, under low equilibrium concentration. These values possibly indicate the excellent capacity of amorphous mesoporous TiO₂ on As(III) removal from low-arsenic water. Given by the b-value of Langmuir isotherm under different pH, the average standard Gibbs free energy changes (∆G ^o) was –11.6 kJ mol⁻¹, which indicated spontaneous adsorption.

Keywords:

• As(III)
• Adsorption
• Amorphous TiO₂
• Drinking water treatment

Acknowledgments

This work was supported by the Natural Science Foundation of China (NSFC, No. 50908001, 51078001), Key Special Program on the S&T for the Pollution Control and Treatment of Water Bodies (No. 2008ZX07316, 2008ZX07103), Special Science and Technology Foundation of Anhui Province (No. 08010301106), International Corporation Project of Science and Technology of Anhui Province (No. 09080703035), and the Anhui Natural Science and Technology Foundation (Excellent Youth Foundation, No. 10040606Y29).