Kinetic study of adsorption of arsenic onto New Zealand Ironsand (NZIS)

Abstract

New Zealand Ironsand (NZIS), an iron-rich sand ubiquitous to the coast of the North Island of New Zealand was examined for the removal of arsenic (both As (III) and As (V)) by adsorption. Batch experiments were performed to evaluate the adsorption kinetics at three different pH conditions (3.0, 7.5 and 11.0). In addition, a column test was conducted to obtain the breakthrough curve and appraise the arsenic removal capacity of NZIS used as a filter media. The kinetic study showed that a very long contact time (>144 h) was needed to reach equilibrium and the nature of the adsorption was well described (R² value more than 0.96 at each pH condition) with a pseudo–second-order adsorption kinetic model for both As (III) and As (V). In column tests, a pore volume (PV) of 700 and 400 yielded a total arsenic level less than the WHO guideline value of 10 μg/L for As (III) and As (V), respectively.

Keywords:

• Arsenic
• ironsand
• adsorption
• water
• New Zealand

Acknowledgments

The authors would like to express their thanks to Mr. Peter McGuigan and Mr. David MacPherson for their excellent technical assistance on this project.

Additional information

Funding

The authors would like to express their thanks to the Department of Civil and Natural Resources Engineering, the University of Canterbury, Christchurch, New Zealand for the internal research grant. Also, the first author is grateful to NZAID for providing a scholarship to study at the University of Canterbury.