Three-Dimensional Macroporous Alginate Scaffolds Embedded with Akaganeite Nanorods for the Filter-Based High-Speed Preparation of Arsenic-Free Drinking Water

Separation of arsenic from water is an urgent worldwide issue because of its serious toxic effect on human health and aquatic life. In this study, a filter device composed of three-dimensional (3D) macroporous alginate/akaganeite composite (MAAC) scaffolds is proposed for the convenient separation of arsenic from contaminated water. Akaganeite nanorods with superior arsenic adsorption capability are incorporated and distributed within the macroporous alginate scaffold, without significant aggregation. The micron-sized pores and oxygen functional groups in the MAAC scaffold offer enhanced mass transport of the contaminated water throughout the scaffold without the need for input of any force and allow easy contact of arsenic with the active adsorption sites of the scaffold. The high mechanical strength of the MAAC facilitates structural stability of the materials in aqueous solutions. Moreover, the scaffold is capable of excellent arsenic adsorption and can reduce the concentration of arsenic in contaminated water to the acceptable drinking-water level (10 μg L–1). We also demonstrate that a column filter device constructed by stacking several MAAC scaffolds enables a continuous supply of drinking water with a permissible limit of arsenic according to the World Health Organization in a high-purification speed (∼22–25 mL min–1 under gravity), which could potentially provide an appropriate technology to obtain arsenic-free drinking water in developing countries.