Nanostructured Zr-Mn binary hydrous oxide as an effective adsorbent for arsenic removal from water and groundwater

Abstract

It is well known that arsenic is a very harmful toxin to humans. Among arsenic species, arsenite is more toxic and more difficult to remove from water than arsenate. In this study, a nanostructured Zr-Mn binary hydrous oxide was synthesized using one-step simultaneous oxidation and coprecipitation method, aiming at removing both arsenate and arsenite effectively and simultaneously. The Zr-Mn binary hydrous oxide particles were aggregated with smaller nanosized particles, resulting in a rough surface. The hydrous oxide was very effective for both As(V) and As(III) removal from water. The maximal sorption capacities for As(V) and As(III) were 52 and 96 mg/g at neutral environment, respectively. The higher sorption capacity for As(III) may be attributed to the As(III) oxidation and reductive dissolution of manganese dioxide, which resulted in the formation of new sorptive sites for arsenic at the solid surface. The presence of sulfate and carbonate had no significantly influence in the arsenic removal. However, the presence of phosphate greatly decreased the removal, especially at high concentrations. Furthermore, the performance of Zr-Mn binary hydrous oxide was further confirmed by an adsorption study with a groundwater. Additionally, the leaching of arsenic from the used sorbent was less serious, indicating that it may not be hazard to the environment after the landfill disposal. Due to its excellent arsenic removal performance and the simple, low-cost synthesis process, the Zr-Mn binary hydrous oxide could be a promising alternate for both As(V) and As(II) simultaneous removal from water or groundwater without the oxidation pretreatment.