Removal of trace arsenic to meet drinking water standards using iron oxide coated multiwall carbon nanotubes

This study presents the removal of trace level arsenic to meet drinking water standards using an iron oxide-multiwalled carbon nanotube (Fe-MWCNT) hybrid as a sorbent. The synthesis was facilitated by the high degree of nanotube functionalization using a microwave-assisted process, and a controlled assembly of iron oxide was possible where the MWCNT served as an effective support for the oxide. In the final product, 11 % of the carbon atoms were attached to Fe. The Fe-MWCNT was effective in arsenic removal to below the drinking water standard levels of 10 μg·L^-1. The absorption capacity of the composite was 1723 μg·g^-1 and 189 μg·g^-1 for As(III) and As(V), respectively. The adsorption of As(V) on Fe-MWCNT was faster than that of As(III). The pseudosecond-order rate equation was found to effectively describe the kinetics of arsenic adsorption. The adsorption isotherms for As(III) and As(V) fitted both the Langmuir and Freundlich models.