Biomimetic System for the Application of Nanomaterials in Fluid Purification: Removal of Arsenic with Ferrihydrite.

The use of nanomaterials has transformed fields such as medicine and electronics. However, aggregation of nanomaterials in aqueous solutions, difficult recovery of spent nano-adsorbents from reactors, and a tremendous pressure loss caused by nano-adsorbents in adsorption columns have prevented the wide-scale use of nano-adsorbents in industrial applications for water purification. An over-reliance on traditional adsorption media for fluid purification practices has slowed innovation in this field. This study serves as a proof of concept for a new approach in utilizing nano-adsorbents in water treatment. A system based on the concept of renal dialysis was used to treat a solution of arsenite using two-line ferrihydrite (Fh) under environmental conditions. The performance was compared to traditional batch studies, and environmental variables pH and Eh were monitored. The system removed 67 and 91% of arsenite at 1.22 and 2.61 g/L Fh loadings, respectively, in comparison to batch experiments that removed 82 and 94% for similar loadings. Operational conditions and the physical design of the vessel limited the extent of removal that could be obtained with the system. Design advantages, shortcomings, and required improvements are discussed.