Virus removal by iron oxide ceramic membranes

Abstract

Nanoporous iron oxide ceramics were studied for the removal of virus contamination from water. Supported and unsupported iron oxide nanostructured hematite was fabricated by a green chemistry route from ferroxane nanoparticles. The material had a surface area of approximately 30 m2/g and a mean pore size of 65 nm. Bacteriophage P22 was chosen as a model for human virus. The kinetics and equilibrium of the attachment process was investigated. P22 adsorption isotherms on iron oxide were described by the Freundlich equation. Batch experiments resulted in 1.5 LRVs. Removal proceeded rapidly for the first 7 h; next, a diffusion-limited stage occurred. Dynamic attachment experiments demanded extensive recirculation to achieve significant reduction levels. Up to 3 LRV were observed. The enhanced performance can be explained by the higher iron oxide area available and the facilitated access to inner porosity sites that were previously unavailable due to slow diffusion. The role of electrostatic interactions in the attachment mechanisms was confirmed by the dependence of the isotherm on the ionic strength of the suspension medium. P22 bacteriophage is expected to attach to the iron oxide by electrostatic forces up to a pH of 6.5. DLVO theory predicts moderately well the interaction energies between P22 particles themselves and between the phage and the ceramic. However, a slight underestimation of the P22–P22 repulsive forces was evident by comparison to the experimental data.