Functional Cellulose Nanofiber Filters with Enhanced Flux for the Removal of Humic Acid by Adsorption

Abstract

Despite great promises of cellulose nanofibers for water treatment, current technologies have lacked the exclusive use of cellulose nanofibers (CNF) in high-flux filters having an affinity for a desired contaminant. To tackle this, we prepared porous and functionalized filters via solvent exchange, supercritical drying, and freeze-drying of cationic CNF and compared them to conventional CNF filters obtained by the paper-making process. Porosity and pore size were evaluated in the dry state qualitatively and quantitatively via scanning electron microscopy and mercury intrusion porosimetry, respectively. The permeance of water and a solution containing a negatively charged model molecule (humic acid) through these filters was measured at various pressures and correlated to the filters’ structure. As compared to the CNF filters made via paper-making, the porosity, pore size, and permeance were increased after processing via solvent exchange, supercritical drying, and freeze-drying routes. Those filters which...