Development of Membrane Filter for Water Treatment Using Anionic and Cationic Cellulose Nanofibers

Abstract

This study examined the effect of cellulose nanofiber (CNF) type on the performance of ion absorbing membrane filters made of anionic and cationic CNFs. Four types of anionic and cationic CNFs were made by beating, micro-grinding, carboxymethylation and quaternization using hardwood bleached kraft pulp (Hw-BKP): refining-CNF (RE-CNF), carboxymethylated CNF (CM-CNF), surface-modified CNF with cationic poly-DADMAC (pD-CNF), and quaternized CNF (Q-CNF). The membrane filters were composed of two-layers: One layer was made of anionic CNF and poly-aminiamide-epi-chlorohydrin (PAE) and the other layer was made of cationic CNF. The membrane filter was produced by vacuum filtration and the use of two CNF slurries. In addition, the capacity to remove Fe and Cl ions from the water was analyzed by carrying out high-pressure filtration experiments with a 500 ppm concentration of the Fe and Cl standard solutions respectively, using the same methods as the previous study.BRFour types of CNFs were sufficiently fibrillated at the nano-level and had electrostatically intended zeta-potential. The CM-CNF, which had a strong negative zeta-potential, was effective in the adsorption of Fe ions, and the Q-CNF, which was strong in cationic property, was effective in the adsorption of Cl ions. Therefore, it was concluded that cationic Q-CNF and anionic CM-CNF could be effectively utilized for the manufacture of a membrane filter to remove metal and anionic ions from water simultaneously.