Development of Cellulose Acetate Membranes for Nano–and Reverse Osmosis Filtration of Contaminants in Drinking Water

Abstract

Cellulose acetate (CA) membrane was produced from CA powder, formamid, and acetone. Annealing temperature of 80C and evaporation times of 30, 60, and 90 seconds were chosen in preparation of the CA membranes named R530, R560, and R590, respectively. The membranes were tested using a dead-end stirred cell for filtration of NaCl salt, iron, manganese, and arsenic in the laboratory-prepared water and groundwater. Results of the tests using a membrane R530 at 400 psi showed, that the rejection efficiencies for salt, iron, and manganese in laboratory-prepared water with 3000 ppm NaCl , 2.0 ppm Fe, and 2.0 ppm Mn were 87%, 99%, and 92%, respectively, with a permeate flux of 21 Lm^-2hr^-1. Tests for the groundwater containing 4815 ppm NaCl and 5.48 ppm Mn without acid treatment showed that membrane R530 gave the flux and rejection for salt and manganese at 24 Lm^-2hr^-1, 85% and 98%, and for iron and manganese at 21 Lm^-2hr^-1, 93% and 99%, respectively. In the filtration of arsenic, the prepared membrane had a As rejection of 68 - 70% at 300 and 400 psi when the feed was the laboratory prepared 1 ppm As⁺³ contaminated water but it was found to be more than 82 - 96% when the feed was a natural water. This is probably because the prepared membrane had a higher rejection efficiency for As⁺⁵ ions than As⁺³ ions. Ion selective capability of the CA membrane shows the potential to use the membrane in filtration of selective ions. Key words: Cellulose acetate membrane, reverse osmosis, nano-filtration, contaminated water, dead-end stirred cell