Preparation of Nano Cellulose Acetate Membranes and Their Use for Removal of Some Ions

Abstract

This study was conducted to prepare cellulose acetate nanoparticles to be used in fabrication of membranes. The membranes were used for water desalination and heavy metal ions removal from aqueous solutions. Cotton was used as a source of cellulose fibers after removing lignin and hemicellulose by treating with alkaline solution. Pure cellulose fibers were converted to cellulose acetate through esterification reaction with acetic anhydride. Cellulose acetate nanoparticles were prepared via two paths: milling and spray. A composite membrane was prepared from mixture of milled cellulose and cellulose acetate to increase mechanical stability. Characterization results of cellulose acetate showed that the produced particles have diameter lower than 100 nm. The study of heavy metal ions removal showed that at long retention time, a completing ions removal from aqueous solution by all membranes. The optimum conditions for heavy metal ions removal were at pH = 6.7 and contact time of 5 min. Therefore, at quick flow rate with a retention time less than 5 min, the best membrane for ions removal was the membrane prepared via path 3 which prepared by combining both milling and spray processes. Water desalination was examined using sodium chloride solution with conductivity 984 µs which was passed through the membranes at flow rates of 0.3, 0.7, and 1 liter/min. The results showed that conductivity of permeate was in range of 4 - 15µs until breaking the membrane. The membranes efficiency was calculated from the amount of salt in the permeate to the amount ofsalt in the passing solution. The efficiency was > 99 % for both membranes. Although, the efficiency of composite membrane begins decreasing gradually to 96 % after passing 130 liters when operating at flow rate of 0.3 l/min. When operating at flow rate of 0.7 l/min, the efficiency begins decreasing gradually to 96 % after passing 115 liters, where the efficiency begins decreasing gradually to 96 % after passing 90 liters when operating at flow rate of 1.0 l/min. On the other side, the efficiency of membrane manufactured via path 3 begins decreasing linearly to 90 % after passing 28 liters when operating at flow rate of 0.3 l/min. When operating at flow rate of 0.7 l/min, the efficiency begins decreasing linearly to 80 % after passing 22 liters, where the efficiency begins decreasing linearly to 98 % after passing 11 liters when operating at flow rate of 1.0 l/min after which the membrane broke. Study effects of chlorine on membranes efficiency showed that the chlorine does not have noticeable influence on life of the membranes.