CNF gel (3 wt%) was supplied by Nano Novin Polymer Co. (Iran). All other reagents and solvents were of analytical grade and were used without further purification. For film formation, mixed cellulose ester (CEM) membrane filter with diameter of 9 cm and pore size of 0.2 μm was used (Toyo Roshi Kaisha Co., Japan). All stock solutions used in this work were freshly prepared to avoid any possible degradation.