Sulfonic acid functionalized dendrimer-grafted cellulose as a charge and hydrophilic modifier of cellulose acetate membranes in removal of inorganic and organic pollutants

In this study, cellulose acetate-based nanofiltration (NF) membranes were modified by sulfonic acid functionalized dendrimer-grafted cellulose (Cel-dend-SO₃H) as a charge and hydrophilic modifier to obtain superior separation and filtration properties. Several concentrations of Cel-dend-SO₃H (0.10, 0.25, 0.50, 1.0, and 2.0 wt%) were considered for fabricating membranes via phase inversion method. Different physical analyses approved the successful synthesis of Cel-dend-SO₃H and its incorporation into the membrane matrix. The results of zeta potential and mechanical properties exhibited an improvement in the negative charge and the mechanical resistance of the modified membranes, respectively. The membranes' performance was assessed by filtering pure water and bovine serum albumin (BSA) and removing organic (Rose Bengal, Reactive Blue 50, and Azithromycin) and inorganic (Pb(II), As(V), Na₂SO₄, and NaCl) pollutants. The results indicated that the water flux increased in the modified membranes compared with the bare membrane and reached its highest level (82.7 L/m² h) for the 1.0 wt% Cel-dend-SO3H membrane. However, the 2.0 wt% Cel-dend-SO₃H membrane demonstrated the maximum removal efficiency of organic and inorganic pollutants among all modified membranes. The removal of Pb(II) by all membranes was higher than 97 %, with an almost constant Na₂SO₄ rejection of 96.9 %. Furthermore, the removal of Rose Bengal, Reactive Blue 50, and Azithromycin improved by 2.1 %, 8.2 %, and 5.3 %, respectively, compared with the bare membrane, in addition to the enhanced flux and porosity. Despite a slight drop in BSA rejection (<1 %) in the modified membranes, the flux recovery ratio (FRR) raised from 73.9 % for the bare membrane to 92.4 % for the 2.0 wt% Cel-dend-SO₃H membrane. Therefore, the currently modified membranes could be a promising candidate for the simultaneous improvement of separation and filtration properties of NF membranes in water treatment applications.