Characteristics of Various Organic MembranesMembrane MaterialCellulosic (cellulose acetate, cellulose triacetate, cellulose nitrate,cellulose esters)Polysulfones/polyethersulfonesPolyvinylidene fluoride Polypropylene Moderately Polyacrylonitriles Polytetrafluoroethylene PolyamidesHydrophobicity/HydrophilicityHydrophilicHydrophobic/moderately hydrophilicHydrophobicModerately hydrophobicHydrophobicHydrophobicHydrophilicChlorine ToleranceModerateTypical ApplicationsEffect of pH on surface charge (expressed in terms of zeta potential) of two RO membranes.Many hydrophilic membranes acquire a pH-dependent surface charge via ionization of weakly acidic or basic functional groups in the membrane structure (primarily carboxyl and amino groups, in the case of polymeric membranes).