Effect of carboxyl and hydroxyl groups on adsorptive polysaccharide fouling: A comparative study based on PVDF and graphene oxide (GO) modified PVDF surfaces

Abstract

We investigated the contribution of different functional groups on polysaccharides to membrane fouling. To achieve so, we examined the adsorption of two typical polysaccharides, i.e., glucan (only –OH) and sodium alginate (enriched –COOH) on surfaces of PVDF membranes with and without graphene oxide (GO) modification. The results suggest that the interaction between carboxyl groups and Ca2+ significantly altered the particle size and charge of sodium alginate. Resultantly, the irreversible fouling of PVDF membrane surface caused by polysaccharide (i.e., sodium alginate) adsorption became more reversible when the concentration of Ca2+ exceeded a critical value. In comparison, glucan containing only hydroxyl groups exhibited unidirectional increase in irreversible fouling along with the increased Ca2+ concentration. Modification of PVDF membrane using GO did alleviate adsorptive fouling, but the Ca2+ bridging between the modified membrane surface and sodium alginate makes the fouling less reversible. Therefore, foulant property and water chemistry should be taken in to account in evaluating the performance of membrane hydrophilization using GO.