Preparation of superhydrophilic sodium alginate/chitosan-Ag composite membranes with antibacterial activity for effective oil-water emulsion separation

Oily wastewater as one of water pollutions has always been a hot issue in the field of chemical engineering and environment protection, and it is still challenge to separate oil water mixture effectively with low energy consumption. Polymer membranes with superhydrophilic and underwater superoleophobic properties are perfect substances for oil-water separation owning to their high separation efficiency, oil anti-adhesion and energy saving. However, these membranes are easily contaminated by microorganisms, leading to biofilms on the surfaces, and reducing their separation flux and efficiency. In order to solve the problems, sodium alginate/ chitosan-Ag composite were successfully coated on commercial nylon membranes by self-assembly method, and the effects of the Ag on separation performance and biological activity of the membranes were investigated in detail. Under the optimized condition, the membrane can effectively separate oil-in-water emulsions containing anionic, cationic or non-ionic surfactants, with a maximum separation efficiency of 99.73%. More importantly, the inhibition ratios of the membrane could reach 95.42% and 98.05% against E. coli and S. aureus, respectively, and thus inhibits the formation of S. aureus biofilm, and maintain a high relative flux after being contaminated by S. aureus. The simple preparation process and incredible emulsion separation performance with antibacterial activity of composite membranes will provide great prospects for potential industrial applications.