Molecular Modeling of Bacterial Alginate Adsorption to RO Membranes Under Crossflow (Shear) Conditions

A novel method is described that permits fully atomistic molecular dynamics (MD) simulations of the adsorption of biomolecules to the surfaces of synthetic membrane materials under fluid shear (crossflow) conditions. The method randomly or systematically assigns velocity vectors to individual components of a fluid phase containing the macromolecular foulant of interest, such as bacterial alginate or a polypeptide. Under the control of an appropriate Newtonian force field, the fluid components are allowed to migrate in a direction parallel to the membrane surface under periodic boundary conditions. The advantage of the technique is that water and foulant molecules can sample large expanses of the membrane surface in a short period of time compared to conventional MD approaches. When the method was applied to oligomers of O-acetylated bacterial alginate and aromatic crosslinked polyamide membranes, involvement of the acetyl groups in adsorption was evident. The method can be readily applied to a variety of biofouling molecules and membrane polymer types, including inorganic and hybrid membrane materials and could be used to help elucidate the molecular mechanisms underlying macromolecular fouling of membranes.