Integrated in silico-experimental approach: graphene driven membrane crystallization

Membrane crystallization (MCr) is an emerging membrane process with the capability to simultaneously extract fresh water and valuable components from various streams. Nano-composite membranes [1,2] enriched with two-dimensional (2D) materials are becoming promising in membrane technology dedicated to water treatment. 2D materials can assist mass transfer through membranes under specific conditions. In the recent year [3-5], molecular dynamics simulations (MD) have provided a detailed picture of the formation of the critical nucleus of salts in supersaturated solution. Herein, we explore the potential of 2D materials in MCr technology from experimental and computational points of view to predict and validate the salts nucleation and growth rate when NaCl solution comes in contact with membrane surfaces. Experimental tests and simulations have been performed using different concentrations of exfoliated 2D flakes, designing three different models: pristine PVDF, PVDF with Graphene at 5% wt and PVDF with Graphene at 10% wt. Both experimental tests and MD simulations demonstrate that the chemical composition of the membrane surface affect the crystallization of salts. A clear indication on the role of the filler in nucleation grow rate, crystal size and shape, and the energy of the system has been obtained: the nanomaterials influence kinetics of crystal formation, reducing the nucleation times. This work was supported by the 'Ministero degli Affari Esteri e della Cooperazione Internazionale, Direzione Generale per la Promozione del Sistema Paese' within the framework of the Great Relevance International Project Italy (MAECI)-China (NSFC) 2018-2020 - New Materials, with particular reference to Two-dimensional systems and Graphene (Prot.MAE0088962).