Membrane-based processes for water treatment, such as reverse osmosis (RO), hold promise in tackling water scarcity locally and globally. Nevertheless, conventional polyamide membranes for RO exhibit low rejection of Small, charge-Neutral Contaminants (SNCs), which endanger human health and biota.
Progress towards highly selective membranes has been hindered by insufficient understanding of the mechanisms that underlie separation efficiency: how water and contaminants sorb into, and diffuse through, polyamide membranes. Both
contaminant sorption and transport require a molecular-level treatment, at far higher resolution than is afforded by conventional (continuum) membrane transport models.
Using molecular dynamics (MD) simulation and free energy calculations, this project aims to computationally design highly selective RO membranes by elucidating the mechanisms governing SNC sorption and transport. The project will focus on SNCs that are insufficiently rejected by state-of-the art RO membranes, e.g., boric acid, a toxic constituent of seawater, and N-nitrosodimethylamine (NDMA), a carcinogenic disinfection by-product whose insufficient removal during RO-based wastewater reuse (rejection ~ 60%) demands additional, and costly, advanced oxidation processes (e.g., high-energy UV).
The specific objectives of this project are:
Objective 1. To gain molecular-level insight into the hydration layer at the polyamide-water interface, to understand how interfacial water molecules determine SNC sorption and transport.
Objective 2. To elucidate the role of interfacial chemistry in SNC sorption to polyamide, in order to computationally develop surface coatings to bolster SNC rejection, and thus establish structure-property-performance relations linking coating composition with SNC rejection.
Objective 3. To characterise the transport mechanisms of SNCs through polyamide, to enable transport models to quantify the trade-off between contaminant rejection and water permeance.
Simulation insights emerging from this project will enable membrane manufacturers to develop highly selective RO membranes. These materials will lower the cost of seawater desalination and wastewater recycling by RO, in addition to producing safer product water for humans and ecosystems.
Research and Training
The successful applicant will conduct research in the School of Engineering at the University of Edinburgh, under the co-supervision of Dr Santiago Romero-Vargas Castrillón and Dr Rohit Pillai. The student will have access to a wide range of computational facilities, including ARCHER2, the UK’s national supercomputer. Educational and research opportunities afforded by this project include:
• training in state-of-the-art molecular simulation techniques
• close mentoring through regular meetings, as well as interactions with other investigators at the Institute of Multiscale Thermofluids (IMT) and the Institute for Infrastructure and Environment (IIE) at Edinburgh
• the opportunity to attend national and international scientific conferences to disseminate your results
• strong emphasis and support to publish research results in leading scientific journals, which will kickstart your career in academia or industry.
Further Information:
The University of Edinburgh is committed to equality of opportunity for all its staff and students, and promotes a culture of inclusivity. Please see details here: https://www.ed.ac.uk/equality-diversity
