New Insights into Salt Transport Mechanism in Membrane Desalination

New Insights into Salt Transport Mechanism in Membrane Desalination

Viatcheslav Freger*, Noga Fridman-Bishop, Vesselin Kolev,

¹Wolfson Department of Chemical Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel

Despite >50 years of industrial membrane desalination, salt transport in membranes (NF and RO) and membrane structure are still insufficiently understood. Our group has studied the mechanism of membrane transport using two basic methods: theoretical analysis using analytical models and molecular dynamics and experimental measurements using filtration data and impedances spectroscopy of genuine and model membrane films. Some open fundamental questions we tried to address were:

1)      Why polyamide has been the best material for RO/NF membranes

2)      What is the actual bottleneck of salt transport in RO/NF: a nanopore or a dense film?

3)      What is the charge of the membrane and how does it uptake salt?

4)      How much salt uptake and salt transport are related;

5)      How much role ion-specific effects (including H⁺ and OH^-) play in salt sorption and transport;

6)      How separation of complex ion mixtures (including pH changes) should be modelled etc.

Even though some question still remain open, we seem to have obtained (partly surprising) answers to some of the above questions, which will be presented in the talk.