Exceptionally Fast Water Desalination at Complete Salt Rejection by Pristine Graphyne Monolayers

TL;DR

This study demonstrates that pristine graphyne monolayers can desalinate seawater with complete salt rejection and water permeability vastly exceeding current membranes, offering a promising energy-efficient solution.

Contribution

The paper introduces the potential of pristine graphyne as an ultra-permeable, salt-rejecting membrane for desalination, based on molecular simulations and first principles modeling.

Findings

Achieves 100% salt rejection for seawater ions.

Water permeability is about 100 times higher than current reverse osmosis membranes.

Ion rejection is independent of salt concentration and pressure.

Abstract

Desalination that produces clean freshwater from seawater holds the promise to solve the global water shortage for drinking, agriculture and industry. However, conventional desalination technologies such as reverse osmosis and thermal distillation involve large amounts of energy consumption, and the semipermeable membranes widely used in reverse osmosis face the challenge to provide a high throughput at high salt rejection. Here we find by comprehensive molecular dynamics simulations and first principles modeling that, pristine graphyne, one of the graphene like one-atom-thick carbon allotropes, can achieve 100% rejection of nearly all ions in seawater including Na+, Cl-, Mg2+, K+ and Ca2+, at an exceptionally high water permeability about two orders of magnitude higher than those for commercial state-of-the-art reverse osmosis membranes at a salt rejection of ~98.5%. This complete ion rejection by graphyne, independent of the salt concentration and the operating pressure, is revealed to be originated from the significantly higher energy barriers for ions than that for water. This intrinsic specialty of graphyne should provide a new possibility for the efforts to alleviate the global shortage of freshwater and other environmental problems.