Ultrathin Graphene Nanofiltration Membrane for Water Purification

TLDR

The study presents a method to fabricate ultrathin (≈22–53 nm) graphene nanofiltration membranes on microporous substrates for efficient water purification using chemically converted graphene. The membranes are produced by depositing chemically converted graphene sheets onto microporous supports, and their rejection mechanism is dominated by physical sieving and electrostatic interactions. The resulting ultrathin membranes achieve a high water flux of 21.8 L m⁻² h⁻¹ bar⁻¹, retain >99 % of organic dyes, 20–60 % of ion salts, require only 34 mg CCG per m², and combine high performance, low cost, and simple fabrication.

Abstract

Abstract A method of fabricating ultrathin (≈22–53 nm thick) graphene nanofiltration membranes (uGNMs) on microporous substrates is presented for efficient water purification using chemically converted graphene (CCG). The prepared uGNMs show well packed layer structure formed by CCG sheets, as characterized by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The performance of the uGNMs for water treatment was evaluated on a dead end filtration device and the pure water flux of uGNMs was high (21.8 L m −2 h −1 bar −1 ). The uGNMs show high retention (>99%) for organic dyes and moderate retention (≈20–60%) for ion salts. The rejection mechanism of this kind of negatively charged membranes is intensively studied, and the results reveal that physical sieving and electrostatic interaction dominate the rejection process. Because of the ultrathin nature of uGNMs, 34 mg of CCG is sufficient for making a square meter of nanofiltration membrane, indicating that this new generation graphene‐based nanofiltration technology would be resource saving and cost‐effective. The integration of high performance, low cost, and simple solution‐based fabrication process promises uGNMs great potential application in practical water purification.