Nanofiltration membranes review: Recent advances and future prospects

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.

Ultrathin Graphene Nanofiltration Membrane for Water Purification

A review of the effects of emerging contaminants in wastewater and options for their removal

Factors affecting the rejection of organic solutes during NF/RO treatment—a literature review

Drawbacks of applying nanofiltration and how to avoid them: A review

Retention of a wide variety of organic pollutants by different nanofiltration/reverse osmosis membranes: controlling parameters of process

Change in membrane performance due to organic fouling in nanofiltration (NF)/reverse osmosis (RO) applications

Rejection mechanism of nanofiltration (NF) membrane for organic solutes (including alkyl phenol, bisphenol A, phthalate acid esters, phosphoric acid esters, other plastic additives, and natural hormones like 17β estradiol, etc) was examined. The experiments indicated almost complete removal of these solutes by the tight NF membranes, while the rejection obtained by the loose membranes was dependent on solute species. Compounds with flat-shaped structure like 2-H-benzothiazol and dimethyl phthalate were more permeable than other target solutes within the same molecular size range. Of the four methods of size determination used, there was no significant difference in the accuracy of prediction of rejection from the solute sizes. The size configurations of molecules have been identified to greatly influence the permeation or retention, yet the size parameter was thought to be incomplete as a single parameter in describing rejection of organic solutes. The logarithm of octanol-water partitioning coefficients of solutes appears not to be an effective parameter in modelling rejections as its contribution was only slight or minor. We obtained better correlations with structural configuration of molecules (by molecular width and length) and polarity of the molecules.

Kenneth O. Agenson

Papers

Retention of a wide variety of organic pollutants by different nanofiltration/reverse osmosis membranes: controlling parameters of process

Change in membrane performance due to organic fouling in nanofiltration (NF)/reverse osmosis (RO) applications

Rejection mechanisms of plastic additives and natural hormones in drinking water treated by nanofiltration