The role of steric hindrance and charge interactions in governing ionic transport through reduced graphene oxide (rGO) and commercial (DOW-Filmtec NF270) membranes was elucidated by a comprehensive study of experimental and established mathematical analysis based on Nernst-Planck equation. A charge-dominated salt exclusion mechanism was observed for the rGO membranes, which exhibited retention from low (7%) to moderate (70%) extent depending on the nature of ions (5 mM). Swelling of GO (1.2 nm interlayer distance) in water beyond the hydrated diameter of ions was attributed as a primary cause for lowering steric hindrance effects. The influence of parameters affecting charge interactions, such as pH and ionic strength, on the extent of salt rejection was modelled. The potential impact of the membrane's charge density, GO loading and interlayer spacing on salt retention was quantified by performing sensitivity analyses. For a high TDS produced water sample, the rGO membranes partially retained divalent cations (Ca:13%) and exhibited high dissolved oil rejection. The membranes were found to be suitable for the treatment of high TDS water with the goal of selectively removing organic impurities, and thus minimizing the impact of osmotic pressure effect. Performance of the membranes was also investigated for retention of water remediation related organic anions, using perfluoro octanoic (PFOA) acid as a model compound. rGO membranes exhibited a charge-dominated exclusion mechanism for retention (90%) of PFOA (1 ppm).
|Journal||Journal of Membrane Science|
|State||Published - Jun 1 2020|
Bibliographical noteFunding Information:
This research was supported by the National Science Foundation under Cooperative Agreement No. 1355438 , and by NIH-NIEHS-SRC (Award number: P42ES007380 ). GO Membrane development and produced water treatment aspects was funded by Chevron Corporation. Clair Jordon was supported by NSF-REU program. Authors also acknowledge the intellectual contributions made by Dr. Andrew Colburn in the analysis of membrane performance. The work was partially funded by the Australian Research Council Research Hub for Graphene Enabled Industry Transformation ( IH150100003 ).
© 2020 Elsevier B.V.
- Perfluoro octanoic acid (PFOA)
- Produced water
- Reduced graphene oxide
ASJC Scopus subject areas
- Materials Science (all)
- Physical and Theoretical Chemistry
- Filtration and Separation