TY - JOUR
T1 - Mechanistic study of pH effect on organic solvent nanofiltration using carboxylated covalent organic framework as a modeling and experimental platform
AU - Duong, Phuoc H.H.
AU - Shin, Yun Kyung
AU - Kuehl, Valerie A.
AU - Afroz, Mohammad M.
AU - Hoberg, John O.
AU - Parkinson, Bruce
AU - van Duin, Adri C.T.
AU - Li-Oakey, Katie D.
N1 - Funding Information:
The authors acknowledge generous support from the U.S. Department of Energy, Office of Basic Energy Sciences - BES under Award Number DE-SC0020100, the University of Wyoming's School of Energy Resources Carbon Engineering Initiative, the Center for Produced Water Management, and University of Wyoming Office of Water Programs. YKS and ACTvD were supported by Multi-Scale Fluid − Solid Interactions in Architected and Natural Materials (MUSE), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under the Basic Energy Sciences Program, Award # DE-SC0019285.
Funding Information:
The authors acknowledge generous support from the U.S. Department of Energy, Office of Basic Energy Sciences - BES under Award Number DE-SC0020100, the University of Wyoming’s School of Energy Resources Carbon Engineering Initiative, the Center for Produced Water Management, and University of Wyoming Office of Water Programs. YKS and ACTvD were supported by Multi-Scale Fluid − Solid Interactions in Architected and Natural Materials (MUSE), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under the Basic Energy Sciences Program, Award # DE-SC0019285.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/2/1
Y1 - 2022/2/1
N2 - Covalent organic framework (COF) membranes for organic solvent nanofiltration (OSN) have attracted growing interest due to their high stability, well-defined pore size, and controllable pore functionality. In aqueous nanofiltration processes, solution pH has a significant effect on membrane permeability, selectivity, and fouling. However, our understanding of pH effects on OSN processes is still limited. Here, we present experimental and reactive force field molecular dynamics (ReaxFF MD) simulation results on the effect of pH on OSN using a well-characterized carboxylated COF (C-COF) membrane. Filtration experimental and modeling results both demonstrate that pH changes can affect solvent permeance and solute rejection dramatically. Specifically, methanol permeance decreases with the increase of NaOH and HCl concentration, respectively. When Alcian Blue dye was used as the solute in methanol, the selectivity increased from 23% to 98% when changing the feed pH from 2.2 to 10.1, respectively. While ReaxFF MD results show that C-COF solvated pore size is only marginally affected by the pH of solution, methanol diffusion is affected by the size of methanol-solvated Na+ and Cl- ions, which increase with increasing Na+ and Cl- concentrations. Solution pH change also affected solute solvation layer thicknesses and C-COF pore charges, contributing to the significant AB dye selectivity increase with pH increase. To summarize, we have shown that dramatic changes in C-COF selectivity are not anomalous in OSN, but are instead controllable by varying feed solution pH to modify solvated solute radii and surface charge.
AB - Covalent organic framework (COF) membranes for organic solvent nanofiltration (OSN) have attracted growing interest due to their high stability, well-defined pore size, and controllable pore functionality. In aqueous nanofiltration processes, solution pH has a significant effect on membrane permeability, selectivity, and fouling. However, our understanding of pH effects on OSN processes is still limited. Here, we present experimental and reactive force field molecular dynamics (ReaxFF MD) simulation results on the effect of pH on OSN using a well-characterized carboxylated COF (C-COF) membrane. Filtration experimental and modeling results both demonstrate that pH changes can affect solvent permeance and solute rejection dramatically. Specifically, methanol permeance decreases with the increase of NaOH and HCl concentration, respectively. When Alcian Blue dye was used as the solute in methanol, the selectivity increased from 23% to 98% when changing the feed pH from 2.2 to 10.1, respectively. While ReaxFF MD results show that C-COF solvated pore size is only marginally affected by the pH of solution, methanol diffusion is affected by the size of methanol-solvated Na+ and Cl- ions, which increase with increasing Na+ and Cl- concentrations. Solution pH change also affected solute solvation layer thicknesses and C-COF pore charges, contributing to the significant AB dye selectivity increase with pH increase. To summarize, we have shown that dramatic changes in C-COF selectivity are not anomalous in OSN, but are instead controllable by varying feed solution pH to modify solvated solute radii and surface charge.
UR - http://www.scopus.com/inward/record.url?scp=85118489953&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85118489953&partnerID=8YFLogxK
U2 - 10.1016/j.seppur.2021.120028
DO - 10.1016/j.seppur.2021.120028
M3 - Article
AN - SCOPUS:85118489953
VL - 282
JO - Gas Separation and Purification
JF - Gas Separation and Purification
SN - 1383-5866
M1 - 120028
ER -