Nanofiltration through pH-regulated bipolar cylindrical nanopores for solution containing symmetric, asymmetric, and mixed salts
Journal
Journal of Membrane Science
Journal Volume
641
Date Issued
2022
Author(s)
Abstract
The rejection of symmetric (1:1 and 2:2), asymmetric (1:2 and 2:1), and mixed (1:1 + 1:2 and 1:1 + 2:1) salts by a polyamide membrane is investigated theoretically taking account of its pH-regulated and bipolar nature. We consider the most compact way of distributing pores (honeycomb-like) on the membrane surface so that the influence of pore-pore distance on rejection performance can be taken into account. Assuming large pore-pore distance (or low porosity) so that the concentration polarization effect is negligible, we can investigate the influence of the intrinsic properties of the membrane on its performance. The results of numerical simulation reveal that, due to high resulting surface potential and high ionic selectivity, asymmetric salts exhibit better rejection performance than symmetric salts. The variation of rejection with the applied pressure shows a local maximum, and the associated mechanism discussed. The variations of local pH and filtration potential are examined to help understanding the ionic transport mechanisms in nanofiltration. The separation of mixed monovalent and divalent ions of the same polarity under the conditions of low ionic strength and low applied pressure is discussed for assessing the feasibility of ion recovery and purification. ? 2021 Elsevier B.V.
Subjects
Bipolar charge
Filtration potential
Ionic separation
Multiple ionic species
Nanofiltration
Ionic strength
Nanofiltration membranes
Purification
Salts
Applied pressure
Cylindrical nanopores
Ionic separations
Ionic species
Mixed salts
Rejection performance
Symmetrics
hydronium ion
hydroxide
inorganic salt
polyamide
polymer
Article
dependent variable
deprotonation
diffusion
electric potential
geometry
hydrodynamics
ion transport
ionic strength
isoelectric point
membrane
nanofiltration
pH
polarization
porosity
rate constant
simulation
surface charge
thermodynamics
Distance
Ionic Strength
Performance
Ph
Pressure
Rejection
SDGs
Type
journal article