Permeation Properties of Ions through Inorganic Silica-Based Membranes

Abstract

The development of inorganic membranes has mainly found applicability in liquid separation technologies. However, only a few reports cite the permeation and separation of liquids through inorganic nanofiltration membranes compared with the more popular microfiltration membranes. Herein, we prepared silica membranes using 3,3,3-trifluoropropyltrimethoxysilane (TFPrTMOS) to investigate its liquid permeance performance using four different ion solutions (i.e., NaCl, Na2SO4, MgCl2, and MgSO4). The TFPrTMOS-derived membranes were deposited above a temperature of 175 °C, where the deposition behavior of TFPrTMOS was dependent on the organic functional groups decomposition temperature. The highest membrane rejection was from NaCl at 91.0% when deposited at 200 °C. For anions, the SO42− rejections were the greatest. It was also possible to separate monovalent and divalent anions, as the negatively charged groups on the membrane surfaces retained pore sizes >1.48 nm. Ions were also easily separated by molecular sieving below a pore size of 0.50 nm. For the TFPrTMOS-derived membrane deposited at 175 °C, glucose showed 67% rejection, which was higher than that achieved through the propyltrimethoxysilane membrane. We infer that charge exclusion might be due to the dissociation of hydroxyl groups resulting from decomposition of organic groups. Pore size and organic functional group decomposition were found to be important for ion permeation.

Annealing and TMOS coating on PSF/ZTC mixed matrix membrane for enhanced CO2/CH4and H2/CH4separation

“…The permeance value can be obtained through equation (2.1) [47] :Pnormali = true0ni x lt A ΔPwhere P i is the gas permeation in mol s −1 m −2 Pa −1 (1 GPU = 3.35 × 10 −10 mol s −1 m −2 Pa −1 ), n i [mol] is the permeated molecules, t [s] is the permeation time (s), ΔP [Pa] is the pressure differential, l is the thickness of the membrane (m), and A is the effective membrane surface area (m 2 ).…”

Development of a P84/ZCC Composite Carbon Membrane for Gas Separation of H2/CO2 and H2/CH4

“…The permeability calculation was performed based on the equation from Yoshiura et al The gas permeance result can be calculated using eq where P i is the gas permeation in mol/(s m 2 Pa) (1 barrer = 3.35 × 10 –16 mol/(s m Pa)), n i (mol) is the permeated molecules, t (s) is the permeation time (s), Δ P (Pa) is the pressure differential, l is the length of the thickness (m), and A is the effective membrane surface area (m 2 ).…”

The Evaluation of Counter Diffusion CVD Silica Membrane Formation Process by In Situ Analysis of Diffusion Carrier Gas

“…The TMOS-derived membrane showed an H 2 /N 2 permeance ratio of about 500 with an H 2 permeance of 9.1 × 10 −8 mol m −2 s −1 Pa −1 , while the PrTMOS-derived membrane showed a lower H 2 /N 2 permeance ratio of 30 with higher a N 2 /SF 6 permeance ratio of 30. The precursors with methyl [23], ethyl [18,24], propyl [24,25], butyl [18,23], hexyl [1,18,[24][25][26][27], phenyl [28,29], 3-aminopropyl [23], and 3,3,3-trifluoropropyl [30] groups were investigated. Matsuyama et al [25] prepared the silica membrane via CVD using hexyltrimethoxysilane (HTMOS) as a precursor.…”

“…A methane/ethane permeance ratio of 10 was found for the ETMOS-derived membrane. These types of membranes succeeded in separating liquids, including sodium chloride [28], sulfuric acid [29], glucose, magnesium chloride, and sodium sulfate aqueous solution [30].…”