ㄽᩥࡢせ᪨㢟 ┠Development of metal-coordinated aminosilica networks for highly permeable
and selective membrane separation(㔠ᒓ㓄఩䜰䝭䝜䝅䝸䜹⭷䛾㛤Ⓨ䛸㧗㏱㐣ᛶ䞉㧗㑅ᢥᛶศ㞳)
Ufafa Anggarini
Membrane processes and technology are considered energy efficient for theseparation of gas and liquid systems. Over the past decades, organosilica membranes haveattracted high attention due to high thermal and chemical stability with no swelling, highflux, high separation performance, and adjustable pore sizes. The primary goal of thisdissertation was to fabricate and optimize a hybrid thin film of metal-coordinatedaminosilica membranes based on sol-gel processing followed by coordination reaction
and investigate their performance in the separation of gas and liquid mixtures via
pervaporation. The best performance of metal coordinated-organosilica based membranes
was achieved by optimizing four parameters including the affinity of transition metal as
Lewis-acid molecules, the affinity of the ligand as Lewis-base molecules, the mole ratioof metal/amine groups, and the existence of metal in a different phase to facilitate thetransport of permeating molecules. At each step of optimization, the fixed variable wasselected and applied, and the investigation proceeded to the next step.
In the first stage of modification of metal coordinated-organosilica membranes,
the effect of metal doping was evaluated using a single gas permeation system. Values
for surface area and pore volume of the metal-doped bis[3-(trimethoxysilyl) propyl]
amine (BTPA) at metal/amine mole ratio of 0.25 mol mol-1 were both expanded byincreasing metal coordination affinity on the order of Ni-BTPA (214 m2 g-1) > Cu-BTPA(75.7 m2 g-1) > Ag-BTPA (20.1 m2 g-1) > BTPA (2.36 m2 g-1). In line with material
characterization, gas permeation was also increased in the same order, which corresponds
to a higher affinity for metal coordination. Ni-BTPA membrane with the highest affinity
for coordination achieved high levels of both permeance of N2 and N2/SF6 at 3.75 × 10-7
mol m-2 s-1 Pa-1 and 1,900, respectively. In the second stage, the optimization ofcoordination was examined by employing the incorporation of different amounts of nickel
dopant (mole ratio of nickel/amine) into BTPA structure that ranged from 0.125 to 0.50

mol mol-1. Higher nickel content increased the rigidity and resulted in a porous membrane
structure with a high specific surface area that beneficially showed high performance forthe pervaporation organic mixture of methanol/toluene on the order of Ni-BTPA 0.50 >Ni-BTPA 0.25 > Ni-BTPA 0.125 > BTPA. Ni-BTPA 0.50 has been found to exhibit
superior performance with a high level of flux at 2.8 kg m-2 h-1 and a separation factor
higher than 900 in a 10 wt% methanol feed solution at 50 ⁰C. In that work, Ni-BTPA 0.50
shows an attractive performance due to the balance between the formation of
microporosity that was induced by nickel-amine coordination and the excessive amountof nickel ions that facilitated the fast transport of methanol while restraining the transportof toluene.
To prove the concept of metal-coordinated aminosilica membranes, in the thirdinvestigation, the affinity of amine-functionalized organosilica as a ligand was evaluated
via different types of precursors. Nickel doping restructured the aminosilica network via
a coordination bond, which then increased both the rigidity of the organic chain and thesurface area or resultant material on the order of nickel doped bis [3-(trimethoxysilyl)propyl] amine (Ni-BTPA) > nickel-doped 3-aminopropyl triethoxy silane (Ni-APTES) >nickel-doped trimethoxy[3-(methyl amino) propyl silane (Ni-MAPTS). The preparedhybrid nickel-composite membranes were used for the pervaporation of various types oforganic mixtures with methanol 10 wt% at 50 ⁰C in the feed solution. Ni-BTPA with thestrongest affinity for coordination recorded the highest separation performance for theflux that reached as high as 1.42 kg m-2 h-1 with an optimum separation factor formethanol/toluene of 5,000. The enhancement for both membrane flux and the separation
factor verifies the balance between higher levels of interconnected micropores fromnickel-amine coordination and the existence of uncoordinated nickel acting as active sites
for the diffusion of methanol.
Based on the previous investigation, two phases of metal can facilitate a specifictransport of components while the coordinated network generates a high flux ofmembrane. In the fourth evaluation, we examine the fabrication of silver-doped BTPA
for facilitating the transport of H2. The evolution of silver in two phases as silver ions andnanoparticles successfully modify the membrane structure from dense into microporous,and silver-modified aminosilica membranes showed hydrogen permeance of 1.46 10-6
mol m-2 s-1 Pa-1 with excellent H2/C3H8 selectivity of 1,500. Based on this result, it isevident that the proposed modification via the two-phase structural evolution of silver
reorganized the organosilica framework and improve the separation performance of themembranes.

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