NAMS 2002 Workshop - ICOM 2008

convective flow liquid phase applications. Silica particle functionalization by
silane chemistry is well studied in the literature. In this particular case, silica
particles were functionalized with 3-mercaptopropylsilane in order to obtain free
surface thiol groups and incorporated into polysulfone matrix. Thiol groups
strongly interact with various metals like Au, Hg, Ag etc which may be applied
advantageously in various applications like water treatment and high value metal
capture processes. In order to demonstrate applicability of the MMMs, silver ion
is selected as the target metal ion for separation from its aqueous silver nitrate
solutions. The silica-polysulfone MMMs were characterized by SEM and
permeability measurements. It was observed that membrane permeability
increased with increasing silica loading (weight fraction) in the membrane. The
effect of silica properties like particle size, specific surface area, and
porous/nonporous morphology on the silver ion capture capacity was studied.
Typical silver capture capacity was in the range of 1.5 to 2 mmole per gram of
silica (20E-4 mmole per square meter of particles). Dynamics of the silver
capture process were studied by performing experiments at various applied
transmembrane pressure. Initially, the dynamic silver capture capacity decreased
from 70% to 40% of equilibrium capacity with increasing membrane flux and
became flux independent thereafter. It was also demonstrated that the
membrane can capture silver selectively in presence of significant concentration
of other metal ions like calcium. One dimensional unsteady state model with
overall volumetric mass transfer coefficient was developed and solved to predict
silver ion concentration in liquid phase and silica phase along the membrane
thickness at varying time. The breakthrough curve data predicted using model
solution is comparable with the experimental observations. Furthermore,
fundamental silver ion thiol interaction was studied by QCM (Quartz Crystal
Microbalance) technique.
Peter Frailie was supported by the NSF-REU program.