|
| |
PRODUCT DATA SHEET
ZK406SMZ
Surfactant Modified Zeolite
Zeolites are naturally occurring aluminosilicates characterized by
high surface areas and high cation exchange capacities. Zeolites have a unique
three-dimensional cage-like structure which ha s led to their use as molecular sieves.
Their cation exchange properties are exploited in many wastewater treatment processes to
remove cations such as ammonium and heavy metals. Naturally occurring sedimentary zeolites
are found in massive deposits in many areas of the world. Typically, the zeolite may be
crushed and sized as desired, tuning its permeability for flow-through applications |
 |
THE SURFACTANT
We have found that the charge-balancing cations present on the raw
zeolite surface (typically Na+, K+, Ca2+, and Mg2+) can be replaced by
high-molecular-weight quaternary amines such as hexadecyltrimethylammonium (HDTMA). These
quaternary amines ( also known as cationic surfactants) exchange quantitatively and
essentially irreversibly with cations on the external surface of the zeolite. The
quaternary amines are too large to enter the internal pore structure of the zeolite, and
the internal or zeo litic exchange sites potentially remain available to sorb smaller
inorganic cations.
SOLUTE-SURFACE INTERACTIONS
 |
Sorption of the quaternary amine profoundly alters the chemistry of the zeolite's
external surface; a bilayer-like structure is formed, causing the charge on the surface to
change from negative to positive and t he organic carbon content of the zeolite to
increase to about 5% by weight. The positive surface charge provides sites for sorption of
anions such as chromate and nitrate. The organic-rich surface layer provides a
partitioning medium for sorption of non polar organics such as chlorinated solvents and
fuel components. Some of the zeolite's original cation exchange capacity is retained for
sorbing positively charged species such as Pb2+ and Hg2+. Thus, surfactant-modified
zeolite (SMZ) can simultaneously sorb the three major classes of water contaminants:
inorganic cations, inorganic anions, and nonpolar organics. |
PRACTICAL APPLICATION
Due to its low cost, ability to sorb multiple types of contaminants
simultaneously, and its "tuneable" permeability, SMZ is suited for applications
where large volumes of sorbent are required. Examples of a few of these potential
applications are shown below.
In particular, SMZ is attractive for use in subsurface permeable
barriers for retarding contaminant migration.
Design schematic of the SMZ Pilot Project Barrier at OGI
All images created by LRJ Graphics
|
