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vironmental
Applications of
Adsorption,
2.4 En Ion Exchange, and Catalysis 49
Special applications: The environmental control and life support system on a space-
craft maintains a safe and comfortable environment, in which the crew can lie and v
work, by supplying oxygen and water and by removing carbon dioxide, water vapor and ,
trace contaminants from cabin air. It is apparent that the processes aimed at the recycling
of air and water are vital for supporting life in the cabin. These recycling processes
include separation and reduction of carbon dioxide, remoal of trace gas-phase contam- v
v
inants, recoery and purification of humidity condensate, purification and polishing of
w
wasteater streams, and are performed totally or in part by adsorption equipment
(Dabrowski, 2001).

Another special application of adsorption in space is presented by Gro er v et al . (1998).
The Uniersity of Washington has designed an v in situ resource utilization system to pro-
vide water to the life-support system in the laboratory module of the NASA Mars
Reference Mission, a piloted mission to Mars. In this system, the apor Adsorption V ater W
Reactor (WAVAR) extracts water vapor from the Martian atmosphere by adsorption in a
bed of type 3A zeolite molecular siee. Using ambient winds and fan power to mo e v
v
V
atmosphere, the W AR adsorbs the water vapor until the zeolite 3A bed is nearly satu- A
rated, and then heats the bed within a sealed chamber by micro v e of f e radiation to dri w a v
water for collection. The water vapor flows to a condenser where it freezes and is later liq-
uefied for use in the life-support system.

2.4.2 Ion exchange

Although there are some applications in gas emissions reduction, for e h xample, ydrogen
sulfide and ammonia remoal by utilizing carboxylic acid resins and ammonium anion-
v
exchange resins, ion exchange is mainly used in water treatment. Some characteris- w aste
erry, tic environmental applications are the following (Noble and T2004):

v
ater:
• treatment of mine drainage w remoal of metal cations and anions using silico-
titanates and layered titanates
• removal of nitrates and ammonia from groundw ater
• treatment of nuclear waste solutions:
v
(1) strontium remoal by clinoptilolite and heulandite (Chernjatskaja, 1988), (2)
cesium removal using hexchanger and phenolic resins (Harjula yanoferrate e xac et al .,
1994; Samanta et al ., 1992), (3) treatment of liquid nuclear wastes using titanate ion
exchangers (Dosch et al ., 1993), and (4) thorium ions remoal using zeolites (Sinha v
et al ., 1994)
• plating industry:
(1) treatment of raw water to produce high-quality rinse water, (2) chemical recoery v
from rinse w (3) treatment of plating baths to remoe contaminants, and (4) as a
v
,
ater
primary end-of-pipe treatment process