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50 2. Adsorption, Ion Exchange, and Catalysis

Some of the cons and pros of ion exchange are
Advants age

• in principle, all ions or ionizable species can be remoed from aqueous liquids v
• recovery of valuable species is possible
• high efficiency
• a large variety of specific resins is a v ailable

Disadvantages
• prefiltration is required (suspended particles in the feed should be less than about 50
mg/L to pre v ent plugging)
• interference of competing cations in the w aste w ater
• low-temperature resistance of organic (resin) ion e xchangers

Special application : Ion exchange was in the foreground in WWar II during the orld
Manhattan Project. The need for separation of reactor fusion products for analysis pur-
eral fusion v w poses led Boyd and coorkers to suggest the use of resins for the uptake of se
products. This study paved the way for the development of several ion-exchange methods.
However, the results of the Manhattan Project in connection with ion exchange were not
. published until 1947 on grounds of conf identiality

2.4.3 Catalysis

Catalysis has been widely used in numerous industrial processes for at least 150 years.
Catalysts are selected to increase the reaction rate and the yield of the desired products.
Heterogeneous catalysis is largely an empirical science, more of an art than a science, and a
large amount of knowledge in this field is empirical. The great range of catalyst applications
v led to the de much arious practical rules concerning their selection and use, elopment of v
earlier than the advance in the experimental techniques for the investigation of catalysis.
The emphasis on environmental protection in the last three decades, as industrial and
economic growth gae birth to many forms of pollution threatening human health and
v
Earth ecosystems, resulted in the growth of environmental catalysis. So, catalysts are not
only used to promote processes in the production field, b ut also to reduce the emissions of
undesirable or hazardous compounds to the enor e catalytic comb xample, vironment. F us-
tion has been proposed and developed as an effective method for controlling the emissions
of hydrocarbons and carbon monoxide.
act,
In f most of us benefit from the use of catalysis. Automotie catalytic con v v erters
have represented the most massie application of environmental catalysis and one of the v
most challenging and successful cases in catalysis, generally. Automobile catalysts deserve
a few more comments. The engine exhaust emission is a comple whose compo- x mixture,
actors such as dri ving ariety of f sition and flow rate change continuously depending on a v
conditions, acceleration, and speed. Despite the variability of the conditions, three-w ay
ydrocarbons,
catalysts hae achieed the reduction of exhaust carbon monoxide, h and
v
v