صفحه 1:
Ion exchange is an adsorption
phenomenon where the mechanism
of adsorption is electrostatic.
hold ions to
charged function. groups on the
surface of the ion exchange resin.
The adsorbed ions replace ions that
are on the resin surface
صفحه 2:
selectivity
Ion exchange resi
certain affinity «
ions in aqueous
affinity or preference for a given
و1 رد۲6 021160 07۲
صفحه 3:
-atomic number 0
-physical roy) of)
-pore size distribution
-the type of functional groups on the polymer
chains
- Radius of hydration
صفحه 4:
Radius of hydration
The group of water molecules
surrounding each ion is called the
radius of hydration and is different
for different io I
صفحه 5:
Comparision of ionic, hydrated radii_,
Molecular Weight, and atomic number
for a number of cations
lon lonic Radii | Hydrated | Molecular Atomic
A |___ Radi, A Weight Number
Lit 0.60 100 | 6.941 3
خلا | _ 5 2 229897 | 4
K 133 | [39.0983 19
Ro | 14 | : | 85.4678 37
(st 169 | 5.05 | 132.9054 55
Mg? 065 | 1058 5 12
Catt 099 | 95 | 00 20
sr 113 | 5 | © 38
Bae | 135 | 88 |] 13 56
صفحه 6:
0
(Cer
صفحه 7:
resin operating on the
sodium cycle
The preference for divalent ions over
monovalent ions dimishes as the ionic
strengh of یت mcreases.
replace sodiu aaa on the resin structure.
In higher حمناهجومومع sodium can
be found in the resin phase.
صفحه 8:
450,000 mg/L
1.
Equivalent fraction Nat in liquid phase
sure 16-4
2 Na*—Ca?* equilibria for sulfonic acid cation exchange resin. (Courtesy of Rohm and ۶
صفحه 9:
Crosslink
The amoun of crosslinking depends
on the proportions of different
monomers used in the polymerization
step. Practical r ;are 4% to 16
%. Resins with ۷0 100 crosslinking
tend to be watery —
صفحه 10:
Moisture holding capacity
Moisture (water retention, or water content) is
related to porosity and ionic form. The water
content is expressed as a percentage of the moist
resin weight in a given ionic form.
About half the weight of all ion exchange resins is
water, unless they ha’ 1 ried or the water has
been replaced with an موم 10 0۲۵و
surrounds the active groups (hydration water) and
fills the voids in the resin matrix.
صفحه 11:
Moisture Content
100 ; Moisture Content vs Crosslinkage
%
water
0
0 % Crosslinking (as % of 6
divinyl benzene in polymerization )
صفحه 12:
lon exchange capacity
1۱ quecctip oP oniive ynoups = total query oF
Feet SNS LS aN ed dl Panic
nn A a Pa cae
Capacities are ee Coens per litre of
۱ 1 er kilogramme of dried
resin. The dry weight capacity indicates if a resin
has been properly functionalised, Whilst a high total
capacity is generally desirable, not all exchange
sites are used in a complete ion exchange cycle
صفحه 13:
Physical factors:
-swelling
-shrinking
Chemical factors:
_oxidation
Effect of fouling:
1)Silica fouling
2)Organic fouling
صفحه 14:
Particle size distribution
Ion exchange resin beads are spherical in shape and
are commercially available in particle diameter sizes
of 0.04 to 1.0 mm.
in the united states ,the p.
according to standard
قمیالم۷ |
Three parameters relat
-particle size range
-effective size (ES)
-UNIFORMIT Y COEFFICIENT (UC)
9 are listed
د or “ mesh “
particle size:
صفحه 15:
The mean diameter is the value of the
(theoretical) sieve opening through which exactly 50
of the resin volume passes, i.e. that retains exactly
50 % of the resin sample. It is abbreviated as "d.,,". In
the language of a تا ا Cereb eva
diameter.
WER ICRA ASG CMEC omnes Ce
opening through which exactly 10 % of the resin
sample passes. It is abbreviated as "d,,".
The uniformity coefficient is defined as: UC =
3 / مر
صفحه 16:
% between sieves “Gaussian” resin
۱2.5 33)
ا ۲
300 400 500 00 800 1000 1200 Brn
Mean diameter = 640 um
Effective sie = 450 um
Uniformity coefficient = 1.53
30
20
10
صفحه 17:
Ceometric Mean
Sie mm
10
050
02
Oil
(1056
Particle Diameter
mm
12-085
085-030
031-01
015-008
00-0
US.Standard
Screen Size
16-20
20-50
50-100
100-200
200-400
صفحه 18:
PARTICLE SIZE
The particle size of an ion exchange resin influences the
time required to establish equilibrium conditions. There
are two types of diffusion that must be considered in an
ion exchange equilibrium. The first is called film diffusion
or the movement of ions from a surrounding solution to
the surface of an ion exchi article. The second is
called internal diffusioi € movement of ions from
the surface to the inte ion exchange particle.
Film diffusion is usually the trolling reaction in dilute
solutions whereas internal diffusion is controlling in more
concentrated solutions. The particle size of an ion
exchange resin affects both film diffusion and internal
diffusion. A decrease in particle size thus shortens the
time required for equilibration.
صفحه 19:
_ TON EXCHANGE
EQUILIBRIUM DEVELOPMENT
-LAWS OF MASS
-using the prin
صفحه 20:
Coefficients
Preference for ions of particular resins is often
expressed through an equilibrium relationship using
the selectivity coefficient, —
Factors which affect the selectivity coefficient:
For a given resin type tivity is a function of
ionic charge and hydrated radius and functional
group-ion chemical interactions.
In most cases the higher fie ont charge the higher
the affinity for a site.
صفحه 21:
Typical applications of on exchange in dnoking water treatment are forthe
removal of hardness (calcium and. magnesium), the removal of nites, and
demineralization. Generally, ion exchange is considered as a simple slochiometc
reaction a8 shown in Equation | fora ction exchanger, Ths reaction ها the
trnfror removal ofA” fom aud phase to a solid pha, ۱ he
removal ol” fom solution
A™ +n(R-)B* 2 nB* +(R>), A™
صفحه 22:
where:
A = cation A
B = cation B
R = cation exchange resin
n = charge
Ks 5 as "Ce A
(as) @ee)”
where:
@a= activity of ion A
ay = activity of ion B
صفحه 23:
#ااااللكتبجهج "# ووم
measuring the selectivity or capacity of a specific resin for a given ion. Note that Kj
includes activity coefficient terms that are functions of ionic strength and thus the
measure of selectivity, or Kj, is not actually constant, but varies with water quality and
is somewhat site specific. However, general engineering calculations can be made
without having selectivity coefficients for all aqueous environments.
s_ BY")
Ka 0
]4 [2 [
where:
Kj - resin's selectivity of A over B
[4] cation A concentration in solution (meq/L)
[2] cation B concentration in solution (meq/L)
[4] = cation A concentration in resin (meq/L)
]8[ = cation B concentration in resin (meq/L)
صفحه 24:
كصادعء
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Selectivity’
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صفحه 25:
Experimental selectivity’s are often represented
using a quantity known asa separation factor, which
is defined in terms of concentration or mole fraction
separation factor [dimensionless]
= concentration of component i inthe resin {mol- I? ]
concentration of component i inthe solution [mol E*]
mole fraction of component iin the resin [dimensionless]
x, =mole fraction of component iin the solution [dimensionless]