Separation techniques - ut.edu.sa
Transcript of Separation techniques - ut.edu.sa
1
Separation techniques
المادة العلمت
همت البدوي/ د
جىزاء الطىهر/أ
:كتابت نقلته
أمنه العبدان/أ
زهرة البلىي/ أ
نهى الجهن/ أ
عائشت السمري/أ
وفاء الجعد/ أ
2
SOLVENT EXTRACTION
GENERAL DISCUSSION
Solvent extraction involves the distribution of a solute between
two immiscible liquid phases. This technique is extremely useful
for very rapid and "clean" separations of both organic and
inorganic substances. The separation that can be performed are
simple, clean, rapid and convenient. In many cases separation may
be effected by shaking in a separatory funnel for a few minutes.
1-The distribution coefficient
A solute S will distribute itself between two phases(after shaking
and allowing the phases to separate)and, within limits, the ratio of
the concentrations of the solute in the two phases will be a constant
KD = [S]1/[S]2
Where KD the distribution coefficient and the subscripts represent
solvent 1 (e.g. an organic solvent) and solvent 2 (e.g. water). If the
distribution coefficient is large, the solute will tend toward quantitative
distribution in solvent 1 .
In the practical application of solvent extraction we are interested
primarily in the fraction of the total solute in one or other phase, quite
regardless of its mode of dissociation, association, or interaction with
other dissolved species.
2-The distribution ratio
It is more meaningful to describe a different term, the distribution ratio,
which is the ratio of the concentrations of all the species of the solute in
each phase. In this example, it is given by:
D = [Cs]1/[Cs]2
3- The percent extracted
3
The fraction of solute extracted is equal to millimoles of solute in the
organic layer divided by the total number of millimoles of solute. The
millimoles are given by the molarity times the millimiters. Thus, the
percent extracted is given by:
%E = [S]0V0/[S]0V0+[S]aVa×100%
Where V0 and Va are the volumes of the organic and aqueous phases,
respectively. It can be shown form this equation that the percent extracted
is related to the distribution ratio by:
%E = 100D/D+(Va/V0)
The apparatus used for solvent extraction is the separatory funnel
illustrated in figure 1. Mostoften, a solute is extracted form an aqueous
solution into an immiscible organic solvent. After the mixture is shaken
for about a minute, the phases are allowed to separate and the bottom
layer (the denser solvent) is drawn off in a completion.
EXPERIMENT 1 : Separation of iodine
You will be given a homogenous mixture of iodine and sodium chloride
in distilled water.
Discussion
The iodine is separated by an extraction process. The aqueous iodine-salt
solution, is shaken together with an approximately equal volume of
carbon tetrachloride (CCL4). Water and carbon tetrachloride do not mix
(they are insoluble in one another)hence two liquid phases will coexist
here. Iodine vastly prefers to dissolve in CCl4, thus it migrates from the
aqueous(H2O) phase into the non –aqueous (CCl4) phase – we say that
CCl4 "extracts" the I2 from the aqueous phase. Cl has no such tendency
(its solubility in CCl4 is nil) and hence it remains behind in the water
phase.
PROCEDURE
4
1-Pour all of filtrate into a clean 125 ml separatory funnel (suspended in
an iron ring on a ring stand) whose stopcock is closed.
2- pour in 20 ml of carbon tetrachloride,
3-Watch the added liquid to see whether it dissolves, floats as an upper
layer, or settles as a lower layer.(Which liquid has the greated density.
CCl4 or H2O?). insert the separatory funnel stopper, and shake the closed
funnel for about sec.(Fig.2).Shake vigorously enough so as to mix the
aqueous and non-aqueous phases intimately. Keep your hand on the
stopper; if internal pressure builds up, the stopper may pop out. To vent
the insife pressure, hold the stopped separatory funnel upside down, allow
the liquids to drain away from the stopcock, and which the tip still
pointing up, open the stopcock momentarily.
Close the stopcock , turn the separatory funnel upright, remove the top
stopper, and allow the layers to separate as completely as possible.
Carefully drain the layer through the stopcocker closing it just before the
last drop og lower layer goes through . What will the lower layer be?
Add another 20ml portion of fresh CCl4to the remaining upper layer and
repeat once more, drawing the second batch of CCl4 into a separate
container . (Why must remove the top stopper from the separatory funnel
each time before attempting to drain out the lower layer?). Repeat a third
time.
Separately save the second and third portions of CCl4, note and compare
their color with the first portion. Show these carbon tetrachloride
solutions to your laboratory instructor. Save the aqueous layer.
IODINE TEST
In the presence of iodine , the white color of the starch paper changes to
deep blue Dip your stirring rod into the solution and then touch it to a
piece of the starch paper. Be sure your stirring rod is thoroughly rinsed
before and after each use.
CHLORIDE TEST
5
To a test tube containing the sample (the aqueous layer), add 2 drops of
(AgNO3). You will observe a precipitate.
EXERCISE
Suggest a volumetric method for the determination of iodine and chloride
after the separation. Discuss the theory of the indicator used in each
method.
Experiment2:Determination of nickel as the dimethylglyoxime
complex
:Discussion
Nickel ( 200_400 microgram)forms the red dimethylglyoxime complex
only slightly soluble Alkaline medium; it is
in chloroform (35_50 g/L) NiCl
The optimum pH range for extraction of the nickel complex is 7_12 in the
presence of citrate . The nickel complex absorbs at 366 nm and also at
465_470 nm .
Chemicals:
Ammonium nickel sulphate (0.135 g ),citric acid (A.R.)5 g, ammonia,
dimethylglyoxime,chloroform and aluminium salt.
Procedure :
A homogenous solution of nickel (200_400 ug)ang aluminium (500 ug
)or iron (500 ug )is prepared.Transfer10.0ml of this solution (Ni content
about 200 ug) to a beaker containing 90 ml of water,add5.0g of A.R.citric
acid, and then dilute ammonia solution until the pH is 7.5.cool and
transfer to a separatory funnel,add20 ml of dimethylglyoxime
solution(1)and, after standing for a minute or two,12ml of chloroform.
6
Shake for l minute,allow the phases to sette out, separate the red
chloroform. Shake for l minute, allow the phases to settle out, separate
the red chloroform layer, and determine the absorbance at 366 nm in a
1.0.cm absorbance cell against ablank .Extract with a further 12ml of
chloroform and measure the absorbance of the extract at 366 nm ; very
little nickel will be found .Test for the iron or aluminium in the aqueous
layer .
Repeat the experiment in the presence of 500ug of iron (III)and 500ug of
aluminium ion ; on interference will be detected.
Note:
The dimethylglyoxime reagent is prepared py dissolving 0.50g of A.R.
Dimethylglyoxime in 250ml of ammonia solution and diluting to 500 ml
with water.
Report
:1- complete
a-Distribution coefficient is……………
b-Distribution ratio is …………………….
7
c-if a solute undergo association,dissociation
or polymerization,isused instead of…………….
2- Like dissolves like. Explain and give examples..
3- Although Ni+2 is an inorganic cation,it can be extracted in
chloroform. Explain
4- Amixture contains ontains only 250ug of Ni and 250ug of fe .can
nickel(II)be separated from iron(III) by solvent extraction and
determined qualitatively?
Experiment 3:Determination of Iron by chloride Extraction
Discussion
8
The extraction of iron (III) chloride from hydrochloric acid with diethyl
ether (probably as the solvated complex H[feCL4]) has long been known,
but the amount of metal extracted depends upon the concentration of the
acid and passes through a maximum at about 6M-hydrochloric acid
Elements that extracted well as chloride complexes include
sb(V),As(III),Ga(III),Ge(IV), TI(III),Hg(II) ,Mo(VI),Pt(II),and
Au(III).Elements which are partially extracted include
Sb(III),As(V),V(V),co(II),sn (II),and Sn(IV).many solvents with donor
oxygen atom, including di-isopropyl ether, B,B-dichloro-
diehtylether,ethyl acetate, butyl acetate, and pentyl acetate, have been
employed.
in most cases the optimum extraction depends upon the acid
concentration.
The extraction of large amounts of iron is conveniently made with iso
butyl acetae : this solvent has the merit of low volatility and of almost
negligible temperature rise during the extraction (unlike diethyl ether )
To gain experience in the procedure, experimental details are given for
the extraction of iron (III) in hydrochloric acid solution with diethyl ether
.
Procedure:
Weigh out 16.486 gm of A.R. hydrated ammonium iron (III) sulephate
and dissolve it in 250ml of 6M _hydrochloric acid in a graduated flask .
Extract,25.0 ml of the iron(III) solution (which contains 200mg of fe )
with three 25-ml portions of pure diethyl ether (1): shake gently for 3
minutes during each extraction . combine the three ether extracts and strip
the iron from the ether by shaking with 25 ml of water : approximately
99.9% of the iron is removed by this method. Boil off any ether
remaining in the aqueous extricate on a water bath (caution) , and
9
determine the iron by titration with standard 0.1 N-potassium dichromate
after previous reduction to the iron (II)state . The iron recovered should
not be less than99.6 %(2)
Notes:
1- The factors of importance in the diethyl ether extraction of iron are :
a- The iron must be in iron (III) state , since iron (II) chloride is not
extracted .
b- The hydrochloric acid concentration must be close to 6M .
c- The extraction should be carried out in subdued light , since ether
photochemicaly reduces iron (III).
11
d- The ether should be free from ethanol and peroxides because these
reduces the ion (III) chloride.
e- The concentration of anions other than chloride should be kept low.
f- Heat is generated be the mixing of the ether and the hydrochloric acid-
iron(III)chloride solution so that cooling of the mixture under the tap or in
ice is essential.
2- The procedure may be adapted to the determination of iron in an iron
ore or a steel . The details are as follows. Dissolve a 0.5gm sample ,
accurately .weighed , in 25 ml of 6M –hydrochloric acid and 4ml of
concentrated nitric acid by heating the mixture on a water bath .
Evaporate the solution to dryness and then dissolve the residue in 15mlof
1:1 hydrochloric acid. Transfer the solution to a continuous extractor and
rinse the vessel with a little 6M-hydrochloric acid Extract the solution
with diethyl ether or with peroxide-free di-isopropyl ether until the ether
iayer above the solution is colorless . Transfer the ethereal solution of the
iron (III) chloride to a separatory funnel, strip the iron from the ethereal
solution by two or three washings with an equal volume of water.
Determine the iron content as above.
Chromatography
Chromatographic techniques may be used for the separation and
analysis of mixture of gases, liquids, or solids . All chromatographic
techniques utilize a tow phase system, one stationary and one mobile .
Separation of the components between the two phase . The process
11
differs from ion exchange in that, transfer of a component from the
mobile phase to the stationary phase does not result in the transfer of an
equivalent quantity of a component originally on the stationary phase,
into the mobile phase . In chromatography the stationary phase is
chemically unchanged after the separation process . The elute will only
contain compounds which were present in the original solution or
mixture, no chemical change will have occurred .
The stationary phase may be a solid , or a liquid supported on an inert
solid . The mobile phase may be a gas or a liquid . Accordingly several
types of chromatographic procedures are recognized :
1 – liquid-solid chromatography .
2- Gas-solid chromatography.
3- Gas-liquid chromatography.
4- Liquid-liquid chromatography, a special case of which is known as
paper chromatography . In paper chromatography the stationary phase is
water supported by the cellulose of the paper .
Experiment 1 : chromatography , ascending the separation of pH
indicator mixture
Principle :
To demonstrate the characteristic . invariable movement of a compound
regardless of whether it is alone or in a mixture with other compounds
which separate well from it .
Running time :
12
At least 1 hour .
Chemicals :
Methyl orange
Ph.ph
Bromphenol blue
Solvents :
Either (a) n-butanol : ethanol : 2M ammonia
( 60 : 20 :20 by volume )
Or ( 60 : 20 : by volume )
(b) n-butanol :acetic acid glacial : water
( 60 : 15 : 25 by volume ) .
Locating agent : Ammonia .
Procedure :
1- Place 50 ml of the chosen solvent at the bottom of the tank and
replace the lid.
2- Prepare a 25 × 25 cm sheet of paper and apply one drop of each of
the three individual indicators and one drop of the mixture
separately to four origins , using the wire loop .
3- Form the paper into a cylinder and dasten with the tongued clips ,
part G .
4- Hold the origins over ammonia fumes to produce the alkaline color
forms of the indicators i.e. the indicator anions .
5- Place the cylinder rapidly into the tank , before the indicators can
revert to their free acid forms . This is important as the free acid
from may travel with an Rf value different from that of the ionic
form . Do not allow the paper to touch the glass walls .
6- Put the lid on and run solvent for at least one hour . Watch the
initial flow of solvent across the origin and note the immediate
commencement of separation of the indicators in the mixture .
13
7- Remove the chromatogram and make the solvent front with a
pencil .
8- Dry the chromatogram .
9- Observe that the mixture of indicators has separated into its three
individual components . Observe the different level reached by
each indicator in the mixture and compare each with the level
reached by the same indicator running by itself from one of the
other origins . Note that the level is the same for each pair of
indicator , regardless of whether they started alone or in mixture
with the other indicators .
Conclusion :
When two or more substances , in a mixture with each other , are
subjected to paper chromatography , each will run independently of the
others and will proceed to the same point that it would have reached had
it been run by itself.
Notes :
1- If the indicators are run in the free acid from they travel to quite
different positions . This can be confirmed by experiment .
2- In this experiment the substances are substances are well separated
. However, in multicomponent mixtures of complex chemical
substances it is likely that some of the components will , at the end
of the run , be found to be located in similar position . Their Rf
values will then be found to differ slightly from the Rf of the
substances run either alone or in simple mixtures .
3- The dyes, also separate well in solvent (a) and can usefully be
included in this experiment .
Report
14
Compute and compare the Rf values of each pH indicator
Other experiments were made using the book
Column chromatography
By this method the stationary phase is loaded into a vertical column ,
usually glass, and the moving phase is allowed to flow down it by gravity
or under pressure. In adsorpation chromatography , the substrate is
adsorbed directly on to the solid stationary phase and the liquid, mobile
phase competes with it for the substrate .
15
A variety of organic and inorganic liquids is used adsorption
chromatography . The eluting power of a solvent depends on its dielectric
constant which is an approximate measure of solvent polarity.
A mixture of the substance to be separated is dissolved in a small amount
of solvent and added to the top of the column. An equal volume of
solvent is removed form the lower end of the column thus allowing the
mixture to enter the column . The upper portion of the tube is filled with
eluting solvent , and solvent (elute) is continuously removed from the
lower end of the column . The separation process can now take tow
forms:
(1)Elution is continued a clear separation of the components of the
mixture can be seen ; examination of the column under UV light may
facilitate this observation . once a separation has been obtained the
stationary phase can be extruded and that potion of the stationary phase
carrying the compound extracted with a suitable solvent. Obviously this
method is most suitable for colored compounds .
(2)Elution is continued until the various components are eluted from the
column aliquot of the eluate are collected and tested for the compenent of
the mixture. Those portion of the elute containing the same compound
may be combined and the compound extracted by some suitable method ,
e.g. evaporation , precipitation , or liqud-liqud extraction .
The glass column used should have a means of supporting the stationary
phase. Commercial columns process either a porous glass plate fused
onto the base of the column , or a suitable device for supporting a
replaceable nylon net which in turn supports the stationary phase.
Packing of column :
Packing a column is normally carried out by gently pouring a slurry of
the stationary phase into a column which has its outlet closed , whilst the
upper part of the slurry in the column is stirred and /or column is gently
tapped to ensure that no air bubbles are trapped and that the packing
settles evently. Poor column packing give rise to uneven flow and
reduced resolution . the slurry is added until the required height is
obtained .
16
Once the required column height has been obtained , the flow of solvent
through the packed column is started by opening the outlet , and
continued until the packing has completely settled. To prevent the surface
of the column from being disturbed either by addition of solvent to the
column or during the application of the sample to the column , it is
normal to place a suitable protection device, such as a filter paper disc or
nylon or rayon gauze, on the surface of the column . once column has
been prepared, it is imperative that no part of it should be allowed to run
dry i.e. a layer of solvent should always be maintained above the column
surface .
Application of the sample :
The sample is first dissolved in the solvent before loading it into the
column . In most experiments, the sample is carefully applied by
capillary tubing and syringe or pump to pass the sample directly to the
column.
This part wasn't performed due to deficiency of chemicals year
2010/2011
Ion exchange
Properties of Ion Exchange
17
Ion exchangers operation is dependent upon certain properties of the system. Each
property has an affect on the efficiency and productivity of an ion exchanger. Below
are select properties which affect the system.
The density of resin has an affect upon how the system performs. Properties of resin
should be understood. For example, the density of the dry, water free resin is
generally smaller for anion exchangers than cation exchangers. The density of water
swollen resin depends on the type counter ion, swelling capacity and on the degree of
crosslinking, besides the density of dry resin. Furthermore, it should be noted that
bulk density is different than the density of the swollen resin. These densities are
important because operation is dependent upon the resins.
The mechanical resistance is a variable that is studied for ion exchangers. The
mechanical resistance is found to vary with structure of the system. It should be noted
that air dried resin is destroyed by certain friction. This needs to be thought of in
design stages.
The grain size, is a major part of the fluid flow and effectiveness of seperation of
systems. For example, condensation type resins are generally broken granules. On the
contrary, polymerization-type resins are small beads that are uniformally packed. To
measure the grain size a mesh is used to keep out larger particles. In addition, for
certain processes grain size is extremely important to efficiency. One such process is
seperations carried out by chromotography. The major point of study of grain size is
that it determines the fluid resistance of an ion exchange column made from ion
exchange resin. This can be the key to success of an industrial operation.
The total capacity is a measurement tool used to rate an ion exchanger. The total
capacity is the amount of exchangeable ions of unit weight of resin. The determination
of such factor is done by acid-base titration. Another capacity is salt splitting. This is
the amount of sodium ions absorbed by the cation exchanger in the hydrogen form
from a sodium chloride solution or hydrogen released by unit weight or unit volume.
For an anion exchanger the amount of base liberated from a salt by unit weight or
unit volume of the hydroxyl-form anion-exchange resin. Dissociation constants of
active groups of the resin is a major part of the salt splitting capacity. Further, noted
is the rest capacity which consists of the difference in monofunctinal strongly acidic
or basic resin of splitting capacity. Also, the apparent capacity can be defined as the
affects of multivalent anions on anion exchanger. Further, the break-through capacity
depends on the pH, grain size, column size and flowrate. These capacities are
properties of a system. Knowing and understanding the capacities allows for proper
design.
The porosity of a system controls much of the capacity of the exchanger. The surface
active groups and capillary groups take part in the characteristics of a ion exchanger.
The pores of IERs are of variable size even for the same resin product. Due to
porosity, the affects on capacity of greater sized ions is because of the sieve effect.
The determination of porosity can be done by means of solution containing ions of
known size and similarity by using capacity measurements. Also, the same
measurement can be done by the use of vapor pressures. Although, these methods
18
only measure mean particle size, it results in useful knowledge. In addition to the
above, it should be noted that crosslinking affects mean pore size.
The operating rate is essential to chemical engineers. Knowing the affects of
controlling the flow is desireable also. For example, natural zeolite exchangeres
operate slower and an ion exchanger of larger pores quicker. A cation exchanger is
also knowed to set up equilibrium quicker. One may image that the process is
controlled by the chemical reaction. But it is known that the diffusivity is a controlling
factor. In addition, the rate depends on diffusivity constants of active groups of the
resins. Other effects are on account of temperature and looseness of crosslinks
Ion Exchange Columns Aim To plot the breakthrough curve of strong acid cation exchange Amberlyst resins, and
determine their capacity by batch and continuous flow processes.
Theory Ion Exchangers
Of all different natural and synthetic products which show ion exchange properties, the most
important are
ion-exchange resins, ion-exchange coals, mineral ion exchangers, and synthetic inorganic exchangers. Ion
exchangers owe their characteristic properties to a peculiar feature of their structure. They
consist of a framework held together by chemical bonds or lattice energy which carries a positive or
negative surplus
charge. Counter ions of opposite charge move throughout the framework and can be replaced
by other ions of same sign. For example, the framework of a cation exchanger can be regarded as a
macromolecular or
crystalline polyanion, while the framework of an anion exchanger can be regarded as a polycation.
Ion Exchange Resins
These constitute the most important class of ion exchangers. Their frame-work called the matrix, consists
of an irregular, macromolecular, 3-D network of hydrocarbon chains. The matrix carries
ionic groups such
as SO32-
, COO− in cation exchangers and NH+3 , NH+2 in anion exchangers. Ion exchange
resins are thus
cross linked polyelectrolytes. The matrix of the resins is hydrophobic. However, hydrophilic
components are introduced by the incorporation of ionic groups such as SO3H. Linear hydrocarbon
macromolecules
with such molecules are soluble in water. So ion exchange resins are made insoluble by introduction of
cross-links which Interconnect the various hydrocarbon chains. An ion-exchange resin is
practically one
single macromolecule . Its dissolution would require rupture of C-C bonds. Thus resins are insoluble in all
solvents by which they are not destroyed. The matrix is elastic and can swell by taking up
solvent , a fact referred to as ”heteroporosity” or ”heterodictality”.
19
The chemical, physical, and mechanical stability and the ion-exchange behavior of the resins
depend primarily on the structure and the degree of cross-linking of the matrix and on the nature and number
of fixed ionic
groups. The degree of cross-linking determines the mesh width of the matrix and thus the
swelling ability of the resin and the mobility of the counter ions in the resin, which in turn determine the rates of
ion-exchange
in the resin. Highly cross linked resins are harder and more resistant to mechanical breakdown.
Amberlyst-15 with sulphonic acid functionality is our resin of interest. It is a highly porous,
macro reticular ion-exchanger prepared by a variation of the conventional pearl-polymerization technique. In
pearl polymerization,
monomers are mixed, and a polymerization catalyst such as benzoyl peroxide is added. The
mixture is then added to an agitated aqueous solution kept at the temperature required for poymerization.
The mixture forms small droplets, which remain suspended. A suspension stabilizer is added
to prevent agglomeration of droplets. In the case of Amberlyst, an organic solvent which is a good
solvent for the
monomer, but a poor solvent for the polymer is added to the polymerization mixture. As polymerization
progresses, the solvent molecules are squeezed out by the growing copolymer regions. In this
way, spherical
beads with wide pores are obtained.
Selectivity
Ion exchangers prefer one species over another due to several causes :
1. The electrostatic interaction between the charged framework and the counter ions depend on the size
and valence of the counter ion.
2. In addition to electrostatic forces, other interactions between ions and their environment
are effective. 3. Large counter ions may be sterically excluded from the narrow pores of the ion exchanger
All these effects depend on the nature of the counter ion and thus may lead to preferential
uptake of a species by the ion exchanger. The ability of the ion-exchanger to distinguish between the various
counter ion species
is called selectivity.
Separation Factor
The preference of the ion exchanger for one of the two counter ions is often expressed by the
separation
factor, defined by… The molal selectivity coefficient , which is used for theoretical studies, is defined as….
The selectivity of the ion exchange process depends on the properties of the ion exchanger
used and the composition of the aqueous phase . In the case of two ions having the same charge and very
similar radii,
the selectivity due to the properties of the ion exchanger (such as acidity, basicity, and the degree of cross
linking ) is not sufficient for ensuring effective separation. In such a case, an appropriate
complexing agent
has to be added to the aqueous phase: the selectivity attained is then either due to the difference in the
21
stability constants or to the different charges or structures of the complexes formed.
Increased selectivity can be brought about in many ways. For eg., one can exploit the preference of an exchanger
for highly
charged ions in dilute solutions, or one can choose a chelating resin.
Capacity Capacity is defined as the number of counter-ion equivalents in a specified amount of
material. Capacity
and related data are primarily used for two reasons:- for characterizing ion-exchange materials, and for use
in the numerical calculation of ion-exchange operations. Capacity can be defined in
numerous ways: 1. Capacity (Maximum capacity, ion-exchange capacity) Definition : Number of inorganic
groups per
specified amount of ion-exchanger
2. Scientific Weight Capacity Units : meq/g dry H+ or Cl− form 3. Technical Volume Capacity Units: eq/liter packed bed in H+ or Cl− form and fully water-
swollen
4. Apparent Capacity (Effective Capacity) Definition : Number of exchangeable counter ions per specified
amount of ion exchanger.
Units : meq/g dry H+ or Cl form (apparent weight capacity). Apparent capacity is lower than maximum
capacity when inorganic groups are incompletely ionized ; depends on experimental
conditions
(pH, conc. ,etc) 5. Sorption Capacity. Definition : Amount of solute , taken up by sorption rather than by
exchange, per
specified amount of ion exchanger 6. Useful Capacity Definition : Capacity utilized when equilibrium is not attained Used at low
ionexchange
rates Depends on experimental conditions (ion-exchange rate, etc.)
7. Breakthrough Capacity ( Dynamic Capacity) Definition : Capacity utilized in column operation, Depends
on operating conditions
8. Concentration of fixed ionic groups Definition : Number of fixed ionic groups in meq/cm3 swollen
resin (molarity) or per gram solvent in resin (molality) Depends on experimental
conditions(swelling, etc.) Used in theoretical treatment of ion-exchange phenomena
…………..
Qv = volume cpacity in equivalents per liter packed bed. Qw = Scientific weight capacity in milliequivalents per gram.
b = fractional void volume of packing
W = water content of the resin in weight percent d = density of the swollen resin in grams per ml
B The molality of fixed groups in meq/g is
m =(100 − W) × Qw W × (1 + PQi−MQw × 10−3)
The molarity of fixed groups in meq/ml is
X =d × (100 − W) × Qw
100 × (1 + PQi−MQw × 10−3)
21
Batch Process Apparatus
Stirred tank reactor with stirrer, belt, stand, pipette, resins, copper sulphate solution, test
tubes ( 15), ion
meter, cupric electrode, Ionic Strength Adjustor (ISA), volumetric flasks
Procedure
1. Calibrate the ion meter using cupric nitrate standards of concentrations 0.6355 ppm ,
6.355 ppm , 63.55 ppm , and 127.1 ppm.
2. Take known weight of resins in the stirred tank reactor. Fit the reactor on the stand and
attach the belt
to the stirrer which is adjusted on the pulleys. Switch on the stirrer . 3. Pour quickly calculated volume of 800 ppm cupric sulphate solution into the tank and start
the timer
. 4. Withdraw 1 ml samples from the tank using a pipette at every 40 seconds for about 10
minutes.
5. Dilute the samples to 50 ml in volumetric flasks and measure their concentrations using ion meter.
6. Plot a graph of concentration vs. time.
7. The amount of cupric ions consumed is calculated from the initial and final concentrations.
Calculations Initial concentration - C0 ppm
Final concentration - Cf ppm
Qty. of cupric ions used Q =(Cf − C0) × 250/1000000
Capacity of resins = (Q/63.55) eq/g of resin
Observation Table
S.N. Time (min) Cu ion concentration (ppm)
Graph Plot a graph of concentration versus time.
Continuous Process Procedure
1. Take 10 g resins and prepare a slurry with distilled water. Charge the column with the
slurry such that
there are no air bubbles trapped. 2. Keep adding cupric sulphate solution to the resin, and let it flow out at approximately 1
ml/min.
3. After every 20 ml, measure out 1 ml of effluent, dilute it to 50 ml in the volumetric flask and measure
its concentration in the ion meter.
4. A graph of concentration versus volume is plotted .
Observation Table
S.N. Time (min) Cu ion concentration (ppm)
Graph
Plot a graph of concentration versus time.
Results and Comments