Download ion exchange

OPERATION ION
EXCHANGE TOOLS
INDUSTRIAL CHEMISTRY
CLASS : XII
SEMESTER : 6
The Principle of Ion Exchange
The most common water softening
method called "ion exchange," is a
reversible chemical process of
exchanging hard water ions for soft
water ions.
Calcium and magnesium are the
hardness ions, sodium can be
considered the "softness" ions and they
are exchanged to create soft water.
The Principle of Ion Exchange
Ion exchange takes place in a "resin
bed" made up of tiny bead-like
material often made of styrene and
divynil benzene.
The beads, having a negative charge,
attract and hold positively charged
ions such as sodium, but will exchange
them whenever the beads encounter
another positively charged ion, such as
calcium or magnesium minerals.
This ion exchange happens very easily
since the sodium ions have a positive
charge of only one, while magnesium
and calcium have a more powerful
positive charge of two
Teknologi dan Rekayasa
Ion Exchange Reactions
Ion exchange is a reversible
chemical reaction wherein an ion
(an atom or molecule that has lost
or gained an electron and thus
acquired an electrical charge) from
solution is exchanged for a
similarly charged ion attached to
an immobile solid particle.
These solid ion exchange particles
are either naturally occurring
inorganic zeolites or synthetically
produced organic resins.
The synthetic organic resins are
the predominant type used today
because their characteristics can be
tailored to specific applications.
Teknologi dan Rekayasa
An organic ion exchange resin
An organic ion exchange resin is
composed of high-molecularweight polyelectrolytes that can
exchange their mobile ions for ions
of similar charge from the
surrounding medium.
Each resin has a distinct number
of mobile ion sites that set the
maximum quantity of exchanges
per unit of resin.
Exchange reaction
Ion exchange reactions are stoichiometric and
reversible. Example of the reaction can be
written as follows:
2(R-SO3H)+ NiSO4 = (R-SO3)2Ni+ H2SO4
R indicates the organic portion of the resin
and SO3 is the immobile portion of the ion
active group. Two resin sites are needed for
nickel ions with a plus 2 valence (Ni+2).
The ion exchange reaction is reversible. The
selectivity of a resin for a given ion is measured
by the selectivity coefficient. K. which in its
simplest form for the reaction
R-A++B+=R--B++A+
is expressed as: K = (concentration of B+ in
resin/concentration of A+ in resin) X
(concentration of A+ in solution/concentration of
B+ in solution).
Teknologi dan Rekayasa
Selectivity of ion exchange
resin
Typical examples of ions that
can bind to ion exchangers:
H+ (proton) and OH− (hydroxide)
Single charged mono atomic ions
like Na+, K+, or Cl−
Double charged mono atomic ions
like Ca2+ or Mg2+
Polyatomic inorganic ions like
SO42− or PO43−
Organic bases, usually molecules
containing the amino functional group
-NR2H+
Organic acids, often molecules
containing -COO− (carboxylic acid)
functional groups
Bio molecules which can be ionized:
amino acids, peptides, proteins, etc.
Teknologi dan Rekayasa
Selectivity of ion exchange
resin
Ion-exchange resin
An ion-exchange resin or ionexchange polymer is an insoluble
matrix (or support structure)
normally in the form of small (1-2
mm diameter) beads, usually white
or yellowish, fabricated from an
organic polymer substrate.
The material has highly developed
structure of pores on the surface of
which are sites with easily trapped and
released ions.
The trapping of ions takes place only
with simultaneous releasing of other
ions; thus the process is called ionexchange.
Teknologi dan Rekayasa
Resin Types
There are four main types differing in their
functional groups:
strongly acidic (typically, sulfonic acid groups,
eg. sodium polystyrene sulfonate or
polyAMPS)
strongly basic, (quaternary amino groups, for
example, trimethylammonium groups, eg.
polyAPTAC)
weakly acidic (mostly, carboxylic acid groups)
weakly basic (primary, secondary, and/or
ternary amino groups, eg. polyethylene amine)
There are also specialised types:
chelating resins (iminodiacetic acid,
thiourea, and many others)
Teknologi dan Rekayasa
Ion exchange resin beads
Exchange capacity
Exchange
Capacity of Weak
Acid Cation and
Weak Base Anion
Resins as a
Function of
solution pH
Batch and Column Exchange
Systems
Ion exchange processing can be
accomplished by either a batch method
or a column method.
In the first method, the resin and
solution are mixed in a batch tank, the
exchange is allowed to come to
equilibrium, then the resin is separated
from solution.
Passing a solution through a
column containing a bed of
exchange resin is analogous to
treating the solution in an infinite
series of batch tanks.
Teknologi dan Rekayasa
Column Exchange Systems
Ion Exchange Process Equipment
and Operation
Most industrial applications of ion
exchange use fixed-bed column
systems, the basic component of
which is the resin column
Typical ion
Exchange Resin
Column
Exchange Batch Tanks
 Concentration Profile in a Series of ion Exchange Batch Tanks
Resin Exchange Capacities
Resin Exchange Capacities
Water Softening Plants
Softeners are based on ion exchange
process.
Steel pressure vessels
containing cation exchange resin in
sodium form.
These resin eliminate dissolved ions
like calcium and magnesium from
water to give high quality soft water.
Necessary salt preparation tank with
injection systems is also offered with
the system.
Teknologi dan Rekayasa
Water softener
Water softening units
The softening cycle
Regeneration
Regeneration consists of 5
cycles:
1.Brine Fill
2.Brining
3.Brine Rinse
4.Backwash
5.Fast Rinse
Salt, dissolved in water, is called brine
and is needed to clean the minerals
from the resin beads.
To make brine, water flows into the
salt storage area during the fill stage as
shown.
The softener continues to produce soft
water during this initial stage
Usage
Processes of purification
Separation
Decontamination of aqueous
and other ion-containing
solutions
Application
Water softening
Water purification
Catalysis
Pharmaceuticals
Chemical &
petrochemical,
Sugar &
sweeteners,
Protein
purification.
Food & beverage,
Hydrometallurgical
,
Metals finishing,
Nuclear,
Semiconductor,
Power.