Deionizer

2. CONTENTS
Introduction
Principle of Deionizer
Types
Two –bed deionizer
Mixed-bed deionizer
Working of deionizer
Applications of deionizer

3. INTRODUCTION
For many laboratory & industrial applications high
Purity water which is essential free from ionic
contaminates is required and this type of water is
produced by “DEIONIZATION”.
Deionization is the process by which mineral ions
in water are removed and the apparatus used
for deionization is known as deionizer.

4.  Deionization water purification can be done by
using ion exchange method.
 Deionizers are most commonly used when
ionic contamination is such that reverse osmosis
alone cannot be relied upon to produce water
of acceptable quality.

5. Principle Of Deionizer
 “Deionizers remove both cations & anions, releasing
hydrogen ions (H+) in exchange for the former and
hydroxyl ions (OH-) for the latter. The hydrogen and
hydroxyl ions subsequently combine to form pure
water”.
 The following Figure illustrates the ion exchange
process

7. Types of deionizer
There are two types of deionizer . These
are :
 Two bed deionizer
 Mixed bed deionizer

8.  The two bed deionizer consists of two vessels –one
containing a cation exchange resin in the hydrogen (H+)
form and the other containing an anion resin in the
hydroxyl ( OH-) form .
 Water flow through the cation column , where upon
all the cations are exchanged for hydrogen ions .
 The same principle applies when considering anion –
exchange .
 The decationised water then flows through the anion
column .This time ,all the negatively charged ions are
exchanged for hydroxide ions which then combine
with the hydrogen ions to form water .
 The specific resistivity of this water is about
250,000ohms/cm.

10.  In mixed bed deionizers the cation – exchange
and anion exchange resins are intimately mixed
and contained in a single pressure vessel .
 The thorough mixture of cation- exchangers and
anion –exchangers in a single column makes a
mixed – bed deionizer equivalent to a lengthy
series of two- bed plants . Water quality obtained
is appreciably higher .
 More sensitive towards the impurities in the
water supply and yield water of
1,000,000ohms/cm 7upto 18,300,000ohms/cm.

12. The hard water is passed through cation exchange
column ,which removes all the cations ( Ca2+,Mg2+)
from it and equivalent amount of H+ ions are released .
2RH+
+ Ca2+ → R2Ca2+ + 2 H+
2RH+ + Mg 2+ → R2Mg2+ + 2H+
For every monovalent cation ,one hydrogen ion is
exchanged and for every divalent cation , two
hydrogen ions are exchanged .

13.  After cation exchange column , the hard water is
passed through anion exchange column, which
removes all the anions (SO4
2- , Cl-) and equivalent
amount of OH- ions are released from this column
to water.
ROH + Cl- → RCl- + OH-
2ROH + CO3
2- → R2CO3
2- + 2OH-
H+ & OH- ions released from cation & anion
exchange column respectively get combine to
form water .
H+ + OH- → H2O
This water is know as deionized or dimineralized
water.

14.  Boilers feed water , Textiles, Pharmaceuticals,
Chemicals , Swimming pools, Potable Water ,
Hospitals, Automobile, Battery and Fertilizers.
 Ion Exchange Plants .
Industrial DM Plant.
Mixed Bed Demineraliser .
Pharmaceutical industry.
Power plant.
Chemical industries .
Textile industries.

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