Hard Water treatment with cation and anion exchanger

It shows method to water soft from hard water

1. Clogged Pipes – Hard Water
limestone ‘hard’ water
carbonic acid
Step 1: Acid rain is formed
Step 2: Acid rain dissolves limestone
Water softener
H
2O + CO
2 H
2CO
3
H
2
CO
3
+ CaCO
3
Ca(HCO
3
)
2
H
2CO
3 + MgCO
3 Mg(HCO
3)
2

2. Pipes develop Scales
Step 3: Hard water is heated and deposits scales
Ca(HCO
3)
2 CaCO
3(s) + H
2O + CO
2
Mg(HCO
3)
2 MgCO
3(s) + H
2O + CO
2
scales on pipes


1 gram =
1
/
7000th
pound
300 gallons / day with 10 grain water supply

3. No More Hard Water Scale
No More Ugly Hard Water Spotting
Protects Plumbing and Appliances
Saves Money on Cleaning Products

4. Water Purification
Hard
Water
Cation
Exchanger
Anion
Exchanger
Deionized
Water
(a) (b) (c)
H
+
H
+
H
+
H
+
H
+
H
+
H
+
H
+
OH
-
OH
-
OH
-
OH
-
OH
-
OH
-
OH
-
OH
-
(a)The cations in hard water are exchanged for H
+
.
(b)The anions in hard water are exchanged for OH
-
.
(c)The H
+
and OH
-
combine to give H
2
O.
Hard water is softened by exchanging Na
+
for Ca
2+
, Mg
2+
, and Fe
3+
.
Corwin, Introductory Chemistry 2005, page 361
Na
+
Ca
2+
Mg
2+
Fe
3+

5. Which ions are removed from hard water
to produce soft water?
Hard water is softened by exchanging Na
+
for Ca
2+
, Mg
2+
, and Fe
3+
.
Na
+
(aq) + H (resin) Na (resin) + H
+
(aq)
Cl
-
(aq) + (resin) OH (resin) Cl + OH
-
(aq)
Notice that the ion exchange resin
produces both hydrogen ions and hydroxide ions
which can readily combine to give water.
H
+
(aq) + OH
-
(aq) H
2
O (aq)
The net result is that the resin removes all ions from water passing through the deionizing system.
Corwin, Introductory Chemistry 2005, page 361

6. Calcium (Ca
2+
)
and
Magnesium (Mg
2+
)
Ions in
Untreated Water
Sodium (Na
1+
)
Ions
on beads
Calcium (Ca
2+
)
and
Magnesium (Mg
2+
)
Ions
on beads
Sodium (Na
1+
)
Ions in
Treated
Water