Define soft water | What is water softening? State the name of method of water softening | Describe the base exchange process for softening hard water?

Define soft water?

The water which does not contain H CO3-, Cl-, SO42- salt of Ca2+, Mg2+, Fe2+, Al3+ & form foam easily by reacting with soap is called soft water e.g. Rain water.

What is water softening? State the name of method of water softening?

WATER SOFTENING: To remove the impurities of hard water by some desirable process is called water softening.

WATER SOFTENING PLANT / METHODS OF WATER SOFTENING:

1.         soda lime process.

2.        Base exchange process (permutit).

3.         Demineralisation.

4.        Soda alum.

5.         Aeration.

6.        Chelation on sequestration.

7.         Calgon process.

Describe the Base Exchange process for softening hard water?

This method depends upon the use of zeolite or base exchange complexes.

The zeolites are hydrated silicates of Na & Al with a generated formula- (Na2O)x (Al2O3)y (SiO2)z (H2O)n

When zeolites or base exchange complexes are brought in contact with hard water, following reaction

For temporary hardness-

Ca(HCO3)2 + Na2O.Z → CaO.Z + Na2CO3 + H2O

Mg(HCO3)2 + Na2O.Z → MgO.Z + Na2CO3 + H2O

For permanent hardness-

CaSO4+ Na2O.Z → CaO.Z + NaSO4.

MgSO4+ Na2O.Z → MgO.Z + NaSO4.

In water Z is an abbreviation for the Al2O3.SiO2.H2O part of zeolite. The soft water obtained from this Base Exchange process is of 0 – 20° hardness or

Levelness. After a long time the whole of the Na in Base Exchange substance is replaced by Ca or Mg. it is said to be exhausted because it will not soften any hard water more. Then it has to be generated.

Regeneration: CaO.Z + 2NaCl → Na2O.Z + CaCl2

The CaCl2 & residual NaCl are washed away & the regenerated Na2O.Z can be used to soften the hard water again.

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Some Impotent Trams About Water Which Is Used In Textile Wet Processing?

##Why water is called universal solvent?

Water is called universal solvent, because the solvency power of water is very high & most of the solute of this world is easily dissolved in the water.

##What do you mean by water hardness?

Hardness is a term applied to water denoting a measurement of its pH & metal salt content. The presence of Ca & Mg salt i.e. Bi-Carbonates, Sulfates, Chlorides in water is called causes of hardness of water. The water which contains these salts is called hard water. Hard water does not easily form lather with soap as the salt of Ca & Mg react with soap to form insoluble organic salts.

CaSO4 + 2 RCOONa →  (RCOO)2Ca ↓ + Na2SO4.

MgSO4 + 2 RCOONa → (RCOO)2Mg ↓ + Na2SO4.

##State different types of water hardness?

Water hardness may be classified into following two types-

1) TEMPORARY HARDNESS:

Temporary hardness is due to the presence of Bi-Carbonates of Ca & Mg. this type of hardness is called temporary hardness, because, it can be removed by easy means like boiling. When temporary hard water is boiled, the Carbonates decompose with liberation of CO2 & precipitation of the insoluble Carbonates which are reformed.

Ca(HCO3)2 ∆→ CaCO3↓  + CO2   + H2O Mg(HCO3)2 ∆→ MgCO3 ↓ + CO2   + H2O

2) PERMANENT HARDNESS:

It is due to the presence of Sulfates, Chlorides of Ca & Mg. this type of hard water is called permanent hardness. These salts do not decompose on boiling. So, permanent hardness cannot be removed.

##Write down the name of mineral metallic salts which is responsible for water hardness?

The name of mineral metallic salts which is responsible for water hardness-

1. Ca(OH)2;    

2. Mg(HCO3)2;

3. Al(HCO3)2;

4. Fe(HCO3)2;       

5. CaSO4;    

6. MgSO4;

7. Al2(SO4)3;         

8. FeSO4;    

9. CaCl2;

10. MgCl2;   

11. AlCl2;      

12. FeCl2.

##Why soap does not create foam easily with hard water? Explain with reaction?

Soap does not create foam easily with hard water as the salt of Ca & Mg react with soap to form insoluble organic salts.

CaSO4 + 2 RCOONa →  (RCOO)2Ca ↓ + Na2SO4.

MgSO4 + 2 RCOONa → (RCOO)2Mg ↓ + Na2SO4.

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Define water? Classification of water?

Water:

Water is a complex compound. It is very important compound in textile wet processing. The total amount of water in the world is about 75%. Natural water is obtained in 3 steps. They are solid, liquid & vapor. Water has a un-comparable power to dissolve other compound. It is very difficult to obtain pure water in nature. Water is consists of two part Hydrogen & one part Oxygen. Its chemical formula is H2O. Water is converted to ice at 0°C & converted to vapor at 100°C the concentration of water is highest at 4°C.

 

Classification of water:

Classify water on the basis of hardness:

DESCRIPTION	TOTAL HARDNESS (degree)
Very soft	0 - 4°
Soft	5 - 8°
Mild	9 - 14°
Fairly mild	15 - 18°
Hard	19 - 30°
Very hard	>30°

 

Classify water on the basis of source:

 

On the basis of source water may be classified into followings-

1)        RAIN WATER:

• Rain, collected immediately after recitation, is the purest of all natural water.
• It may contain traces of gases dissolved out of the atmosphere & possibly an almost infinitely small amount of finely divided solid matter derived from the air.
• It also contain dissolved or Sulfur DI-oxide or Sulfuric acid, CO2, NH3, NO2 & other by products of industrialization.
• Suspended impurities present in it, can be filtered by using sand bed.
• Suitable for boiling, washing & dyeing process.

2)       SURFACE WATER:

• Surface water may consists of  rain water which has collected from streams, rivers or lakes.
• This type of water contains organic & inorganic matters which are dissolved in it
• & also contain suspended impurities.
• Then the nutrifying bacteria will  in time convert the organic substances into nitrates which are not objectionable in dyeing & printing.
• Surface waters may receive considerable additions of dissolved mineral salts from shallow springs which feed the streams.
• It contains Chloride, Sulfate, Carbonate, Bicarbonate of Na, P, Ca & Fe.
• Not suitable for dyeing & finishing.

3)       SUBSOIL WATER:

• This type of water is collected from shallow springs & wells which are about 50 ft (15 m) or so deep.
• It is usually free from suspended impurities because it has been filtered by its passage through the soil. It'll however contain dissolve organic water.
• Subsoil water is often rich in dissolved Carbon di oxide, a gas abundantly present in the skin of the soil.
• Subsoil waters are very variable with regard to the impurities which they contain.
• Not suitable for dyeing & finishing.

4)       DEEP WELL WATER:

• This type of water is obtained from 500 m below the surface. It is free from organic matters.
• The soluble impurities in water may be composed of a variety of substances. Soluble organic compounds, ammonium salts, Nitrates & Nitrites of animal; or vegetable origin may be found. If they are present in considerable quantities, the sewage contamination is undesirable for many textile purposes.
• The presence of salts of Ca or Mg in solution can be most undesirable in many finishing process.

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