Multiplication factors for converting to equivalents of CaCO3

Ca= 40Mg=24Fe=56Al=26

Hardness Estimation by EDTA- Numerical Problems

1. Standard hard water: Convert to Normality or MolarityNormality = Weight in gram per Lit / Eq.weightMolarity = Weight in gram per Lit / Molecular weight

2. Estimate EDTA strength (N or M)

Use N1V1= N2V2 Formulae

3. By using EDTA Strength (N or M), Find out hardness producing salts strengthin unknown hard water

Use N1V1=N2V2 Formulae

4. Using strength of hardness producing salt, find out the quantity of salts in mg per liter (ppm)

Hardness producing salt strength X 50 (for N) or 100 for M)X1000 mg /L or ppm

50 ml of sample hard water (CaCO3 :1mg per ml) requires 100 ml of EDTA for titration. 200 ml of hard water requires 80 ml of EDTA with same strength. Total hardness will be

1. Standard hard water: Convert to Normality or MolarityNormality = Weight in gram per Lit / Eq.weightMolarity = Weight in gram per Lit / Molecular weight

1mg /mL = 1000mg/Lit = 1g per LitSample Hard water CaCO3 strength = 1/100 = 0.01 M

= 1/50 = 0.02 N

2. Estimate EDTA strength (N or M)Use N1V1= N2V2 FormulaeEDTA Volume = V1 = 100mLSample hard water Volume = V2 = 50 mLSample hard water strength = 0.01 MEDTA strength = 0.01X50/100 = 0.005 M

= 0.02X50/100 = 0.01N

50 ml of sample hard water (CaCO3 :1mg per ml) requires 100 ml of EDTA for titration. 200 ml of hard water requires 80 ml of EDTA with same strength. Total hardness will be

2. Estimate EDTA strength (N or M)EDTA strength = 0.01X50/100 = 0.005 M

= 0.02X50/100 = 0.01N

3. By using EDTA Strength (N or M), Find out hardness producing salts strengthin unknown hard water Use N1V1=N2V2 Formulae

200 ml Hard water requires 80 ml of 0.005M EDTA (0.0025N)hardness producing salts strength = 80X0.005/200= 0.002M

= 80X0.01/200 = 0.004N

4. Using strength of hardness producing salt, find out the quantity of salts in mg per liter (ppm)Hardness producing salt strength X 50 (for N) or 100 for M)X1000 mg /L or ppm

Hardness = 0.002 (M)X100X1000 = 200 ppm= 0.004 (N) X50X1000= 200 ppm

Zeolite or Permutit process

X= 2-10, Y= 2-6

Natural Zeolite : non porusNatrolite, Na2OAl3O34SiO2.2H2O

Synthetic Zeolite: Porous and possess gelStructure. This type zeolite used for softening purpose is called permutitPrepared by heating together china clay, faldspar and soda ashThis has higher exchange capacity per unit weight than natural zeolite

2. Zeolite or Permutit process

Hence out goingWater contains sodium salt

Ion exchange or de-ionization or de-mineralization process

Cation Exchange resin

Cation: Positive charged ions Na+, H+, K+, Ca2+

Cation exchange resin: Cation can be exchangedSince anion is attached in solid (Resin)

SO

OOH S

O

OO- H+

OOH

OO- H+

Resin

Cation exchange resin

SO

OO- H+

OO- H+

+ Ca2+Cl2 SO

OO- Ca2+

+ Ca2+Cl2O

O- Ca2+

+ HCl

+ HCl

2

2

Cation exchange resin: Cation can be exchangedSince anion is attached with solid by covalent bond

Cation Resin Regeneration

SO

OO- Ca2+

OO- Ca2+

+ 2HCl

+ 2HCl

SO

OO- H+

OO- H+

+ CaCl2

+ CaCl2

2

2

Anion exchange resin

Anion: Negative charged ions Cl-, OH-,

Anion exchange resin: Anion can be exchangedSince cation is attached in solid (Resin) by covalent bond

NR

RR OH-Resin

Anion exchange resin

NR

RR OH- + Cl- + OH-N

R

RR Cl-

Anion exchange resin: Anion can be exchangedSince cation is attached with solid (Resin)

Anion Resin Regeneration

+ Na+OH-NR

RR Cl- N

R

RR OH- + Na+Cl-

Ion exchange or de-ionization or de-mineralization process

Mixed Bed De-ionizer

Municipal Water Treatment

3O2Silent electric discharge

2O3

Silent electric dischargeO2 + OO3