First of all, we need to remove the hardness of water before using hard water in textile dye processing. There are two type of hardness, a) Temporary, b) Permanent hardness.
Temporary hardness:
1. Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 ↓ +2H2O
2. Mg(HCO3)2 + 2Ca(OH)2 →2MgCO3 +2H2O
MgCO3 + Ca(OH)2 → Mg(OH)2 + CaCO3
Permanent Hardness:
- CaSO4 + Na2CO3 → CaCO3+ Na2SO4
2. MgSO
4 + Na
2CO
3 → MgCO
3+ Na
2SO
4 MgCO3 + Ca(OH)2 → Mg(OH)2 + CaCO3
Temporary hardness is remove by both boiling and temporary treatment and permanent hardness remove by the chemical treatment.