Deliming is a critical processing step in the beamhouse for leather production. The main function of deliming is to remove residual unhairing chemicals from hides such as sodium sulphide and lime.
Calcium must be removed so that insoluble calcium salts such as calcium sulphate are not formed during pickling. Excess sodium sulphide if not removed during deliming will cause the formation of hydrogen sulphide when the PH decreases which is a very dangerous and toxic gas.
Typical deliming agents for leather production are:
- Ammonium sulphate
- Ammonium chloride
- Formic acid
- Lactic acid
- Sodium metabisulphite
- Carbon dioxide
2NH4 + Ca(OH)2 = Ca + 2NH3 + 2H2O
Use of ammonium salts result in the liberation of free ammonia as can be seen from the above equation.
Special deliming agents are available which improve deliming efficiency as well as the environmental profile such as: