Lime Free Unhairing: Sodium Aluminate as an Alternative Towards a Cleaner Process

Sodium aluminate as an alternative to calcium hydroxide was tested in the hide unhairing process and the possibility of such replacement was confirmed. Qualitative unhairing is achieved using water solution containing sodium aluminate 2-3% and sodium sulphide 1.3-1.5%. The effect on collagen during unhairing using the sodium aluminate is significantly less than that of conventional liming. An addition of 0.5% NaOH allows better opening up of the derma to be obtained. Industrial trials of lime-free unhairing using sodium aluminate have shown that the leather produced meets the quality requirements for shoe upper leathers. Lime-free unhairing using sodium aluminate leads to less pollution of wastewater by TSS, Kjeldhal nitrogen and sulphides.