Abstract:

Since the environmental requirements for leather manufacture as well as for other industry branches are becoming stricter, investigations of unhairing have been directed towards conditions of the process which allow the saving of hair: enzymatic unhairing or unhairing with hair immunization conventionally achieved by using lime and sodium sulphide. The problem is that lime forms a big quantity of liquid waste which contains lime sludge polluted by sulphides and protein degradation products. The research is devoted to the replacement of Ca(OH)₂ as hair immunization material with some other soluble non-hazardous material with a similar immunization effect. The preliminary tests showed that alkaline sodium aluminate suits this purpose very well. Its immunisation efficiency increases with prolonged treatment duration and increased concentration of the treatment solution. Treatment with 20 g/l of sodium silicate solution for 3 h allows to reach a high immunization ability almost the same as that of calcium hydroxide under the same conditions. The immunisation effect lasts when the pH is approx. 13.