Hair-saving Enzyme-assisted Unhairing: Effects of Sodium Hydrosulfide and Peroxide

In a traditional dehairing process with sodium sulfide and lime, the hair is degraded to some extent so that it can not be recovered. Thus, the old process is a major contributor to wastewater pollution. Enzymatic dehairing is a cleaner process, but its results were not satisfactory. In this study, an attempt was made to modify the disadvantages of the two unhairing methods in the tannery. Several commercia l enzyme formulat ions were chosen, and the effects of sodium hydrosulfide and peroxide on proteases activity were studied. Then, hair-saving enzymat ic unhairing experiments with the two reagents were performed in paste and pile method. Activity of enzyme 2709 stabilized with the addition of sodium hydrosulfide; but peroxide would affect the activity of protease 3942. Hair was completely removed, which was confirmed with the scanning electron microscope analysis. Strength and bulk properties of the experimental leathers were also comparable to the controls. Biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS) and total suspended solids (TSS) significant ly reduced with the two new processes. Therefore, the hair-saving enzyme-assisted unhairing is a cleaner technology to replace the traditional method.