No abstract

Leather industry is one of the sources, which releases keratin-containing wastes. Still now, most of the tanneries are following hair-burning process, which contribute high amount of COD, BOD, TDS etc., to the effluent. This is a reason why numerous investigations are done reaching to replace the hair burning process by hair save unhairing: enzymatic or unhairing with hair immunization. The aim of the study was to investigate the biodegradability peculiarities of native hair, hair after enzymatic unhairing and hair obtained by unhairing with immunization effect. The soil burial test was carried out and the biodegradability of the wool was estimated. The biodegradability of the wool was estimated analysing their mass loss and fungal colonization. It was established that hair samples behave differently during the exposition in the soil: there were determined different species of fungi after 3-month exposition. The mass loss was different as well. Accordingly, the hair obtained after different method of unhairing are different in their properties as well. The different properties should mean different behaviour of the hair during biodegradation.

Recently, increasing attention has been paid to the application of enzymes in a wide variety of leather production processes. The aim of the present study was to investigate the action of enzymatic pickling on derma’s collagen and the influence of this action on subsequent processes and properties of chromed and finished leather. The application of active in acidic medium proteolytic enzymes in the pickling process led to an additional impact on derma structure: collagen was more strongly affected and the porosity of the pelt dermis was reduced, but the hide became more thermally stable. The enzymatically pickled pelt bonded more chromium and reached higher shrinkage temperature while chroming; dyes penetrated deeper; such leather bonded more fatliquors. On the other hand, the action of enzymes worsened the physical–mechanical properties of the leather, as the experimental leather was weaker than the conventional one. The first was characterised by weaker grain layer and had significantly higher relative elongation. Therefore, as some properties improve and others worsen during such a process, the application of every enzyme should be carefully investigated and optimized to produce a leather with defined properties.

The research was aimed to investigate the influence of deliming with peracetic acid on leather dyeing kinetics. Hydrophobic C.I. Acid Red 213 and hydrophilic C.I. Acid Red 423 dyes were used. Sorption of dye depends on hydrophobicity/hydrophility of dye and dyeing temperature. Equilibrium of process is reached faster using hydrophobic C.I. Acid Red 213 at 45 ºC. However, both control and experimental leather fibres adsorb more hydrophilic dye C.I. Acid Red 423 and this fact does not depend on temperature. The diffusion coefficient of dye C.I. Acid Red 423 calculated according to Weisz model is higher when dyeing conventional leather. The change of deliming method has influence on chromed leather dyeing but this influence is not significant. The adsorption ability of control leather fibres at 30 ºC and 45 ºC is higher using both dyes as compared to the dyeing the experimental one. The increase of dyeing temperature increases the adsorption ability independently on the sort of leather fibres. Such dependence of the adsorption ability on the temperature shows that hydrophobic action and van der Waals forces prevail between dye and fibres during dyeing process. The Gibbs energy changes show that adsorption of both dyes by leather fibres independently on their sort is a spontaneous process. The affinity of both dyes to conventional leather fibres is higher comparing with experimental one. The change of enthalpy is positive in all cases, and it means that the driving force of the dyeing is the change of entropy.

DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4431

Chrome shavings are posing a pollution threat. An alkali-enzymatic hydrolysis method was utilized to get collagen hydrolysate (CH) as possible constituent for leather finishing formulations. The new enzyme preparation Vilzim PRO Conc was exploited for the hydrolysis. The dependence of CH properties on conditions of hydrolysis was explored. The direct addition 5% CH into finishing compositions increases tensile strength and relative elongation of films obtained from the compositions. Further increase of the collagen hydrolysate content in the films leads to worse mechanical properties of the films.