Production of dye from green and brown walnut shells for leather coloration

Abstract

Nowadays, it is observed that there is an increasing approach to the use of natural substances instead of synthetic ones. As the synthetic materials and products are more complex in comparison to natural substances, it will take a long time to complete their natural cycles and return to nature, thus, causing a lot of environmental pollution. Green and brown shells of walnuts that are not only valuable crops but also important components of the Mediterranean diet are by-products of the walnut production, having scarce use (especially green shell). Thus, using shells as a source of dye will increase the value of the walnut production, as well as offering utilization for a by-product, which is produced in large quantities. The purpose of this study is to produce dye from waste green and brown walnut shells, compare quality of these dyes and apply them separately in untreated leather. Before chemical processes, the walnut shells were chopped in a grinding mill. They were dried in an oven to eliminate the humidity and extracted in Soxhlet apparatus by using ethanol solution. Then, the ethanol solution was evaporated in controlled way and the produced dyes were mordanted by using potassium aluminium sulphate (PAS). The dyes were analysed by TLC and UV-Vis, whereas dyed leathers were analysed by colorfastness test. The present study showed that brown walnut shell dye having higher color values was better for yield, dye penetration and fastness properties compared to green walnut shell dye. Luminous effect was observed when these dyes were applied in leather. It is interesting, uncommon and economically valuable for leather industry. This study would be a positive step to meet the need of leather industry in Turkey and a good example for cleaner production.