A Novel Application of Refinery Merox Unit Wastewater for Bovine Hide Unhairing

Abstract

Unhairing is one of the major steps of the leather tanning process which removes the hairs, epidermis and to some degree inter-fibrillary proteins. This process needs high amounts of chemicals that cause environmental difficulties. On the other hand, these chemicals are available in the wastewater of the Merox unit of Kermanshah Refinery. For reducing chemical consumption and decreasing environment pollution, we used the aforementioned wastewater for bovine unhairing. A unhairing liquor was prepared in order to unhair skins and different parameters such as the concentration of CaCO₃ and Na₂S, process time, and temperature were considered to evaluate their impact on the unhairing process and to obtain optimum condition. Response surface methodology based on Box-Behnken design was applied to model the unhairing efficiency in terms of four independent variables. A second-order polynomial equation was suggested to predict the response with high certainty. ANOVA revealed the validity and importance of that model by P-value of < 0.0001, large F-values, and, R² of 98.8. The maximum unhairing efficiency of about 98.5 % was obtained under the optimum condition of 1.7 wt% Na2S, 5.8 wt% CaCO₃, 114 min process time and 29.5 ºC.