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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.

Chrome tanned leathers are definitely unique in comparison with leather made from any other known tanning agents, especially in terms of thermal stability, cost and its reactive mechanism with collagen fibers. In our current studies, self basifying chrome tanning materials masked with different percentages of organic acid were prepared and applied after the de-liming stage of leather processing. This eliminated the need for pickling and basification steps. Tanned leathers resisted shrinkage up to 103 and 105±2°C while conventional chrome tanned leathers resisted up to 108±2°C. Also, interaction of anionic chrome species in tanning was studied. It was observed that the percentage of anionic species in the experimental chrome tanning material was higher than conventional chrome tanning material and the shrinkage temperature achieved by application of experimental tanning material proves that anionic species do involve in tanning. Tanned leathers were crusted and analysed for strength and organoleptic properties.

Leather tanning is a stabilisation process of skin fibers. This is achieved by the interaction of collagen amino acids with tanning agents to stabilise skin from putrefaction. Tanning of collagen with oil is a special class of tanning known as chamois tanning. Chemically, the oil tanning involves oxidation of unsaturation present in the oil, which is generally achieved by exposing oil treated skins to air. In this study, Benzoyl peroxide has been used as an accelerating agent for oxidation of unsaturated bonds present in the linseed oil for oil tanning process. Results shows remarkable reduction in tanning duration from fifteen days to two days. The chamois leathers prepared using oxidation accelerant (Benzoyl peroxide) have been evaluated for physical properties such as water absorption (611%), tensile strength (18 N/mm2) and percentage of elongation (66 %) which are found to be better than control leathers.