Utilization of wastewater of Merox unit for un-hairing of sheep skin

In this work, the effluent of Merox unit of Kermanshah Oil Refinery was used for un-hairing (tanning) regional sheep skin in leather production process. Four main factors influencing the hair removal process were studied in three levels including: the weight percentage of sodium sulfide (0.2-2%), calcium carbonate (4-6%), temperature (25-45°C) and time (30-90 min). Design of experiments (Design Expert software) was conducted with four mentioned variables and their effect on un-hairing efficiency (response factor) was investigated. The results showed the highest efficiency (99%) was achievable under optimum conditions of highest level of variables, while the 63% efficiency was obtained using tap water (instead of wastewater) under similar experimental conditions (level of variables). Moreover, the qualitative characteristic of un-haired hide was the same in two experiments. Adding calcium carbonate had no significant effect on un-hairing due to high alkalinity of wastewater. Using wastewater, considering 2% content of sodium hydroxide, increased efficiency and decrease the needs for calcium carbonate and sodium sulphide significantly. Using wastewater of Merox unit in skin-tanning leads to a decrease in unpleasant effluents of oil refineries and therefore the needs for chemicals and raw water in leather production industry, and as a consequence a reduce in environmental pollution generation.