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Title: Mathematical Model of Raw Hide Curing with Brine

Author
item HERNANDEZ BALADA, EDUARD - VISITING SCIENTIST
item Marmer, William
item KOLOMAZNIK, KARAL - TOMAS BATA UNIVERSITY
item Cooke, Peter
item Dudley, Robert

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2007
Publication Date: 5/1/2008
Citation: Hernandez Balada, E., Marmer, W.N., Kolomaznik, K., Cooke, P.H., Dudley, R.L. 2008. Mathematical Model of Raw Hide Curing with Brine. Journal of American Leather Chemists Association. 103(5):167-173.

Interpretive Summary: The preservation of raw hides and skins with sodium chloride is the most traditional and cost effective method. Nevertheless, it is a lengthy process and impacts the environment due to the eventual disposal of the salt from the cured hide during the hide's conversion into leather. In this present study, we developed a mathematical model to describe the diffusion of sodium chloride into the hide during the curing process. By doing this, we were able to study the effect that initial concentration of brine and the amount of brine per hide ("float") exerted on the diffusion rate. We demonstrated that larger floats and higher initial brine concentrations yielded higher rates of diffusion. We also proved that a minimum brine concentration of 30.8% was needed in order to attain the standard 85% salt saturation of the moisture remaining in the hide, if a 300% float was selected. Larger floats would shorten the time to reach the aforesaid saturation level. Finally, 85% saturation would not be reached using diluted brines, e.g., 20 or 25%, regardless of the float. Our mathematical model may be used to optimize the curing process under any given conditions and thus rationalize the amount of salt and time employed to properly preserve raw hides and skins.

Technical Abstract: The most common method of preserving raw hides is brine curing with sodium chloride. However, this process has three important disadvantages: first, the length of time that it takes, which is a minimum of 18 hours; second, the insufficient degree of curing reached in some hides due to an overload and possibly the low efficiency of the brine raceway; and finally, the environmental impact associated with the discharge of large quantities of electrolytes in the soaking step. Our long term goal is to address all three issues. Initially, we have carried out a study of the salt uptake and its diffusion mechanism in order to attempt a reduction in the curing time. A continuous reaction mathematical model of a closed one dimensional system that describes the diffusion of sodium chloride in the hide during the curing process was chosen in the search for the optimum brine curing conditions such as the optimum brine concentration and percent float. The effect of these two parameters on the values of transport coefficient lambda was reported. Brine diffusion into the hide was tracked by measurement of the chloride concentration of the residual brine solution. In addition, a piece of hide was cured with a fluorescently labeled brine solution and analyzed by means of epifluorescent microscopy for direct visualization of the sodium location within the hide.