Clean operations in the tanning industry: aqueous degreasing coupled to ultrafiltration. Experimental and theoretical analysis

A process of aqueous degreasing is proposed, avoiding the use of organic solvents, in order to reduce fat substances present in sheepskins. Efficiency of the new process was increased coupling the degreasing to a pressure-driven membrane operation such as ultrafiltra- tion. Increasing ultrafiltration time from 200 to 300 minutes yielded an increase of fats removal from 46% to 55% of the initial content. At 527C, the permeate flux decreased only 12.7% in 300 minutes. Recycling the permeate, that is the aqueous surfactant solution, permitted to save fresh water significantly compared to the open-washing system. Studies of membrane cleaning, using an enzymatic washing solution, showed a restore of the initial flux. A theoretical analysis was developed to decribe the behaviour of the mentioned system.