Innovative application of ultrasound to reduce solvents in tanning industry

Gennaro Bufalo, Luciano Di Donato, Raffaele d'Angelo, Rossella Nardella, Luigi Ambrosone


The tanning industry is considered to be a source of serious environmental pollution and risks to workers' health. As a result, prevention measures are extremely important. Although protection works are easily implemented, risk prevention cannot be practiced without detailed knowledge of the production cycles. Indeed, often such interventions worsen the workings. This study proposes an effective intervention applied to the tanning of fur skins. Among the different stages of the leather processing, the greasing has the purpose of improving its softness while the subsequent one, of degreasing, allows evenly distributing the grease/oil and eliminating the excess.

For the processing of mink fur, oil tanning is used, where the oil is both tanning and greasing, obtaining a high commercial quality of the product. However, large quantities of oil are used, so that large quantities of solvent must be used in the degreasing phase and the excess is recovered by means of complex recycling plants with a consequent increase in the risk to the environment and the health of workers.

In order to simplify processing and avoid the use of solvents, a tanning method with alum greasing in an aqueous-bath could be used, however a finished product of poor quality is obtained inasmuch as the skin absorbs only small quantities. To increase absorption, it is proposed to irradiate the bath with ultrasound. Experimental measurements on mink skin indicate the method to be effective and competitive. Indeed, results show that cavitation is triggered by ultrasonic powers between 20 and 30 W. Optical microscopy shows that the diameter of the grease globules is reduced by 50%, while the comparison between furs exposed to ultrasound and not exposed shows an absorption increase of 25%. With the suggested method, fur skins are manufactured in a simpler way, with reduced environmental impact and lower risks for workers connected to the use of solvents. The newly developed tanning process can therefore be considered a Best Available Technology.


Leather, ultrasound, mink fur, environmental impact, safety

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