Integration of ultrafiltration into unhairing and degreasing operations

A study of some wet processing steps in the tanning industry was carried out in order to improve their efficiency and save raw materials. Ultrafiltration was integrated in the unhairing and degreasing steps to carry out a continuous separation of some species during operation. Results showed that by combining the enzyme unhairing reaction with simultaneous separation of products, better control of the unhairing operation was obtained. Ultrafiltration of the bath during the aqueous degreasing step permitted the recovery of fatty substances and the recycling of the surfactant. Physical and chemical analyses on samples of skins treated in these new processes showed similar characteristics with respect to the traditional ones. On the basis of the experimental results, cleaner processes were obtained thanks to the use of less harmful solvents; a reduction of the environmental impact, a simplification of water purification processes, a convenient re-use of sludges, a decrease of disposal costs and a saving of chemicals and water, without change of the final product, are other important advantages.