Development of leather processing method in narrow pH profile: Part 2. Standardisation of tanning process

Conventional methods employed in leather processing subject the skin or hid e to wide variations and alterations in pH. This contributes to an increase in GOD, TDS, chlorides, sulphate and other minerals in tannery waste water s. A process sequence has now been explored to limit the pH range in leathe r processing from 4.0 to 8.0. In the previous investigation, development of a dehairing process at pH 8.0 was demonstrated.(1) In this investigation, an appropriate tanning system with adequate opening-up at a pH range of 4.0-5.0 has been investigated. Th e required fibre opening was achieved by means of lyotropic rather than osm otic swelling. The conditions for chrome tanning were standardised without conventional pickling. A sequence of operations, viz., enzyme assisted zero -lime dehairing, lyotropic swelling for fibre opening and pickle-less chrom e tanning provides leathers matching the functional performance of commerci al upper leathers. The modified process leads to a substantial environmenta l benefit as observed in the reduction of chemical oxygen demand and total solids when compared to conventional processes. The process explored appear s to be economically viable.