es026474a_si_001.pdf (5 MB)
Biointervention Makes Leather Processing Greener: An Integrated Cleansing and Tanning System
journal contribution
posted on 2003-05-03, 00:00 authored by Palanisamy Thanikaivelan, Jonnalagadda Raghava Rao, Balachandran Unni Nair, Thirumalachari RamasamiThe do−undo methods adopted in conventional leather
processing generate huge amounts of pollutants. In other
words, conventional methods employed in leather
processing subject the skin/hide to wide variations in pH. Pre-tanning and tanning processes alone contribute more
than 90% of the total pollution from leather processing.
Included in this is a great deal of solid wastes such as lime
and chrome sludge. In the approach described here, the
hair and flesh removal as well as fiber opening have been
achieved using biocatalysts at pH 8.0 for cow hides.
This was followed by a pickle-free chrome tanning, which
does not require a basification step. Hence, this tanning
technique involves primarily three steps, namely, dehairing,
fiber opening, and tanning. It has been found that the
extent of hair removal, opening up of fiber bundles, and
penetration and distribution of chromium are comparable
to that produced by traditional methods. This has been
substantiated through scanning electron microscopic,
stratigraphic chrome distribution analysis, and softness
measurements. Performance of the leathers is shown to be
on par with conventionally processed leathers through
physical and hand evaluation. Importantly, softness of the
leathers is numerically proven to be comparable with
that of control. The process also demonstrates reduction
in chemical oxygen demand load by 80%, total solids load by
85%, and chromium load by 80% as compared to the
conventional process, thereby leading toward zero discharge.
The input−output audit shows that the biocatalytic three-step tanning process employs a very low amount of
chemicals, thereby reducing the discharge by 90% as
compared to the conventional multistep processing.
Furthermore, it is also demonstrated that the process is techno-economically viable.