ASSESSMENT OF LEATHER QUALITY PRODUCED BY OPTIMIZING LIMING AND INCREASING REACTIVITY OF TANNINS OBTAINED FROM CAESALPINIA CORIARIA AND PARKIA CLAPPERTONIANA
ASSESSMENT OF LEATHER QUALITY PRODUCED BY OPTIMIZING LIMING AND INCREASING REACTIVITY OF TANNINS OBTAINED FROM CAESALPINIA CORIARIA AND PARKIA CLAPPERTONIANA
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Date
2017-12
Authors
AKAWU, IRIMIYA
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Abstract
Tannin chemically stabilizes hides and skins against bacterial attack, transforming the
raw material into leather. In the search for alternative sources of tanning materials, only
a few of these materials have shown true value as commercial products in the vegetable
tannin field. The negative effect of trivalent chromium both to the tanners and the
environment has increased the search for alternative tanning materials which could be
eco-friendly.Pods of Caesalpinia coriaria (DD) and husk of Parkia clappertoniana
(PC) tannins were extracted using Procter apparatus and Soxhlet apparatus. The crude
extracts of both DD and PC were purified using gel permeation chromatography and
modified using sodium bisulphite and pancreatic trypsin .The modified tannins were
characterized using UV-VIS, FT-IR, TLC, sorptive capacity and binding ability. The
modified tannin and 16different tannin ratios of DD and PC were used in the tanning of
goat skin. The result of the qualitative and quantitative assessment placed DD to be
hydrolysable tannins with 47% pure tannins and PC to be condensed tannins with
42.33% pure tannins. This shows that the two plants have more than 10 % threshold
tannin content required for commercial extraction. The TLC of methanolic extract of
DD and PC using glacial acetic acid indicated the components of the tannins to be
3,4,6,tri- O- Galloyl-D-glucose, tannic acid ,pyrogallol and gallic acid for DD, and
catechol, gallic acid for PC. The ultraviolet visible absorption spectra for the modified
PC and DD was found to be lower than that of the unmodified. A peak for modified PC
was found to be at 460 nm while the unmodified was at 480 nm. The use of sodium
bisulphite to modified PC and DD shows a good effect by reducing the large molecular
weight of PC and increasing the reactivity of PC and DD. The use of pancreatic trypsin
was found to be suitable for PC. PC extract has the best properties in terms of binding
and sorption by 45.50% and 95% respectively at 10% sodium bisulphite followed by
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DD extract which has 15.33% and 46% binding and sorptive capacity respectively at 10
% sodium bisulphite. On the contrary, DD showed no significant change as the
concentration of pancreatic trypsin increased. Also, the binding capacity of PC
increased from 12% to 25% with the increase in the concentration of pancreatic trypsin
from 2% to 8%,whereas DD showed no significant change. The pH (4.03) of DD could
inhibit enzyme activity. The FT-IR spectra of modified sample of DD gave similar
absorption bands with the unmodified except with the removal of three bands (1624.5,
965.4 and 670.9 cm-1) which arose from C = O, C = CH and Ar-H bending out of plane.
Also, PC spectra gave similar bands except the presence of C – H stretching in aromatic
methoxyl groups (2926.0; 84.933 cm-1) in the modified which was not found in the
unmodified. This could be attributed to the break of bond or hydrolysis of the high
molecular weight of the tanning by the reagent (sodium bisulphite).The liming process
was optimized using Box Behnken design The quadratic polynomial model was used to
characterize the liming process. The plots showed that these independent variables
significantly influenced the liming conditions. In this work, it was established that the
best condition for the liming process was found to be: 1.5 %, lime concentration, 20 hr
and 300 % water. The quality of the leathers was determined according to the
International Union of Leather Technologists and Chemist Society (IULTCS) official
methods. The values obtained, met the standard requirement for vegetable leathers. A
careful selection of the percentage liming used in the liming process and Fatliquoring
of the tanned leather with vegetable tannins such as DD and PC with modification
using sodium bisulphite and pancreatic trypsin could be used to produce a quality
leather and serve as a substitute for chrome tanning or as complementary, since it is
possible to get Shrinkage Temperature of 90 oC.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY IN ANALYTICAL CHEMISTRY DEPARTMENT OF CHEMISTRY, FACULTY OF PHYSICAL SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
ASSESSMENT,, LEATHER QUALITY,, OPTIMIZING LIMING,, TANNINS,, REACTIVITY,, CAESALPINIA CORIARIA,, PARKIA CLAPPERTONIANA,