Abstract:
Leather industry is a key player in most developing countries’ economy. However, its tanning process has been associated with environmental and human health hazards due to formation of Cr (V I). To address these concerns, this study investigated effects of Aloe barbadensis Miller (ABM) mixed with carrageenan and of crusting operations on physical and structural properties, and elemental concentrations and on formation of Cr (VI) in leather crusts. Raw cow hide was conventionally processed to tanning, retanning, dyeing and fatliquoring and after each step, samples were cut for testing and others treated with ABM mixed with carrageenan. Results from the Instron tester showed that all the crusting operations significantly affect both physical and organoleptic properties of leather. Confocal Raman spectroscopic data showed that crusting operations and the incorporation of ABM and carrageenan causes structural alterations as indicated by shifls in peak positions and variations in intensities especially of amide bands. Predicted strength properties using empirical models and equations showed closer agreement with experimental data. The ideal quantity of ABM was calculated to be 3.78% and the incorporation stage done at fatliquoring process. Interaction of ABM/carrageenan is only majorly physical with minor interactions involving hydroxyl bonds and sulphur. Results from EDXRFs showed that the incorporation increases the levels of S, K, Ca, V, Fe and Zn. All the crusting processes affect the levels of Cr (VI) formed in both aged and non-aged leather crusts. The levels of Cr (VI) in leathers is detectably higher in retanned and fatliquored and minimum in dyed crusts. The levels of Cr (VI) in leather crusts processed with ABM Miller and carrageenzm, aged and unaged, were below detection level. ABM and carrageenan have shown total inhibition of Cr (VI) formation. For purposes of crosslinking and improving the physical properties, flie study recommends the incorporation process to be done during pretanning operations. However, for antioxidant purposes, the incorporation should be done afier tanning process especially fatliquoring stage and at most 3.784 wt % of the ABM and carrageenan used. The study recormnends more research to determine the ideal particle sizes of the ABM and carrageenan molecules to enhance the penetration and distribution within the matrix. The study suggests activation of the ABM and carrageenan by sulphiting for improved wetting and adhesion. More appropriate coupling agents need to be determined for adhesion and wetting back
