Joel Musyoka Mwondu, Jackson Nyarongi Ombui, Geoffrey Kironchi, Arthur Onyuka
2021 / Volume 4 / Pages 364-391
Received 21 July 2021; Accepted 8 December 2021; Published 30 December 2021
Huge quantities of chromium-containing leather solid wastes are generated during the production of chrome-tanned leather worldwide. Disposal of these huge quantities of leather solid wastes is a major challenge due to the presence of chromium, which is highly toxic (mainly in its hexavalent form) and detrimental to the environment. Sustainable and environmentally friendly methods of their disposal and treatment options for removing chromium are required so that the dechromed waste can be utilized to make useful products, such as fertilizer for soil conditioning, to improve agriculture, or other applications. In this study, therefore, a new method of dechroming leather solid wastes was designed, whose procedure and results were compared with three other commonly used methods. The focus of the various dechroming methods was on the evaluation of the degree of chromium extraction from chrome-tanned leather wastes without destroying the collagen tissues. The average total amount of extractable chromium content (Cr2O3) in the dried leather waste samples was found to be 3.67%.
The new method was found to be relatively more efficient, environmentally sound and less cumbersome than all the other methods investigated in this work. At P-Value of < 0.05, concentrations of chromium extracted and %TKN in residual collagen hydrolysate reached up to 99.89% and 52.89%, respectively. The levels of total ash and total organic carbon were also relatively high in the resultant collagen hydrolysate (i.e. 12.42% and 23.27%, respectively). The t distribution test on the results of the various dechroming methods confirmed that there was a significant difference at 95% confidence interval, since t (calculated) was greater than t (tabulated). It was concluded that nearly all the chromium in chrome-tanned leather wastes can be removed with a simple technology, which is sustainable and environmentally sound.
dechroming, hydrolysis, leather waste, sustainable method