Browsing by Author "Kanth, Swarna"

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Alternative tanning technologies and their suitability in curbing environmental pollution from the leather industry: A comprehensive review.
(Elsevier Ltd., 2020-04-18) China, Cecilia; Maguta, Mihayo; Nyandoro, Stephen; Hilonga, Askwar; Kanth, Swarna; Njau, Karoli
Chrome tanning remains the most favourite technology in the leather industry worldwide due to its ability to produce leather with attributes desirable for high-quality leather such as excellent hydrothermal stability, better dyeing characteristics and softness. Nevertheless, the technology has been censured globally for its severe environmental detriments and adverse effects on human health and other organisms. Developing alternative eco-friendly tanning technologies capable of producing leather of high quality has remained a challenging scientific inquiry. This review article provides an assessment of various eco-friendly tanning attempts geared towards improving or replacing the chrome technology without compromising the quality of the produced leather. The reviewed publications have ascertained that, these attempts have been centred on recycling of spent liquors; chromium exhaustion enhancement and total replacement of chromium salts. The research gaps and levels of key environmental pollutants from the reviewed technologies are presented, and the qualities of the leather produced from these technologies are highlighted. Of all the examined alternative technologies, total replacement of chromium salts sounds ideal to elude adverse effects associated with chrome tanning. Combination tanning, which implies blending two tanning agents that individually cannot impart desired properties to the leather, is anticipated to be an alternative technology to chrome tanning. Apart from being an eco-friendly technology, combination tanning produces leather with similar features to those produced by chrome tanning. In this regard, blending vegetable tannins with aluminium sulphate provides a promising chrome-free tanning technology. However, further studies to optimize combination tanning technologies to suit industrial applications are highly recommended.
Optimizing Natural Dye Extraction from the Bark of Bridelia micrantha for Dyeing Vegetable-Tanned Leather Using Statistical Modeling
(Springer Nature Link, 2025-08-20) Kalangali, Vaileth; China, Cecilia; Kanth, Swarna; Njau, Karoli
This study focuses on extracting natural colorants from the bark of Bridelia micrantha (SBBM) using a solvent extraction method with a magnetic stirrer under different operating conditions. The dyeing potential of the colorants obtained was evaluated by coloring vegetable-tanned leather alone and in combination with mordants at different dyeing conditions using Response Surface Methodology (RSM) with Box–Behnken Design. The properties of extracted dyes were analyzed for absorbance, functional groups, particle size distribution, and zeta potential. The dyed leather samples were evaluated for color strength, coordination, fastness, antibacterial activity, and physical–chemical properties. The results indicate that RSM effectively identified optimal conditions for extraction and dyeing processes with the coefficient of determination (R2) values of 0.9902 and 0.9909, respectively. Maximum absorbance of natural dye (3.88) was achieved at 89 °C, 67 min, and 0.1 g/mL SBBM-to-solvent ratio with a high combined desirability of 1.00. The absorbance analysis showed a peak for flavonoids, tannins, and phenolic acids. Further, Fourier-transform infrared spectroscopy characterized the presence of flavonoids, tannins, terpenoids, carotenoids, and phenolic acids. The optimum dyeing conditions were 40 °C, 4 h, and 25% colorant concentration, resulting in a maximum color strength of 4.45 with a desirability value of 1.00. Various shades and respectable color fastness of dyed samples were observed. Therefore, the eco-friendly natural dye extracted from the SBBM can be prominent for dyeing vegetable-tanned leather to sustain the leather value chain.
Suitability of selected vegetable tannins traditionally used in leather making in Tanzania
(Elsevier Ltd., 2020-04-01) China, Cecilia; Hilonga, Askwar; Nyandoro, Stephen; Schroepfer, Michaela; Kanth, Swarna; Meyer, Michael; Njau, Karoli
The use of chromium salt has dominated in tanning industry worldwide due to its high versatility in quality leather production. However, Environmental concerns of chromium have shifted the interest of current research to chrome-free and greener chemical processing options. Vegetable tannins, especially when used in combination with some benign metals, have been proven to be environmentally safe and manageable, while producing good quality leather with similar shrinkage temperature as that of chromium tanned. As such, shortage of vegetable tannin supply necessitates characterization of non-commercialized sources locally available to feed cottage tanneries. In the present work, extracts from Acacia mearnsii, Acacia xanthophloea, Euclea divinorum and Euclea racemosa, leached by simple technique at 30–80 °C temperature range were characterized for extract yield, tannin, total flavonoid and phenolic contents, crosslinking ability as well as properties of tanned leather. Results indicate that at 50 °C extraction temperature, A. xanthophloea bark gave extract with properties similar to that of A. mearnsii (commercialized source of tannin). Extract from E. divinorum bark contain fairly less extract yield, tannin, total flavonoid and phenolic contents than that of A. mearnsii, but had good crosslinking ability and tanning performance similar to that of A. mearnsii when used in combination with Aluminium Sulphate [Al2(SO4)3]. The 2% Aluminium Oxide (Al2O3) equivalent was established to be optimal dose of Al2(SO4)3 for extract pre-treatment. E. racemosa barks have high extract yield, but very low crosslinking ability, making it not suitable as a tannin source. This work provides useful information on the potential source of tannins for cottage leather industries in Tanzanian and beyond.