Browsing by Author "Kalangali, Vaileth"

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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.