Natural Dye Extraction from Merbau (Intsia bijuga) Sawdust: Optimization of Solid–Solvent Ratio and Temperature

The ecofriendly lifestyle has attracted considerable support for sustainable development. Natural dyes, as sustainable products,
have become a research focus and development area for many scientists. Ecofriendly processing also supports circular
sustainable development. This study effectively obtained tannins as a natural dye from merbau (Intsia bijuga) sawdust using
water as an ecofriendly solvent. Merbau sawdust is an underutilized industrial waste. Temperature and solid–solvent ratio
variations were performed to extract tannins from merbau sawdust. Temperature and solid–solvent ratio positively affected
solution yield and tannin concentration. The optimal condition was identified using response surface methodology and
experimental observations. A yield of 0.2217 g tannins/g merbau was obtained under the conditions of 333.15 K and 0.125
solid–solvent ratio. Extraction was controlled by convective mass transfer at the interface of solid particles