Statistical Optimization of Process Variables for the Dyeing of Jute with Marigold Petals Using a Dual Mordant System

Natural dye was extracted from the petals of orange-colored marigold flowers in aqueous medium, and extraction process parameters were optimized based on the color yield (optical density) of an aqueous extract of marigold petals. The extracted natural colorant was used to dye jute fabric and characterized by ultraviolet–visible spectroscopy. Extracts from gallnut and natural alum (fitkiri) were applied as mordants onto the bleached jute fabric by padding method followed by drying in air. The fabrics were treated with the mordants separately before dyeing, and then, both mordants were applied in sequence. Jute was premordanted first with gallnut followed by alum. Jute fibers were mordanted prior to dyeing with either gallnut or alum or both mordants (gallnut followed by alum treatment). Premordanted jute fabric was dyed with the natural dye extracted from marigold petals, and process conditions were standardized. The dual-mordanting process was found more effective to produce better color yield than the single mordanting process. Standardization of the process conditions was also examined statistically by the Box–Behnken design method after choosing the significant variables by the Plackett–Burman design method. The standardized dyeing process conditions were found to be dyeing temperature: 90°C; material to liquor ratio: 1:40; dyeing time: 60 min; dye concentration: 30% o.w.f.; and pH: 11.