Extracted dyes' stability as obtained from spent coffee grounds on silk fabrics using eco-friendly mordants

Spent coffee grounds (SCGs) are commonly known as a waste resource and a raw material useful for dyeing. SCG is a rich source of natural colorant from the class of flavonoids and anthocyanins. In this research, silk fiber dyeing with the dye which was extracted from SCGs with different metallic and natural mordants was done by applying pre-, meta-, and post-mordanting methods. Metal salts like tin chloride and copper sulfate as well as such natural materials as pinecone, tannic acid, and lemon peel were used to act as mordants. Color strength and color parameters of the dyed silk fabric samples were evaluated by applying a reflective spectrophotometer. Also, the evaluation of wash and light fastness was done based on ISO standards. The results indicated that in all methods, the metal samples had higher color strength when compared to the bio-mordant ones. Among the used methods and bio-mordants, the use of the pre-mordanting method and pinecone led to the highest amount of color strength. Also, the used bio-mordant could be a suitable substitute for metal mordants in terms of fastness parameters. Among the used methods and mordants, the post-mordanting method and pinecone mordant could provide the best washing and light fastness.