Investigating the effect of various extraction solvents on the colorimetric and fastness properties of silk fabrics dyed with spent coffee grounds as the natural colorant

Abstract

Todays, natural colorants have attracted those working in the dyeing industry due to their biodegradability and less damage to the environment. Meanwhile, one of the very important issues in the use of natural colorants is the extraction of the colorant from its natural source. In this study, the colorants present in the spent coffee grounds were extracted using aqueous solvents of 1% citric acid, 20% ethanol, 1% sodium hydroxide and pure distilled water. Then the effect of the type of solvent used on the dyeing and fastness properties of the dyed silk fabric was investigated. Pre-, meta- and post-mordanting methods were used for dyeing, and copper sulfate was used to serve as the mordant. Evaluation of color strength and colorimetric parameters of the samples was performed using a reflective spectrophotometer; also, wash and light fastness were assessed based on standard methods. The results indicated that the highest color strength was obtained in the meta-mordanting method by applying sodium hydroxide extraction solvent, while the lowest one was achieved in the pre-mordanting method by using the citric acid extraction solvent. Also, the use of pre-mordanting method and ethanol extraction solvent, and post-mordanting method and distilled water and ethanol extraction solvents led to the best washing and light fastness properties.