Valorization of Agro-industrial Waste from Peanuts for Sustainable Natural Dye Production: Focus on Adsorption Mechanisms, Ultraviolet Protection, and Antimicrobial Properties of Dyed Wool Fabric

Abstract

A semiquantitative dye adsorption analysis of agro-industrial waste from peanuts (skins) on the wool fabric in conjunction with chlorophyll and tannin-rich biomordants was successfully carried out. The dye was extracted from the powdered peanut skins in 50% aqueous ethanol at various pHs, temperatures, concentrations, and times. Qualitative identification [ultraviolet (UV)–visible and Fourier transform infrared] and the thermal stability (thermogravimetric analysis and differential thermogravimetric analysis) of the extracted dye were determined. The extracted dye was subjected to the total phenolic and flavonoid content analysis, which was expressed in terms of gallic acid and catechin equivalents, respectively. The optimal dyeing conditions, dye adsorption (kinetic and isotherm parameters), and dye performances were also reported. The build-up properties and fastness characteristics were studied in the presence and absence of metal and biomordants using the corresponding ISO standards. Quercus infectoria bark, Punica granatum peel, Terminalia arjuna bark, and Sapium sebiferum and Cinnamomum camphora green leaf extracts were used as biomordants to alter the colorimetric and functional finishing properties of dyed fabric samples with ferrous sulfate (Fe2+) and alum (Al3+) as reference mordants. An optimized amount of peanut skin extract on wool fabric exhibited good antibacterial and UV-protective behaviors. Premordanting enhanced antibacterial properties, while postmordanting enhanced UV-protective properties. In particular, wool fabric with peanut skin dye exhibited diverse color variations (pre- and postmordanting with biomordants) and proved to have great potential for industrial applications as a source of natural biocolorant, as well as a value-adding application for the plant in addition to its normal use as a food.