Nanoclay-Stabilized Hybrid Pigments from Plant and Biowaste Extracts for Cotton Printing: Color and Fastness Performance

Abstract

Selected low-impact extracts from red cabbage, spent coffee grounds, Pisolithus sp., orange peel, Iris germanica petals, dragon fruit peel and pine bark were immobilized on halloysite (HA), hydrotalcite (HT) and laponite (LAP) and evaluated as hybrid pigments for cotton printing. A four-run 2(3−1) fractional factorial screening design examined acidification, surfactant and silane additions. Diffuse reflectance, CIELAB coordinates and K/Smax within 400–700 nm characterized powders and prints; HA and LAP formulations with the most useful colors were additionally evaluated for light, washing and rubbing fastness. The clay host strongly influenced the optical response. LAP generally produced the darkest powders and highest color strength, whereas HT gave paler, more yellow and less saturated prints and was not advanced to the fastness stage. HA offered the best balance between color development and durability. HA-based coffee, red cabbage and Pisolithus prints reached light-fastness ratings of 5–7, washing ratings around 4–5 and dry/wet rubbing ratings up to 5/4–5. The combined HCl/surfactant/silane formulation (run 4) consistently provided the best fastness among tested HA and LAP systems. The results extend a companion extraction-screening study and demonstrate a mostly aqueous route from plant and biowaste residues to printable hybrid pigments with potential for sustainable and multifunctional textile coloration.