Reactive Red 195‐loaded halloysite for cotton dyeing and printing: Adsorption, characterisation and comparison with conventional exhaustion dyeing

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Textile wet processing generates dye‐containing effluents that require effective recovery and valorisation strategies. Halloysite nanoclay was used to capture Reactive Red 195 from a model aqueous solution, and the resulting dye‐loaded solid (REDHA7) was subsequently applied once to cotton by exhaustion dyeing and pigment‐type printing. Reactive Red 195 was quantified in the filtrate by UV–Vis spectrophotometry at 542 nm using A542 = 34.357C − 0.0148 (C in g/L; R 2 = 0.9991). For C 0 = 200 mg/L, V = 0.500 L and m = 12.0 g, C e was 1.56 mg/L, corresponding to 99.22% removal and an adsorption capacity of 8.27 mg/g. Fourier transform infrared (FTIR), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) supported the formation of an organic–inorganic dye‐halloysite hybrid through non‐covalent association involving electrostatic interactions, hydrogen bonding and surface deposition. REDHA7 was evaluated in printing pastes at 40–100 g/kg and compared with a Reactive Red 195‐only printed control at 80 g/kg, while exhaustion dyeing was benchmarked against conventional reactive dyeing. Increasing REDHA7 concentration in printing decreased L * and increased chroma and K / S . Scanning electron microscopy (SEM) showed halloysite‐rich surface particles on REDHA7‐printed cotton, whereas pristine, conventionally dyed and REDHA7‐dyed fibres had comparable morphologies. REDHA7‐dyed samples showed washing fastness of 4–4/5 and rubbing fastness generally around grade 4. Printed samples showed moderate washing resistance, while the highest hybrid loading achieved grade 4 for dry and wet rubbing. Light fastness reached blue‐wool grades 6–7 for printed samples. These results demonstrate the feasibility of coupling dye capture with direct textile application, although industrial wastewater validation and life‐cycle assessment remain necessary before industrial implementation.