Montmorillonite nanoclay as a sustainable adsorbent for removal of Acid Blue 113 dye from textile industrial effluent

Abstract

Abstract This study investigates the application of Montmorillonite Nanoclay (MNC) as a sustainable, low-cost, and scalable adsorbent for removing the bisazo dye Acid Blue 113 (AB113) from aqueous solutions and textile industrial effluent (TIE). Considering the mutagenic potential of azo dye degradation products, the development of efficient and environmentally compatible remediation strategies is essential. A notable finding is the minimal influence of pH (2–12) and temperature (30–50 °C) on adsorption performance, demonstrating the robustness and practical applicability of the process. The effects of key operational parameters—including initial dye concentration (25–200 mg L −1 ), contact time (15–180 min), and adsorbent dosage (0.5–6.0 g L −1 ), were systematically evaluated. Adsorption equilibrium was analysed using various isotherm models, with the Vieth–Sladek model showing the best fit, while kinetic analysis indicated that the pseudo-second-order model governed the adsorption process. Diffusion modelling (film diffusion, Weber–Morris, and Dumwald–Wagner) revealed that mass transfer mechanisms predominated over intraparticle diffusion. Thermodynamic evaluation based on ΔG°, ΔH°, and ΔS° confirmed the feasibility and nature of adsorption. A two-level fractional factorial experimental design (FFED) combined with multiple regression analysis identified significant variables and optimised the process. Under optimal conditions (pH 7, adsorbent dosage 0.5 g L −1 , initial dye concentration 858 mg L −1 , contact time 204 min, 30 °C), a maximum adsorption capacity of 589 mg g −1 was achieved. These results demonstrate that MNC is an efficient and resilient adsorbent for AB113 removal and supports circular economy strategies through valorisation of dye-loaded sludge into composite materials.