Effective removal of Indigo Carmine dye from aqueous solution onto Cellulose/Polyvinyl Alcohol/Attapulgite composite

The introduction of Indigo Carmine (IC) into aquatic environments poses considerable risks to both human health and marine ecosystems. This has sparked immediate concerns for creating efficient, affordable, and eco-friendly adsorbents designed to eliminate harmful dyes from textile wastewater. An innovative strategy for the elimination of IC dye was successfully executed in batch adsorption experiments utilizing a new composite of Cellulose/Polyvinyl alcohol/Attapulgite (CEL/PVA/ATP). Factorial design statistical approach was employed to evaluate the impacts of various experiment factors such as the initial concentration of IC dye solution, contact time, pH levels, and the adsorbent dosage. This methodology helped to develop a predictive mathematical model that establishes relationships among these factors. The ANOVA results highlighted the statistical significance of the developed response surface model with its individual terms in determining recovery efficiency. The process of adsorption was found to align well with the Langmuir and Dubinin-Radushkevich (D-R) isotherm models. The maximum adsorption capacity of 143.9 mg g-1 makes the produced composite material a promising adsorbent for real-scale purification systems characterized by high adsorption efficiency. The kinetic data matched with the pseudo-second-order and intraparticle diffusion modeling results. The calculated thermodynamic parameters (ΔG in the range of -16.7 and 18.0 kJ/mol), ΔH = -21.2 kJ/mol and ΔS = -11.8 J/mol.K) indicated the spontaneous and exothermic nature of the adsorption process besides the decreased randomness at the interface solution-adsorbent. The spectral results and kinetic data suggested the adsorption process to occur mainly via hydrogen bonds, dipol-dipol and π - π interactions between the functional groups of the composite's components and IC dye molecules. Repeated adsorption-desorption tests revealed that the composite mantained an adsorption efficiency of 65% even after five repeated cycles of use. Overall results suggest that the synthesized CEL/PVA/ATP composite presents a viable alternative for the treatment of textile industrial wastewater contaminated with dye pollutants.