A green synthesis of cellulose nanocrystals biosorbent for remediation of wastewater containing industrial dye

Abstract

A novel cellulose nanocrystals biosorbent (CNCs) that has been synthesized, characterized, and used to remove indigo carmine blue (ICB) dye from wastewater. The characteristics of the cellulose nanocrystals biosorbent were assessed using various methods, including N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), SEM, and Fourier-transform infrared spectroscopy (FTIR). To examine the influence of various reaction parameters, for instance temperature, initial dye concentration, pH, and contact time, on the adsorption of the ICB, a comprehensive study was carried out. Under the ideal conditions, the highest adsorption capacity reached 746.24 mg/g, achieved after 100 min at pH 4. The Langmuir model was employed to describe the adsorption isotherm, and the pseudo-second-order model was applied to describe the kinetics of the adsorption process. The adsorption of ICB is more accurately represented by the Langmuir model rather than the Freundlich model, indicating the formation of a selective monolayer on the CNCs surface. Both film and intraparticle diffusion contribute to the adsorption of the dye. The adsorption process is characterized as chemisorption, with an adsorption energy of 17 kJ/mol. The values of enthalpy change (∆H°) and entropy change (∆S°), which are 86.55 kJ/mol and 303.69 J/mol/K, respectively, suggest that the removal process of ICB is endothermic. The interaction mechanism between ICB dye and CNCs biosorbent likely involves various forces, such as π-π interactions, hydrogen bonding, electrostatic interactions, and pore filling. Furthermore, even after undergoing five consecutive cycles of reuse, the results consistently showed that the CNCs biosorbent maintained its effectiveness. These findings indicate that porous CNCs hold significant promise as an innovative biosorbent for the treatment of wastewater containing ICB.