New modification of chitosan-based composite for methyl orange uptake from aqueous solutions: kinetic, isotherm, thermodynamic and mechanism studies

Methyl orange (MO) is a fundamental dye that is exceedingly toxic to human health. The present study aims to investigate MO adsorption from an aqueous solution using a novel crosslinked chitosan with epichlorohydrin (ECH), functionalized by tris(hydroxymethyl)-aminomethane (THAE), and stabilized by glycerol (GC) to create CS@ECH-THAE@GC. A series of batch experiments were performed to reveal the influence of pH, adsorbent dose, initial MO concentration, contact time, and temperature on adsorption efficiency. The isotherm data was fitted with Sips followed by the Freundlich isotherm model. Maximum adsorption capacity of MO under optimal experimental conditions (pH 4, 0.32 mg/L SD, 90 min, and 298 K) onto CS@ECH-THAE@GC was 184.6 mg/g. The process was most efficient at a slightly basic pH of 4, achieving up to 97 % removal efficiency. However, efficiency dropped below 65 % in both strongly acidic (pH 1–2) and strongly basic (pH 7–11) conditions. Kinetic data was well fitted by Elovich followed by the pseudo-first-order model. Thermodynamic results suggest the spontaneous and exothermic nature of the MO adsorption. The use of CS@ECH-THAE@GC as a novel MO adsorbent could be considered a wastewater decontamination material in addition to its reusability in a green way.