Functionalization of chitosan/alumina nanoparticles with carboxylic groups using phthalic anhydride for adsorption of methylene blue dye via response surface methodology

The application of polymer-based nanocomposites for the removal of organic dyes from water bodies presents a relevant approach. In the present study, a chitosan/alumina nanoparticles were chemically modified with carboxylic groups using phthalic anhydride to develop an effective adsorbent of chitosan-phthalic anhydride/alumina nanoparticles for methylene blue dye adsorption. The physicochemical characteristics of the developed adsorbent (carboxylated chitosan-phthalic anhydride/alumina nanoparticles, CHI-PHA/ANPs) have been thoroughly examined using various methods such as pH_pzc, CHN–O, XRD, FTIR, BET, and FESEM–EDX. The study thoroughly investigated the modeling of adsorption using response surface methodology. It carefully examined the various factors that influence adsorption, such as the dose of CHI-PHA/ANPs (0.02–0.08 g), the duration of time (10–140 min), and the pH level (4–10). The Freundlich isotherm exhibits the equilibrium behavior of MB by CHI-PHA/ANPs. The kinetics results of MB adsorption by CHI-PHA/ANPs were accurately explained using a pseudo-second-order model. The adsorption process was shown to be endothermic by the positive value of enthalpy (∆H°, 5.002 kJ/mol), spontaneous by the negative values of Gibbs free energy (ΔG°, 4.706–5.683 kJ/mol), and more random at the adsorbate/adsorbent contact by the positive value of entropy (∆S°, 0.032 kJ/molK). The Langmuir’s maximum adsorption capacity of CHI-PHA/ANPs is 207.7 mg/g. The efficient adsorption of MB on the CHI-PHA/ANPs can be attributed to various interactions (electrostatic forces, π–π, n–π, and H-bond interactions). This study highlights the significant potential of CHI-PHA/ANPs as a promising adsorbent for effectively removing cationic dyes from wastewater.