Cross-linked chitosan/H-ZSM-5 zeolite composite film for chromium removal from aqueous solutions: optimization using response surface methodology and adsorption mechanism assessment.

Abstract

The present work investigates, for the first time, the synthesis of a composite film based on glutaraldehyde-cross-linked chitosan (GA-CS) and a natural zeolite (H-ZSM-5) and its application for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions under wide experimental conditions. The composite film (GA-CS-ZEO) characterization by using various analytical techniques confirms its successful production with promising physical, chemical, and thermal properties. The use of the response surface methodology (RSM) for the optimization of the Cr(VI) adsorption by this composite shows that that the maximum removal efficiency (82.39%) was achieved for a Cr(VI) concentration of 50 mg L^-1, an initial pH of 2.0, a contact time of 100 min, and a temperature of 20 °C. Moreover, the analysis of variance (ANOVA) and 3D graphs indicated that the pH and initial Cr(VI) concentration were the main factors that influence the Cr(VI) uptake efficiency. Besides that, the Cr(VI) removal by the GA-CS-ZEO was found to be spontaneous and endothermic and occurs mainly via physical mechanisms involving electrostatic interactions and hydrogen bonding. Regeneration study of the Cr(VI)-loaded composite showed that Cr(VI) can be rapidly and efficiently desorbed by 0.1 M sulfuric acid. The results of the current research work highlight the important adsorption potential of Cr(VI) by the GA-CS-ZEO composite film and underscore its attractiveness and suitability for water treatment applications.