Kinetic, equilibrium, adsorption mechanisms of RBBR and MG dyes on chitosan-coated montmorillonite with an ecofriendly approach

Abstract

In this study, by modifying the montmorillonite mineral with chitosan, chitosan/montmorillonite composites were synthesized, and research was performed as to its usage as an adsorbent in removing Remazol Brillant Blue R and Malachite Green dyestuffs from aqueous solutions. SEM, FT-IR, XRD, and BET analysis techniques were utilized to determine the characteristics of the synthesized composite. The effects of different batch parameters such as initial pH value (2−9), contact time (5–120 min), initial dyestuff concentration (50–300 mg/ L), adsorbent dose (0.05–0.5 g/100 mL), and process temperature (293–313 K) on the adsorption process were examined. The optimum pH was 2 for RBBR, whereas it was 8 for MG. Also, the optimum removal time was 120 min for RBBR; it was 210 min for MG. As per the Langmuir isotherm model, the maximum adsorption capacity (qmax) was found as 332.58 mg/ g for RBBR, and it (qmax) was 400 mg/ g for MG. This capacity was interpreted as an indicator of usability in removing the RRBR and MG dyes specified in the study from wastewater. The results revealed that the equilibrium isotherm follows the Langmuir equation, and the kinetic model shows consistency with the pseudo-second-order equation. The thermodynamics of adsorption was studied, too. The experimental results demonstrated that CCS/MTs are suitable adsorbents for RBBR and MG removal from aqueous solutions because of their high adsorption capacity.