Production of sustainable adsorbent of crosslinked chitosan-oxalate and modified mango (Mangifera indica L.) seed for highly efficient adsorption of crystal violet dye: Water treatment and biomass valorization

This work aims to the biomass valorization in advancing sustainable water treatment by converting agricultural waste into highly effective adsorbents for pollutant removal from contaminated water sources. Herein, a bioadsorbent material (CHI-OX/MS-HN) was developed from crosslinked chitosan-oxalate and chemically modified mango (Mangifera indica L.) seed with nitric acid (HNO3) to remove crystal violet (CV) dye from aquatic systems. The influence of three parameters on the CV dye adsorption was investigated using response surface methodology (RSM). These factors are as follows: A: dosage of CHI-OX/MS-HN (0.02-0.08 g), B: pH (4-10), and C: duration (10-40 min). Freundlich and pseudo-first-order kinetic models adequately described the CV adsorption by CHI-OX/MS-HN, as shown by the isotherms and adsorption kinetics. Employing a desire function approach, the optimum conditions for maximum dye removal efficiency of 97.0 % are: adsorbent dose 0.046 g/L, solution pH 9.7, and contact time 33.8 min. The CHI-OX/MS-HN composite had a maximum CV dye adsorption capacity of 306.51 mg/g. The thermodynamic analysis reveals positive values for enthalpy (Delta H degrees) and entropy (Delta S degrees), along with a negative value for free energy (Delta G degrees), indicating that the process is both endothermic and spontaneous. Electrostatic interaction, hydrogen bonding, and n-pi interactions were suggested as the mechanisms for CV dye adsorption onto CHI-OX/MS-HN composite. Based on the findings of this study, CHI-OX/MS-HN is an adsorbent that effectively removes cationic dyes from wastewater. The acquired results also show an ecofriendly, long-term strategy for making chitosan/modified biomass adsorbents that effectively remove cationic dyes from wastewater. It supports environmental sustainability by minimizing biomass waste, using fewer resources, and improving water quality by using advanced materials and methods.