Efficient adsorption of fast green dye by chitosan modified with cyanoguanidine: statistical modelling, kinetic, and isotherm studies

Owing to the widespread usage of synthetic dyes, water contamination prompted by these materials has led to a severe menace on aquatic ecosystem and also on living organisms health. Chitosan modified with cyanoguanidine (CCs), prepared in our previous study, was investigated herein for the first time to assess its adsorbing ability of Fast Green (FG) dye, to widen its applications. The free amino groups beside the integrated nitrogen-rich cyanoguanidine moieties for cross linking the chitosan chains resulted in an augmentation in the cationic positions suitable to bind anionic FG dye, offering valuable insights for environmental remediation applications. A hybridized response surface method was successfully developed to model the adsorption. The synergistic impacts among four critical non-dependent parameters (temperature (25-55 °C), initial concentration (400-1000 mg L^{- 1}), pH of the dye solution (4.7-10), and time) were statistically investigated to optimize the adsorption. The approach was found to have highly effective performance. The adsorption complies with a polynomial quadratic model due to the high obtained regression parameters ( R²-value 94.95% and adjusted R²-value 93.94%). The validation of the proposed model was confirmed using ANOVA, the analysis of variance. Contour plots were used to visually represent the interactions between variables and their impact on adsorption. The adsorption was consistent with the Langmuir isotherm model and both the pseudo-second order and the Elovich kinetic models. The maximum capacity of monolayer coverage, q_max, equals 416.66 mg g^{- 1}. The adsorption was endothermic, and characterized as a chemisorption process.