An Eco-friendly Adsorbent of Chitosan/Montmorillonite/Algae for Removal of Basic Green 1 and Reactive Blue 19 Dyes: Box-Behnken Design Optimization Mechanistic Study

In this study, a green and effective adsorbent of chitosan/montmorillonite/algae (CHI/MMT/ALG) composite was developed to be an alternative adsorbent to remove dyestuffs including basic green 1 (BG1) and reactive blue 19 (RB19) from the aqueous solutions. The physicochemical characteristics of CHI/MMT/ALG were analyzed using XRD, CHN-O, BET, FTIR, pH(pzc), and SEM analytical techniques. The findings of the characterization revealed that the increased surface functionalities offered an enticing platform for the improved adsorption of cationic and anionic dye molecules. The essential adsorption variables, such as A: CHI/MMT/ALG dosage (0.02-0.08 g), B: pH (4-9), and C: duration (5-30 min), were optimized using the Box-Behnken design (BBD) approach. The BG1 adsorption process demonstrated a better match with the Langmuir model, whereas the RB19 adsorption process exhibited a better fit with both the Temkin and Langmuir models. The fitting of the kinetic analysis illustrates that the BG1 and RB19 adsorption by CHI/MMT/ALG could be better represented by a pseudo-second-order model. The maximum adsorption capacity of CHI/MMT/ALG for BG1 and RB19 was specified to be 509.5 mg/g and 227.9 mg/g, respectively. The endothermicity and spontaneity of the BG1 and RB19 adsorption processes are evidenced by thermodynamic analysis. The improved surface functionalities of CHI/MMT/ALG inspired the adsorption mechanism of CHI/MMT/ALG for BG1 and RB19 could be essentially ascribed by electrostatic attraction, n-pi stacking, and hydrogen bonding. Overall, the study's findings indicate that the newly developed CHI/MMT/ALG has significant potential for the removal of synthetic dye from aqueous.