Synthesis and characterization of chitosan-bentonite biocomposite: Parametric optimization and adsorption potential

Abstract

The study investigates the fabrication of chitosan-bentonite biocomposites through an ultrasonic-assisted technique. The influence of the chitosan: bentonite molar ratio, ultrasonication temperature, and ultrasonication time on the yield of biocomposites was assessed and juxtaposed using the response surface methodology, employing both Box Behnken design (BBD), and central composite design (CCD) methodologies. The pristine compounds and synthesized biocomposites were characterized using various spectral techniques viz. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The optimal conditions for the synthesis of biocomposites were: uni-molar ratio of chitosan: bentonite, ultrasonication temperature of 60 °C, and ultrasonication time of 30 min. BBD demonstrated a slightly better fit (R² > 0.981) as compared to CCD (R² > 0.936). Additionally, the error values for BBD and CCD were determined to be 0.307 and 0.459, respectively, highlighting the higher accuracy of the BBD model compared to the CCD model. The structural analysis through FT-IR and XRD revealed the intercalation of chitosan into the bentonite interlayer. TGA indicated elevated thermal stability and increased resistance of the biocomposites toward degradation. Furthermore, the consistent bonding mechanism observed between chitosan and bentonite remained unchanged regardless of the molecular weight variations. The results revealed that synthesized biocomposites have the potential to be exploited as adsorbents for the removal of pesticides, dyes, drugs, and heavy metals from aqueous solution, demonstrating their application in wastewater remediation technology.