Removal of quinclorac herbicide from aqueous solution by chitosan/montmorillonite bionanocomposite

Chitosan-montmorillonite bionanocomposite (CTS-MMT) was prepared for removing the herbicide quinclorac (QC) from aqueous solution. The resulting nanocomposites were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution analysis. The adsorption of QC onto CTS-MMT as a function of adsorbent dosage, pH, temperature, ionic strength, contact time, and initial QC concentration was investigated by conducting batch adsorption experiments. The results showed that CTS-MMT exhibited higher adsorption affinity and higher adsorption capacity towards QC than the unmodified montmorillonite. The adsorption kinetics data of QC onto CTS-MMT were well described by the pseudo-second-order kinetics model. Adsorption isotherms fitted well with the Freundlich isotherm model in the heterogeneous adsorption process. Adsorption thermodynamics study indicated that the adsorption of QC onto CTS-MMT was a spontaneous and endothermic process. The QC molecules on CTS-MMT could hardly be desorbed by water, but could be desorbed by 0.1mol/L NaOH solution. QC adsorption on CTS-MMT may involve electrostatic attraction, cation-dipole, hydrogen bonding, and van der Waals interactions. The findings of this study suggest that CTS-MMT is a potential adsorbent for quinclorac pollution remediation.