Abstract
Herein, a novel hydrothermally cross-linked chitosan-benzil (CTS-BZ) was prepared by a facile hydrothermal process. The physicochemical characteristics of the developed adsorbents were analyzed using CHN-O, BET, XRD, FTIR, pH(pzc), and SEM analytical techniques. The characterization results demonstrated the mesoporous and crystal line nature of the CTS-BZ as well as the successful grafting of the aromatic ring of the BZ onto the CTS chains. The hydrothermally cross-linked CTS-BZ and chitosan (CTS) were employed for the removal of reactive orange 16 (RO16) dye in a comparative way. Response surface methodology (RSM) was adopted in collaboration with Box-Behnken design (BBD) to optimize the important parameters impacting RO16 adsorption, namely; adsorbent dose (A: 0.02-0.08 g), pH (B: 4-10), and time (C: 5-25). The Langmuir and Freundlich models accurately described the isotherm adsorption data of RO16 by CTS and RO16 by CTS-BZ, respectively. Kinetic adsorption results for RO16 by both CTS beads and CTS-BZ were well-described by the pseudo-second-order model. Remarkably, the hydrothermally cross-linked CTS-BZ revealed a maximum adsorption capacity for RO16 of 291.8 mg/g, as compared with the CTS's adsorption capacity of 227.5 mg/g. The adsorption of RO16 onto the hydrothermally cross-linked CTS-BZ surface is largely controlled by a variety of mechanisms including electrostatic forces, H-bonding, pi-pi stacking, and n-pi interactions. This study shows that novel hydrothermally cross-linked CTS-BZ outperforms pristine CTS beads as a very effective adsorbent for the removal of hazardous contaminants from water.