Development of a chitosan/nanosilica biocomposite with arene functionalization via hydrothermal synthesis for acid red 88 dye removal.

Herein, the polymer nanomatrix of chitosan/SiO 2 (CHI/n-SiO 2) was enriched with a π-π electron donor-acceptor system using diaromatic rings of benzil (BEZ) assisted via a hydrothermal process to obtain an effective adsorbent of chitosan-benzil/SiO 2 (CHI-BEZ/n-SiO 2). The polymer nanomatrix (CHI/n-SiO 2) and the resulting adsorbent (CHI-BEZ/n-SiO 2) were applied to remove the anionic acid red 88 (AR88) dye from aqueous media in a comparative mode. Box-Behnken design (BBD) was adopted to optimize AR88 adsorption onto CHI/n-SiO 2 and CHI-BEZ/n-SiO 2 with respect to variables that influence AR88 adsorption (adsorbent dose: 0.02–0.1 g/100 mL; pH: 4–10; and time: 10–90). The adsorption studies at equilibrium were conducted with a variety of initial AR88 dye concentrations (20–200 mg/L). The adsorption isotherm results reveal that the AR88 adsorption by CHI/n-SiO 2 and CHI-BEZ/n-SiO 2 are described by the Langmuir model. The kinetic adsorption profiles of AR88 with CHI/n-SiO 2 and CHI-BEZ/n-SiO 2 reveal that the pseudo-first-order model provides the best fit results. Interestingly, CHI-BEZ/n-SiO 2 has a high adsorption capacity (261.2 mg/g), which exceeds the adsorption capacity of CHI/n-SiO 2 (215.1 mg/g) that relates to the surface effects of SiO 2 and the functionalization of chitosan with BEZ. These findings show that CHI-BEZ/n-SiO 2 represents a highly efficient adsorbent for the removal of harmful pollutants from water, which outperforming the CHI/n-SiO 2 system. • Chitosan/SiO 2 (CHI/n-SiO 2) was functionalized with benzil to yield CHI-BEZ/n-SiO 2. • CHI/n-SiO 2 and CHI-BEZ/n-SiO 2 adsorbents afford removal of acid red 88 (AR88) dye. • Box-Behnken design (BBD) enabled optimized removal of AR88 by the adsorbents. • The adsorption capacity of CHI/n-SiO 2 for AR88 dye was 215.1 mg/g. • The adsorption capacity of CHI-BEZ/n-SiO 2 for AR88 dye was 261.2 mg/g. [ABSTRACT FROM AUTHOR]