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.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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