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Highly adsorptive chitosan/saponin-bentonite composite film for removal of methyl orange and Cr(VI)
- Laysandra, Livy, Ondang, Immanuel Joseph, Ju, Yi-Hsu, Ariandini, Benedikta Hervina, Mariska, Agatha, Soetaredjo, Felycia Edi, Putro, Jindrayani Nyoo, Santoso, Shella Permatasari, Darsono, Farida Lanawati, Ismadji, Suryadi
- Environmental science and pollution research international 2019 v.26 no.5 pp. 5020-5037
- adsorption, bentonite, chitosan, chromium, composite films, composite materials, equations, methyl orange, models, pH, saponins, sorption isotherms, temperature, thermodynamics
- Robust and simple composite films for the removal of methyl orange (MO) and Cr(VI) have been prepared by combining chitosan, saponin, and bentonite at a specific ratio. There are several composite films (chitosan-saponin-bentonite (CSB)) prepared; among them, the composite films CSB₂:₃ and CSB₁:₁ have the highest removal efficiency toward MO and Cr(VI) where the maximum removal is 70.4% (pH 4.80) and 92.3% (pH 5.30), respectively. It was found that different types of adsorbate have different thermodynamic properties of the adsorption process; the adsorption of MO onto CSB₂:₃, chitosan, and acid-activated bentonite (AAB) proceeded endothermically, while the adsorption of Cr(VI) onto CSB₁:₁, chitosan, and AAB proceeded exothermically. The parameters of the adsorption were modeled by using isotherm and kinetic equations. The models of Langmuir, Freundlich, Redlich-Peterson, Sips, and Toth were used for fitting the adsorption isotherm data at a temperature of 30, 45, and 60 °C; all of the isotherm models could represent the data well. The result indicates that CSB₂:₃ has the highest adsorption capacity toward MO with qₘ of 360.90 mg g⁻¹ at 60 °C; meanwhile, CSB₁:₁ has the highest adsorption capacity toward Cr(VI) with qₘ 641.99 mg g⁻¹ at 30 °C. The pseudo-second-order model could represent the adsorption kinetics data better than the pseudo-first-order equation. The adsorption mechanism was proposed, and the thermodynamic properties of the adsorption were also studied.