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Open AccessArticle

The Effect of SBA-15 Surface Modification on the Process of 18β-Glycyrrhetinic Acid Adsorption: Modeling of Experimental Adsorption Isotherm Data

1
Institute of Chemistry and Technical Electrochemistry, Faculty of Chemical Technology, Poznan University of Technology, Berdychowo 4, 60-965 Poznań, Poland
2
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(22), 3671; https://doi.org/10.3390/ma12223671
Received: 13 October 2019 / Revised: 2 November 2019 / Accepted: 4 November 2019 / Published: 7 November 2019
(This article belongs to the Special Issue Recent Advances in Mesoporous Materials)
This study aimed at the adsorption of 18β-glycyrrhetinic acid (18β-GA), a pentacyclic triterpenoid derivative of oleanane type, onto functionalized mesoporous SBA-15 silica and non-porous silica (Aerosil®) as the reference adsorbent. Although 18β-GA possesses various beneficial pharmacological properties including antitumor, anti-inflammatory, and antioxidant activity, it occurs is small amounts in plant materials. Thus, the efficient methods of this bioactive compound enrichment from vegetable raw materials are currently studied. Siliceous adsorbents were functionalized while using various alkoxysilane derivatives, such as (3-aminopropyl)trimethoxysilane (APTMS), [3-(methylamino)propyl]trimethoxysilane (MAPTMS), (N,N-dimethylaminopropyl)trimethoxysilane (DMAPTMS), and [3-(2-aminothylamino)propyl] trimethoxysilane (AEAPTMS). The effect of silica surface modification with agents differing in the structure and the order of amine groups on the adsorption capacity of the adsorbent and adsorption efficiency were thoroughly examined. The equilibrium adsorption data were analyzed while using the Langmuir, Freundlich, Redlich-Peterson, Temkin, Dubinin-Radushkevich, and Dubinin-Astakhov isotherms. Both linear regression and nonlinear fitting analysis were employed in order to find the best-fitted model. The adsorption isotherms of 18β-GA onto silicas functionalized with APTMS, MAPTMS, and AEAPTMS indicate the Langmuir-type adsorption, whereas sorbents modified with DMAPTMS show the constant distribution of the adsorbate between the adsorbent and the solution regardless of silica type. The Dubinin-Astakhov, Dubinin-Radushkevich, and Redlich-Peterson equations described the best the process of 18β-GA adsorption onto SBA-15 and Aerosil® silicas that were functionalized with APTMS, MAPTMS, and AEAPTMS, regardless of the method that was used for the estimation of isotherm parameters. Based on nonlinear fitting analysis (Dubinin-Astakhov model), it can be concluded that SBA-15 sorbent that was modified with APTMS, MAPTMS, and AEAPTMS is characterized by twice the adsorption capacity (202.8–237.3 mg/g) as compared to functionalized non-porous silica (118.2–144.2 mg/g). View Full-Text
Keywords: bioactive agent; silica; mesoporous materials; surface modification; adsorption modeling bioactive agent; silica; mesoporous materials; surface modification; adsorption modeling
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MDPI and ACS Style

Moritz, M.; Geszke-Moritz, M. The Effect of SBA-15 Surface Modification on the Process of 18β-Glycyrrhetinic Acid Adsorption: Modeling of Experimental Adsorption Isotherm Data. Materials 2019, 12, 3671.

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