Effect of the SBA-15 N-functionalization on the adsorption of organic contaminants

• Published in: Desalination and water treatment 2023-11, Vol.312, p.39-49
• Main Authors: Derylo-Marczewska, A., Zienkiewicz-Strzalka, M., Kusmierek, K., Skrzypczynska, K., Swiatkowski, A.
• Format: Article
• Language: English
• Subjects: (3-Aminopropyl)triethoxysilane (APTES); 4-Chloro-2-methylphenoxyacetic acid (MCPA); Adsorption; Ibuprofen; SBA-15
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2023.29947

This work aimed to investigate the adsorption of selected organic molecules as models of water contaminants on unmodified and N-functionalized mesoporous silica adsorbents. In particular, ibuprofen and 4-chloro-2-methylphenoxyacetic acid (MCPA) were chosen as organic adsorbates. The surface of the mesoporous ordered silica phase containing free silanol groups was enriched with (3-aminopropyl)triethoxysilane by post-synthesis functionalization. The textural properties of synthesized silica phases were evaluated by low-temperature nitrogen adsorption–desorption isotherms, X-ray diffraction, scanning and transmission electron microscopy, infrared spectroscopy as well as thermal analysis. The SBA-15 type ordered mesoporous silica functionalized with amino groups (SBA-15_NH2) was used as the highly porous adsorbent for analyzing the carrier-drug interactions and mutual affinity. The adsorption experimental data were analyzed and well-fitted using the Freundlich, Langmuir, and Temkin isotherms. Ibuprofen was better adsorbed on SBA-15 while MCPA showed greater adsorption affinity for SBA-15_NH2. The better adsorption of MCPA on the N-functionalized silica was the result of interactions (hydrogen bond formation) between SBA-15_NH2 and the adsorbate molecule. The mesoporous silica phases were also tested as carbon paste electrode (CPE) modifiers. Electrochemical measurements were conducted using cyclic voltammetry and differential pulse voltammetry. The mechanism of the electrooxidation process was controlled by diffusion. Compared with the bare (graphite) electrode, the silica-modified electrodes greatly increased the oxidation peak current of MCPA and ibuprofen. The peak current was strongly correlated with the adsorptive properties of the silica modifiers. The CPE modified by amino-functionalized SBA-15 type mesoporous silica (SBA-15_NH2) showed a larger peak current and higher sensitivity for MCPA, while the CPE modified by pure silica phase electrode was much more appropriate for the detection of ibuprofen.