Competitive adsorption of pharmaceuticals from multicomponent solutions on functionalized mesoporous silica: comparing β-cyclodextrin and amine surface modifications

Abstract

The article compares the effectiveness of removing ibuprofen (IBU), sulfamethoxazole (SMX), and tetracycline (TC) from their mixture using mesoporous silica SBA-15 modified with β-cyclodextrin (CD) and aminosilane (APTES). SBA-15 was synthesized using a waste solution from the synthesis of zeolites from fly ash as a source of silicon. X-ray diffraction (XRD), CHN elemental analysis, Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption isotherms, and scanning electron microscopy (SEM) were performed to obtain structural, chemical, and surface characteristics of the hybrid materials. Batch adsorption tests were performed to evaluate adsorbent-adsorbate interactions and competition between adsorbates at pH 6.5 and 9.0. Among the tested pharmaceuticals, TC showed the highest adsorption capacity, which indicates its greater affinity resulting from the presence of numerous functional groups that enable interactions with the adsorbent surface. The highest adsorption capacity q_e for TC was 186.5 mg/g and 100.9 mg/g for SBA-15-CD and SBA-15-APTES, respectively, whereas the q_e values for IBU and SMX were similar, amounting to ~ 150 mg/g and ~ 71 mg/g, respectively, at pH 6.5. SBA-15-CD showed similar removal efficiency at both tested pH values, whereas SBA-15-APTES clearly lost its affinity for the adsorbates at pH 9.0, where q_e value for SMX decreased by approx. 20% compared with that at pH 6.5. The results indicate the high potential of waste-derived functionalized SBA-15 for the treatment of water and wastewater contaminated with pharmaceuticals.