Cetyltrimethylammonium Bromide (CTAB) Bloated Micelles and Merged CTAB/Bolaamphiphiles Self-Assembled Vesicles toward the Generation of Highly Porous Alumina as Efficacious Inorganic Adsorbents.

Abstract

Herein, in a new approach, highly porous alumina materials (HiPAs) have been synthesized through cetyltrimethylammonium bromide (CTAB) bloated micelles or merged CTAB/dicarboxylic acid vesicular aggregates (di-acids with 8, 10, and 12 carbon atoms) as novel templates and characterized by N2 sorption, low- and wide-angle XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), TEM (transmission electron microscopy), HR-TEM (high-resolution transmission electron microscopy), DLS (dynamic light scattering), and AFM (atomic force microscopy) analyses. In the absence of dicarboxylic acids, CTAB bloated micelles in ethanol-aqueous solutions were conductive to the formation of mesoporous γ-alumina hollow spheres (HiPA-CT) with high surface area (394 m2 g-1) and ultralarge pore volume (1.8 cm3 g-1). Notably, merged giant vesicular assemblies formed between dicarboxylic acids and CTAB endowed the mesoporous alumina nanoparticle aggregates with tunable and unprecedented pore features (surface area of 415-735 m2 g-1 and ultrahigh pore volume of 1.37-2.57 cm3 g-1), in which their pinnacle was obtained via CTAB/10 (HiPA-CT-10). Due to the tailored porosity, the HiPA-CT and HiPA-CT-10 were exploited for ciprofloxacin (CIP) adsorption experiments. The adsorption efficiency attained a climax at pH 6. At CIP concentrations below 1 ppm, 91 and 86% of CIP were removed by HiPA-CT and HiPA-CT-10, respectively. The maximum adsorption capacities of HiPA-CT and HiPA-CT-10 are 120 and 184 mg g-1, respectively, in which the latter is surpassing those of inorganic antibiotic adsorbents reported so far. The kinetic results showed that the removal of CIP by HiPA-CT was faster due to the presence of macropores and more accessible active sites on mesoporous surfaces. The reusability test was acceptable after eight runs. The results signify that these novel materials have high potential for reducing our environmental concerns.