Bimodally-porous alumina with tunable mesopore and macropore for efficient organic adsorbents

Since it is of great importance to remove aqueous pollutants for distributing clean water, the adsorption of toxic chemicals on solid adsorbent has been the most practical technique. As one of the widely-accepted design for an adsorbent, hierarchical channel or structurally-connected large and small pore networks take several advantages for application in catalysis and adsorption in liquid or gaseous environment. Mesoporous networks can provide size and shape selectivity for foreign molecule, while macropores can reduce transport limitations and increase the accessibility to the active sites. In this study, we adopted alumina as an adsorbent of organic pollutants due to its easy structural engineering in crystal structure, textural properties, and morphology. As an efficient organic adsorbent, bimodally-porous alumina (BPA) was synthesized to contain mesopores and macropores, which were able to be structured in a separately-controllable manner via solvent-deficient hydrolysis method. The macropores are formed by using polymer beads as a sacrificial template. Additionally, the mesoporous framework is structured through controlling hydrolysis reaction between aluminum alkoxides and water. After calcination, the BPA was pelletized into cylinder or coin shapes for recycling adsorbents without separation and collection steps. We examined the systematic characteristics of the BPA samples, which are associated with the optimal adsorption capability in terms of surface conditions and structural/morphological difference.