Adsorption Capacity of Nanosized Fibrous Aluminum Oxide

Abstract

The ability of oxide-hydroxide samples made from water oxidizing nanosized electroexplosive aluminum to adsorb has been investigated. It is demonstrated that the samples contain non-fibrous phases of various hydroxides and oxides as well as AlO(OH) nanofibers. Specific surface area (400 m2/g), the percentage of micro- and mesopores on the surface (about 90%), the pH of the isoionic state (7.7), which corresponds to a positive potential on the surface, and the exchange capacity for H+ and OH-, which is the same for both ions and 3.18 mmol/g, indicate that the sample's entire surface is involved in the exchange, were all measured. For a variety of compounds comprising As3+, As5+, Cr6+, and Ni2+, adsorption isotherms were developed, and the influence of adsorption on pH was identified. It is demonstrated that As3+ is adsorbed as nickel - Ni2+, chromium-chromate, and dichromate ions as well as molecules of the corresponding acid, As5+ - H2AsO4. The maximal capacity for anions was found to be rather low, at around 0.12 meq/g, and for Ni2+, at 0.24 meq/g, which is consistent with ion adsorption occurring solely on the sample's outer surface and in its macropores.