Nickel–Aluminum Oxide Aerogels: Super-adsorbents for Azo Dyes for Water Remediation

Highly porous nickel-aluminum oxide aerogels were prepared according to a one-pot sol-gel process and dried under supercritical carbon dioxide conditions. Although the surface properties of these materials were very appealing for applications in catalysis, these aerogels were never applied in adsorption. The nickel effect on the structure and surface properties of the aerogels has been investigated via a broad range of structural, textural, and morphology characterization of the aerogels before and after heat treatment. The adsorption capacity of the as-synthesized and calcined aerogels for azo dyes was assessed under various experimental conditions. The presence of nickel in the aerogel boosts tremendously the surface reactivity and improves noticeably the adsorption capacity of the material. The adsorption capacities for the nickel-aluminum oxide aerogel with 40% nickel ( q max ) are 900 mg g -1 for methyl orange, 1484 mg g -1 for orange II, and 1660 mg g -1 for Congo Red. The adsorption process is exothermic and follows pseudo-second-order kinetics.