Green template-free synthesis and characterization of mesoporous alumina as a high value-added product in aluminum black dross recycling strategy

Aluminum black dross (ABD) is a solid waste of aluminum smelting process that causes serious environmental and public health problems. In addition, it imposes significant disposal costs to the aluminum industry. In this study, synthesis and characterization of mesoporous alumina (MA) from the ABD using a novel recycling procedure consisting of leaching at low temperature (85 °C) and atmospheric pressure, co-precipitation, separation through selective dissolution, re-precipitation, aging and finally calcination at 600 °C for 2 h. No hard or soft template was used during the formation of the gel. The as-synthesized MA had a specific surface area, total pore volume and average pore diameter of 123–162 m2/g, 0.37 cm3/g and 10.6 nm, respectively which were obtained by nitrogen sorption analysis. The as-synthesized MA possessed more than 98% purity. Its XRD pattern exhibited the characteristic peaks of gamma, eta, theta, and delta phase alumina. FESEM and TEM analyses revealed nanoscale morphology of the as-synthesized MA; having crystal size of ∼11 nm. The TGA analysis showed that the as-synthesized MA is thermally stable and exhibits only ∼5 wt% mass loss for heating from 30 to 800 °C. The characterization of solid residue at the end of the proposed process proved that it contains mainly silica phase which can alternatively be reused as filling agent or aggregate in concrete materials applications. It is quite clear that the process of production of MA from the ABD is feasible and practical and provides a novel mitigation to the environmental problems of the ABD.