Synthesis of Nanostructured Alumina from Byproduct Aluminum Filings: Production and Characterization

Abstract

Aluminum oxide production from aluminum filings, which are a byproduct of several industrial machining processes and cannot be recycled to attain bulk aluminum (Al), is vital due to its wide use in scientific research and industry. The goal of this paper is to produce ultrafine and down-to-the-nanoscale alumina powder (Al2O3), starting from a waste Al filings. The microstructure and composition of the starting Al used were investigated using scanning electron microscopy (SEM), which was equipped with an attached energy dispersive spectrometer (EDS) unit. The results of this investigation confirmed that the starting Al was mainly Al–Mg alloy. Al2O3 was produced using two routes: The first involved the burning of aluminum hydroxide Al(OH)3 that was precipitated from aluminum chloride solution (AlCl3) resulting from dissolving the Al filings in 2M HCl. The second route involved direct precipitation as a reaction product of aluminum chloride with sodium carbonate solution. The Al2O3 produced using both routes, as well as the intermediate product Al(OH)3, were studied by SEM. The results demonstrate that the nanoscale range size was reached after milling of the produced Al2O3. Following thorough washing with distilled water, the EDS and the XRD techniques confirmed the formation of Al2O3, with no residual salt detected. The EDS results showed that the ratios of Al and O in the produced Al2O3 were about 96% of the ideal compound ratios. The XRD analysis also revealed the amorphous structure of the standard and the produced Al(OH)3, whereas the phases of the produced Al2O3 were either crystalline or amorphous. In our study, the Al2O3 percentage yield was about 77%, and this value obviously depends on the percentage of Al dross in the original Al filings. Overall, this research provides a novel contribution to the production of alumina powder in the nano-range starting from an aluminum filings byproduct, thereby reducing the dependence on known sources of aluminum.

Keywords

• aluminum filings
• alumina nanoparticles
• aluminum chloride
• aluminum hydroxide