Effects of acid concentration on the synthesis of alumina nanoparticles from waste aluminum shavings using chemical precipitation technique

Abstract

In recent times, efforts have been tailored towards sustainable practices and environmental preservation through recycling and use of waste materials. In this regards, this study explores the possibility of synthesizing alumina nanoparticles from waste aluminum shavings (Alsc) using chemical precipitation method. Waste Alsc were initially obtained from aluminum profiles machining workshops dump. Appropriate amount of Alsc powder was reacted with varying concentrations of 3, 4, 5 and 6 M hydrochloric acid (HCl), respectively at 120 °C for 2 h to obtained AlCl₃ solution. Alumina nanoparticles (AlNPs) were precipitated following the addition of 4 M NaOH to each AlCl₃ filtrate obtained. The precipitated AlNPs were aged for 24 h followed by drying, then calcined at 600 °C to obtain pure alumina (Al₂O₃) powder. The AlNPs were then characterized for their phase, morphology, functional group, particle size, and alumina yield. The results showed the synthetized AlNPs are highly amorphous alumina (γ-Al₂O₃) while the morphology showed particle agglomeration increase with increased HCl concentration. TEM showed the particle size ranged within 7.22–14.40 nm, 5.53–5.54 nm, 15.20–17.30 nm, and 15.20–17.30 nm for 3, 4, 5 and 6 M HCl respectively. The quantitative analysis showed alumina purity increase at increasing acid concentration with value ranged from 76.9, 84.5, 85.2, and 88.7 wt% for 3, 4, 5 and 6 M HCl, respectively, while trace amounts of other constituents are noticeable. This research highlights the potential of converting aluminum waste into high-value materials for sustainable applications.