Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

Khamirul Matori,Mohd Zaid,Mansor Hashim,Ismayadi Ismail,Loy Wah

doi:10.3390/ijms131216812

Khamirul Matori, Mohd Zaid + Show 3 more

Open Access

https://doi.org/10.3390/ijms131216812

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Abstract

We report on a recycling project in which α-Al2O3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H2SO4 solution to form an Al2(SO4)3 solution. The Al2(SO4)3 salt was contained in a white semi-liquid solution with excess H2SO4; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al2(SO4)3·18H2O. The Al2(SO4)3·18H2O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C/min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al2(SO4)3·18H2O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al2O3 at high temperatures. The X-ray diffraction results indicated that the α-Al2O3 phase was realized when the calcination temperature was at 1200 °C or higher.

Highlights

Alumina is one of the most important ceramic oxides and has a wide range of uses, including high-temperature applications and microelectronics
In the process of aluminum sulfate formation, the conditions within the digester were set to optimize the reaction. This process revealed that the heated aluminum cans were converted into aluminum sulfate Al2(SO4)3 after being mixed with 8.0 M of sulfuric acid, H2SO4
For the sample calcined at 1100 °C, a few small and sharp peaks of α-alumina started to emerge along with the amorphous hump compared to the XRD results for the 900 °C and 1000 °C calcinations

Summary

Introduction

Alumina is one of the most important ceramic oxides and has a wide range of uses, including high-temperature applications and microelectronics. Attention has been focused on the preparation of high-purity α-Al2O3 nano-powders by various routes such as gas phase deposition, hydrothermal synthesis [2], plasma synthesis [3], the sol-gel method [4], freeze drying of sulfate solutions [5], controlled hydrolysis of metal alkoxide [6], decomposition of organo-metallic compounds in supercritical fluids and aerosol methods [7]. Many of these techniques produce nanometer-sized particles that are either amorphous or in γ-phase. They consist primarily of aluminum with a small amount of other additional metals such as magnesium, manganese, iron, silicon and copper

Results and Discussion

Experimental Section

Conclusions