Production of alpha-alumina nanoparticles using aquatic humic substances

The aim of this work was to employ the complexation capacity of natural organic matter (NOM) to synthesize α-alumina nanopowder, using a procedure that was efficient, eco-friendly and economically viable. Several synthesis parameters were tested, such as pH and concentration of the starting sol, stirring time and calcination temperature. The best conditions determined to produce α-alumina through this method are pH 4.0, stirring time of 120 min at room temperature, drying at 100 °C and final calcination at 1000 °C for 4 h. This temperature was 200 °C lower than that usually reported for the synthesis of α-alumina. Spherical particles with average sizes of 52 ± 1 nm were produced by this method. The stoichiometry Al2O3 and the low level of impurities in the samples were confirmed by several methods. The water used in the synthesis was recycled and analysed according to its physico-chemical and bacteriological features. From the results, it could be concluded that the recycled water met the standards required by current legislation for potable water, highlighting the technological and environmental advantages offered by the proposed method of synthesis.