Aluminium oxide (Al 2 O 3) nanoparticles (AlNPs) are class of metal oxide nanoparticles that have diverse biomedical applications owing to their exceptional physicochemical and structural features such as resistance towards wear, chemicals, mechanical stresses as well as their favourable optical properties and a porous vast surface area. Other reasons for widespread applications of AlNPs are their low cost of preparation and easy handling. Therefore, owing to the economic importance, the recent achievements and possible health risks associated with the biomedical applications of AlNPs are overviewed in this work.

The effect of pH and seeding were studied on phase, particle size, morphology, purity and conversion of aluminum hydroxide produced by carbonation of solution of sintered nepheline syenite alkaline leaching. Carbonation experiments were done at initial pH range of 9-11 and variable during carbonation, seed ratio range of 0.5-2 and constant temperature and time of 80֯ C and 8 h respectively. The main phase of products at pH of 9, 10 and 11 were dawsonite, a mixture of dowsonite and imogolite and bayerite respectively. Adding seed did not change the phase of products but improved the particle size and conversion of the products. The particle size increased due to agglomeration and crystal growth mechanisms but by increasing the seed ratio crystal growth was the dominant mechanism. According to results, at 80°C, initial pH 11 and variable during carbonation and seed ratio of 2, a desirable product can be produced.