(513ec) Effect of High Energy Ball Milling Assisted By Acids on the Structural and Physicochemical Properties of Ilmenite Concentrates Used As Photocatalyst

Ilmenite is one mineral used as natural source of TiO₂ and as photocatalyst. In previous research using ilmenite-rich black for photocatalytic applications found that the specific surface area of the mineral is quite low compared to that of common photocatalysts. With the aim increase of the surface area; this research proposes to submit ilmenite-rich concentrates to high energy ball milling assisted by acid solutions of acetic and sulfuric acid, since acids can producing pores and cracks on the surface. However, this treatment can significantly modify the crystallography of material, therefore, is important analyse particle size, surface area, composition and microstructure. The product of the acid treatment was obtained by evaluating the concentration of acid in the solution 1,3 and 5 w/v%, time (1-3h), milling speed 650 rpm, ball to power weight ratio BPR (3:1,10:1 and 20:1) and size of grinding medium (4.0 and 4.8 mm).

The minimum average particle size (325 nm) was measured by DLS and was reached by milling for 1h, BPR 20:1 and grinding medium of 4.0mm. Analysis of the XRD pattern of the samples showed the presence of ilmenite, hematite and rutile as crystalline phases (Fig.1). Although no changes were observed in the position of the peaks, decreasing in the intensity and widening of these were noticed (Fig.1), which evidenced amorphization of the phases as result of the stress applied. The morphology evaluated by SEM ratify the decrease in particle size and it was noted that acetic acid slightly favours the decrease in particle size (Fig.2). The samples exhibited photocatalytic activity under UV irradiation towards the degradation of cyanide. No significant changes in the performance was noted by changing the concentration of the acid solution. In order to further improve the properties of the material it was decided to increase the concentration of the acid solutions.