Milled zircon, d 50 ≈ 9 μm, was fused with caustic soda pearls in open reaction vessels at temperatures between 650 and 850 °C. Fusion times of 1, 2, 4, 24, and 336 h (with intermittent milling) were investigated. The fusion products were characterized by X-ray diffraction and by wet-chemical analysis. For prolonged fusion times, the fusion products approached equilibrium compositions. However, the phases Na2ZrSiO5 and Na4Zr2Si3O12 observed at 850 °C did not form at 650 °C. Because these compounds do not hydrolyze completely in water, they limit the recovery of alkali in the sodium silicate product stream. With short fusion times (2 h), a nonequilibrium product spectrum is obtained. It is dominated by sodium zirconates and sodium silicates, allowing reasonable zirconia yields and high alkali recovery in a sodium silicate product stream. This allows efficient fusion of two moles of NaOH per mole of zircon at 850 °C with a zirconia yield of ca. 57% and an alkali recovery of ca. 78%.

In this study a novel process for extraction of titanium valuables from its minerals is presented. The process entails roasting of titanium ore with alkaline metal salt, hydrolysing fused cake and dissolution in acid. Optimum conditions were found to be 1 hr fusion at 850 °C, using 2:1 mole ratio, NaOH:FeTiO 4 , irrespective of the particle size interval used in this work. It was found that under these conditions » 80% of titanium was recovered. Na 0.75 Fe 0.75 Ti 0.25 O 2 , NaFeTiO 4 and Na 2 Fe 2 Ti 3 O 10 were the dominant phases at this temperature. The presence of these phases is viewed as beneficial to the economics of the process, it consumes less NaOH. Fusions conducted at 550 °C or below produced chiefly binary phases, Na 2 TiO 3 and NaFeO 4 , reducing process economy. Optimum leaching conditions were S/L= 0.26, leaching at 75 ºC, for 15 min. 85% of NaOH were recovered, under these conditions. Leaching obeys shrinking core mechanism model. IntroductionTitania (TiO 2 ) is a white pigment used in paints, paper, plastics, cosmetics and coatings. Its wide application is due to its higher opacity and covering power. There are two commercial methods of TiO 2 production, the chloride and the sulphate process. In the chloride process titanium mineral is converted into TiCl 4 which is subsequently oxidized at high temperatures.In the sulphate process the ore is converted into sulphate solution and then thermally hydrolysed to hydrous titanium. The later is calcined to produce the pigment (Braun et al, 1992;Nielsen and Chang, 1996;Xue et al, 2009).According to Pong et al (1995) a commercially viable process has to be environmentally benign, to generate a minimum waste, be able to use all grades of ores and be economically favourable. The above processes are, either environmentally unfriendly, costly, generate high levels of waste or recycle, are unable to process low grade ores, as well as, ores such as anatase, sphene, and perovskite (Bulatovic, 1999;Cole, 2001;Nielsen and Chang, 1996;Van Dyk et al, 2004;Yuan et al, 2005).Generally low grade titanoferrous ores are submitted to slagging process. The slagging process however faces uncertain future due to its higher energy consumption and green house gases emission. Additionally slagging is unable to treat radioactive ores, since the radionuclides remain in the solid solution during slagging process. With increasingly restringent environmental policies on radionuclides content, further treatment has to be conducted to reduce it. This will result in additional production costs (Nielsen and Chang, 1996; Habashi, 1997;Doan, 2003; Jha et al, 2005;Lahiri et al, 2006;Lahiri and Jha, 2007

Poly(ε-caprolactone) MgAl -layered double hydroxides (MgAl-LDH) nanocomposites were prepared by melt intercalation. Two organically modified MgAl-LDH, stearic acid (stearate) and sodium dodecyl sulphate (SDS), were used. Nanocomposites morphology was studied by XRD and TEM. Thermal properties were analysed by TG and DSC. Although both systems showed presence of a mixed morphology, exfoliated and intercalated, MgAl-LDH stearate nanocomposites showed a better dispersion of inorganic platelets. TEM images showed the presence of individual platelets in the PCL matrix. MgAl-LDH SDS nanocomposites 1.