Investigation of Dissolution Kinetics of A Nigerian Tantalite Ore in Nitric Acid
A study of the kinetics of the dissolution of a Nigerian tantalite ore in Nitric acid has been examined. A detailed investigation on the quantitative leaching of the mineral was also carried out. The effects of some parameters such as acid concentration, contact time, temperature, particle size and the stirring rate on dissolution action have been investigated. Experimental results indicate that the dissolution rate is diffusion controlled via hydrogen ion [H + ] action, with reaction order of 0.64. About 81.3% of tantalite ore was dissolved within 120min., using 8.06M HNO 3 solution with <0.040mm particle size. Activation energy, Ea, of 22.37kJ/mole was obtained for the process. However, elemental analysis by inductively coupled-plasma mass spectrophotometry showed that the major elements in the ore are Ta(39.9%), Fe(24.9%), Ti(4.03%), S(12.4%) and Mn(2.39%). The x-ray diffractometry also confirmed the ore to exist in a single phase with tantalite characteristics peaks at 3.31A 0 , 2.55A 0 and 1.74A 0 . The ore is not radioactive by its virtue of its very low thorium and uranium contents.
INVESTIGATION OF DISSOLUTION KINETICS OF A NIGERIAN COLUMBITE IN HYDROFLUORIC ACID USING THE SHRINKING CORE MODEL
A study of the kinetics of the dissolution of a Nigerian columbite in hydrofluoric acid has been examined and an investigation on the quantitative leaching of the mineral was also carried out. The effects of some parameters such as acid concentration, contact time and temperature were investigated. Elemental analysis of the ore was done using Particle-induced X-ray Emission (PIXE) spectroscopy with 2.5 MeV protons and this showed the major elements in the ore to be Si (8.82 %), Fe (10.74 %), Mn (4.72 %), Ta (6.80 %),Nb (28.90 %) and W(2.61%), with K, Ni, Zn, Sr and Y occurring in traces. Experimental results indicate that the dissolution rate is chemical reaction controlled, with reaction order of 0.57. Dissolution of over 90 % of the columbite was achieved in 5 h, using 20 M HF at 90 o C with 100 µm particle sizes. Activation energy, E a of 15.70 KJ.mole -1 was obtained for the process. http://dx.doi.org/10.4314/njt.v35i4.19
Thermodynamics on the Carbochlorination of Titanium-bearing Ores
The equilibrium compositions of the multi-component, multi-phase and multi-reaction system of carbochlorination of titanium-bearing ores are calculated with HSC, a computational chemistry software. The thermodynamic equilibrium calculation of the reaction system shows that a complete conversion of titanium-bearing ores is feasible at a temperature near 200oC. At temperatures ranging from 800 to 1600oC, the products of the reaction system are all in gaseous phase. Thermodynamic analysis accords with the industrial practice. The simulated results provide reasonable scientific basis for improving suitable technological conditions of the carbochlorination reduction.