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.
Dissolution Kinetics and Leaching of Rutile Ore in Hydrochloric Acid
Experiments on the dissolution kinetics and leaching of rutile ore by hydrochloric acid have been 
carried out. The influence of acid concentration, temperature, stirring speed and particle 
diameter on the leaching of the ore were examined. The dissolution rates were greatly influenced 
by the hydrogen ion concentration, temperature, stirring speed and particle diameter. Kinetic 
data analysis showed that the dissolution mechanism followed a diffusion controled shrinking 
core model with the surface chemical reaction as the rate controlling step. The study showed that 
with 4M HCl solution, about 82.3 % of 10g rutile ore per litre of leachant at 80oC was dissolved 
within 120min., using 0.045-0.075mm particle diameter at a stirring speed of 360rpm. The 
reaction order with respect to hydrogen ion concentration was found to be 1.0, while 
42.28kJ/mol was calculated for the activation energy of the dissolution process. Finally, the Xray 
diffraction spectrum showed that the residual solid which amounted to 18% of the initial 
solid material contained silica (a-SiO2) and are formed around the shrinking core of the unreacted material.
Refractory behaviour of two sphalerite concentrates to dissolution in ferric sulphate solutions
Crundwell, F.K., 1987. Refractory behaviour of two sphalerite concentrates to dissolution in ferric sulphate solutions. Hydrometallurgy, 19: 253-258. The dissolution of concentrates from the Rosh Pinah and Black Mountain deposits failed to exceed a conversion of 50% zinc to solution after 5 hours at 80 ° C with 0.5 M Fe (III) in an acidic ferric sulphate solution. The final conversion was proportional to the particle size, suggesting that the problem concerned a surface phenomenon. Removal of the sulphur product-layer did not result in any additional dissolution. X-ray diffraction analysis suggested the formation of an insoluble PbSO4 or lead jarosite coating. These concentrates both have lead contents (about 2%) higher than those of concentrates (about 0.4% ) studied previously which dissolve beyond 90%. Neither concentrate displayed passivation in ferric chloride solutions in which basic lead sulphates are soluble. Electron microprobe analysis was unable to detect a significant layer of material covering the leached particles.