A fractal kinetic model for heap leaching of uranium ore with fractal dimension of varied particle size distribution

The varied particle size distribution of uranium ore for heap leaching, with its particle sizes ranging from 0 to 9 mm, is taken from a uranium mine in South China. Five uranium ore samples with the fractal dimensions (D) of particle size distribution of 1.6, 1.8, 2.0, 2.2 and 2.4, respectively, are further prepared by mixing different weights of the uranium ores for the size fractions of +8/-9, +7/-8, +6/-7, +5/-6, +4/-5, +3/-4, +2/-3, +1/-2, +0.5/-1 and -0.5 mm, respectively. The five samples are leached in columns to investigate the influences of the fractal dimensions of particle size distribution on their leaching performances. The leaching data are analyzed using the shrinking core model, and the whole process of the column leaching is divided into two phases based on the pH and the potential vs. saturated calomel electrode (SCE) of the pregnant leach solution (PLS) from the columns. When the value of pH is greater than 2.0 and the potential vs. SCE is less than 400 my, the leaching is in the first phase, the rate constant during the first phase k(1) is controlled by initial rate constant k(0) and the increase rate parameter lambda, and k(0), lambda and the length of the period for the first phase T-1 all have linear relationships with D. When the value of pH is less than or equal to 2.0 and the potential vs. SCE is greater than or equal to 400 mV, the leaching is in the second phase, and the rate constant during the second phase k(2) has non-linear relationship with D. From these analytical results, a fractal kinetic model for heap leaching of the uranium ore with fractal dimension of varied particle size distribution is established. And the experimental results show that the model is capable of predicting the recovery of uranium for heap leaching of uranium ore with fractal dimension of varied particle size distribution. (C) 2013 Elsevier B.V. All rights reserved.