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

• Fractal dimension (D) is used to characterize the ore particle size distribution.
• Uranium ores with different D are leached in columns for kinetic model.
• The two key parameters of PLS for uranium ore leaching are pH and potential vs. SCE.
• The leaching process can be divided into two phases based on the two key parameters.
• A fractal kinetic model for heap leaching of uranium ore is established.

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 mV, the leaching is in the first phase, the rate constant during the first phase k1 is controlled by initial rate constant k0 and the increase rate parameter λ, and k0, λ and the length of the period for the first phase T1 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 k2 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.