Selective leaching kinetics and upgrading of low-grade calcareous phosphate rock in succinic acid

Selective leaching kinetics of calcareous phosphate rock in succinic acid solution was investigated. Using a known particle size range of the sample, liquid/solid ratio and acid concentration, the influence of various reaction temperatures was studied in order to elucidate the kinetics of calcareous material in the rock. The leaching rate increased with increasing temperature. A kinetic model was suggested to describe the selective leaching process of calcareous material analyzing the kinetic data. The selective leaching curves were evaluated in order to check the validity of shrinking core models for liquid-solid systems. The experimental data were tested by graphical and statistical methods and it was found that the leaching of calcareous material in the rock was controlled by chemical reaction, i.e., 1 -(1 - x)(1/3) = 1.47 x 10(6) e (-64.92/RT)t. The apparent activation energy of the leaching process was found as 64.92 kJ mol(-1) over the reaction temperature range from 313 to 353 K. (c) 2005 Elsevier B.V. All rights reserved.