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The effect of various factors on the kinetic characteristics of the acid decomposition of phosphate raw material has been investigated in a number of studies [1][2][3][4][5]. For example, the rate of decomposition of a flotation concentrate from Karatau phosphorite is governed by a first-order equation and the activation energy is 12.6 kJ/mol [1]. In the temperature range 40-60°ë at an HNO 3 concentration of 35-50%, the rate of decomposition of phosphorites from various deposits is limited by the diffusion of the reaction products and the supply of the acidic reactant to the reaction zone, with the apparent activation energy of decomposition being 14.3 kJ/mol [2]. Il'yasov et al. [3] studied the kinetics of dissolution of Karatau phosphorites with a particle size of no more than 10 mm by 55% ç NO 3 in the temperature range 45-58°ë . The activation energy of the reaction was determined to be 40 kJ/mol, which was supposed [3] to be indicative of the selective character of dissolution. The investigation of the kinetics of nitric acid decomposition of various fractions of the flotation concentrate and the lump Karatau phosphorite [4] showed that the rate of these processes is directly proportional to the surface area of the solid phase: thus, a decrease in the surface area of the solid phase leads to a decrease in the activation energy. It was found [5] that the energies of decomposition of apatite concentrates from the Belozimenskoe, Oshurovskoe, and Novopoltavskoe deposits are rather close, whereas the kinetic constants are different. Similar regularities were also observed for the Seligdarskoe and Kovdorskoe deposits [5]. Thus, the activation energy values presented by different authors differ substantially and there is no consensus on factors determining these values.The purpose of this work was to study the effect of the charge of particles of phosphate raw material in aqueous solutions on the activation energy of decomposition of fluorapatites and hydroxyapatites by nitric, sulfuric, and phosphoric acids.EXPERIMENTAL A schematic diagram of the experimental setup for kinetic investigations at various temperatures, the procedure of measurements, and the preparation of samples for investigation were described previously [6,7]. In this work, we used a fluorapatite concentrate from the Khibinskoe deposit (GOST (State Standard) 3277-54), which was calcined at 900°ë for 3 h and had a solid-state grain size of 0.063-0.1 mm; hydroxyapatite, which was synthesized according to a published procedure [8]; and acids of reagent grade. As cationic and anionic surfactants, we used cetylpyridinium chloride and sodium dodecyl sulfate of reagent grade, respectively. To increase the reproducibility of kinetic measurements, an apatite sample was placed into a reactor containing 100 ml of distilled water or an aqueous surfactant solution, thermostated, and stirred for the time necessary to attain adsorption equilibrium. Then, 100 ml of a separately thermostated acid solution was placed into the reactor. The zero time reference in th...