Particle Size On Dissolution Of Thermodynamics And Kinetics Of Nanoparticle

There are differences between the thermodynamic and kinetic of nanoparticles dissolving and the corresponding block material dissolving. Classical chemistry theory did not consider the surface effect of reactants, as a result, can not solve the problem of the thermodynamic and kinetic for the nanoparticles dissolving. The studies on nanoparticles dissolving are few; and the study of the dissolving theory of the thermodynamics and dynamics has not been reported.At first, the effects of the nanoparticle size on the thermodynamics and the equilibrium constant were studied in theory, introducing surface variables in Gibbs function of the dissolving system, and so as to obtaining the expressions between dissolving equilibrium constant, the dissolving thermodynamic functions and nanoparticle size; and establishing the dissolving kinetics models, the expressions of the effects of nanoparticle size on kinetic parameters were obtained in theory, and the essence of the effect of nanoparticle size on the dissolving dynamics was discussed. And, on the basis of the chemical reaction transition state theory, through the basic assumptions and theoretical derivation, the relationship between dissolve the kinetic parameters and size are derived, and the essence influence of particle size on dissolution kinetics parameters were discussed.Secondly, nano-barium sulfate with different particle size was prepared by complexation precipitation method and nano-copper of different particle size was prepared by liquid phase reduction method. The crystal structure and the shapes were characterized by X-ray diffraction and transmission electron microscopy. The solubility of nano-barium sulfate in the water and nano-copper in the dilute acid were measured; By the experimental data analyzing, the regularities of effects of particle size on dissolving the equilibrium constant dissolving the thermodynamic functions and dissolving kinetics parameters were obtained. At the same time, Surface thermodynamic functions of nanoparticle with different size were obtained, the regularities of effects of particle size on surface thermodynamic functions were obtained.Finally, the comparison and analysis between the regularities of effects of particle size on dissolving the equilibrium constant、dissolving the thermodynamic functions and dissolving kinetics parameters and nanoparticle dissolving thermodynamics theory and dynamics theory. The experimental results are consistent with nano dissolved thermodynamics theory and dynamics theory.The experimental results show that:(1) The high purity nano-barium sulfate、nano-copper with average particle size can be prepared by complexation precipitation method、liquid phase reduction method; For these two kinds of preparation methods, reaction temperature, concentration of reactants, reaction time have a significant influence on the particle size. Particle size decreases with increasing the reaction temperature, with the increasing reactant concentration, particle size decreases, with the increase of reaction time the particle size increases.(2) For both dissolution system, Particle size has obvious influence on dissolution thermodynamic functions:With the decrease of the nanoparticles size, dissolve the standard equilibrium constant increase, dissolve the standard molar Gibbs free energy, dissolve standard molar enthalpy change and dissolve the standard molar entropy were decreased; and the logarithm of dissolving equilibrium constant、dissolve the standard molar enthalpy change and dissolve the standard molar entropy has a linear relation with the reciprocal of size.(3) For both dissolution system, Particle size has obvious influence on dissolution kinetics parameters:With the decrease of the nanoparticles size, the apparent activation energy and pre-exponential factor decrease, and rate constant and reaction order increase; logarithm of the reaction rate constant, apparent activation energy and logarithm of pre-exponential factor have corresponding linear relations with the reciprocal of particle size, respectively; and the essences of the effect of particle size on kinetic parameters:the apparent activation energy is influenced by the molar surface energy of nano particle, reaction order by the molar surface area, pre-exponential factor by the male surface entropy, and reaction rate by both the molar surface energy and the mole surface entropy.