The Thermal Dynamics Of The Solvent Extraction Of Rare Earth And Extractant Nature

Solvent extraction is an important and useful analytic technology. Due to the good effect, easy manipulation and easy massive production, it is popularizing in the fields of chemistry, environment protection and industry -agriculture. The thermokinetic property of solvent extraction is an important aspect of solvent extractant chemistry and is mainly about the study of extraction equilibrium, reaction rate and thermokinetic parameters. Microcalorimetric method is a new method to study the thermokinetic property of solvent extraction and the property of extractant. The thermokinetic data will supply a theory basis for ion extraction system and will propel the development of extraction separation technology.In this paper, the solvent extraction of Pr³⁺,Gd³⁺,Tb³⁺,Dy³⁺ ,Ho³⁺ with l-phenyl-3-methyl-4-benzoyl-pyrazolane-5 has been studied. The composure of extracted compound, the equilibrium constants, the reaction rate constants and the thermodynamic functions have been obtained. The reaction mentioned above and the extractant's properties have been studied by the microcalorimetric method.1. The chief contents and conclusions1.1 Study of the extraction thermokinetic propertyIn this paper, these ions (Pr³⁺,Gd³⁺,Tb³⁺,Dy³⁺,Ho³⁺) were extracted. The equilibrium equations are:Pr³⁺+3 HPMBP_o = Pr(PMBP)_3(o)+3H⁺ Gd³⁺+3 HPMBP_o = Gd(PMBP)_3(o)+3H⁺ Tb³⁺+3 HPMBP_o = Tb(PMBP)_3(o)+3H⁺Dy³⁺+3 HPMBP_o = Dy(PMBP)_3(o)+3H⁺ Ho³⁺+3 HPMBP_o = Ho(PMBP)_3(o)+3H⁺The reaction rate constant, reaction rate equation and activity energy were obtained and △_rH^θ_m was calculated.The thermodynamic function △_rH_m^θ was measured by microcalorimetric method. The determined △_rH^θ_m was compared with the calculated results. 1.2 Study of the extractant's propertySaponification-extractant has the structure of surfactant, the property of surfactant, so it is not in the present of unimolecuar in the organic phase, but easy to form revered micelles.The thermodynamic property of the micelle's formation procession has been studied by the microcalorimetric method with the mass action model of the surfactant.In the paper, saponificcation-salts of HPMBP have been made first. It was diluted by acetone. The property of this system was studied by the microcalorimetric method. The cirtical micelle concentration(CMC), aggregation number(n), formation constant of micelle(K_m) and the thermodynamic function(△_rH_m^θ,△_rH_m^θ,△_rH_m^θ) were calculated. Under the condition of identical alcohol's concentration, the values of CMC and △_rH_m^θ decrease with the increment of alcohol's carbon number, otherwise the values of the n, K_m, △_rH_m^θ, △_rH_m^θ increase with the increnment of alcohol's carbon number. Under the condition of the identical alcohol, the values of the n, △_rH_m^θ decrease with the increment of the alcohol's concentration, and the values of CMC, △_rH_m^θ, △_rH_m^θ increase with the increment of the alcohol's concentration. This result is identical to the thermodynamic theory.2. The main innovative points(1) Microcalorimetric method is a new method to determine the reaction heat of solvent extraction process quickly and correctly.(2) The CMC and the thermodynamic functions determined by microcalorimetric method establish theoretical basis to understand the surfactant's property in non-aqueous solutions.