Naumenko V. Regularities of removal of oxygen-containing impurities from molten chlorides and bromides of some s-elements by carbohalogenation method.

This thesis is devoted to revealing regularities of behavior carbohalogenation processes in halide melts of alkali and alkali-earth metals and estimating quantitative characteristics of affinity of melt cationic base to oxide-ions (oxobasity indexes).The oxobasicity indices of KBr-NaBr, KBr-BaBr2 and KBr-LiBr melts at 973 K by oxide solubility method were determined. The oxobasicity indices of the bromide melts and their chloride analogs with similar cationic composition were close. The chemical stage of the process is characterized by 2nd order with respect to oxide ions. The activation energy was estimated as ca. 200 kJ/mol for processing of chloride melts by CCl4 and ca. 35 kJ/mol for processing of bromide melts by C+Br2 pair. Such a difference in the activation energies was explained by different binding energy of the halogen atom in the used halogenation agents. The thermodynamic parameters of the activation complex formation were calculated.The increase of the oxygen-ions affinity of melts cationic base leads to retarding overall speed of the process and increase of residual concentration of oxygen-containing impurities. The obtained results permit to estimate processing time and residual concentration of oxide ions by the carbohalogenation method in halide melts going from their oxobasity indexes.