The dissertation is devoted to the scientific development and practical stays the regeneration processes improvement in galvanic technological solutions using a membrane electrolysis method.
An analytical review of scientific and technical information on the areas of application and operating conditions of membrane electrochemical devices were conducted. Analyzed scientific sources show the effectiveness of the membrane electrolysis method in the purification processes of aqueous solutions from hazardous substances. Polarization curves the dependences of the magnitude of the current on the applied voltage level for the cathodic release of cadmium and zinc at different temperatures. The presence of cadmium and zinc in the cathode deposit, the ions of which were present as impurities in the anolyte, was confirmed by electron microscopy with the functions of X-ray microanalysis.
The experimentally determined optimal range of pH values in the area of 1.5-1.8 allows obtaining in the appearance of valuable products metallic cadmium and zinc, which can use in metallurgy.
As a result, the conducted researches laboratory model of the membrane electrochemical device has developed, the regularities of mass transfer of Zn2+ and Cd2+ ions through the cation exchange membrane RALEX®CM-PES 11-66 had experimentally investigated. In the course of work, the regularities of influence of the following factors on the membrane electrolysis process have been investigated: concentration of polluting metal ion, current density, temperature, hydrodynamic conditions of the anolyte near-membrane zone. Particular attention was paid to the use of forced mechanical stirring of the membrane zone of the anolyte. As a result of generalizations, the current limit density for simulated solutions of cadmium and zinc galvanic coatings passivations are determined. The increase in metal yields up to 50% as a result of forced mechanical mixing. As a result of improving the known mathematical model, the kinetic parameters of research results with changes in the concentrations of contaminating ions of passivation baths and with changes in hydrodynamic conditions had established, instantaneous rate constants of cathodic metals electrodeposition had found. As a result of general mathematical processing of the experiments results from data with changes in concentration, current density, temperature, and different hydrodynamic conditions, multifactor regression equations of membrane cathode electrodeposition of cadmium and zinc had constructed. The statistical significance of multifactorial regression equations was confirmed by the criteria of Student, Fisher, and Darbin-Watson.
An industrial electrochemical device has been created that allows to effectively regenerate the composition of technological passivations baths of cadmium and zinc galvanic coatings. The adequacy of multifactor regression mathematical models of cadmium and zinc electroreduction has been practically confirmed on real passivation production baths. As a result of industrial implementation and operation of membrane electrochemical devices, in addition to effective purification of these process baths from Cd2+ and Zn2+ ions, the regeneration process of hexavalent chromium ions from Cr3+ ions has been proved.
An experimental study of the anodic regeneration process confirmed the gradual increase in the concentration of hexavalent chromium ions and the gradual decrease in the Cr3+ ions concentration in the passivation baths of galvanic coatings. As a result of the conducted researches, the chromate regeneration efficiency was established at the level of 0.6-1.59g/l per day in working passivation baths with 150l volume.
It is proved that the operation of the created membrane electrochemical devices reduces the load on the treatment facilities of the galvanic section. The reduction of working concentrations of sodium dichromate in technological baths was established, which as a result, allowed to reduce their ecological danger by 3.75 times. The calculation procedure on the ecological and economic efficiency of the electrochemical devices operation has been applied for the first time. Thanks to the calculations, the effectiveness of the created industrial modules of electrochemical in technological baths of passivation of cadmium and zinc galvanic coatings is shown.
Experimental and statistical researches and also the introduction of technological processes electrochemical regeneration of chromium-containing technicality galvanic solutions in JSC Sumy plant "Nasosenergomash" (appendices Д,E,Ж), allow recommending to use this membrane electrolysis method for regeneration industrial chromium-containing technological solutions of Ukraine.
