Environmentally safe technology of waste processing of galvanic production

Abstract

It is known that waste is difficult to purify using existing reagent methods to the standards of the MPC. In addition, the formed sediments contain poorly soluble hydroxy compounds of heavy metals and gypsum, which makes it impossible to dispose of iron- and copper-containing electroplating sludges. The purpose of the study was to study the possibility of ion exchange separate and simultaneous extraction of iron and copper ions from acidic solutions of pickling and copper plating in galvanic production to obtain ferrites. In the course of research, the highly acidic cation exchange resin Dowex HCR S/S in the H+ form was chosen as the cationite. The choice of a strongly acidic cationite is justified, based on the fact that cationites of this type are able to easily lose hydrogen ions due to their displacement from the cationite matrix by other cations of the solution. The sorption processes of iron (II) and copper (II) ions were carried out under dynamic conditions. In the course of experimental studies, it was shown that with an increase in the concentration of sulfuric acid, the full exchangeable dynamic capacity of the cationite significantly decreases both during the sorption of iron ions and during the sorption of copper ions. For iron-containing solutions, full dynamic exchange capacity decreases from 1.39 g-eq/dm3 in the absence of H2SO4 in the initial solution and decreases to 0.3-0.46 g-eq/dm3 at a concentration of sulfuric acid at the level of 1-3 g/dm3. An increase in the concentration of iron (II) ions leads to a significant increase in full dynamic exchange capacity, even with a concentration of sulfuric acid of 8 - 13 g/dm3, full dynamic exchange capacity was at the level of 1.35 g-eq/dm3, which corresponds to the level of sorption of diluted solutions even in the absence of acid. However, the total concentration shows that the efficiency of sorption of metals from acidic solutions remains quite high and increases with the increase of the initial total content of sorbed ions. The main indicator used when choosing an ion exchange method is the possibility of effective regeneration of the cation exchange material. When using 5% solution of sulfuric acid already at the specific consumption of the regeneration solution, it was possible to achieve a degree of regeneration at the level of 95-98%, and when using 10% solution, the degree of regeneration reached 100%. According to the developed technological scheme, regeneration solutions are processed by precipitation into magnetite in a ferritizer reactor. To remove iron ions from concentrated iron-containing regeneration solutions by the ferrite method in order to obtain ferrite particles (magnetite) with maximum magnetic properties, a mixture of Fe (II) and Fe (III) sulfates was used with their concentration ratio K = [Fe2+]/[Fe3+] = 0.5, as a stable relationship between magnetic properties and sediment volume was noted. At maximum magnetic properties, the sediment volume is minimal, and vice versa. Obtaining highly dispersed magnetic particles from a mixture of ferric and ferric sulfates by precipitating them with 10% NaOH solution during heating allows to significantly reduce the duration of the process, simplify it and increase the productivity of the equipment. To obtain magnetic particles of copper ferrites from regeneration solutions by precipitation with alkali at normal temperatures, the concentration ratio K1 = [Fe2+]/[Cu2+] = 3.15-7.76 should be maintained. With an increase in the concentration of Cu2+ ions, there is an increase in the period of crystallization of the obtained sediments and their acquisition of magnetic properties. The formed ferrite material can be used for environmental purposes as a valuable raw material for carbon monoxide neutralization catalysts, as part of alkaline cement for concrete products, or sent for safe disposal. The obtained results on the application of ion-exchange extraction of iron and copper ions from acidic solutions of galvanic production are expedient as the first stage of complex ecologically safe processing of galvanic wastes with the production of ferritic materials for industrial use.