ELECTROCHEMICAL INVESTIGATION OF COBALT ABSORBTION PROCESSES BY SOILS OF UKRAINE

Abstract

In this paper, the processes of cobalt absorption by soils of Ukraine are investigated by using the electrochemical method of pulsed inversion chronopotentiometry. It has been established that the absorption capacity of cobalt by soil varieties from complexing media is 64–98 %. In solutions of KNO3, NH4OH and CSN2H4 mobile compounds of cobalt are part of [Co(H2O)n]2+, [Co(NH3)n]2+, [Co(CSN2H4)n]2+, and in solutions of Na4P2O7, Na5P3O10 and ЕДТА4– anionic complexes [Со(Р2О7)n]2–4n, [Co(P3O10)n]2–5nі [СоЕДТА]2–are formed. The cobalt cationic complexes [Со(Н2О)n]2+, [Co(NH3)n]2+, [Co(CSN2H4)n]2+are almost completely absorbed by the soils. Anionic complexes – [Со(P2O7) n] 2–4n, [Со(P3O10) n]2–5n і [СоЕДТА]2– largely remain mobile in the soil profile. The sorption effect depends on the charge of the complex ions, their strength and on the steriомеtric parameters of the complex ions. A close positive relationship was established between the cobalt absorption by soils and the cation exchange capacity of soils, the correlation coefficient was 0,7976, and between the cobalt absorption by soils and the humus content (0,7034). In the study of biohumus, it was found that cobalt goes into the solution of 0,02М ЕДТАNa2 + 0,09M NH4Cl by the mechanism of competitive complexation, its transition to the HCl solution occurs due to the protonization of the functional groups of biohumus with which the metal is bound. Biohumus has rather high sorption properties of cobalt and may be promising for its use as an effective carrier matrix in various combinations with basic fertilizers. Isotherms of sorption or exchange of cobalt for exchange ions of biohumus in various solutions correspond to isotherms of Langmuir single layer adsorption. The method of IIHP analysis is important to use to control the content of trace elements at the level of their trace concentrations necessary for plant development.