Physicochemical simulation of the ion exchange between humus acids and cations of different valencies

Abstract

An approximate calculation was made for the ion exchange of black humic acids and the related fulvic acids with the cations H⁺, K⁺, Na⁺, Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Fe³⁺, and Al³⁺. The calculation was based on the method of physicochemical simulation, the concepts of the chemical potentials of the elements, the experimental study of the equilibriums, and the determination of the activity coefficients of the monoionic forms of humus acids. Because of the presence of different functional groups, humus acids are considered as two-phase systems with specific activity coefficients for the monoionic forms of these acids in each phase. Examples of experimental studies and practical calculations of ion-exchange equilibriums in wide ranges of humus and solution cationic compositions were compared. Although the proposed approaches require perfecting, they can be used for solving practical problems and controlling equilibriums at the experimental stage.