Home – Home – Jornals – Chemistry for Sustainable Development 2025 number 6

The sorption of sodium, silver, magnesium, calcium, copper, lead and iron cations on the sulphocationite obtained by sulphonation of non-coking long-flame coal of the early stage of metamorphism from the Zadubrovsky open-cast coal mine in the Kemerovo Region was studied. The work primarily focuses on the selective sorption of heavy metal cations (Pb²⁺, Mn²⁺, Ni²⁺, Fe³⁺), which pose a special danger to water resources and human life. The sulphocationite under investigation was obtained by treating the coal with concentrated sulphuric acid and oleum. The dynamic ion exchange capacity of the sulphocationite by strongly acidic groups is 1.4 mg-eq per 1 g of the H-form of dry sulphonic coal (0.7 g-eq/dm³). The equilibrium of cation exchange of protons in SO₃H groups of sulphocationite with Na⁺, Ag⁺, Ca²⁺, Cu²⁺, Mg²⁺, Pb²⁺, Fe³⁺ cations from aqueous solutions at 298 K was studied using the dynamic method. It has been shown that the logarithms of the corrected selectivity coefficients of binary cation exchanges Cat/Н (Cat = Na⁺, Ag⁺, Mg²⁺, Ca²⁺, Cu²⁺, Pb²⁺, Mn²⁺, Ni²⁺, Fe³⁺) depend linearly on the equivalent fraction of cations in the sulphocationite based on long-flame coal. The slopes of the straight lines are associated with the energy inequality of the exchange sites, which make an additive contribution to the Gibbs energy of the system when the counterionic composition of the sulphocationite changes. The studied sulphocationite has unique properties: high capacity and selectivity of metal cation sorption from aqueous solutions. The sorption selectivity of heavy metal cations and the factors of metal/proton separation between the solution and sulphocationite phases increase sharply as the concentration of cations in water decreases. The revealed trend increases in the sequence of heavy metal cations Mn²⁺ < Ni²⁺ < Cu²⁺ < Fe³⁺ < Pb²⁺. The results obtained in the work are promising for the advance in the methodology of deep demineralisation of water using the ion-exchange sorption of metal cations by the sulphocationite based on long-flame coal.