Impact of coal-rock interactions on the geochemical evolution of major cations in mine water

This study investigates the release patterns of major cations from coal and gangue collected from the Pingdingshan mining area under various conditions, including particle size and solution chemistry, with the aim of elucidating the underlying mechanisms controlling mine water mineralization. Laboratory experiments were conducted to analyze ion release characteristics and pH evolution. The results show that particle size plays a critical role in controlling ion release and solution pH. Finer particles enhance the dissolution of aluminosilicates and carbonate materials in coal-bearing strata, leading to enhanced release of key ions such as Si⁴⁺ and Al³⁺. Gangue is identified as the primary source of Si⁴⁺ and Al³⁺, whereas coal predominantly contributes Ca²⁺; moreover, the presence of gangue suppresses the release of Ca²⁺. Ion release patterns in actual mine water differ from those observed in deionized water, with Ca²⁺ and Mg²⁺ concentrations in mine water mainly governed by coal. Overall, the findings demonstrate that the interactions between coal and gangue significantly impacts the geochemical evolution of mine water, while the initial solution environment primarily regulates the dynamics of ion release and pH changes.