KINETICS OF NATURAL-TECHNOGENIC SULFIDE DECOMPOSITION PROCESSES AS AN ANALOGUE TO EXOGENOUS PROCESSES AT THE DEGTYARSK DEPOSIT. EXPERIMENTAL DATA

To develop economically efficient nature-inspired technologies for processing technogenic-mineral formations of sulfide deposits and rehabilitating altered territories, it is essential to understand the transformation processes of sediment composition, water, and biota interacting within waste dumps and mining excavations (mines and pits). Changes in the composition of technogenic sediments and waters under exogenous conditions are analogous to geological processes of physical-chemical weathering. Among natural processes, freezing and thawing of mineral matter are particularly important. The objective of this study is to investigate the kinetics of destruction and changes in the material composition of sulfide minerals and the resulting aqueous solutions using samples from waste dumps of the Degtyarsk deposit subjected to multiple freeze-thaw cycles. The experimental data include the decomposition of sulfides resistant to hypergenic alteration through a sequence of operations: crushing, sieving crushed dump samples into eight size fractions, and subjecting each fraction to freeze-thaw cycles between –15°C and +20°C in open containers with distilled water (3–15 cycles). In all experiments, pH, redox potential and sample mass were measured. Each fraction was analyzed before and after experiments using a benchtop X-ray diffractometer. Mineral grains were examined via scanning electron microscopy, and the chemical composition of post-experimental water was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The most significant changes in sediment composition were observed in the –0.1 mm fraction, the measurement results of which are presented in this study. The maximum mass loss rate of sulfides from the Degtyarsk deposit samples reached 2% per cycle, whereas sulfides from other deposits lost up to 20% of their initial mass per cycle. The primary mass loss in the samples (more than half) was attributed to the mechanical removal of fine particles with water, while a smaller portion resulted from physical-chemical decomposition of sulfides through the formation of iron sulfate crystal hydrates, their dissolution, and carbonate dissolution. These experimental studies will serve as a foundation for building a database on sulfide behavior under cryogenic exposure and subsequently developing nature-inspired technologies for managing mineral matter transformation.