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Even though sulfate and sulfide concentrations do not adequately describe the total sulfur pool in mine waters influenced by microbial sulfate reduction, detailed speciation of sulfur and the significance of different sulfur species in mine waters are so far less poorly understood in acid mine drainage research. Therefore, this study offers small-scale research on different sulfur species in mine waters and their relevance in total mass balance of sulfur species. The conventional determination of sulfur species is usually carried out using ion chromatography and involves considerable sample preparation, incl. derivatization of the sulfur species. Therefore, methods for easy, effective, and low-cost spectrophotometric determination of sulfur species other than sulfate and sulfide were tested. Additionally, the cross-reactions of organic sulfur species with the spectrophotometric methods were also investigated. Besides sulfate, thiosulfate, sulfite, and sulfide coexist in real mine waters and are determinable with easy and cheap methods suitable for smaller water laboratories. These methods were applied on real mine waters originating from active and remediated mining sites. The results were evaluated regarding potential sulfur imbalances. Sulfur from sulfate usually represents most of the sulfur pool. Thiosulfate is present in considerable quantities; however, it constitutes yet a minor proportion of the total sulfur and ‘other-than-sulfate’ sulfur. It has become clear that some mine waters contain multiple inorganics and possibly, organic sulfur species that would require more advanced analytical methods.

The modeling of ion exchange processes could significantly enhance their applicability in mine water treatment, as the modern synthetic resins give unique advantages for the removal of metals. Accurate modeling improves the predictability of the process, minimizing the time and costs involved in laboratory column testing. However, to date, the development and boundary conditions of such ion exchange systems with complex mine waters are rarely studied and poorly understood. A representative ion exchange model requires the definition of accurate parameters and coefficients. Therefore, theoretical coefficients estimated from natural exchange materials that are available in geochemical databases often need to be modified. A 1D reactive transport model was developed based on PhreeqC code, using three case scenarios of synthetic mine waters and varying the operating conditions. The first approach was defined with default exchange coefficients from the phreeqc.dat database to identify and study the main parameters and coefficients that govern the model: cation exchange capacity, exchange coefficients, and activity coefficients. Then, these values were adjusted through iterative calibration until a good approximation between experimental and simulation breakthrough curves was achieved. This study proposes a suitable methodology and challenges for modeling the removal of metals from complex mine waters using synthetic ion exchange resins.

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