Bioleaching Process for Copper Extraction from Waste in Alkaline and Acid Medium

Flotation wastes are becoming a valuable secondary raw material and source of many metals and semimetals worldwide with the possibilities of industrial recycling. The flotation tailings contain oxide and sulfide minerals that have not been sufficiently stabilized and form acidic mine waters, which in turn contaminate groundwater, rivers, and reservoi6sediments. An effective way to recycle these mine wastes is to recover the metals through leaching. While the focus is on acid bioleaching by iron- and sulfur-oxidizing bacteria, alkaline leaching, and the removal of iron-containing surface coatings on sulfide minerals contribute significantly to the overall environmental efficiency of leaching. For this study, static and percolate bioleaching of copper from flotation waste at the Bor copper mine in Serbia was investigated in alkaline and then acidic environments. The aim of the study was to verify the effect of alkaline pH and nutrient stimulation on the bioleaching process and element extraction. A sample was taken from a mine waste site, which was characterized by XRF analyses. The concentration of leached copper was increased when copper oxide minerals dissolved during alkaline bioleaching. The highest copper yield during alkaline bioleaching was achieved after 9 days and reached 67%. The addition of nutrients in acidic medium enhanced the degradation of sulfide minerals and increased Cu recovery to 74%, while Fe and Ag recoveries were not significantly affected. Combined bioleaching with alkaline media and iron- and sulfur-oxidizing bacteria in acidic media should be a good reference for ecological Cu recovery from copper oxide and sulfide wastes.

Numerical analysis of the transport of brine in the Odra River downstream of a mine's discharge

The mining of underground deposits causes the inflow of water to workings and the necessity of pumping them to the surface. The mining plant of KGHM Polska Miedź S.A. extracts copper ore in plant branches with different hydrogeological conditions. The inflowing water into the workings is characterised by variable mineralisation, which depends on the location of the branch. In the south-western part of the deposit, a low-mineralised stream with a relatively high flow rate can be observed, while the outflow of highly saline waters occurs in the north-eastern branch. Despite the activities undertaken that aim at using the pumped-off mine waters industrially, it is necessary to deposit them into the Odra River. Reducing the environmental impact on the Odra River is one of KGHM's goals, which is being implemented by stabilising its salt concentration at a safe level. The paper presents the results of a 3D simulation of brine plume propagation based on a numerical model of advection–diffusion and turbulent flow. Bathymetric data from a section of the river approximately 500 m long and point data from an Odra water quality test were used to develop and validate the model. The paper discusses the types of factors that minimise the impact of brine discharge. The developed model will be used in the future to propose solutions that accelerate the mixing of mine waters with the waters of the Odra River.

Microbial Diversity of Bacteria Involved in Biomineralization Processes in Mine-Impacted Freshwaters

In order to increase the knowledge about geo-bio interactions in extreme metal-polluted mine waters, we combined microbiological, mineralogical, and geochemical analyses to study the indigenous sulfate-reducing bacteria (SRB) involved in the heavy metal (HM) biomineralization processes occurring in Iglesiente and Arburese districts (SW Sardinia, Italy). Anaerobic cultures from sediments of two different mining-affected streams of this regional framework were enriched and analyzed by 16S rRNA next-generation sequencing (NGS) technique, showing sequences closely related to SRB classified in taxa typical of environments with high concentrations of metals (Desulfovibrionaceae, Desulfosporosinus). Nevertheless, the most abundant genera found in our samples did not belong to the traditional SRB groups (i.e., Rahnella, Acinetobacter). The bio-precipitation process mediated by these selected cultures was assessed by anaerobic batch tests performed with polluted river water showing a dramatic (more than 97%) Zn decrease. Scanning electron microscopy (SEM) analysis revealed the occurrence of Zn sulfide with tubular morphology, suggesting a bacteria-mediated bio-precipitation. The inocula represent two distinct communities of microorganisms, each adapted to peculiar environmental conditions. However, both the communities were able to use pollutants in their metabolism and tolerating HMs by detoxification mechanisms. The Zn precipitation mediated by the different enriched cultures suggests that SRB inocula selected in this study have great potentialities for the development of biotechnological techniques to reduce contaminant dispersion and for metal recovery.

Choosing the chemicals and advanced filter media for enhancing the process of mine water purification

В настоящее время строительство сооружений для очистки шахтных вод является одним из важных мероприятий, направленных на сохранение поверхностных водотоков и водоемов. Количество сбрасываемых шахтных вод в поверхностные водоемы может быть сокращено в результате их использования для комплексного обеспыливания в шахтах, технического водоснабжения и других наиболее водоемких технологических процессов. Одним из эффективных способов очистки шахтных вод от взвешенных веществ и тяжелых металлов является реагентная обработка высокомолекулярными флокулянтами, использование которых позволяет уменьшить расход неорганических коагулянтов и интенсифицировать процесс осаждения взвешенных веществ и тяжелых металлов. Предварительная обработка шахтной воды перед контактными осветлителями позволяет значительно увеличить пропускную способность действующих очистных сооружений, стабилизировать их работу при колебании качественного состава и температуры шахтной воды, снизить нагрузку на последующие стадии очистки на скорых фильтрах. Представлены результаты экспериментальных лабораторных исследований пробной коагуляции и флокуляции с последующим фильтрованием на скорых фильтрах с применением каталитической фильтрующей загрузки Orefilter В, сорбента АС и сорбционной загрузки Extrasorb, а также удаления (отдувки) аммиака из шахтной воды. Currently, the construction of facilities for the purification of mine waters is one of the important measures aimed at preserving surface watercourses and water reservoirs. The amount of mine water discharged into surface water bodies can be reduced by reusing it for complex dedusting in mines, process water supply and other most water-intensive technological processes. One of the effective ways of removing suspended solids and heavy metals from mine water is chemical treatment with high-molecular flocculants that provide for reducing the consumption of inorganic coagulants and enhancing the process of suspended solids and heavy metals precipitation. Pretreatment of mine water upstream contact clarifiers can significantly increase the capacity of existing treatment facilities, stabilize their operation in case of fluctuations in the quality composition and temperature of mine water, and reduce the load on the subsequent stages of filtration in rapid filters. The results of experimental laboratory studies of trial coagulation and flocculation with subsequent filtration in rapid filters using Orefilter B catalytic filtering media, AS sorbent and Extrasorb sorption media, as well as removing (stripping) ammonia from mine water are presented.

Modeling of Ion Exchange Processes to Optimize Metal Removal from Complex Mine Water Matrices

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.

Long-term changes in the chemical composition of the water of the Inhulets and Saksahan rivers within the Kryvorizkyi Iron Ore Basin (1980–2020)

The article presents the generalized results of chemical composition research of waters from Inhulets and Saksahan rivers on the territory adjacent to the Northern and Inhulets with pumping of underground waters (mine and quarry), which have an abnormal chemical composition, high mineralization and contain high concentrations of microcomponents. The following scheme of mine water utilization is used in the Kryvyi Rih iron ore basin: the mines of the northern part of Kryvbas discharge water into the tailings dam of Northern Iron Ore Dressing works (Northern GZK); mines of the southern part discharge mine waters into the storage pond of the Svistunov creek during the year, and in the winter its waters are discharged into the Inhulets River with subsequent washing of the river in the spring-summer period. Such treatment of mine and quarry waters has led to the formation of a hydrochemical anomaly on the territory of Northern GZK with the center in the tailings. The mineralization of water in the pond reaches 23 g / l (2020). There is a high content of microcomponents: lead, cadmium, vanadium, manganese, boron, bromine, nickel, mercury, thiocyanates. As a result, the mineralization of the Saksahan River water increases over time (up to 5.4 g / l), the content of microcomponents also increases and becomes quite high. Prolonged use of the Inhulets River for utilization of mine water from the Svistunov creek storage pond has led to a change in the type of water: instead of type II (river water), Inhulets water belongs to the type III (metamorphosed waters). There are no regularities in the change of chemical composition of water (hydrochemical regime) in Inhulets, which is a consequence of the introduction of the scheme "discharge – flushing" for the disposal of mine water. Among the microcomponents in the water of Inhulets there is an increased content of vanadium, boron and bromine (7–8 times), single excess of lead content. The analysis of equilibria in the carbonate-calcium system of the Inhulets and Saksahan rivers confirmed that the existing hydrochemical regime for the studied rivers is stationary, thus, the environmental measures implemented will not have rapid consequences.