The conventional settling column test, commonly employed to assess the sedimentation characteristics of mine drainage precipitates, provides valuable data but is constrained by its reliance on batch sampling and discontinuous measurement, which limits the ability to observe continuous settling dynamics. To address this limitation, this study introduces a novel real-time measurement system for continuous observation of precipitate behavior within a settling column. This innovative system employs real-time turbidity measurements to provide a detailed temporal and spatial distribution of total suspended solids (TSS) within the column. By capturing the dynamic changes in TSS over time, the method enables precise identification of the hindered settling zone and allows for the prediction of concentration trends within the column. The study also evaluates percent removal efficiency and overflow rates at various column depths, revealing a high settling velocity within the hindered settling region and identifying the optimal depth range for achieving efficient overflow conditions. This advanced experimental approach significantly enhances the understanding of sedimentation processes in settling ponds. Its applications extend beyond mine drainage treatment, offering valuable insights for water treatment facilities, mining operations, and various industrial processes where sedimentation plays a critical role.

Successive alkalinity-producing systems (SAPS) effectively treat acid mine drainage but suffer reduced efficiency and lifespan due to sludge accumulation in the limestone layer. Flushing systems, comprising perforated pipes, periodically discharge water to restore limestone porosity. However, existing designs lack scientific rigor. This study introduces a hydrodynamic approach to optimize flushing system design by evaluating orifice size and spacing. A novel performance index, orifice influence radius, was developed to calculate optimal configurations. The results provide a practical framework for improving flushing efficiency, extending SAPS lifespan, and enabling predictable facility management, offering critical insights into the engineering of mine drainage treatment systems.

Batch settling column tests are among the most effective and practical methods for assessing sedimentation characteristics. These tests measure the settling velocity of the interface between suspended solids and the supernatant, providing insights into the overall sedimentation behavior. However, they are limited in their ability to capture localized sediment dynamics within the column. Additionally, traditional batch settling tests can be prone to errors, such as misinterpretation of the interface between the clear supernatant and settling particles, or subjective readings by operators. In this study, we present a novel experimental apparatus and methodology that enables continuous monitoring of sediment characteristics, allowing for the identification of shifts in sedimentation behavior. This method was applied to mine drainage sludge, and the results revealed a time-resolved distribution of total suspended solids throughout the column. A key outcome of this work is the identification of critical transition points in sedimentation behavior, which informed the development of a schematic model depicting the spatial and temporal distribution of settling types within the column. This model offers predictive insights into sediment behavior in batch settling columns and has potential applications in optimizing the design and operation of full-scale sedimentation tanks for various engineering and environmental

This study was conducted to find a way to reduce the production of cakes generated in the domestic aggregate production process. Cakes from 8 wet aggregate producers were collected and particle size was analyzed. Samples were collected step by step from an aggregate producer A, particle size analysis was performed, and the material balance was calculated before and after an sand recovery unit by modeling the production process. As a result of the particle size analysis of eight cakes, one sample contained 50% sand, and the rest contained about 5% to 25% sand. The results showing that the cake contained a variety of sand in cakes may indicate that the recovery efficiency of the sand recovery units in the field varied. Sieve analysis of the samples showed that the generation of sand particles increased 2.8 times during the third crushing compared to the second crushing, and more cake particles were generated. As a result of simulating the sand recovery unit model, the lower the cut point of the cyclone and dewatering screen, the higher the sand production and the less cake production appeared. In order to reduce the production of cake in the field, it was determined that an optimal operation of the sand recovery unit was necessary in the aggregate production process.

This study investigated the effect of hydrogen peroxide treatment on the removal pH for Fe, Al, and Mn and sludge production in the lime neutralization process. In the laboratory, the AMD collected from the coal mine was oxidized with 5% H2O2, and then neutralized to pH 3, 5, 7 and 9, respectively, with 20% lime slurry. In the control experiment, the same neutralization experiment was performed without H2O2 treatment. During the experiment, the supernatant was measured for pH and Eh and analyzed for Fe, Al, Mn, Ca and SO42- ions. Simple neutralization without H2O2 treatment up to pH 8 resulted in almost 100% Fe (<0.3 mg/L), Al (<0.3 mg/L), and Mn (2 mg/L) removal. Neutralization with pre H2O2 treatment also eliminated Fe and Al at pH 6 to the same removal efficiencies and Mn remained at 15 mg/L. The use of lime was 17% less and the weight of sludge was 35% less, and the volume of sludge decreased by 47%. As a result of evaluating the pH-Eh-Fe diagram for hydrogen peroxide/lime neutralization facilities, it was evaluated that Fe could be removed at pH 5-6. It can be concluded that neutralizing up to pH 6 after oxidation effectively minimizes the amount of sludge generated by removing Fe and Al and suppressing gypsum production.

In order to effectively manage the sludge in the settling ponds, it is necessary to understand the physical properties of the sludge according to the depth in the pond. A new sludge sampling device and method was proposed in this study. Sludge was sampled at three depths in four facilities in South Korea, and the water content, particle size, density, composition, and viscosity of the sediment according to the depth were measured and evaluated. These results can be used to predict the shape of sediment and the lifetime of the settling pond, and to plan and effectively implement sediment removal.

Nano Fe(III) oxide (FO) was employed as an additive material for CO2-aided pyrolysis of spent coffee grounds (SCG) and its impacts on the syngas (H2 & CO) generation and biochar adsorption characteristics were examined. Amendment of FO led to 153 and 682% increase of H2 and CO in pyrolytic process of SCG, respectively, which is deemed to arise from enhanced thermal cracking of hydrocarbons and oxygen transfer reaction mediated by FO. Incorporation of FO successfully created porous structure in the produced biochar. The adsorption tests revealed that the biochar exhibited bi-functional capability to remove both positively charged Cd(II) and Ni(II), and negatively charged Sb(V). The adsorption of Cd(II) and Ni(II) was hardly deteriorated in the multiple adsorption cycles, and the adsorption of Sb(V) was further enhanced through formation of surface ternary complexes. The overall results demonstrated nano Fe(III) oxide is a promising amendment material in CO2-aided pyrolysis of lignocellulosic biomass for enhancing syngas generation and producing functional biochar.

There are totally 5,396 mines located in South Korea, and 2,033 mines are presently closed or abandoned. According to the current status of mine hazard by mine damage type (2017) of the Korea Mine Rehabilitation and mineral Resources Corporation, mine hazard could be caused by tailings loss in 237 mines. Mining stream/void inside the mines are inevitably formed during resource development, and therefore the appropriate management for the mine stability is continuously needed. Mining filling is regarded as one of the best options since the filling mass acts as a secondary support material that can ensure the stability of the mine void and increase the yielding rate of mining. This study evaluated the suitability of harmless tailings, generated from mine development, as a paste backfill material to secure the stability of mine. The particle size of tailings collected at the tungsten mine used in the study was suitable to be used as a paste backfill materials. The strength of cement solidified using test materials was affected by the content of cement and curing duration of the backfill materials sample. It turned out that above 3.5% the cement content and curing for two weeks were an optimal condition to produce the safe cement. In the Environment Ministry's water pollutant emission acceptance standards (South Korea), the tested backfill materials passed all domestic standards for As, Cd, Cr+6, Pb, Cu, and Hg. The environmental/physical properties of tailings obtained from the results demonstrated that the use the tailings as a paste backfill material to fill the inner space of mines could be considered as a promising option. This evaluation results will contribute to the stabilization of mining enemies and restoration of mine damage in abandoned mine areas through economical and efficient treatment of tailings.

Scale is widely observed in the hydrated lime mine drainage treatment plant of the Daedeok Mine in South Korea. In order to understand the environment in terms of the formation of scale minerals, scale and water were collected from the AMD treatment facility and analyzed. In addition, the saturation index was calculated based on geochemical modeling to predict the minerals that could be produced in the AMD treatment facility, and the results were then compared with an analysis of onsite scale minerals. Furthermore, the onsite mine drainage was neutralized from pH 3 to pH 9 in the laboratory, and the precipitates produced were identified. The changes in the Ca2+ and SO42− concentrations were also identified over time for each pH. The results of geochemical modeling predicted the possible precipitation of gypsum, anhydrite, and bassanite after AMD neutralization. Scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) analysis results showed that the main mineral in scale formed at the AMD treatment facility was gypsum, produced by the reaction of SO42− and Ca2+ from lime during AMD. The laboratory neutralization experiment showed that gypsum was produced in all neutralization ranges from pH 3 to pH 9, and the higher the neutralization pH, the greater the amount of gypsum produced. It was demonstrated that simulated amounts of 2 g/L and 7 g/L gypsum at pH 5 and 9 were well matched with the experimental results. Iron (Fe), a major pollutant in the mine drainage system, was rapidly precipitated in the form of iron hydroxides after neutralization. As gypsum is produced slowly and continuously for a long period of time, it results in the growth of scale throughout the flow path. As a method of minimizing gypsum production in the AMD treatment facility using hydrated lime, it is recommended that the facility should be operated at the lowest pH possible, which will also enable the removal of major pollutants, such as iron and aluminum.

This study evaluated the effect of the degree of weathering on the particle size distribution and the amount of tine particles generated in the aggregate production process during the crushing of igneous rock. Rock samples were collected from three areas with differences in strength from the Schmith hammer measurement at the aggregate quarry in Geochang, Gyeongsangbuk-do. After crushing with a jaw crusher under the same conditions in laboratory, particle size analysis, mineral analysis, chemical analysis, and weathering index were calculated. The Schmidt hammer measurements were 56, 28, and <10, and the CIA and CIW values of weathering index were also diftinvnt, so the rock samples were classified into hard rock, soft rock, and weathered rock according to the weathering degree. It shows a smaller particle size distribution toward weathered rocks under the microscope, and the proportion of altered clay minerals such as sericite increased. The composition of feldspar and quartz was high for hard rock, and the ratio of muscovite and kaolinite was low. As a result of the crushing of the jaw crusher, hard rock produced a lot of coarse crushed material (13.2mm), while soft rock and weathered rock produced fine crushed material (4.75mm). The former showed the characteristics of the beta distribution curve, and the latter showed the bimodal distribution curve. The production of fine rock particles (based on 0.71mm of sieve, wt. %) increased to 13%<21%<22% in hard rock, soft rock, and weathered rock, and the greater the degree of weathering, the more fine rock particles were generated. The fine particles are recovered by the operation of the sand unit in the wet aggregate production process. Therefore, in order to minimize the amount of sludge generated in the aggregate production process, it was judged that a study on the optimal operation of cyclones could he necessary.

광산배수 및 슬러지 내 희토류(REE)의 자원화 가능성 평가를 위하여 REE 분석과 연구 동향을 조사하였다. 석탄 및 셰일에서 총 희토류(TREE) 평균은 각각 268 mg/kg 및 283 mg/kg로 분석되었다. 광산배수의 TREE 농도는 pH 값이 낮은 산성배수에서 높았다. REE/NASE 비는 중간 희토류(MREE)가 부화한 특징을 보였다. 대덕탄광의 광산배수가 pH 8.5로 중화되면서 REE 성분이 <0.1 ppb 이하로 감소하여 슬러지로 농축되었다. 금속광산과 석탄광 슬러지의 평균 THREE 는 290 mg/kg 및 532.6 mg/kg으로 조사되었다. 총 17개소의 슬러지 내 REE의 시장가치는 790,493 U$에 달할 것으로 추정하였다. 문헌 조사 결과 REE 회수 연구는 원수 및 슬러지별 흡착 및 침전법으로 회수하는 연구가 수행중이다. 폐광산이 흩어져 있는 현장을 고려한 REE 회수 시스템으로 개별 AMD 처리시설에서 REE를 1차로 농축하고 산 용출 및 용매추출 공정을 갖춘 시설에서 2차로 고순도 REE를 생산하는 개념이 제시되고 있다.

The vulnerability of the rare earth element (REE) supply in a global context of increasing demands entails important economic and political issues, and has encouraged several countries to develop their own REE production projects. This study comparatively evaluated the production of REEs from primary and secondary resources in terms of their sustainability and contribution to the achievement of the Geoethics concept as responsibility towards oneself, colleagues, society, and the Earth system. Twelve categories of potential environmental and social impacts were selected: human health toxicity, global warming or climate change, terrestrial and aquatic eutrophication, acidification potential, particulate matter, resource depletion, water consumption, fresh water ecotoxicity, ionizing radiation, fossil fuel consumption, and ozone depletion. The results showed that the environmental impact of REE production from secondary sources is much lower relative to primary sources. A comparison of conventional and non-conventional REE resources showed that significant impact categories were related to particulate matter formation, abiotic resource depletion, and fossil fuel depletion, which could result from avoiding the tailings disposal before reuse. Based on these findings, governments and stakeholders should be encouraged to increase the recycling of secondary REE sources with Geoethics in mind, in order to balance the high demand of REEs while minimizing the overexploitation of non-renewable resources.

Lime has been used for the neutralization of acidic waste because it is cheap and available in large quantities. The resulting sludge often contains a considerable amount of unreacted lime due to alkali overdosing, even during automatic neutralization processes, which mainly arises from the poor solubility of lime. The sludge cake from lime neutralization of Ilkwang Mine also contained high percentages of calcium and magnesium. The elemental content of the sludge cake was compared with those obtained from a simulation of the lime neutralization facility installed at Ilkwang Mine. A Goldsim (R) model estimated the degree of lime overdosing to be 19.1% based on the fractions of ferrous oxide. The analysis suggests that resolubilization of aluminum hydroxide could occur in the settling basin, in which pH exceeded 10 due to the continued dissolution of the overdosed lime. The present study demonstrated that chemical analysis of sludge combined with process simulation could provide a reasonable estimate of mass balance and chemistry in a neutralization facility for acid mine drainage.

This work introduced a new way of fabricating a granular material with the supply of Al-rich precipitates selectively obtained from acid mine drainage (AMD), and its potential as a promising adsorbent for fluoride (F) was evaluated. Through the selective sequential precipitation (SP) process in the field, Al-rich precipitates with high purity (>81%) were collected at the high recovery rate (>99.8%) as a raw material for adsorbent fabrication. The granular adsorbent (ALB) was synthesized through encapsulation of precipitate powders by chemically inducing polymeric bead formation. The characterization results revealed that ALB possessed a highly porous structure and embedded a large number of nanoparticles of amorphous Al hydroxides inside its framework. Less adsorption of F occurred at an alkaline pH condition due to the competitive effect of hydroxyl ions. The adsorption process can be divided into fast adsorption by the outer surface and slow diffusion in the inner phase. The maximum adsorption capacity of ALB for F was calculated to be 17.7 mg g−1 in the Langmuir isotherm model fitting results. By the repetitive adsorption/desorption and XPS results, it turned out that both chemisorption and physisorption gave a contribution in the removal of F, and the regeneration of adsorbent using NaOH was effective to restore the adsorption capability but accompanied the loss of adsorption sites. As a result, it can be concluded that a granule-type material fabricated using Al-rich precipitates selectively recovered from AMD neutralization can be considered as a promising adsorbent for F removal in aqueous solution.

As a successive alkalinity-producing system pond for purifying mine drainage is operated, sediment accumulates in the limestone layer of the pond, and as the amount of accumulated sediment increases, the water permeability and treatment efficiency of the pond decrease. Hence, a flushing system is required, comprising of a network of perforated pipes installed in the limestone layers, to periodically discharge sediment and mine drainage to the outside. The performance of a flushing system depends on four distinct characteristics of the system: the characteristics of the limestone layer, the sediment, the flow, and the flushing device. However, existing studies have evaluated the performance of the entire system without considering these conditions. In this study, a new experimental method for designing a flushing system is proposed. This method is based on an experiment to evaluate the influence radius of orifice, which is the radius of the spherical volume around an orifice that can suck sludge by flushing. The results showed that the flow rate of water through the orifice in the glass bead layer matched well with the Blake–Kozeny formula, and that the greater the diameter of the orifice is, the greater the influence radius of orifice. The influence radius of orifice according to the diameter and spacing of the orifice was evaluated, which provides a key criterion for designing a flushing system.

When crushing rocks to produce aggregates, solid stone dust or sludge is generated as a by-product. These by-products are classified as waste and are not utilized, and most of them are disposed of landfills. This by-product differs in mineral composition, chemical composition, and physical properties depending on the rock type and aggregate production process. Therefore, if a technology that can make good use of the inherent physical or chemical properties of by-products is developed, economic and environmental benefits can be achieved instead of disposal. In this study, stone dust and sludge were collected from domestic aggregate producers and physical and chemical properties were investigated by performing XRD mineral analysis, particle size analysis, and chemical analysis. In addition, the research trend was identified through a domestic and international research case studies on the use of stone powder and sludge.

Aggregate collection is taking place in many areas in Korea, resulting in large cut slopes or large amounts of cut rocks. If the development site for such aggregate collection is a stratum accompanied by sulfide minerals, Acid Rock Drainage (ARD) may occur, which may cause environmental pollution in the development site and surrounding areas. As a result of the study on forest aggregate samples, most of the samples were classified as acid-forming potential samples, and among them, some samples from Gwangju, Goyang, and Sokcho were classified as potential acid-generating samples. This can be expected to affect the quality of aggregates when a large amount of aggregate is used in the future. Therefore, it is judged that these forest aggregates need to be managed when they are used. By predicting the occurrence of ARD through the acid-generating ability test, it is expected that economic losses that may occur in the future can be reduced, and it is judged that the problem of surrounding environmental pollution can be further alleviated.