Next Article in Journal
Tidal Effects on Dissolved Organic Matter Dynamics in a Brackish Water Front Adjacent to Yangtze River Estuary
Next Article in Special Issue
Nitrogen and Gray Water Footprints of Various Cropping Systems in Irrigation Districts: A Case from Ningxia, China
Previous Article in Journal
Sources, Water Quality, and Potential Risk Assessment of Heavy Metal Contamination in Typical Megacity River: Insights from Monte Carlo Simulation
Previous Article in Special Issue
Analysis of the Distribution and Influencing Factors of Antibiotic Partition Coefficients in the Fenhe River Basin
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Water
Volume 17
Issue 2
10.3390/w17020225
water-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Treatment of Acid Mine Water from the Breiner-Băiuț Area, Romania, Using Iron Scrap

by
Gheorghe Iepure
* and
Aurica Pop
Nord University Center of Baia Mare, Faculty of Engineering, Technical University of Cluj Napoca, V. Babes St., 62A, 430083 Baia Mare, Romania
*
Author to whom correspondence should be addressed.
Water 2025, 17(2), 225; https://doi.org/10.3390/w17020225
Submission received: 12 December 2024 / Revised: 9 January 2025 / Accepted: 13 January 2025 / Published: 15 January 2025
(This article belongs to the Special Issue Basin Non-Point Source Pollution)
Browse Figures
Versions Notes

Abstract

:
Acid mine drainage (AMD) forms in mining areas during or after mining operations cease. This is a primary cause of environmental pollution and poses risks to human health and the environment. The hydrographic system from the Maramureș mining industry (especially the Baia Mare area) was heavily contaminated with heavy metals for many years due to mining activity, and after the closing of mining activity, it continues to be polluted due to water leaks from the abandoned galleries, the pipes, and the tailing ponds. The mineralization in the Băiuț area, predominantly represented by pyrite and marcasite associated with other sulfides, such as chalcopyrite, covelline, galena, and sphalerite, together with mine waters contribute to the formation of acid mine drainage. The Breiner-Băiuț mining gallery (copper mine) permanently discharges acidic water into the rivers. The efficiency of iron scrap (low-cost absorbent) for the treatment of mine water from this gallery was investigated. The treatment of mine water with iron shavings aimed to reduce the concentration of toxic metals and pH. Mine water from the Breiner-Baiut mine, Romania, is characterized by high acidity, pH = 2.75, and by the association of many heavy metals, whose concentration exceeds the limit values for the pollutant loading of wastewater discharged into natural receptors: Cu—71.1 mg/L; Zn—42.5 mg/L; and Fe—122.5 mg/L. Iron scrap with different weights (200 g, 400 g, and 600 g) was put in contact with 1.5 L of acid mine water. After 30 days, all three treatment variants showed a reduction in the concentrations of toxic metals. A reduction in Cu concentration was achieved below the permissible limit. In all three samples, the Cu concentrations were 0.005 for Sample 1, 0.001 for Sample 2, and <LOQ for Sample 3. The Zn concentration decreased significantly compared to the original mine water concentration from 42.5 mg/L to 1.221 mg/L, 1.091 mg/L, and 0.932 mg/L. These values are still above the permissible limit (0.5 mg/L). The Fe concentration increased compared to the original untreated water sample due to the dissolution of iron scrap. This research focuses on methods to reduce the toxic metal concentration in mine water, immobilizing (separating) certain toxic metals in sludge, and immobilizing various compounds on the surface of iron shavings in the form of insoluble crystals.

1. Introduction

In areas with mineral deposits, acidic water primarily originates from the oxidation of iron sulfide, also known as pyrite, which is often found together with other minerals of valuable metals. Acid mine drainage (AMD) forms in mining areas, metal recovery sites, or in connection with these sites, and continues even after the closure of mining activities. Acid mine drainage is the main cause of environmental pollution [1]. The oxidation of sulfides associated with acid mine drainage, in addition to the low pH (1–3), produces extremely high concentrations of Fe3+ and −SO42−, along with other potentially toxic elements [2,3,4,5,6,7]. In mining waste, alongside sulfides, other mineral components may be present, which can positively influence the interaction of the waste with environmental factors. These mineral components can include metallic oxides, clay minerals, hydrated salts, arsenates, carbonates, phosphates, and native elements [8].
Over time, abandoned mines have not been subject to environmental protection regulations [9], which has prolonged closure activities at very high costs. Abandoned mines, along with other related products like mine tailings and tailing ponds represent unstable structures that can pose a potential hazard and an existing or potential environmental impact [9,10]. High concentrations of copper pose risks to aquatic and terrestrial ecosystems as well as to human health [11]. There is a health risk associated with heavy metal exposure to fish fauna and the consumption of fish from rivers polluted with mine water [12] due to the bioaccumulation of trace elements (As, Cd, Cr, Cu, Ni, Pb, Pt, Zn) in edible fish species [13], as well as the accumulation of heavy metals in plants grown in soils irrigated with water from rivers polluted by mine water [10,14,15].
Untreated acid mine drainage degrades habitats, influencing the reduction in species diversity [16]. The methods for treating mine water can be effective if they meet the conditions set by legislation regarding water quality [17]. Many recent studies have compared the results of mine water treatment methods based on the water quality requirements at discharge and have tried to scientifically explain the differences in performance for various materials used to raise pH levels [18].
Water discharged from abandoned mines is a major cause of surface water degradation in many parts of the world, as well as groundwater [19,20,21]. Untreated iron from mine water discharges tends to rapidly form a solid (oxy)hydroxide precipitate in surface watercourses [22]. Due to high metal concentrations, mine waters require treatment [23,24,25].
Acid mine drainage treatment technologies can generally be classified into active treatment, passive treatment, and in situ treatment [26,27]. Active treatment technologies present high operating and maintenance costs, so passive treatments are widely used [27]. Active systems require the periodic purchase of alkaline materials [26]. Active treatment methods include the precipitation or adsorption of metals by adding alkaline chemicals: calcium hydroxide Ca(OH)2 or limestone (CaCO3), metallic hydroxides, and sulfate precipitated as gypsum sludge (CaSO4·2H2O) [28]. Passive systems may include limestone drains, alkalinity-producing systems, sulfate-reducing bioreactors, slag drains [26,27,29], and the use of a permeable reactive barrier [28].
Many studies have experimented with using chemicals for the treatment of acid mine drainage. According to the data presented [29], the chemicals that can be used for mine water neutralization and their neutralization efficiency can be limestone (CaCO3)—30%; Ca(OH)2—90%; CaO—90%; Na2CO3—60%; NaOH—100%; NH3—100%; phosphate rocks; products synthesized from zeolites [1,30,31,32,33,34,35,36]; and sulfated reactants generated as chemical sulfide through the ChemSulphideTM process [37].
Acidity and the metal concentrations play an important role in the treatment of mine waters. Through neutralization processes, heavy metals are removed from acidic aqueous solutions through precipitation [38]. Many new research techniques are being developed using a wide variety of methods, such as the use of organic materials like eggshells, lemon peels [39], chitosan from shrimp waste [40], algae, sulfate-reducing microbes, and bacteria [29,41], as well as ultrafiltration and nanofiltration techniques, as presented in [42,43,44]. The filtration stages (ultra- and nanofiltration) are recommended as final stages before discharging treated waters into surface waters [45], with RO membranes being highly sensitive to fouling in mine waters, leading to membrane degradation and physical damage.
Among the approved and commercialized techniques for mine wastewater treatment and widely applied in the laboratory and pilot stages are technologies such as SAVMIN®, SPARRO®, biogenic sulfide, and DESALX®, the MF/UF-RO system [23]. Adsorption and coagulation are the most commonly used methods; they are simple to use and have several advantages, such as low cost, practicability, and efficiency [46]. These technologies show that it is necessary to implement adsorption systems in wastewater, using low-cost adsorbents and recovering precious metals at low concentrations to favor water reclamation for circular mining processes [23]. The characteristics of low-cost adsorbents for wastewater treatment, as well as adsorption capacities, have been analyzed in the specialized literature, with low-cost adsorbents being divided into the following groups: agricultural and household waste; industrial by-products; sludge; marine materials; soil and ore; and new low-cost adsorbents (for example, titanium oxide) [47]. The modification of natural adsorbents and coagulants can be explored for increased efficiency in all types of wastewaters [46].
Passive systems are inexpensive to operate but involve fundamental disadvantages, such as large land requirements and an extended treatment period [41].
Biosorption is an alternative to physicochemical methods for removing toxic metals from wastewater [48]. For example, the effects of heavy metal waste generated by gold extraction activities on the environment and the different mechanisms used by bacteria to counteract the impact of these heavy metals in their immediate environment are analyzed [49]. Significant amounts of heavy metals are bound to resistant cells that contribute to the processes of bioprecipitation/intracellular accumulation and the bioremediation process [49]. Sulfate-reducing bacteria (SRB) remove sulfate and heavy metals, reducing the toxicity of mine water [41]. Bioreactors have high operational predictability and faster treatment times but require higher investment costs. The remediation of AMD through treatment in bioreactors can lead to the recovery of metals from biotreatment systems and the valorization of the resulting metals [41]. “AMD is the most widespread and harmful environmental concern associated with mining activities” [50], leading to efforts focused on the development of prediction techniques and quantification of solution loads from mining sites, as well as the monitoring of rivers affected by mine drainage [50].
Acid mine drainage (AMD) is a negative outcome of mining activities, with most studies analyzing the negative impact of mining operations without considering the positive factors. In this regard, Ref. [51] proposed a holistic model for a realistic assessment of the individual and overall sustainability score of mining activities.
Iron scrap combined with organic materials has been used with good efficiency for treating mine waters in dynamic mode, aimed at reducing metal concentration and adjusting pH levels [52]. Iron and iron compounds have been successfully applied for the removal of heavy metals from mine waters in the laboratory or pilot-scale installations [53,54]. Cementation (the process of copper cementation) is the oldest and most efficient method for recovering solutions with low concentrations of Cu, and it can also be used for recovering many metallic cations found in solutions [55].
The main objective of this article was to identify a method to reduce the concentrations of toxic metals (Cu, Pb, Zn, and Cd), which strongly affect aquatic life. This study also monitored changes in pH levels. This research involved a chemical analysis of mine water before and after treatment with iron shavings, focusing on the concentrations of toxic metals. Additionally, chemical and structural analyses were performed on the by-products formed during the reaction between mine water and iron scraps.
The influence of the quantity of iron scrap on the decrease in the quantity of Cu was also monitored. During the experiment, orange and black crystalline deposits on the surface of the iron scrap were obtained. Another objective of this study was the identification of individualized crystalline forms, their size, and chemical composition.

2. Materials and Methods

Site Description

Acid mine drainage (AMD) is predominant in the Baia Mare area following the closure of mining activities. It is caused by the presence of iron sulfide, pyrite (FeS2). Pyrite, through oxidation, produces highly acidic water (pH < 3), which can solubilize heavy metals and other elements. Acid production is favored by the size of the pyrite particles, as well as the influence of temperature, porosity, and the hydrological conditions of the site [56].
The mining activities in the Baia Mare region, in relation to associated industrial processes, have generated acid mine drainage (AMD), which has had long-term negative effects on the environment and has not diminished over time according to [41]. AMD is characterized by low pH and high concentrations of heavy metals. This phenomenon is associated with mining dumps, tailing ponds, and mine galleries from which water leaks from closed mining works. The abandoned mine galleries containing metal sulfides and that are in contact with water become sites of physicochemical processes between mineral components with sulfur concentration and various metals. From the abandoned mine galleries in the Baia Mare area, acidic waters are continuously discharged without treatment due to the lack of wastewater treatment plants or the lack of function of existing ones. In the case of mining operations in the Baia Mare area, in non-ferrous metal deposits, the specific pollutants are Pb, Cu, Zn, Cd, Fe, and As [57].
Mining activity in the Breiner-Băiuţ area began in the 15th century and continued until 2006 for the valorization of Cu, Pb, and Zn. The Breiner-Băiuţ mining area comprises sedimentary rocks (mainly sandstones and siltites interspersed with marls) intruded by Neogene magmatic rocks (mainly porphyry quartz-microdiorites and pyroxenic andesites [57]. The Neogene sedimentary rocks are represented by conglomerates, sandstones, tuffs, marls, and clays of the Badenian, Sarmatian, and Panonnian ages. These rocks are intruded by magmatic bodies, represented mainly by quartz-microdiorite porphyritic and pyroxene andesites. They present obviously porphyritic structures with fresh plagioclase phenocrysts, substituted illite-sericite, or kaolinite aggregates. The second mineral component is the femic one represented by pyroxenes in an unaltered state or with different degrees of hydrothermal transformation being substituted with chlorite and carbonates. These rocks are black-gray in fresh state, and gray-green in altered state, with a clear porphyritic structure and massive texture. Among the porphyritic components, plagioclases (between 0.3 to 1.5 mm), clinopyroxenes, biotite, and sometimes quartz are recognized. The rocks present fine disseminations of magnetite and pyritizations [58].
The predominant association of mineralizations with magmatic intrusions suggests a genetic relationship between the magma that generated the intrusions and the hydrothermal circulation. The penetration of magmatic intrusions into the upper parts of the mineralized structures generally create a system of tension fractures, which constitute the access routes of mineralizing fluids and meteoric waters. Magmatic intrusions represent the apical part of a pluton [59].
The common iron sulfides in the Băiuț area are predominantly represented by pyrite and marcasite (FeS2), but other metals can form copper sulfides, chalcopyrite (CuFeS2), covellite (CuS), galena (PbS), and sphalerite (ZnS). Pyrite is often found associated with these other metal sulfides, thus causing the formation of acid mine drainage in mining areas where Cu, Pb, and Zn are exploited [60].
The Breitner mine gallery is a source of heavy metal pollution due to the continuous discharge of mine water, which contributes to the pollution of the Lăpuș River. Since the mine’s closure in 2006, no measures have been implemented to treat the discharged water.
According to [61], a critical analysis of the environmental impact of acid mine drainage (AMD), which is a residual product of mining activities containing iron, heavy metals, and sulfates that contribute to severe environmental degradation, is presented. The paper also analyzed proposals for the phytoremediation of affected areas. Due to the mixed nature of contaminants in AMD-impacted environments, a tailored strategy must be developed for each site, environment, community, and individual point in time [61]. The area for water sampling (collection) used in the treatment trials was the Baiuț mine area, located in Maramureș, Romania (47°37′31.0″ N 24°00′32.5″ E, Figure 1a) The discharge of mine water generates strong acid drainage around the discharge pathways, which increasingly covers larger areas near the source of the discharge, specifically the mine gallery entrance (Figure 1b,c). The mine water is discharged externally without any treatment being applied.
Attempts to treat a mine water sample were made using iron scrap. Under the name of iron scrap, turnings from the mechanical machining of iron parts were used (Figure 2).
Metals with negative oxidation potentials (relative to hydrogen) can be precipitated in aqueous solutions containing ions of metals with less negative or positive potentials. For example, zinc and iron precipitate copper from a copper sulfate solution, copper precipitates silver from silver nitrate etc. [62]. The mechanism of the cementation process involves the formation of micro-galvanic elements, where the metal being cemented acts as the cathodic sector, and the metal used for cementation serves as the anodic sector. Based on the series of normal electrode potentials, it is estimated that one metal can be cemented from a solution using another metal that is more electronegative. The industrial applications of the cementation process are synthesized according to [63] in Table 1.
In the research concerning the reduction (removal) of copper from mine waters, a material with a high iron concentration was used as the cementation (precipitation) substrate. According to the literature data (Table 1), zinc (Zn), iron (Fe), cadmium (Cd), and nickel (Ni) are used for the cementation of copper from solutions; however, Fe and Zn are recommended for more types of anions.
Compared to iron, zinc is a much more expensive non-ferrous metal and is only recommended for copper-rich solutions (waste electrolytes from the electrolytic refining of copper and the production of electrolytic copper powder) with the valorization of the cement (of both metals Cu and Zn) obtained to produce alloys. In solutions with low copper concentrations, metal wastes with high iron concentration are recommended.
The material used for the research was a high-iron concentration material, specifically low-carbon steel (steel S235—according to SR-EN 10025-2 [64]), introduced in the form scrap, which is waste material from the metal cutting process, making it a low-cost material. The cementation material should have as large a specific surface area as possible; steel shavings fulfill this requirement.
Pure iron is relatively expensive; powdered iron used in powder metallurgy can also be utilized as a cementing material, but this is also very expensive compared to iron shavings, which represent waste and are relatively easy to procure.
The chemical composition of steel S235 is provided in Table 2, with an iron concentration of approximately 98%.
The purpose of treating the mine water sample with iron scrap was to verify the ability of the iron shavings to retain copper from the mine water.
The iron scrap, freshly obtained from the cutting operation, was prepared for reaction by washing with a solvent (acetone) to remove emulsions and cooling oils from the surface of the shavings due to the cutting process.
The washing operation was performed in plastic (PET) containers by introducing the shavings and the solvent and continuously agitating for 10 min. Then, the iron shaving sample was left on a watch glass to allow the solvent to evaporate.
To ensure contact between the iron and the mine water, three samples of iron scrap with different weights were taken—200 g, 400 g, and 600 g—aiming to increase the contact surface with the mine water. The iron scrap was weighed from the degreased and dried material. The next step was to place the three samples of iron scrap in contact with a quantity of mine water, 1.5 L each. The samples were introduced into 2 L plastic (PET) containers, sealed, and left in contact for approximately 30 days. After the 30-day contact period between the water and the iron scrap, three samples of mine water were collected from each container by filtering through filter paper. The resulting sludge with the scrap remained on the filter paper (pore size: 10–15 μm).
The iron scrap was dosed in different quantities to highlight the influence of the amount of shavings that would ensure a larger specific surface, which would determine the extraction of a greater quantity of copper from the solution.
Cementation was carried out as follows:
(Cu2+)solution+ Fe(s) = (Fe2+)solution + Cucement
The overall reaction can be interpreted as an electrochemical reaction:
Cu2+ + Fe → Cu + Fe2+
Copper is deposited on iron, and iron can combine with iron ions to form iron hydroxide. Copper cement is an impure black product according to the literature data and may contain between 50 and 85 wt% copper, primarily in the form of oxides and insoluble impurities.
The sample was collected from the Baiuț mining area from the mine water discharged through the Breiner gallery. The mine water used in the experiment had high concentrations of Cu, Fe, and Zn, exceeding the allowed concentrations from NTPA001/2005 [65] and law 161/2006 [66], and lower concentrations of Pb and Cd (Table 3). Copper concentrations far exceeded the permissible levels in mine water according to legislation (Table 3).
The chemical analysis of raw and treated water was carried out using the atomic absorption spectrometry (AAS) method, with a PerkinElmer Analyst 800 spectrometer (Perkin Elmer, Llantrisant, UK). The chemical analysis of the sludge was performed using the ICP/MS method, after digestion with aqua regia.
The chemical composition of the sludge deposited on the walls of the experimental vessel was determined using electron microprobe analysis (EMPA) at the Slovak Academy of Sciences in Banská Bystrica, Slovakia. The microprobe measurements were performed on carbon-coated polished sections using a JEOL JXA-8530F (JEOL, Tokio, Japan). It is outfitted with five WDS spectrometers and ten different crystal types (TAPJ 2x, LIFL, LIFH, LIF, PET, PETJ, PETH, LDE1, LDE2) as well as with an SDD (silicon drift detector) energy-dispersive spectrometry (EDS) system with 133 eV resolution. All elements (from Be to U) can be detected because each element has a specific set of X-rays that it emits. The device was operated under an acceleration voltage of 15 kV, a 20 nA sample current, a 2–5 m beam diameter, 10–30 s of counting time for peaks, and 5–15 s for the background
For the structural analysis of sediments, the X-ray diffractometry (XRD) technique was employed using a Rigaku SmartLab diffractometer (X-ray tube target = Cu, voltage = 40.0 (kV), current = 30.0 (mA), 2Theta = 5.000–70.000 degree, scan speed = 2.0000 (deg/min, sampling pitch = 0.0200 deg)—Shimadzu, Kyoto, Japan).
Microscopic analysis of the scrap iron surface was performed using optical microscopy with a Kruss stereoscopic microscope (KRÜSS Optronic GmbH, Hamburg, Germany)

3. Results and Discussion

3.1. Water Analysis

From the analysis of the untreated mine water sample, it was observed that the pH and the concentrations of the analyzed toxic metals exceed the maximum limits permitted by national legislation [NTPA001/2005, law 161/2006, Table 3].
The high acidity of the mine water from the Breiner Băiut gallery (pH) was quite elevated, comparable to values from other areas impacted by mining industry activities [67].
For the analysis of the treated water, 0.5 L were collected from each 2 L bottle of treated mine water, which was analyzed using atomic absorption spectrometry (AAS), a method considered suitable for determining the ions of Cu, Zn, and Cd [68].
In treating the mine water sample with iron scrap, neutralization was achieved, resulting in a slight increase in pH from 2.75 to values between 4.82 and 4.91 for the three samples (Table 4). The pH value did not reach the permissible limits set by legislation. This situation may be due to the maintenance of high sulfate concentrations. Higher values were noted in the sample with the smallest amount of iron scrap (Sample 1—200 g, pH = 4.91), while lower values were observed in the samples where the amount of shavings increased (Sample 2—400 g, pH = 4.83; Sample 3—600 g, pH = 4.82). A significant portion of the iron oxyhydroxides precipitated and settled on the walls of the reaction vessel. The pH increased very little due to the deposition of copper and zinc sulfates on the iron shavings and in the sludge, compounds highlighted by XRD, SEM, and WDS.
Comparatively, in the three treatment variants, a decrease in Cu and Zn concentrations was observed with the increasing amount of iron scrap, from Sample 1 to Sample 3 (Table 4). After treating the mine water with iron scrap, all three treatment variants, which differed in the amount of shavings used, showed a decrease in the concentrations of toxic heavy metals. A considerable decrease in Cu concentration was obtained, being much lower than the permissible limit (Table 4). In all three samples, the Cu concentrations were 0.005 for Sample 1, 0.001 for Sample 2, and below the detection limit (<LOQ) for Sample 3.
The Zn concentration decreased significantly compared to the original mine water concentration from 42.5 mg/L to 1.221 mg/L, 1.091 mg/L, and 0.932 mg/L. The Zn concentration decreased in the mine water because it was deposited as sulfates in the mud and on the iron scrap. These values are still above the permissible limit (0.5 mg/L) according to the data from NTPA001/2005 [65]. The iron concentration increased (Table 4) compared to the original untreated sample (Table 3) due to the dissolution of iron from the introduced iron scrap.
The images in Figure 3 are illustrative for exemplifying the variations in metal concentrations in the three samples of mine water treated with iron shavings. A significant decrease in the concentration of Cu (Figure 3a) is observed compared to the concentration of Zn (Figure 3b), and an increase in the concentration of Fe is noted with the increase in the quantity of iron scrap introduced into the mine water.

3.2. Sludge Analysis

3.2.1. Chemical Analysis

The sludge resulting from the deposits on iron chips in the three treatment variants was chemically analyzed using the ICP/MS method.
The chemical analysis of the sludge showed a wide variety of chemical elements present. Their origin can be explained as follows: Cu, Zn, and Cd enter the mine water through the alteration of elements from sulfide ores; Na, Mg, Al, K, and Ca are dissolved elements from the rocks that mine water passes through; Cr and Mo can be dissolved from the iron scrap and used for cementation. Mn, Fe, Co, and Ni may come both from the corrosion of the iron scrap and from the mine water. A large part of the toxic metals (Cu, Zn, Cd, Pb, Fe) has been immobilized in the sludge under various combinations (Table 5) through precipitation, a process demonstrated in [38], or the adsorption of metals onto ferric (hydr)oxides [69].
Following the treatment of the mine water, the concentration of Cu decreased below the admissible limit stipulated by national legislation (NTPA001/2005) in the treated water (0.001–0.005 g/L—Table 4), with its concentration in the sludge in all samples being close to 1 g/kg (around 1000 mg/kg, see Table 5). According to data from the literature [52], this may be in the form of cement or sulfates. Zn also precipitated in significant amounts in the sludge, but the amount of zinc remaining in the treated water exceeded the admissible limit by approximately two times (0.93–1.221 g/L, Table 4) because zinc forms soluble compounds. The concentration of Fe precipitated in the sludge is high (Table 5), due to the dissolution of iron from the scrap and the formation of copper cement. Due to the high concentration of heavy metals in the sludge, it is toxic, a fact presented in the specialized literature. Also, the scientific literature states that there is not enough research on the reuse, toxic sludge management, and economic analysis of such systems [23].
The images in Figure 4 are illustrated to exemplify the variations in heavy metal concentrations in the three sludge samples.
From our experiments, it can be seen that the different types of combinations of polluted water–metal scrap deposit different amounts of heavy metals. Zinc and iron are deposited in large quantities at low iron scrap concentrations. The copper deposits are approximately equal in the three experimental situations. The highest copper concentrations are in the second version, as well as for cadmium. These values indicate that the introduction of small amounts of iron scrap into polluted waters can reduce the heavy metal concentration to acceptable levels according to current legislation.
The sludge contains, along with heavy metals, other chemical elements that are not listed in NTPA001/2005. These elements, such as Na, Mg, Al, K, and Ca, originate from the dissolution of silicate minerals, such as clay minerals and tectosilicates, which are common in the investigated area [70].
From the fine sludge material deposited on the walls of the experimental vessel (flask), a compressed pellet was made for analysis using an electron microprobe, using the WDS technique. Ten analyses were performed, with the results shown in Table 6.
The highest concentrations in the sludge have K, Al, and Si, which, in correlation with X-ray diffraction (see Section 3.2.2), demonstrate the presence of significant amounts of Al2O3, SiO2, and K2O, along with low amounts of Fe and Mn oxides. The presence of these elements is consistent with the data presented in [8]. The predominant elements (Table 6) come from the deposition of a clay material, such as illite and montmorillonite. The total concentration is around 95–96 wt% due to the significant amount of structural water in the clay minerals

3.2.2. XRD Analysis

XRD analysis was performed on the fine sludge material deposited on the walls of the experimental vessel.
Following the X-ray diffraction (XRD) analysis of the sludge, weak crystallization of the compounds was observed. In the XRD diagram, poorly crystallized compounds with structures similar to certain minerals were identified (Figure 5). Copper was found in the sludge according to the ASTM [71] powder diffraction file (pdf) in the form of copper sulfate hydroxide—brochantite (Cu4(OH)6SO4, pdf-85-1316); copper oxide—cuprite (Cu2O, according to pdf 03-0892); and copper oxide—tenorite (CuO, pdf 02-1041). Iron was present as iron oxide hydrate—goethite (Fe2O3·H2O·x H2O, according to pdf 02-0273) and iron oxide hydrate—lepidocrocite (Fe3+O(OH)) according to pdf 06-0098), while zinc appeared as zinc sulfate hydrate—goslarite (ZnSO4·7H2O, according to pdf 09-0395). In addition to these metallic compounds, illite (pdf 09-0343 Potassium Iron Magnesium Aluminium Silicate Hydrate K0.59Al,Fe,Mg)3(SiAl)4O10(OH)2) was identified based on the d = 10.1 peak, and montmorillonite was identified based on the d = 13.9 peaks (03-0009—iron Magnesium Aluminium Silicate—Si3.74Al2O3FeO0.03Mg0.2O11) [31]. The detected silicates have diffraction lines identical to those of natural illite and montmorillonite [60,72], but with low crystallinity, as they were deposited from polluted waters at ambient temperatures. Along with these clays, the presence of copper components is likely due to the reduction in copper with metallic iron in the mine water. Additionally, goslarite, which commonly precipitates from mine waters, and iron oxyhydroxides (lepidocrocite and goethite) were also observed.
A series of such compounds were identified in [73] in river sediments, generated by small streams that drain mining waste deposits and flow into the main rivers near their confluences. The production of these compounds in the sediments is the result of the simultaneous dissolution of the most important minerals from the ore [73]. When precipitating some heavy metals (V) from wastewater at a mining site using granular ferric oxyhydroxide, a certain degree of crystallization of the sorbent into goethite was observed [53].

3.3. Microscopic Analysis of Iron Shavings

The iron scrap samples were examined using optical and electron microscopy.
An optical microscopy analysis was conducted with the help of a stereoscopic microscope (Kruss) to distinguish the color of the sludge and the crystals on the surface of the iron shavings. In Figure 6, the orange and black crystalline deposits on the surface of the iron scrap can be observed.
In Figure 6c, the salt crystals detached from the iron scrap have been separated. The black crystals are representative of the CuFe cement formed according to reaction (1).

Electron Probe Analyses

The shaving surfaces observed by optical microscopy were also investigated by electron microscopy. In the overview image (Figure 7a), clusters of crystals of various shapes and sizes are observed. The shape of the crystals clustered on the surface of the shavings is spectacular, showing deposits and clusters of relatively compact crystals observed at low magnification (Figure 7a). However, at higher magnifications, needle-like and plate-like crystal forms can be seen (Figure 7b,c at point 1).
The crystals were also analyzed using the electron microprobe technique (Figure 8a). The obtained spectra mainly indicate the presence of heavy metal oxide compositions (Table 7). Figure 8a shows an image of the analyzed crystal (C2) at a magnification of 400×. It can be observed from the analysis of the EDS spectrum at point 3 (Figure 8b).
In examining the analyses in Table 7 correlated with the images in Figure 8, it was observed that within a crystal concretion, there can be both iron oxide crystals and a mixture of oxides on the iron structure. It is noted that these crystals preferentially developed (mainly) on irregular surfaces, while iron oxides primarily formed on flat surfaces.
Another crystal (C3) subjected to analysis (Figure 9) displayed aggregates of crystals of various shapes and chemical compositions, which can be observed at high magnifications. The spectral analysis shows the presence of Fe crystals and Fe oxides mainly in points 1 and 2 (on the flat surfaces), while crystals of various compounds are found in points 3 and 5, primarily a mixture of iron hydroxides and Zn, alongside other oxides. The point represents a composition that is a mixture of iron hydroxides and zinc sulfate.
Based on the spectral analysis (EDS) at the marked points in Figure 9b, iron oxides were identified, deposited on metallic iron as a result of the reaction between mine water and steel scrap. The values of these measurements are presented in Table 8. It can be observed that a series of compounds (crystal formations) can develop on the surface of the iron scrap, represented by iron hydroxides alongside ZnO, which originates from the deposits of goslarite. Together with the iron oxides and goslarite, Na2O, SiO2, MgO, K2O, and Al2O3 are also deposited. These components are predominant in the sludge deposited on the walls of the experimental vessel and analyzed by X-ray diffraction. The chemical analyses, those from the microprobe, and the XRD are similar. All these components were extracted from mine water, immobilizing heavy metals on the surfaces of the iron scrap and reducing the acidity of the treated mine water by fixing SO3 ions in the form of insoluble compounds (Figure 9c and Table 8, points 1 and 3).

4. Discussion and Conclusions

Mine waters that produce acid mine drainage in abandoned mining areas contain heavy metals and metalloids that exhibit high toxicity and pollute surface waters. Due to their acidity and heavy metal concentration, mine waters must be treated to reduce their concentrations to the limits set by legislation. For this purpose, treatments are necessary to facilitate the retention of heavy metal ions.
Based on the results obtained from the attempt to treat mine water with iron scrap, this method can be considered an effective solution at low costs. The treatment method applied to the mine water from the Breiner-Baiut gallery was based on the high acidity of the water, the concentrations of heavy metals that exceed the permissible limit, especially for Cu, Fe, and Zn, the high flow rates of water discharged from the gallery, the impact on environmental factors, and the requirements for environmental protection.
The decrease in acidity in the water after treatment with iron scrap, approaching the permissible limit (approximately pH = 5), necessitates an additional pH correction stage, possibly through the addition of lime(stone) milk.
The applied procedure led to the precipitation of iron oxyhydroxides on the scrap. The concentration of heavy metals was achieved at values in the soluble phase within the limits permitted by national legislation (NTPA001/2005) for Cu, Cd, and Pb. The Zn concentration decreased significantly from the original concentration of mine water of 42.5 mg/L to around 1 mg/L (1.221 mg/L, at 1.091 mg/L, and 0.932 mg/L, Table 4) but remained above the permissible limit (0.5 mg/L) according to data from national legislation (NTPA001/2005 [61]). The concentrations of heavy metals below the minimum allowable limits demonstrate the efficiency of the method that can be applied.
The method applied aimed to reduce the concentration of heavy metals, especially copper, which is present in large amounts in the mine water from the Breiner-Băiuț sampling area. The treatment method with iron scrap is a procedure applied where copper is recovered from spent electrolytes in the copper industry. Thus, copper can be precipitated with the help of metallic iron, a method presented in the specialized literature and patented by Stern (1974). Such methods have also been applied in other studies [54,74,75,76,77]. The precipitation of copper with iron has been used in recovery processes for valorizing copper from various metallurgical wastes [54,74,75,76,77]. Scrap iron obtained from lathe-cut waste represents a material with a high specific surface area and a low cost [78].
For environments affected by AMD, there is no general (universal) remediation technology [59]. Following a critical analysis of environments affected by AMD and attempts at phytomanagement, phytoprotection, and phytorestoration, a customized strategy is needed for each site, environment, community, and individual moment in time due to the mixed nature of AMD contaminants and variations in the affected environment [62].
The results obtained using iron scrap are consistent with those of other research, which indicates that this method of treating mine water can be considered a classic approach. It has the advantage of being applicable at low pH levels, without the need for expensive reagents [78].

Author Contributions

Conceptualization, G.I. and A.P.; methodology, G.I. and A.P.; software, G.I.; validation, G.I. and A.P.; formal analysis, A.P.; investigation, G.I. and A.P.; resources, A.P. and G.I.; data curation, G.I.; writing—original draft preparation, G.I. and A.P.; writing—review and editing, A.P.; visualization, G.I.; supervision, G.I.; project administration, G.I. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Valente, T.M.; Gomes, C.L. Occurrence, properties and pollution potential of environmental minerals in acid mine drainage. Sci. Total Environ. 2009, 407, 1135–1152. [Google Scholar] [CrossRef] [PubMed]
  2. Schwertmann, U. The effect of pedogenic environments on iron oxide minerals. Adv. Soil Sci. 1985, 1, 172–200. [Google Scholar]
  3. Regenspurg, S.; Brand, A.; Peiffer, S. Formation and stability of schwertmannite in acidic mining lakes. Geochim. Cosmochim. Acta 2004, 68, 1185–1197. [Google Scholar] [CrossRef]
  4. Accornero, M.; Marini, L.; Ottonello, G.; Vetuschi Zuccolini, M. The fate of major constituents and chromium and other trace elements when acid waters from the derelict Libiola mine (Italy) are mixed with stream waters. Appl. Geochem. 2005, 20, 1368–1390. [Google Scholar] [CrossRef]
  5. Blowes, D.W.; Ptacek, C.J.; Jambor, J.L.; Weisner, C.G. The geochemistry of acid mine drainage. In Treatise on Geochemistry; Lollar, B.S., Environmental Geochemistry, Holland, H.D., Turekian, K.K., Eds.; Elsevier–Pergamon: Oxford, UK, 2005; Volume 9, pp. 149–204. [Google Scholar]
  6. Nagy-Korodi, I.; Ionescu, C.; Forray, L.F.; Hoeck, V.; Tippelt, G. Environmental Impact and Polymetallic Mining in the Nistru-Băiţa, North Romania. Ph.D. Thesis, BABEŞ-BOLYAI” University of Cluj-Napoca, Cluj-Napoca, Romania, 2009. [Google Scholar]
  7. Nagy, I.; Weiszburg, G.T.; Fodorpataki, L.; Bartha, A. Environmental impact of acid mine drainage in the Turţ Creek. Satu Mare County, Romania. Acta Mineral. Petrogr. 2006, 5, 80. [Google Scholar]
  8. Hammarstrom, J.M.; Seal, R.R., II; Meier, A.L.; Kornfeld, J.M. Secondary sulfate minerals associated with acid drainage in the eastern US: Recycling of metals and acidity in surficial environments. Chem. Geol. 2005, 215, 407–431. [Google Scholar] [CrossRef]
  9. Jordan, G.; D’Alessandro, M. Mining, Mining Waste and Related Environmental Issues: Problems and Solutions in the Central and Eastern European Candidate Countries; Joint Research Centre of the European Commission: Ispra, Italy, 2004; LB-NA-20868-EN-C. [Google Scholar]
  10. Poggere, G.; Gasparina, A.; Barbosa, J.Z.; Meloc, G.W.; Corrêa, R.S.; Motta, A.C.V. Soil contamination by copper: Sources, ecological risks, and mitigation strategies in Brazil. J. Trace Elem. Miner. 2023, 4, 100059. [Google Scholar] [CrossRef]
  11. Larsson, M.; Nosrati, A.; Kaur, S.; Wagner, J.; Baus, U.; Nydén, M. Copper removal from acid mine drainage-polluted water using glutaraldehyde-polyethyleneimine modified diatomaceous earth particles. Heliyon 2018, 4, e00520. [Google Scholar] [CrossRef]
  12. Kortei, N.K.; Heymann, M.E.; Essuman, E.K.; Kpodo, F.M.; Akonor, P.T.; Lokpo, S.Y.; Boadi, N.O.; Ayim-Akonor, M.; Tettey, C. Health risk assessment and levels of toxic metals in fishes (Oreochromis noliticus and Clarias anguillaris) from Ankobrah and Pra basins: Impact of illegal mining activities on food safety. Toxicol. Rep. 2020, 7, 360–369. [Google Scholar] [CrossRef]
  13. Erasmus, J.H.; Malherbe, W.; Zimmermann, S.; Lorenz, A.W.; Nachev, M.; Wepener, V.; Sures, B.; Smit, N.J. Metal accumulation in riverine macroinvertebrates from a platinum mining region. Sci. Total Environ. 2020, 703, 134738. [Google Scholar] [CrossRef]
  14. Naidoo, S. An assessment of the impacts of acid mine drainage on socio-economic development in the Witwatersrand: South Africa, Environment. Dev. Sustain. 2015, 17, 1045–1063. [Google Scholar] [CrossRef]
  15. Stylianou, M.; Gavriel, I.; Vogiatzakis, I.N.; Zorpas, A.; Agapiou, A. Native plants for the remediation of abandoned sulphide mines in Cyprus: A preliminary assessment. J. Environ. Manag. 2020, 274, 110531. [Google Scholar] [CrossRef] [PubMed]
  16. Reinhardt, C.H. Acid Mine Drainage in Pennsylvania Streams: “Ironing Out” the Problem, Restorasion and Reclamation Review; University of Minnesota: Minneapolis, MN, USA, 1999; Volume 5, pp. 1–10. [Google Scholar]
  17. Kuyucak, N. Water in Mining and Environment for Sustainability. Mine Water Environ. 2021, 40, 815–817. [Google Scholar] [CrossRef]
  18. Kaur, G.; Couperthwaite, S.J.; Hatton-Jones Bradley, W.; Millar Graeme, J. Alternative neutralisation materials for acid mine drainage treatment. J. Water Process Eng. 2018, 22, 46–58. [Google Scholar] [CrossRef]
  19. Lei, L.-Q.; Song, C.-A.; Xie, X.-L.; Li, Y.-H.; Wang, F. Acid mine drainage and heavy metal contamination in groundwater of metal sulfide mine at arid territory (BS mine, Western Australia). Trans. Nonferrous Met. China 2010, 20, 1488–1493. [Google Scholar] [CrossRef]
  20. Adamovic, D.; Ishiyama, D.; Kawaraya, H.; Ogawa, Y.; Stevanovic, Z. Geochemical characteristics and estimation of groundwater pollution in catchment areas of Timok and Pek Rivers, Eastern Serbia: Determination of early-stage groundwater pollution in mining areas. Groundw. Sustain. Dev. 2022, 16, 100719. [Google Scholar] [CrossRef]
  21. Weiersbye, I.M.; Witkowski, E.T.F. Impacts of acid mine drainage on the regeneration potential of highveld phreatophytes. In Conference: Multiple Use Management of Natural Forests and Woodlands: Policy Refinements and Scientific Progress; Department of Water Affairs and Forestry of South Africa: Pretoria, South Africa, 2007; pp. 224–237. [Google Scholar]
  22. Tipping, E.; Jarvis, A.P.; Kelly, M.G.; Lofts, S.; Merrix, F.L.; Ormerod, S.J. Ecological Indicators for Abandoned Mines, Phase 1: Review of the Literature Centre for Ecology and Hydrology Report; SC030136/R49; Environment Agency: Bristol, UK, 2009.
  23. Matebese, F.M.; Mosai, A.K.; Tutu, H.; Tsentu, Z.R. Mining wastewater treatment technologies and resource recovery techniques: A review. Heliyon 2024, 10, e24730. [Google Scholar] [CrossRef]
  24. Wildeman, T.R.; Schmiermund, R. Mining influenced waters: Their chemistry and methods of treatment. In Proceedings of the America Society of Mining and Reclamation and the 25th West Virginia Surface Mine Drainage Task Force, Morgantown, WV, USA, 18–24 April 2004; ASMR: Lexington, KY, USA, 2004; Volume 40502, pp. 2001–2013. [Google Scholar] [CrossRef]
  25. Akcil, A.; Koldas, S. Acid Mine Drainage (AMD): Causes, treatment and case studies. J. Clean. Prod. 2006, 14, 1139–1145. [Google Scholar] [CrossRef]
  26. Hansen, E.; Collins, A.; Zegre, S.; Hereford, A. The Benefits of Acid Mine Drainage Remediation on the North Branch Potomac River, Downstream Strategies, Water Quality Advisory; Committee Garrett County, Maryland Economic Development Office: Oakland, MD, USA, 2010.
  27. RoyChowdhury, A.; Sarkar, D.; Datta, R. Remediation of acid mine drainage-impacted water. Water Pollut. 2015, 1, 131–141. [Google Scholar] [CrossRef]
  28. Kefeni, K.; Msagati, T.; Mamba, B. Acid mine drainage: Prevention, treatment options, and resource recovery: A review. J. Clean. Prod. 2017, 151, 475–493. [Google Scholar] [CrossRef]
  29. Skousen Jeffrey, G.; Alan, S.; Ziemkiewicz Paul, F. Acid Mine Drainage Control And Treatment Reprinted from 2000. In Reclamation of Drastically Disturbed Lands; American Society of Agronomy: Madison, WI, USA; American Society for Surface Mining and Reclamation: Butte, MT, USA, 2000. [Google Scholar]
  30. Moreno, N.; Querol, X.; Ayora, C.; Fernández-Pereira, C.; Janssen-Jurkovicová, M. Utilization of zeolites synthesized from coal fly ash for the purification of acid mine waters. Environ. Sci. Technol. J. 2001, 35, 3526–3534. [Google Scholar] [CrossRef] [PubMed]
  31. Wingenfelder, U.; Hansen, C.; Furrer, G.; Schulin, R. Removal of Heavy Metals from Mine Waters by Natural Zeolites. Environ. Sci. Technol. 2005, 39, 12. [Google Scholar] [CrossRef]
  32. Xue, C.; Zhang, Q.; Li, W.; Ownes, G.; Chen, Z. Removal mechanism of Sb(V) by a hybrid ZIF-8@FeNPs and used for treatment of mining wastewater. Chem. Eng. J. 2023, 451, 138691. [Google Scholar] [CrossRef]
  33. Damian, F.; Damian, G.; Lăcătușu, R.; Postolache, C.; Iepure, G.; Jelea, M.; Nasui, D. The heavy metals immobilization in polluted soils from Romania by the natural zeolites use. Carpathian J. Earth Environ. Sci. 2013, 8, 231–250. [Google Scholar]
  34. Damian, F.; Damian, G. Geochemical characterization of some old mine waste dumps from Baia Mare area and their influence on the natural vegetation. Carpathian J. Earth Environ. Sci. 2006, 1, 63–72. [Google Scholar]
  35. Pop, A.; Vida-Simiti, I.; Damian, G.S.; Iepure, G. Removal of heavy metals from wastewater by using zeolitic tuff. Carpathian J. Earth Environ. Sci. 2012, 7, 239–248. [Google Scholar]
  36. Udayabhanu, G.; Prasad, B. Studies on environmental impact of acid mine drainage generation and its treatment: An appraisa. Indian J. Environ. Prot. 2010, 30, 953–967. [Google Scholar]
  37. Lawrence, R.; Philippe, R.; Fleming, C. Sulphide and ion exchange technologies for metal recovery and water treatment in the copper mining industry. In Proceedings of the HydroCopper Conference in Santiago, Vina del Mar, Chile, 16–18 May 2007. [Google Scholar]
  38. Ayangbenro, A.S.; Olanrewaju, O.S.; Babalola, O.O. Sulfate-Reducing Bacteria as an Effective Tool for Sustainable Acid Mine Bioremediation. Front. Microbiol. 2018, 9, 1986. [Google Scholar] [CrossRef]
  39. Meseldzija, S.; Petrovic, J.; Onjia, A.; Volkov-Husovic, T.; Nesic, A.; Vukelic, N. Utilization of agro-industrial waste for removal of copper ions from aqueous solutions and mining-wastewater. J. Ind. Eng. Chem. 2019, 75, 246–252. [Google Scholar] [CrossRef]
  40. Benavente, M.; Moreno, L.; Martinez, J. Sorption of heavy metals from gold mining wastewater using chitosan. J. Taiwan Inst. Chem. Eng. 2011, 42, 976–988. [Google Scholar] [CrossRef]
  41. Rambabu, K.; Banat, F.; Pham, Q.M.; Ho, S.-H.; Ren, N.-Q.; Show, P.L. Biological remediation of acid mine drainage: Review of past trends and current outlook. Environ. Sci. Ecotechnol. 2020, 2, 100024. [Google Scholar] [CrossRef] [PubMed]
  42. Bachtlin, A. Acid Mine Drainage and the Techniques to Cleanup This Issue. DU Quark 2019, 3, 28–34. [Google Scholar]
  43. Grossi, L.B.; Magalhaes, N.C.; Araujo, B.M.; De Carvalho, F.; Andrade, L.H.; Amaral, M.C.S. Water conservation in mining industry by integrating pressureoriented membrane processes for nitrogen-contaminated wastewater treatment: Bench and pilot-scale studies. J. Environ. Chem. Eng. 2021, 9, 104779. [Google Scholar] [CrossRef]
  44. Naidu, G.; Ryu, S.; Thiruvenkatachari, R.; Choi, Y.; Jeong, S.; Vigneswaran, S. A critical review on remediation, reuse, and resource recovery from acid mine drainage. Environ. Pollut. 2019, 247, 1110–1124. [Google Scholar] [CrossRef]
  45. Samaei, S.M.; Gato-Trinidad, S.; Altaee, A. Performance evaluation of reverse osmosis process in the post-treatment of mining wastewaters: Case study of Costerfield mining operations, Victoria, Australia. J. Water Process Eng. 2020, 34, 101116. [Google Scholar] [CrossRef]
  46. Sukmana, H.; Bellahsen, N.; Pantoja, F.; Hodur, C. Adsorption and coagulation in wastewater treatment—Review. Prog. Agric. Eng. Sci. 2021, 17, 49–68. [Google Scholar] [CrossRef]
  47. De Gisi, S.; Lofrano, G.; Grassi, M.; Notarnicola, M. Characteristics and adsorption capacities of low-cost sorbents for wastewater treatment: A review. Sustain. Mater. Technol. 2016, 9, 10–40. [Google Scholar] [CrossRef]
  48. Acheampong, M.A.; Okwaning Ansa, E.D. Low-Cost Technologies for Mining Wastewater Treatment. J. Environ. Sci. Eng. 2017, 6, 391–405. [Google Scholar] [CrossRef]
  49. Fashola, M.O.; Ngole-Jeme, V.M.; Babalola, O.O. Heavy metal pollution from gold mines: Environmental effects and bacterial strategies for resistance. Int. J. Environ. Res. Public Health 2016, 13, 1047. [Google Scholar] [CrossRef]
  50. Nordstrom, D.K.; Blowes, D.W.; Ptacek, C.J. Hydrogeochemistry and microbiology of mine drainage: An update. Appl. Geochem. 2015, 57, 3–16. [Google Scholar] [CrossRef]
  51. Hosseinpour, M.; Osanloo, M.; Azimi, Y. Evaluation of positive and negative impacts of mining on sustainable development by a semi-quantitative method. J. Clean. Prod. 2022, 366, 132955. [Google Scholar] [CrossRef]
  52. Wang, X.; Di, J.; Dong, Y.; Yang, Y.; Liang, B.; Meng, F.; Wang, T.; An, W.; Li, Z.; Guo, J. The dynamic experiment on treating acid mine drainage with iron scrap and sulfate reducing bacteria using biomass materials as carbon source. J. Renew. Mater. 2021, 9, 163–177. [Google Scholar] [CrossRef]
  53. Zhang, R.; Walder, I.; Leiviska, T. Pilot-scale field study for vanadium removal from mining-influenced waters using an iron-based sorbent. J. Hazard. Mater. 2021, 416, 125961. [Google Scholar] [CrossRef]
  54. Temur, H.; Yartaşi, A.; Kocakerim, M.M. A study on the optimum conditions of the cementation of copper in chlorination solution of chalcopyrite concentrate by iron scraps. BAÜ Fen Bil. Enst. Derg. 2006, 8, 63–73. [Google Scholar]
  55. Shahrivar, E.; Karamoozian, M.; Gharabaghi, M. Modeling and optimization of oxide copper cementation kinetics. Appl. Sci. 2020, 2, 469. [Google Scholar] [CrossRef]
  56. Pozo-Antonio, S.; Puente-Luna, I.; Lagüela-López, S.; Veiga-Ríos, M. Techniques to correct and prevent acid mine drainage: A review. DYNA 2014, 81, 73–80. [Google Scholar] [CrossRef]
  57. Chira, I.; Gh, D.; Chira, R. Spatial distribution of heavy metals in the soils of Băiuţ area, Maramureş County, Romania. Carpathian J. Earth Environ. Sci. 2014, 9, 269–278. [Google Scholar]
  58. Costin, D. Major Elements Geochemistry of the Breiner Baiut Ore Deposits (Gutai Mts. Eastern Carpathians). Stud. UBB Geol. 2000, 45, 55–66. [Google Scholar] [CrossRef]
  59. Borcoş, M. Neogene Volcanicity—Metallogeny in the Oaş—Gutâi Mts., Plate Tectonics and Metallogeny in the East Carpathians and Apuseni Mts.; Borcoş, M., Vlad, Ş., Eds.; Springer Science and Business Media LLC.: Berlin, Germany, 1994; pp. 20–22. [Google Scholar]
  60. Damian, F.; Damian, G. Mineral parageneses of the hydrothermal ore deposits from Baia Mare area, Romania. Bul. Ştiinţific Univeritatii Nord. Baia Mare Ser. D Mine Prep. Geoogie Ing. Mediu. Metal. 2004, 18, 155–170. [Google Scholar]
  61. Thomas, G.; Sheridan, C.; Holm, P.E. A critical review of phytoremediation for acid mine drainage-impacted environments. Sci. Total Environ. 2022, 811, 152230. [Google Scholar] [CrossRef]
  62. Neniţescu, C.D. Chimie Generală; Editura Didactica si Pedagogica, Bucureşti: București, Romania, 1985. [Google Scholar]
  63. Gâdea, S.; Rău, A.; Oprea, F.; Tripşa, I.; Geru, N. Manualul Inginerului Metalurg; Tehnică Bucureşti: Bucharest, Romania, 1978; Volume I. [Google Scholar]
  64. SR EN 10025-2:2004; Hot Rolled Construction Steel Products (Produse Laminate la Cald din Oţeluri de Construcţii). British Standards Institution: London, UK, 2004.
  65. NTPA 001/2005; The Regulation Regarding the Establishment of Pollutant Loading Limits for Industrial and Urban Wastewater Discharges into Natural Receivers. Editura Academica Brâncuşi: Târgu Jiu, Romania, 2005.
  66. Law 161/2006; Normative Regarding the Classification of Water Quality Surface in Order to Establish the Ecological Status of Water Bodies. Statute Law Database: Online, 2006.
  67. Johnson, D.B.; Hallberg, K.B. Acid mine drainage remediation options: A review. Sci. Total Environ. 2005, 338, 3–14. [Google Scholar] [CrossRef] [PubMed]
  68. Moalla, S.M.N.; Rashed, M.N.; El Aziz, A.A.; Maghazy, M.A. Determination of Cd2+, Cu2+, Mn2+, Pb2+, and Zn2+ in aqueous solution after their separation and preconcentation as metal—Dithizone complexes on activated carbon. Aswan Univ. J. Environ. Stud. 2020, 1, 157–170. [Google Scholar] [CrossRef]
  69. Liu, J.; Zhao, J.; Du, J.; Peng, S.; Tan, S.; Zhang, W.; Yan, X.; Wang, H.; Lin, Z. Machine learning predicts heavy metal adsorption on iron (oxyhydr)oxides: A combined insight into the adsorption efficiency and binding configuration. Sci. Total Environ. 2024, 950, 175370. [Google Scholar] [CrossRef]
  70. Skousen, J.; Zipper, C.E.; Rose, A.; Ziemkiewicz, P.F.; Nairn, R.; McDonald, L.M.; Kleinmann, R.L. Review of Passive Systems for Acid Mine Drainage Treatment. Mine Water Environ. 2017, 36, 133–153. [Google Scholar] [CrossRef]
  71. ASTM. Powder Difraction File, Alphabetical Index (Chemical and Mineral Name), International Center for Difraction Data; American Society for Testing and Materials: West Conshohocken, PA, USA, 1987. [Google Scholar]
  72. Nemecz, E. Agyagásványok (Clay Minerals); Akadémiai Kiadó Bp.: Budapest, Hungary, 1973; p. 507. [Google Scholar]
  73. Miler, M.; Bavec, S.; Gosar, M. The environmental impact of historical Pb-Zn mining waste deposits in Slovenia. J. Environ. Manag. 2022, 308, 114580. [Google Scholar] [CrossRef]
  74. Eltaweel Yehia, A.; Nassef Ehssan, M.; Hazza Riham, A. Recovery of Copper from Wastewater by Cementation Technique. World Environ. 2014, 4, 199–205. [Google Scholar] [CrossRef]
  75. Toro, N.; Pérez, K.; Saldaña, M.; Salinas-Rodríguez, E.; Hernández, P. Treatment of black copper with the use of iron scrap—Part l. Hem. Ind. 2020, 74, 237–245. [Google Scholar] [CrossRef]
  76. Loibl, A.; Tercero Espinoza, L.A. Current challenges in copper recycling: Aligning insights from material flow analysis with technological research developments and industry issues in Europe and North America, Resources. Conserv. Recycl. 2021, 169, 105462. [Google Scholar] [CrossRef]
  77. Ma, Y.; Dai, W.; Zheng, P.; Zheng, X.; He, S.; Zhao, M. Iron scraps enhance simultaneous nitrogen and phosphorus removal in subsurface flow constructed wetlands. J. Hazard. Mater. 2020, 395, 122612. [Google Scholar] [CrossRef]
  78. Sánchez-España, J.; Ilin, A.; Yusta, I. Metallic Copper (Cu [0]) Obtained from Cu2+-Rich Acidic Mine Waters by Two Different Reduction Methods: Crystallographic and Geochemical Aspects. Minerals 2022, 12, 322. [Google Scholar] [CrossRef]
Water 17 00225 g001
Figure 1. Mine water sampling area in the Baiuț region: (a) location in the Baia Mare area (Baiut, Romania—47°37′31.0″ N 24°00′32.5″ E (source: Google Maps); (b) overview of the mine entrance; (c) detailed view of the mine gallery and sampling point.
Figure 1. Mine water sampling area in the Baiuț region: (a) location in the Baia Mare area (Baiut, Romania—47°37′31.0″ N 24°00′32.5″ E (source: Google Maps); (b) overview of the mine entrance; (c) detailed view of the mine gallery and sampling point.
Water 17 00225 g001
Water 17 00225 g002
Figure 2. Iron scrap (iron borings).
Figure 2. Iron scrap (iron borings).
Water 17 00225 g002
Water 17 00225 g003
Figure 3. Graphical representation of the concentration of heavy metals in mine water samples treated with iron shavings for each element: (a) Cu; (b) Zn; (c) Fe; (d) Cd.
Figure 3. Graphical representation of the concentration of heavy metals in mine water samples treated with iron shavings for each element: (a) Cu; (b) Zn; (c) Fe; (d) Cd.
Water 17 00225 g003
Water 17 00225 g004
Figure 4. Graphical representation of the distribution of heavy metals in the sludge: (a) Cu; (b) Zn; (c) Fe; (d) Cd.
Figure 4. Graphical representation of the distribution of heavy metals in the sludge: (a) Cu; (b) Zn; (c) Fe; (d) Cd.
Water 17 00225 g004
Water 17 00225 g005
Figure 5. Diffractogram of the sludge (P3-600): M—montmorillonite; I—illite; T—tenorite; Gs—goslarite; B—brochantite; L—lepidocrocite; G—goethite.
Figure 5. Diffractogram of the sludge (P3-600): M—montmorillonite; I—illite; T—tenorite; Gs—goslarite; B—brochantite; L—lepidocrocite; G—goethite.
Water 17 00225 g005
Water 17 00225 g006
Figure 6. Microscopic image of iron scrap fragments with deposits of yellow-orange salts: (a) aggregation of iron scrap; (b) crystals grown on the surface of an iron scrap; (c) crystals detached from the shavings, magnification 80×.
Figure 6. Microscopic image of iron scrap fragments with deposits of yellow-orange salts: (a) aggregation of iron scrap; (b) crystals grown on the surface of an iron scrap; (c) crystals detached from the shavings, magnification 80×.
Water 17 00225 g006
Water 17 00225 g007
Figure 7. Secondary electron images (SEIs) showing crystals clustered on the surface of iron scrap: (a) overview image, sample C1, magnification 95×; (b) detail of point (1), sample C1, magnification 1700×; (c) detail point (1), sample C1, magnification 2700×.
Figure 7. Secondary electron images (SEIs) showing crystals clustered on the surface of iron scrap: (a) overview image, sample C1, magnification 95×; (b) detail of point (1), sample C1, magnification 1700×; (c) detail point (1), sample C1, magnification 2700×.
Water 17 00225 g007
Water 17 00225 g008
Figure 8. SEM image of a concretion on the surface of a steel chip (crystal C2). (a) Image of crystal C2; (b) spectral analysis at point 3.
Figure 8. SEM image of a concretion on the surface of a steel chip (crystal C2). (a) Image of crystal C2; (b) spectral analysis at point 3.
Water 17 00225 g008
Water 17 00225 g009
Figure 9. Microstructure (COMPO) of crystal C3. (a) Image of crystal C3, 190×; (b) detail 1800×; (c) point 5 spectral analysis.
Figure 9. Microstructure (COMPO) of crystal C3. (a) Image of crystal C3, 190×; (b) detail 1800×; (c) point 5 spectral analysis.
Water 17 00225 g009
Table 1. Data indicating the industrial applications of the cementation process (according to [63]).
Table 1. Data indicating the industrial applications of the cementation process (according to [63]).
Cemented
Metal		Reducing
Metal		Difference Between Electrode PotentialsAnion Present in the
Solution from Which the Metal is Cemented
CuZn1.10SO42−, Cl−, NO3−
Fe0.78SO42−, Cl−, NO3−
Cd0.74SO42−
AsFe0.69SO42−, Cl−
PbZn0.63SO42−, Cl−
Fe0.31Cl−
SnZn0.62SO42−, Cl−
Fe0.30SO42−
CdZn0.36SO42−
HgCu0.35SO42−
Table 2. Chemical composition (maximum concentration) of steel, weight percent (wt%).
Table 2. Chemical composition (maximum concentration) of steel, weight percent (wt%).
Steel TypeFe, %C, %Mn, %S, %P, %N %
S235 (OL37)97.720.171.40.350.350.012
Table 3. Chemical analysis of mine water before treatment with iron shavings.
Table 3. Chemical analysis of mine water before treatment with iron shavings.
ParameterConcentrations—Metals in Mine Water Before Treatment
[mg/L]		Allowed Concentrations (NTPA001/2005)
pH2.756.5–8.5
Zn42.50.5
Cu71.10.1
Pb0.0040.2
Fe122.55.0
Cd0.0420.2
Table 4. Concentrations of heavy metals in water samples treated with iron scrap.
Table 4. Concentrations of heavy metals in water samples treated with iron scrap.
Sample
no.		Treatment Variant (Sample—Iron Shavings)Cu (mg/L)Zn
(mg/L)		Pb
(mg/L)		Fe
(mg/L)		Cd
(mg/L)		pHCE
(mS/cm)
1P1-200 g 0.0051.221<LOQ2750.0034.912.97
2P2-400 g 0.0011.091<LOQ3020.0024.832.98
3P3-600 g<LOQ0.932<LOQ3850.0034.822.96
NTPA001/20050.10.50.25.00.26.5–8.5-
Table 5. Chemical composition of the sludge (mg/kg).
Table 5. Chemical composition of the sludge (mg/kg).
SampleNaMgAlKCaCrMnFeCoNiCuZnAsMoCdTlPb
P1-200991.8428.72034.3179.7348.3378.64154.4599,287.269.6872.4833.74182.368.779.85.14.528.2
P2-4001109.7273.9356141.4300342.93382.5556,343.775.6799.21034.410,347.3145.271.110.23.914.4
P3-6001114.23062038.244.1298.23483899.1571,009.270.5832.2872.1588681.669.95.42.79
Table 6. Chemical composition of the sludge deposited on the walls of the experimental vessel.
Table 6. Chemical composition of the sludge deposited on the walls of the experimental vessel.
Analysis no.CaO
wt,%		K2O
wt,%		P2O5
wt,%		Al2O3
wt,%		SiO2
wt,%		Na2O
wt,%		MgO
wt,%		BaO
wt,%		SrO
wt,%		FeO
wt,%		MnO
wt,%		TiO2
wt,%		Cl
wt,%		Cr2O3
wt,%		Total
wt,%
10.129.39-35.98350.0140.1440.4510.01800.24700.102--96.469
20.1299.279-35.41249.8340.1380.390.0520.0330.2480.031---95.546
30.1639.0930.01335.61550.240.1990.4310.0420.0520.204----96.052
40.1539.131-35.54949.8370.1640.4160.028-0.230.0530.102--95.663
50.1439.125-36.1549.7980.1330.459--0.2580.048-0.0020.00596.121
60.1348.946-36.30950.2640.1060.436--0.2460.11-0.004-96.555
70.1659.062-35.65949.4520.110.412--0.2210.0130.0450.010.01195.16
80.1939.032-36.07450.1750.0990.368--0.16-0.1130.0040.01196.229
90.2128.94-36.25150.2930.1470.449--0.2250.0130.0790.0030.08596.697
100.0989.232-36.2849.4340.0750.378--0.1560.079--0.07995.811
Average0.1519.1230.00335.92849.9340.1320.4190.0350.0210.2200.0350.0440.0040.032-
Table 7. Concentration of compounds (elements) in points 1–3, Figure 8.
Table 7. Concentration of compounds (elements) in points 1–3, Figure 8.
PointElement/FormulaFeOClNa2OSiO2SO3K2OCaOFeO
1wt%60.1239.88-------
Atom, %30.1669.84-------
2wt%100--------
Atom, %100--------
3wt%--5.4311.011.394.462.211.1574.35
Atom %--10.2911.931.563.741.581.3869.52
Table 8. Concentration (proportion) of the compounds from points 1–5 marked in Figure 9b.
Table 8. Concentration (proportion) of the compounds from points 1–5 marked in Figure 9b.
PointElement/FormulaFeSiCrNa2OSiO2SO3K2OCaOFeOZnOMgOAl2O3Cr2O3
1wt%87.880.5511.57----------
Atom, %86.661.0811.57----------
2wt%100------------
Atom, %100------------
3wt%---2.541.221.280.450.4889.304.74---
mol%---2.941.451.150.350.6189.314.19---
4wt%--------89.6310.37---
mol%--------90.739.27---
5wt%----1.040.94-0.4991.133.910.750.181.56
mol%----1.250.85-0.6391.593.471.340.130.74
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Iepure, G.; Pop, A. Treatment of Acid Mine Water from the Breiner-Băiuț Area, Romania, Using Iron Scrap. Water 2025, 17, 225. https://doi.org/10.3390/w17020225

AMA Style

Iepure G, Pop A. Treatment of Acid Mine Water from the Breiner-Băiuț Area, Romania, Using Iron Scrap. Water. 2025; 17(2):225. https://doi.org/10.3390/w17020225

Chicago/Turabian Style

Iepure, Gheorghe, and Aurica Pop. 2025. "Treatment of Acid Mine Water from the Breiner-Băiuț Area, Romania, Using Iron Scrap" Water 17, no. 2: 225. https://doi.org/10.3390/w17020225

APA Style

Iepure, G., & Pop, A. (2025). Treatment of Acid Mine Water from the Breiner-Băiuț Area, Romania, Using Iron Scrap. Water, 17(2), 225. https://doi.org/10.3390/w17020225

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop