Mining Residues Research Articles

TD-DAQ: A low-cost data acquisition system monitoring the unsaturated pore pressure regime in tailings dams

Tailings dams are large, often self-contained, storage facilities of mine residue. On self-contained tailings dams the tailings material itself is used to raise the containment embankments holding newly deposited residue. To develop the necessary strength, it is essential that material must dry out sufficiently. Despite substantial advancements in the field of instrumentation, these parameters are rarely measured on tailings dams and their evolution over time is poorly understood. Understanding the role of pore water suction and water content evolution over time can benefit from the installation of sensors and data acquisition systems (DAQ) capable of continuously monitoring these parameters. Such monitoring remains difficult and expensive owing to the challenges of measuring negative water pressures and the often-remote locations and harsh operating environments typical of mining operations. This paper describes the development, testing and validation of a low-cost DAQ for the measurement of the unsaturated pore pressure regime in a platinum tailings dam located in the Limpopo province of South Africa. The Tailings Dam DAQ (referred to as TD-DAQ) is designed to measure the negative pore pressure, moisture content and temperature in fine-grained material over extended periods of time. These measurements are stored on the DAQ and transmitted in parallel using new wireless network communications technologies (Sigfox) suited to remote, battery powered applications. The successful deployment of the TD-DAQ presents a real-time, low-cost instrumentation solution to improve the efficiency of condition monitoring of tailings storage facilities, contributing to a reduction in the probability of failure events.

Effects of dominant plant growth on the nutrient composition and bacterial community structure of manganese residues

The rhizospheres of three dominant plant species (Miscanthus floridulus, Buddleja lindleyana, and Erigeron annuus) growing in manganese residue disposal sites in eastern Guizhou Province, China, were analyzed to study the effects of plant growth on the nutrient levels and bacterial community structure of two types of manganese residues. The results showed that the growth of the three species improved the nutritional composition of manganese residues; the available nitrogen (AN) contents of the manganese mine residue significantly increased by 29.56–60.78% while the available phosphorus (AP) contents of the electrolytic manganese residue significantly increased by 30.24–44.41% compared to those in unvegetated manganese residue. The diversity of the bacterial community in the manganese mine residue increased significantly due to plant growth. Proteobacteria, Acidobacteria, and Bacteroidetes were the dominant phyla in both manganese residues. Sphingomonas and GP6 were the dominant bacterial genera. The relative abundance of the Firmicutes phylum was significantly higher in the manganese mine residue than in the control and that of the Thiobacillus genus was lower, which indicated improvements in the microenvironment. Correlation analysis showed that OM and AN were the main nutrient factors affecting the bacterial community structure in the manganese mine residue. Novelty statement At present, research on the phytoremediation of manganese residue disposal sites focuses mostly on the investigation of different plant types and their heavy metal accumulation and transformation characteristics. However, comparative studies of the differences in growth matrix characteristics between plant growth areas and exposed areas are lacking. In addition, dominant plant species are regionally distributed. The previous studies were mostly concentrated in Chongqing, Guangxi, and Hunan in China. The eastern region of Guizhou Province is located in the “Manganese Triangle” area of China, where the manganese resources account for about 50% of the national total. There is no report on the phytoremediation of manganese residue disposal sites in this region. Therefore, the rhizospheres of three dominant plant species (Miscanthus floridulus, Buddleja lindleyana, and Erigeron annuus) growing in manganese residue disposal sites in eastern Guizhou Province, China, were analyzed to study the effects of plant growth on the nutrient levels and bacterial community structure of two types of manganese residues (manganese mine residue and electrolytic manganese residue). This study could provide useful theoretical information to benefit the ecological restoration of manganese residue disposal sites.

Study on Impacts of Mining Development in Wanjiang City Belt on Urban and Rural Environment

This paper made a general introduction to the industrial and agricultural production, population and physical geography in the Wanjiang City Belt (hereinafter referred to as the Belt) and analyzed the regularity of ore formation, the distribution and characteristics of mineral resources and the status of mining development in the Belt. Besides, it studied the impact of mining development on urban and rural environment of the region, namely damage to soil resources, surface landscape and groundwater, geological disasters, hazards of mine waste water and residues and other types of plant-related pollution. It also put forward specific countermeasures for environmental problems arising from mining development in the Belt from the perspectives of rule by law & management and technology & economy. In addition, it introduced soil pollution in urban and rural areas of the region and ideas and methods for soil environmental governance, taking the Tongling region for example.

Sources of sedimentary organic matter and assessment of heavy-metal levels in estuarine sediments after Fundão dam breach

Mining tailing is one of many anthropogenic stressors affecting estuarine systems around the world. On the November 5, 2015, the Fundão dam breached, releasing 52 million m3 of iron mining residues affecting Doce River until its estuary, spreading a large plume along the Brazilian coast. The present study characterizes the impact of the mining tailing in these environments and the changes in sedimentary organic matter (SOM) sourced at Doce River estuary (DRE) and adjacent estuaries over time. Three sediment cores and surface sediment samples were collected along the coast of Espírito Santo State. Elemental (C, N) and stable isotope (δ15N and δ13C) fingerprint methods were used to characterize sedimentary organic matter sources. The indexes of sedimentary organic matter stability (recalcitrance index) were quantified by FTIRS technique. Besides, WDXRF analyzes were carried out to statistically determine metal baseline levels and assess the present and past pollution degrees of sediments using pollution indexes (PLI). Results indicate that Doce River estuary significantly provides Fundão dam's tailings (77 % ± 9 %) to the coastal region, with a PLI categorized as moderately polluted to highly polluted (PLI = 3.1), even two years after the dam breach. Estuaries north from Doce River Estuary presented a more significant influence of marine organic sedimentation sources with lower PLI (unpolluted). In contrast, estuaries south from DRE presented greater terrestrial influence with higher PLI values (unpolluted to moderate polluted). Further, changes in SOM stability were noticed mainly at Doce River Estuary, where the recalcitrance index did not show the expected natural pattern. Finally, the findings indicate that Fundão dam failure had a significant impact on Doce River Estuary sediment quality at different moments after Fundão breach, and this ecosystem is expected to continue to suffer from this indefinitely. However, the direct effect of tailings deposition was not observed in the sampled estuaries, PLI shows that ecosystems in the south already suffer from other pollution sources, which increases the environmental risks in a possible tailing deposition scenario.

Sustainable Recovery of Secondary and Critical Raw Materials from Classified Mining Residues Using Mycorrhizal-Assisted Phytoextraction

In this work, mycorrhizal-assisted phytoextraction (MAP, Helianthus annuus–arbuscular mycorrhizal fungus Rhizophagus intraradices–Zn-volcanic ashes) was applied for the recovery of secondary and critical raw materials (SRMs and CRMs, respectively) from Joda West (Odisha, India) mine residues, within a novel multidisciplinary management strategy. Mine residues were preliminarily characterized by using advanced analytical techniques, and subsequently mapped, classified and selected using multispectral satellite Sentinel-2A images and cluster analysis. Selected mine residues were treated by MAP at laboratory scale, and the fate of several SRMs (e.g., Zn, Cr, As, Ni, Cu, Ca, Al, K, S, Rb, Fe, Mn) and CRMs (such as Ga, Ti, P, Ba and Sr) was investigated. Bioconcentration factors in shoots (BCS) and roots (BCR) and translocation factors (TF) were: 5.34(P) > BCS > 0.00(Al); 15.0(S) > BCR > 0.038(Ba); 9.28(Rb) > TF > 0.02(Ti). Results were used to predict MAP performance at larger scale, simulating a Vegetable Depuration Module (VDM) containing mine residues (1 m3). Estimated bio-extracting potential (BP) was in the range 2417 g/m3 (K) > BP> 0.14 g/m3 (As), suggesting the eventual subsequent recovery of SRMs and CRMs by hydrometallurgical techniques, with final purification by selective electrodeposition, as a viable and cost-effective option. The results are promising for MAP application at larger scale, within a circular economy-based approach.

Heavy Rainfall Events Following the Dry Season Elevate Metal Contamination in Mining-Impacted Rivers: A Case Study of Wenyu River, Qinling, China.

Heavy metal pollution of a mining-impacted river-the Wenyu River-and a short section of the river it joins, the Luo River, were investigated after heavy rainfall following a dry season in March 2015 and during a normal flow season in May 2015. Water samples were collected during these two periods, and sediment samples were obtained in May as the rain washed out the sediments in March. The results showed the following: (1) The Wenyu River was severely polluted by acid mine drainage from an open-pit molybdenum (Mo) mine, and the major pollutants in the water according to Chinese national standard values were acid (pH), sulfate, Cu, Zn, Mn, Ni, and Cd. The major pollutants in the sediment were Cu, Zn, and Cd, as indicated by the geoaccumulation index and potential ecological risk index. (2) The major pollutants in the water were naturally attenuated along the river and met the national standard values after joining the Luo River, except Mn in both water samples and Cd in the samples after rain in March. The major pollutants in the sediments showed an increasing tendency along the Wenyu River and Luo River. (3) The heavy rainfall following the prolonged dry season increased acid and heavy metal contamination in the river, which might be attributed to the dissolution of efflorescent salts and the weathering and erosion of mining residues. Thus, the first heavy rain following a dry season should receive particular attention from mining enterprises and regulators. Several mitigation options and recommendations are also discussed.

The ‘Green’ Ni-UGSO Catalyst for Hydrogen Production under Various Reforming Regimes

A new spinelized Ni catalyst (Ni-UGSO) using Ni(NO3)2·6H2O as the Ni precursor was prepared according to a less material intensive protocol. The support of this catalyst is a negative-value mining residue, UpGraded Slag Oxide (UGSO), produced from a TiO2 slag production unit. Applied to dry reforming of methane (DRM) at atmospheric pressure, T = 810 °C, space velocity of 3400 mL/(h·g) and molar CO2/CH4 = 1.2, Ni-UGSO gives a stable over 168 h time-on-stream methane conversion of 92%. In this DRM reaction optimization study: (1) the best performance is obtained with the 10–13 wt% Ni load; (2) the Ni-UGSO catalysts obtained from two different batches of UGSO demonstrated equivalent performances despite their slight differences in composition; (3) the sulfur-poisoning resistance study shows that at up to 5.5 ppm no Ni-UGSO deactivation is observed. In steam reforming of methane (SRM), Ni-UGSO was tested at 900 °C and a molar ratio of H2O/CH4 = 1.7. In this experimental range, CH4 conversion rapidly reached 98% and remained stable over 168 h time-on-stream (TOS). The same stability is observed for H2 and CO yields, at around 92% and 91%, respectively, while H2/CO was close to 3. In mixed (dry and steam) methane reforming using a ratio of H2O/CH4 = 0.15 and CO2/CH4 = 0.97 for 74 h and three reaction temperature levels (828 °C, 847 °C and 896 °C), CH4 conversion remains stable; 80% at 828 °C (26 h), 85% at 847 °C (24 h) and 95% at 896 °C (24 h). All gaseous streams have been analyzed by gas chromatography. Both fresh and used catalysts are analyzed by scanning electron microscopy-electron dispersive X-ray spectroscopy (SEM-EDXS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) coupled with mass spectroscopy (MS) and BET Specific surface. In the reducing environment of reforming, such catalytic activity is mainly attributed to (a) alloys such as FeNi, FeNi3 and Fe3Ni2 (reduction of NiFe2O4, FeNiAlO4) and (b) to the solid solution NiO-MgO. The latter is characterized by a molecular distribution of the catalytically active Ni phase while offering an environment that prevents C deposition due to its alkalinity.

Effect of crossflow on trapping depths of particle plumes: laboratory experiments and application to the PLUMEX field experiment

The fate and transport of sediment plumes in the ocean, such as those resulting from the disposal of deep-sea mining residuals, are affected by ambient crossflow. We present laboratory measurements of the depth at which a particle plume is trapped by ambient stratification for various crossflow and particle settling velocities. Results suggest that the trap depth declines exponentially with crossflow velocity but is relatively insensitive to settling velocity in the range studied. An empirical correlation based on the laboratory data is validated by a larger scale field experiment involving simulated disposal of deep-sea mining wastes.

Aqueous mineral carbonation of Fe rich olivine by cation complexation using 2,2′-bipidine; concept validation and parameters optimization

Mineral Carbonation can significantly reduce GHG emissions and it is one of the most promising methods to sequester postcombustion CO2 emissions. In this work, a novel pH-swing indirect mineral carbonation approach by cation complexation using 2,2′-bipyridine has been developed. A mining residue mainly composed of Fe (II)-rich olivine was used as a feedstock. The leaching of the mining residue was performed using NH4HSO4 as solvent (pH 2–3), at 61 °C with 250 rpm of stirring during 2 h of reaction time. A total of 28 and 41 wt% of iron and magnesium was leached respectively. Then, the iron leachate was stabilized as [Fe(bipy)3]2+ complex using 2,2′-bipyridine avoiding iron hydroxide precipitation when the solution pH is raised using NaOH. Finally, the mineral carbonation reaction was performed, using a CO2 gas stream into the solution at alkaline pH. Different parameters such as the temperature, the pH, the reaction time and the vol% CO2 gas injected were optimized in batch mode reactions. This innovative approach allows the use of mild temperature and pressure conditions to obtain iron carbonates. The best results shows that 50 wt% of the CO2 gas stream have been removed from the gas phase giving a ratio of 0.11 kg of CO2 sequestered per kg of residues, which represent an important improvement regarding past studies on Fayalite.

Characterization and pH neutralization products of efflorescent salts from mine tailings of (semi-)arid zones

Acidic water-soluble efflorescent salts in mining residues commonly form from sulfide oxidation and are particularly prevalent in semi-arid to arid environments. These salts are easily carried by winds and may contaminate the environment and affect human health, especially because they contain potentially toxic metals and have high solubilities. In this work, efflorescent salts from four mining sites in Mexico were characterized by X-ray diffraction and chemical analysis. They produced acidic pH values upon dissolution, and were found to be composed mostly of soluble sulfates of Ca(II), Mg(II), Zn(II) and/or Cu(II), and to a lesser extent of Fe(II/III) and/or Al, of variable stoichiometries, crystal water contents and crystallinity. Their physical and chemical characteristics varied highly depending on the underlying geochemical matrix and on the composition of the original mining residues, but gypsum was present in all samples. Two selected samples were dissolved and the solution neutralized, causing substantial precipitation of solids. The precipitates, at pH 7 were found to contain the Cu and/or Zn - rich hydroxysulfates: lahnsteinite [Zn4(OH)6SO4·3H2O], or schulenbergite [Cu3Zn4(OH)10(SO4)2]. Solubility product constants were determined on these, and on other solids produced in the absence of certain major components [such as sulfate or Zn(II)], by a combination of chemical measurements and geochemical code calculations to speciate some of the components found. These results should enhance thermodynamic properties of databases and help to predict what phases form if pH neutralization occurs or is used for remediation purposes.

An Integrated Multi-Approach to Environmental Monitoring of a Self-Burning Coal Waste Pile: The São Pedro da Cova Mine (Porto, Portugal) Study Case

The São Pedro da Cova waste pile (Porto, Portugal) is composed of coal mining residues that have been self-burning since 2005 and is located close to an inhabited area and social infrastructures, further adding to effects on the environment and human health. Therefore, there is a great interest in the environmental monitoring of this waste pile. This work describes an integrative multi-approach that allows the environmental monitoring of several parameters of the waste pile, applying several technologies. The temperature measurements were obtained by a thermal infrared (TIR) sensor on board an unmanned aerial vehicle (UAV) and supplemented with field measurements. In order to evaluate the altimetric variations, for each flight, a digital elevation model (DEM) was generated considering a multispectral sensor also on board the UAV. The hydrogeochemical characterization was performed through the analysis of groundwater and surface water samples, with and without the influence of mine drainage. The soil monitoring included the analysis of waste material as well as the surface soil in the surrounding area of the waste pile. All the data were analyzed and integrated in a geographical information system (GIS) open-source application. The adopted multi-approach methodology, given its intrinsic interdisciplinary character, has proven to be an effective way of encompassing the complexity of this type of environmental problem.

Valorization of apatite mining flotation residues by the manufacture of artificial aggregates

Mining residues are usually stockpiled because of their understudied physico-chemical properties and of their abundance, which make their valorization challenging. In this work, a cold-bonding granulation apparatus was built in order to transform a mining residue sludge from an apatite ore, into artificial aggregates suitable for use in civil engineering. A 25 rpm rotation speed, 15° angle relative to horizontal, and an ideal feeding amount of the granulation drum, as such as the liquid (supernatant) distribution method, were preliminary determined. Effects of rotation speed, liquid content, and granulation time were then studied to evaluate the best combination for appropriate aggregate size distribution. Box-Behnken experimental designs were used to investigate the evolution of compressive strength of the individual aggregates when Portland cement is added to the mix, and when granulation time varies, around the critical liquid content of 14% of total weight. Thus, the possible parameters combinations which allow a maximization of compressive strength without exclusively increasing cement content, were determined and used to confirm the Box-Behnken predictions. Spherical aggregates were thus manufactured, with diameters mainly comprised between 5 and 40 mm, and compressive strength comparable to those of commercialized aggregates, up to 7 MPa and to 3 MPa for aggregates with diameters respectively below and above 10 mm. Paths for greater consolidation as prior homogenization, use of humid cure conditions, and use of other additives emerge from literature and from the results presented.

Response of Benthic Diatom Assemblages to Contamination by Metals in a Marine Environment

Studies on marine benthic diatoms in environments contaminated by metals are scarce. The typical structure of benthic diatom assemblages (species richness, diversity, dominance, dominant taxa) from undisturbed environments may be used as reference for contrasting with contaminated environments in order to observe how said assemblages respond to such disturbance. Thus, the Ho that the structure of benthic diatom associations and morphology of their frustules under contamination by metals would be normal, as in unpolluted environments was tested. To do this, concentrations of 24 metals were surveyed in a coastal zone impacted by mining residues, and the structure of benthic local diatom assemblages was described. Metal concentrations measurements for 15 metals surpassed the normal values of the upper earth cortex, seven were under the low range effect, and three (Cd, Cu, Zn) surpassed the medium range effect values. At a control site no element concentration was above the reference values for low range effect (LRE) or medium range effect (MRE) standards. There, diatom species richness (S) was high, particularly on seaweeds; where, 397 diatom taxa were recorded. In contrast, at the contaminated area 217 diatom taxa were recorded, but diversity (H’) ranged from 2.4 to 4.3. Relative high frequencies of deformed diatom valves mainly of Achnanthes spp. were recorded in contaminated sediments. In general, diatom taxocenoses presented a typical structure for non-contaminated environments. However, scarceness of specimens, lower S, and frequency of deformed valves suggest responses to metal contamination. For marine environments, the latter values corresponding to A. longipes may be considered a reliable reference to the response of benthic diatoms to metal contamination.

Mapping of Aluminum Concentration in Bauxite Mining Residues Using Sentinel-2 Imagery

There is a growing interest in the characterization of mining residues, both for environmental assessments and critical raw materials recovery. The lack of sufficient in situ samples hampers an effective geostatistical modelling of material concentrations variability. This paper proposes a method to characterize the aluminum spatial variability in a mine residue from remote sensing data and imprecise information from daily dumping procedures. The method is proposed for the mapping of aluminum within a Greek bauxite residue, using Sentinel-2 imagery. The spatial correlation between metal concentrations and remote sensing indicators (e.g., spectral band ratios) is the premise for mapping aluminum varieties. The proposed method is based on Conditional Gaussian Co-Simulation, where Sentinel-2 images can be used as auxiliary variables. Simulation results are compared with the Co-kriging estimation method. To perform the Co-kriging estimation, the same conditions as simulation are used (same inputs, models, and neighborhoods). Simulation results quantified the metals variability in mining residues, presenting the metal concentration of piled materials in two time periods. For results validation and selecting the best map, fourteen validation samples were used. For the best representative maps of aluminum concentration, a correlation coefficient of about 0.7 between the validation data and obtained aluminum concentration map was obtained.

Characterization of mine tailings in their natural state and stabilized with cement, focused on construction

This work presents the physical-chemical, geotechnical and mechanical characterization of a sample of mine tailings from the state of Zacatecas, Mexico with the objective of evaluating their possible use as a construction material for pavement support layers or as an aggregate of a hydraulic concrete. The material analyzed was classified as a poorly graded silty sand (SP-SM) according to the SUCS classification and is composed mainly of quartz and calcite. The analyzed sample satisfies the necessary requirements, according to current Mexican regulations, to be used as i) a subgrade layer in a pavement, without the addition of virgin aggregates, or ii) as fine aggregates in the production of hydraulic concrete, previously sieved to correct its grain-size distribution. The mining residues studied do not require stabilization because the material transported in the leaching process is below the permissible limits for heavy metals according to Mexican regulations; this may be caused by the neutral pH of the sample, demonstrating a high adsorption of the heavy metals that avoids potential leaching. However, the sample was stabilized with Portland cement with 3 and 5% respectively to corroborate the decrease in heavy metal transport based on the consulted bibliography; the concentrations of the analyzed elements decreased except for chrome due to its presence in the stabilizing material and an increase in the pH value was observed.

Multistep concentration of lizardite/antigorite from chrysotile mine tailings – case of the Carey Mine site in East-Broughton (Québec)

Abstract Revalorization of mining residues is of central concerns to the mining industry and the environment. Specifically, environmental management of residual products from the exploitation of chrysotile in the Thetford Mines region is one of the government concerns in Quebec and Canada. This work uses mining wastes in a second resource generation for production of magnesium from cheap and health-friendly mineral sources; the goal being to produce chrysotile-depleted pre-concentrates for a use as precursors in the leach off extraction of magnesium. The concentration of lizardite/antigorite from chrysotile containing serpentine rock mine tailings originating from the Carey Mine site in East-Broughton (Québec) was carried out using a suite of hydrocyclone, settling/decantation and magnetic separations. Four size classes of the mining residue, namely (−3150,+1580), (−1580, +600), (−600, +300) and (−300, +150) μm, were tested with an aim to reduce the level of objectionable asbestos fibers to allow access to the safer Mg-bearing minerals contained in the mine waste sources. The asbestos fibers clean-up consisted of subjecting the sieved fractions to two hydrocyclone steps, six settling/decantation steps and two magnetic separation steps. The best results were achieved when the hydrocyclone separators led to Mg recovery of 85% (±4) for the coarsest size fraction size. Both hydrocyclone underflow streams underwent settling/decantation separations. The settling tests lasted 30 min and led to Mg recoveries of 82.5% (±1.8) of Mg in the ultimate concentrate. SEM characterizations revealed that it was possible to reduce substantially the amount of chrysotile fibers to render the coarse-sized fraction in the mining waste usable while significantly lowering the health risk of the fibers. A two-step magnetic separation was applied to the final settling/decantation underflow to remove magnetic minerals such as magnetite from the lizardite/antigorite concentrate. The final quasi-non-magnetic chrysotile-depleted lizardite/antigorite concentrate allowed sample recovery of 62.5% (±0.9) wt. of Mg. These preliminary results are intended as a first compulsory step in support of viable restoration and sustainable development scenarios for the Thetford Mines mining sites as second-breath sources for valuable magnesium.

Identification of mining waste using remote sensing technique: A case study in El Triunfo town, BCS, México

Mining in México is directly responsible for serious environmental impacts due to the lack of control in the management of mining shafts with high concentrations of potential toxic elements (PTE). These residues are subject to erosion and weathering processes, becoming high risk pollution sources for the health of the inhabitants. In the study area, El Triunfo, Baja California Sur, it is necessary to determine the location and composition of the mining shafts to carry out soil remediation in the near future. High resolution multispectral images of Pleiades satellite are appropriate tools for monitoring and classification of environmental risks, especially useful for the study of sediment distribution. For identify and georeferenced mining tailings within a semi-desert environment, we used remote sensing technique, by using the supervised classification tool and Maximum Likelihood algorithm. The results revealed 32 potential zones with mining residues which were visited to validate the technique, confirming that 87.5% had mining residues. Mining tailings in the area are collected in hills up to 20 m in height with scarce to nil vegetation and are composed of uncompacted reddish material. Laser diffraction analysis showed that the mean grain size is medium silt (25 μm). The maximum concentrations of PTE were determined by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry and validated with certified reference material giving the next results: As: 15000 mg/kg; Cd: 327 mg/kg; Cu: 1920 mg/kg; Pb: 88900 mg/kg; and Sb: 20200 mg/kg. We classified the mining wastes as extremely enriched in PTE using the normalized enrichment factor and extremely contaminated using the geoaccumulation index. We concluded that the remote sensing technique is a very useful tool for identifying local mining waste, the composition of which puts the health of inhabitants at risk; it is advisable that remediation work should be carried out in the short term.

Phytoremediation of potentially toxic elements using constructed wetlands in coastal areas with a mining influence.

This paper proposes the use of wetlands as a phytoremediation strategy for areas of mining and maritime influence in the southeast of Spain. Potentially toxic elements (PTEs) tolerant and salinity-resistant macrophytes (Phragmites australis, Juncus effusus and Iris pseudacorus) have been used. The experiment is carried out in an aerobic artificial wetland using representative sediments affected by mining activities in the study area. Selected species were placed in pots containing substrates made with different mixtures of topsoil and/or peat, mining residues (black or yellow sand). After six months, rhizosphere, root and aerial parts were collected. A transfer study of As, Pb, Zn and Cu is performed, determining contents in rhizosphere and plant (aerial and underground part). From these data, the TF and BCF were calculated for each plant in 15 different substrates. The work is complemented by an initial study of scanning electron microscopy (SEM-EDX) of plants. The obtained results indicate a tolerance of the metallophytes to these PTEs, which may favour the obtaining of a naturalized habitat that acts as an effective protective barrier to the ecosystem, that is easy to maintain and that avoid the risk of transfer to the trophic chain. The use of these species can be a complement to the chemical stabilization proposed for the whole area and carried out in experimental plots. Because they are perennial plants, it is necessary to continue with the experiments and obtain results in a longer period of time that allows to evaluate yield and stabilization.

Microporous and macroporous materials state-of-the-art of the technologies in zeolitization of aluminosilicate bearing residues from mining and metallurgical industries: A comprehensive review

For decades, the world has experienced a steadily increasing demand in the extraction of a variety of different minerals from the earth's crust through mining processes. This has resulted in two major consequences: i) depletion of limited mineral resources of the earth, and ii) generation of large amounts of residual products in the mining and metallurgical sectors, that are disposed of in tailing ponds or landfill sites. These issues have caused that the world is encountering with incredibly serious economic and environmental challenges. Reuse, repurposing and valorization of these residues have been determined as effective and sustainable approaches towards struggling with economic and environmental issues related to the exploitation of low-grade deposits. These residues are divided into several categories according to their chemical and mineralogical compositions, since these parameters play essential roles in their repurposing/valorization. Among these residues, aluminosilicate bearing residues have demonstrated promising potential as inexpensive raw resources to produce valuable materials. In the recent years, these residues have been intensively investigated for their use in the production of cost-effective zeolites, which are crucial materials for catalysis and adsorption–separation industries. This alternative in zeolite production is of continuous interest in the field of zeolite science due to: i) important reduction in zeolite production costs, ii) sustainable development concepts as well as iii) helping to tackle the environmental concerns related to long-term management of residues. Herein, the endeavor is to discuss about the state-of-the-art technologies for zeolitization of aluminosilicate bearing residues including coal fly ash, clay minerals residues, Li slag, Al production residues, with an emphasis on the ongoing struggles in improvement of their corresponding zeolitization processes. • Valorization of mining and metallurgical residues can result in sustainable development. • Aluminosilicate bearing residues can contain zeolite precursors. • Several synthesis procedures exist to produce zeolites form aluminosilicate residues. • Zeolitization of aluminosilicate residues is influenced by a wide range of parameters. • More researches on technology development, process optimization as well as economic assessment are still needed.

Recycling of mining waste in the synthesis of magnetic nanomaterials for removal of nitrophenol and polycyclic aromatic hydrocarbons

Iron mining residues were successfully used in the fast and inexpensive sol-gel synthesis of magnetic hybrids (CoFe2O4/NOM), with water rich in natural organic matter (NOM) as solvent. XRD analyses revealed formation of the cobalt ferrite phase, while SEM and TEM images showed the formation of nanostructures. The hybrids obtained (HbSF and HbLM) providedexcellent rates of conversion (99%) of nitrophenol in short times of 50 and 120 s, respectively. The hybrids also showed high performance in the adsorption of PAHs,achieving removals of 75–88% (HbSF)and 72–81% (HbLM).This work contributes to the conversion of industrial operations from linear to cyclic processes.