Leaching Extraction Research Articles

17. The State of Belle Park

Our group used the Belle Park Golf course, located at 713 Montreal Street, as our project site. The course is located on top of a pre-existing dump that served as the city’s waste disposal site between the early 1950’s until 1974, it still shows signs of leachate seepage. The wildlife issue we explored is the effect of this leachate on the surrounding ecosystem, including tree species, fish and mammals. We researched case studies in similar situations that have been done in the past as a base for our understanding. The community entity are working with is the Environment Division of the City of Kingston, in charge of monitoring the hybrid poplar trees planted along the fairways. They are used as a means to extract contaminants from the soil, based on their proven ability for rapid growth. We will evaluate the effectiveness of this technique along with the vertical leachate extraction wells on site. Also, our group hopes to obtain the history of the water sample data that is collected from monitoring wells around the site for our analyses and interpretation. The latest budget information shows that the golf course lost $203,000 last year. This has prompted city council to reconsider the future of the property and open the doors for new innovative ideas. As part of our project we hope to come up with a sustainable solution that preserves the natural habitat and serves the community, such as a park.

A comparative study of bulk leach extractable gold (BLEG) and fire assay methods on the Wassa deposit at Golden Star Limited, Wassa mine

Golden Star Resources Limited conducts Bulk Leach Extractable Gold (BLEG) and Fire Assay methods on samples from its exploration program. Additionally, for mining control and as part of the sampling and analytical protocol, residues of samples whose assay values are greater than 10 g/t are subjected to fire assay to determine the quantity of gold. However, there is gold retained in the tails or residue after leaching and to verify the suitability and efficiency of the analytical method, drill samples (RC and DD) with control samples were analysed using BLEG method based on the accelerated cyanide leach extraction and Fire Assay method on the tails.Percentages of the prepared samples were subjected to BLEG orientation study to investigate the leachability and efficiency of the BLEG method on the ore samples. Fire Assay analysis was also carried out on the selected tailing samples to find out the assay reproducibility of the samples. The analytical analyses carried out on the samples revealed that the ore samples were leachable with gold recovery levels ranging between 96% and 100% when there is total pulverization of samples to make BLEG method possible and that this procedure is also cheaper than the conventional Fire Assay.

Microwave-Assisted Grinding of Bolkardag (Nigde, Turkey) Gold Ore and Enhanced Cyanide Leachability

This experimental work aims at studying the effect of particle size on the microwave pre-treatment for the grindability of Bolkardag (Nigde, Turkey) gold ore for cyanide leaching. Three different particle size batches (−8 + 4.7 mm, −4.75 + 2 mm and −2 + 1 mm) were used for microwave treatment. Each sub-samples were exposed to four different power levels of microwave energy (0.09, 0.18, 0.36 and 0.6 kW) at exposure times of 5, 10, 15 and 30 minutes and then grindability characteristic of the treated samples were investigated with Berry and Bruce comparative grindability method. It was clearly seen that increasing power level and exposure time caused a reduction in comparative Bond Work index. A maximum reduction in Bond Work index (73.54%) was achieved by 0.6 kW at 30 minutes of microwave treatment. Compared to the untreated sample’s results, gold and silver extraction rates increased, using microwave-treated samples, about 7% and 9% after 77 hours cyanide leaching, respectively. Additionally, the hydrated lime added samples (after 0.6 kW at 30 minutes of microwave treatment) were used in the cyanide leaching tests to determine the possible effect. It was observed that there was no significant difference on leaching extraction rates using lime free or lime added samples. Applying microwave pre-treatment before cyanide leaching, the gold and silver extraction rates could be increased and also the cost of communition could be reduced due to easier breakage of the ore due to a significant decrease in Bond Work index.

Valorization of low-grade copper-cobalt ore from the Mukondo mine by heap leaching and solvent extraction

Valorization of low-grade copper-cobalt ore from the Mukondo mine by heap leaching and solvent extraction

Geochemical Behavior of Rare Earth Elements in Weathered Granitic Rocks in Northern Palawan, Philippines

AbstractWeathered crust of granitic rocks of two geochemically similar plutons that differ in age of magmatism were investigated in the Philippines. These are the Cretaceous Daroctan Granite and the Middle Miocene Kapoas Granitoid located in Palawan Island, a part of the Palawan Continental Block derived from the continental margin of southeastern Eurasia. Both plutons are composed of biotite granodiorite and biotite granite and are geochemically characterized as ilmenite series, high‐K calc‐alkaline, intermediate I‐ and S‐types, and peraluminous.Light rare earth element (LREE) content of the weathered granitic crusts in the Kapoas Granitoid is higher than that in the Daroctan Granite, and LREE are enriched in the Daroctan Granite compared to the parent granitic rocks. In both plutons, the residual REE‐bearing minerals are mostly monazite. Allanite is only present in the Kapoas Granitoid while the Daroctan Granite contains xenotime. The Kapoas Granitoid pluton shows potential for placer‐type LREE deposit as observed in the elevated LREE content of the stream and beach sediments containing La, Ce, Nd and Sm up to >10,000 ppm. Sequential leaching extraction of REE using eight reagents which selectively dissolved REE with different mode of occurrence (i.e. water soluble, ion‐exchangeable salts, Pb‐displaceable, acid soluble, Mn‐oxide occluded, organically‐bound, amorphous Fe‐oxide occluded, and crystalline Fe‐oxide occluded forms), show that the Daroctan Granite has a potential for ion‐adsorption type REE resource with proportion of extracted REE ranging from 53 to 74 % among ΣREE. Formation of secondary REE‐bearing minerals, such as cerianite formed on the surface of clay minerals, results in enrichment of REE.

An investigation of the immunotoxicity of oil sands processed water and leachates in trout leukocytes

Increased oil sands (OS) mining activity has raised concerns about impacts on aquatic organisms. This study sought to examine the effects of single representative compounds from OS (benzo(a)pyrene, naphthalene), a mixture of naphthenic acids (NAs), OS-processed water (OSPW) and OS leachate (OSL) extracts on rainbow trout leukocytes. Primary cultures of trout leukocytes were exposed to increasing concentrations of benzo(a)pyrene, naphthalene, NAs, OSPW and OSL for 48h at 18°C. Immunocompetence was followed by measuring changes in lymphocyte and macrophage viability and phagocytosis. Changes in the expression of 10 transcripts were also followed: interleukin 1, 2 and 6 (Il-1, Il-2 and Il-6), calreticulin (CRT), caspase 9 (Cas9), aryl hydrocarbon receptor (AhR), cyclooxygenase-2 (COX2), glutathione S-transferase (GST), catalase (CAT) and p53 tumor suppressor. The results revealed that exposure to OSPW extracts decreased the capacity of macrophages to engulf three beads or more, while the other compounds generally increased phagocytosis activity. Lymphocyte apoptosis was increased by all compounds and mixtures except naphthalene. Both OSPW and OSL induced apoptosis in macrophages. At the gene expression level, Cas9, CRT, Il-1 (inhibition) and Il-2 were specifically influenced by OSPW, while CAT, p53, COX2 and Il-1 (induction) transcripts were specifically expressed by OSL. Leukocyte exposure to OSPW produced characteristic changes in immunocompetence and genes involved in proinflammatory, apoptosis and protein damage (CRT) pathways which could not be explained by OSL, benzo(a)pyrene, naphthalene and NA mixture.

Chemical Composition and Phytotoxicity of Cupressus sempervirens Leaves Against Crops

The present study aims to evaluate the Cupressus sempervirens leaves phytotoxicity. Their leachate (100, 200, 300, 400 and 500 g/l), aqueous (10, 20, 30 and 40 g/l) and organic (petroleum ether, chloroform and acetone, at 2000, 4000 and 6000 ppm) extracts were tested on radish, lettuce, barley and tomato. Pot cultures were conducted by incorporation of leaves powder (50 and 100 g/kg) in soil and by irrigation with leaves leachate and aqueous extracts at IC50 and MIC, concentrations causing, respectively 50% and 100% inhibition. Over all, rate germination did not affected, however germination speed was significantly delayed. For growth, aqueous extracts had the most significant toxicity at 40 g/l and leachate at 500 g/l, inducing up to a total inhibition. The strongest toxicity of organic extracts, was recorded at 6000 ppm (30 mg) for the three ones. Radish seedling growth was more sensitive, especially to petroleum ether and acetone fractions whereas tomato showed a great sensitivity especially to petroleum ether fraction. Residues incorporation in soil (at 100 g/kg) significantly decreased root (86–99%) and shoot (65–100%) length of target species. Irrigation with aqueous extracts and leachate was harmful for especially, tomato and lettuce. Quantitative and qualitative analysis of the extracts were carried out by gas chromatography-mass spectrometry (GC-MS). Results showed that C. sempervirens had a significant allelopathic potential. This plant may be favorably used for incorporating in agricultural systems for sustainable weed management.

Precious Nickel Recovery from Palm Oil Mill Fuel Ash Waste (Ni-POMFAW) Using Acidic Leaching Extraction (ALE)

This paper demonstrates precious recovery of nickel from physical pre-treated raw palm oil mill fuel ash waste (POMFAW). The acidic leaching extraction (ALE) using sulphuric and hydrochloric acids agents were carried out in a bath stirrer flask. Process parameter effects of acid concentration, solution pH and treatment time were investigated in the nickel recuperation. The highest nickel recovery (96.83%) was found by treatment time of 1 h, pH of 2.5 and hydrochloric acid concentration of 2.0 M. At the acids leaching higher than 2 M, the nickel recovery decreased. Results from acids leaching imply that nickel complex can be formed at substantial percentages within the acid concentration higher than 1 M. The hydrochloric acid provides impressive nickel compared sulphuric acid, and the POMFAW can be proposed as a substitute of non-renewable sources derived nickel for a promising material and the used ALE can be considered as a beneficial technique.

Thermal, Strength and Leachability Characteristics of Cellulose Fibre Reinforced Lime-Soil Brick

This research studies on the possibility of producing a more sustainable lightweight brick. Natural cellulose fibre produced from leaf and wood aggregates, lime and soil from local area of Thailand were added into the brick with minimizing Portland cement content. Effects of varied amount of cellulose fibre contents typically (10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 %) on mechanical and thermal properties of bricks are studied. Mechanical performances have been investigated with compressive, flexural strength and thermal conductivity of the samples. Also, the Leachate Extraction Procedure is observed. Results showed that adding more cellulose fibre contents can reduce the thermal conductivity, density including the compressive and flexural strength of the brick. On the other hand, the water absorption increases. It is also shown that the composite bricks can add fibre contents up to 55% by weight that can be used as non-load bearing concrete masonry units considered by the compressive strength. By conclusion, this application may be an interesting solution in order to improve sustainability and energy efficiency of the low cost house in local area of Thailand.

Impact of aging on leaching characteristics of recycled concrete aggregate.

The focus of this study was to evaluate the effects of stockpiling (aging) on leaching of elements in recycled concrete aggregate (RCA) that may contribute to tufaceous constituent formation. Speciation and leaching controlling mechanisms of these elements were identified via geochemical modeling. The effects of stockpiling were simulated by comparing freshly produced RCA with RCA aged as part of this study for 1year both in the laboratory and in the field. Leachate samples were generated following batch water leach test (WLT) and US Geological Survey leach test (USGSLT) methods. USGSLTs were conducted both on the laboratory and field samples while WLT was only conducted on laboratory samples. During the laboratory aging, it is observed that the carbonate content of RCA, measured as calcite equivalent, increased 20% (i.e., from ∼100 to 120mg/g) within a year time frame. The leachate extracted from RCA showed minor changes in pH and more significant decreases in electrical conductivity (i.e., ∼300 to 100μS/cm). A comparison between laboratory and field samples revealed that the RCA aged much slower in the field than in the laboratory within a year. Comparisons between two leach extraction methods on the laboratory conditions showed that the total leached concentrations (TLCs) of most of the constituents from USGSLT were appreciably lower than the ones measured via WLT method. The results of geochemical modeling analyses showed that Al, Si, Fe, Ca, Mg, and Cu exist in their oxidized forms as Al3+, Fe3+, Si4+, Ca2+, Mg2+, and Cu2+ and results revealed that these elements are primarily controlled by the solubility of gibbsite, hematite, silica gel, calcite, magnesite, and tenorite solid phases, respectively. One of the significant findings of the study was to identify the changes in leaching behavior of Ca, Si, Mg, Al, Fe, and Cu due to carbonation.

Determination of optimum heap height from column leach tests: 1. Model development and initial results

A method to determine optimum heap leach height has resulted from design work for a uranium heap leach project on the Macusani Plateau in south-eastern Peru. The on-off/racetrack heap leach process, the base case design parameters and the relevant column leach test results are described. In the problem development, a maximum leach extraction versus grade relationship, the leach extraction model, a recovery discount model, the financial parameters utilised and the calculation sequence are described before a spreadsheet solution for optimum heap height is presented. Equations used in the spreadsheet solution are detailed in the algebraic optimisation problem formulation. Symbolic solution proved too challenging for the computer algebra system utilised (Maxima). The subsequent algebraic simplification to the leach extraction model yields a succinct solution for an optimum heap height estimate. The estimate is affected by recovery discount and pad maintenance costs but is independent of theoretical recovery and pad capital costs. The initial results were approximately 50% of the spreadsheet calculation results. A correction factor is required to compensate.

Determination of optimum heap height from column leach tests: 2. Sensitivity analysis

A method to determine optimum heap leach height has resulted from design work for a uranium heap leach project on the Macusani Plateau in south-eastern Peru. An analysis of the optimum heap height estimate details its sensitivity to the constituent variables algebraically, graphically, and, in contour plot format. A comparison is drawn against a Namibian uranium project with design details in the public domain and agreement is found to be reasonable. The leach extraction model and dynamics are analysed in terms of solution to ore ratio (SOR), reaction extent and acid consumption efficiency to address model time dependence loss in the model simplification step. The rate of change in the acid efficiency is used to specify the target extraction and determine leach SOR and leach time. The validity of the optimum height estimate equation is supported by favourable comparison against the spreadsheet calculation results and data from another uranium heap leach project. The estimate is dependent on recovery discount and pad maintenance costs but is independent of theoretical recovery and pad capital costs.

Effects of extraction methods and factors on leaching of metals from recycled concrete aggregates.

Leaching of metals (calcium (Ca), chromium (Cr), copper, (Cu), iron (Fe), and zinc (Zn)) of recycled concrete aggregates (RCAs) were investigated with four different leachate extraction methods (batch water leach tests (WLTs), toxicity leaching procedure test (TCLP), synthetic precipitation leaching procedure test (SPLP), and pH-dependent leach tests). WLTs were also used to perform a parametric study to evaluate factors including (i) effects of reaction time, (ii) atmosphere, (iii) liquid-to-solid (L/S) ratio, and (iv) particle size of RCA. The results from WLTs showed that reaction time and exposure to atmosphere had impact on leaching behavior of metals. An increase in L/S ratio decreased the effluent pH and all metal concentrations. Particle size of the RCA had impact on some metals but not all. Comparison of the leached concentrations of metals from select RCA samples with WLT method to leached concentrations from TCLP and SPLP methods revealed significant differences. For the same RCA samples, the highest metal concentrations were obtained with TCLP method, followed by WLT and SPLP methods. However, in all tests, the concentrations of all four (Cr, Cu, Fe, and Zn) metals were below the regulatory limits determined by EPA MCLs in all tests with few exceptions. pH-dependent batch water leach tests revealed that leaching pattern for Ca is more cationic whereas for other metals showed more amphoteric. The results obtained from the pH-dependent tests were evaluated with geochemical modeling (MINTEQA2) to estimate the governing leaching mechanisms for different metals. The results indicated that the releases of the elements were solubility-controlled except Cr.

Porosity and Permeability of Round Top Mountain Rhyolite (Texas, USA) Favor Coarse Crush Size for Rare Earth Element Heap Leach

Water-saturation porosity and dye-penetration permeability measurements of Round Top Mountain rhyolite confirm that a ½-inch (13-mm) crush size would permit efficient acid heap leaching of yttrium and heavy rare earth elements (YHREEs) hosted in yttrofluorite, a YHREE-substituted variety of fluorite. Laboratory acid leaching has extracted up to 90% of the YHREEs. The bulk insoluble gangue mineralogy of the rhyolite, 90% to 95% quartz and feldspars, assures low acid consumption. Different crush sizes were weighed, soaked in water, and reweighed over time to determine water-penetration estimated porosity. Typical porosities were 1% to 2% for gray and 3% to 8% for pink varieties of Round Top rhyolite. The same samples were re-tested after soaking in dilute sulfuric to simulate heap leaching effects. Post-leach porosity favorably increased 15% in pink and 50% in gray varieties, due to internal mineral dissolution. Next, drops of water-based writing ink were placed on rhyolite slabs up to ~10 mm thick, and monitored over time for visual dye breakthrough to the lower side. Ink penetration through 0.5 to 2.5-mm-thick slabs was rapid, with breakthrough in minutes to a few hours. Pink rhyolite breakthrough was faster than gray. Thicker slabs, 4 to 10 mm, took hours to three days for breakthrough. Porosity and permeability of the Round Top rhyolite and acid solubility of the yttrofluorite host should permit liberation of YHREEs from the bulk rock by inexpensive heap leaching at a coarse and inexpensive nominal ½-inch (13-mm) crush size. The rate-limiting step in heap leach extraction would be diffusion of acid into, and back-diffusion of dissolution products out of, the crushed particles. The exceptional porosity and permeability that we document at Round Top suggest that there may be other crystalline rock deposits that economically can be exploited by a coarse-crush bulk heap leach approach.

Modeling the Quasi-Equilibrium of Multistage Phytoextractions

A model describing multistage leaching phytoextractions based on a nonideal quasi-equilibrium line of an inverted McCabe–Thiele diagram is proposed in this study. The model is able to simulate the temperature dependence of the amount of extractable target component. It was applied to the extraction of artemisinin from Artemisia annua with ethanol at different temperatures. All model parameters were determined via single-stage extractions only. The model was able to represent the experimental data of multistage leaching extractions, including the temperature-dependent extractable amount of artemisinin. Therefore, the model can be used to reduce the number of experiments and accelerate the process design of phytoextraction processes.

Landfill aeration for emission control before and during landfill mining

The landfill of Modena, in northern Italy, is now crossed by the new high velocity railway line connecting Milan and Bologna. Waste was completely removed from a part of the landfill and a trench for the train line was built. With the aim of facilitating excavation and further disposal of the material extracted, suitable measures were defined. In order to prevent undesired emissions into the excavation area, the aerobic in situ stabilisation by means of the Airflow technology took place before and during the Landfill Mining. Specific project features involved the pneumatic leachate extraction from the aeration wells (to keep the leachate table low inside the landfill and increase the volume of waste available for air migration) and the controlled moisture addition into a limited zone, for a preliminary evaluation of the effects on process enhancement. Waste and leachate were periodically sampled in the landfill during the aeration before the excavation, for quality assessment over time; the evolution of biogas composition in the landfill body and in the extraction system for different plant set-ups during the project was monitored, with specific focus on uncontrolled migration into the excavation area.Waste biological stability significantly increased during the aeration (waste respiration index dropped to 33% of the initial value after six months). Leachate head decreased from 4 to 1.5m; leachate recirculation tests proved the beneficial effects of moisture addition on temperature control, without hampering waste aerobization. Proper management of the aeration plant enabled the minimization of uncontrolled biogas emissions into the excavation area.

Effects of detritus chemical composition on the anaerobic mineralization of Salvinia auriculata and Utricularia breviscapa

Aim: This study was conducted to evaluate the effect of the detritus composition on the anaerobic mineralization of two species of aquatic macrophytes with different life forms (submerged and free floating). The hypothesis that guided this study was that the carbon concentration derived from detritus hydrosoluble fraction can act as a facilitating factor on its degradation.Material and MethodsIncubations containing detritus and water sample from the Óleo Lagoon (21° 33’ to 21° 37’ S and 47° to 47° 45’ to 51’ W) for each specie (Salvinia auriculata and Utricularia breviscapa) were set-up with: (i) integral detritus (sample of dried plant), (ii) lignocellulosic matrix (particulate organic matter (POM) remaining from leachate extraction) and (iii) leachate. The incubations were kept in the dark under anaerobic conditions. Daily rates of gas formation were evaluated and after 138 days, the incubations were fractioned in dissolved and particulate fractions and the mass balances were performed. A mass loss experiment (180 days) was performed for assessment of the dissolved organic carbon, particulate organic carbon and mineralized carbon variations.ResultsRegardless of the type of detritus (S. auriculata and U. breviscapa), C-mineralization was faster and higher in the DOC incubations (ca. 85%). For U. breviscapa the POM mineralization was slower than the corresponding integral detritus and S. auriculata mineralization was slower than U. breviscapa.ConclusionsThe composition of the detritus (i.e. macrophyte type, presence and proportion of leachate) interfered synergistically in anaerobic degradation of these plants. The leachate tends to act as a facilitator, supporting the growth of microorganisms and intensifying mineralization.

Reduction of acid rock drainage using steel slag in cover systems over sulfide rock waste piles.

The extraction of gold, coal, nickel, uranium, copper and other earth-moving activities almost always leads to environmental damage. In metal and coal extraction, exposure of sulfide minerals to the atmosphere leads to generation of acid rock drainage (ARD) and in underground mining to acid mine drainage (AMD) due to contamination of infiltrating groundwater. This study proposes to develop a reactive cover system that inhibits infiltration of oxygen and also releases alkalinity to increase the pH of generated ARD and attenuate metal contaminants at the same time. The reactive cover system is constructed using steel slag, a waste product generated from steel industries. This study shows that this type of cover system has the potential to reduce some of the adverse effects of sulfide mine waste disposal on land. Geochemical and geotechnical characterization tests were carried out. Different proportions of sulfide mine waste and steel slag were studied in leachate extraction tests. The best proportion was 33% of steel slag in dry weight. Other tests were conducted as follows: soil consolidation, saturated permeability and soil water characteristic curve. The cover system was numerically modeled through unsaturated flux analysis using Vadose/w. The solution proposed is an oxygen transport barrier that allows rain water percolation to treat the ARD in the waste rock pile. The results showed that the waste pile slope is an important factor and the cover system must have 5 m thickness to achieve an acceptable effectiveness.

Orthogonal zirconium diol/C18 liquid chromatography–tandem mass spectrometry analysis of poly and perfluoroalkyl substances in landfill leachate

Leachates coming from landfills contain a myriad of compounds of potential environmental and human health concern, including per- and polyfluorinated alkyl substances (PFASs). Micro liquid-liquid extraction was combined with a 900μl large volume injection (LVI) for the analysis of 70 PFASs in landfill leachate by orthogonal LC-MS/MS. The LVI approach introduced 7 times more extract than conventional injection approaches. Two zirconium-modified diol guard columns effectively retained PFASs from the organic leachate extract and an analytical C18 column was used for separation. Method accuracy and precision for PFASs with analytical grade reference materials ranged from 81–120% and 5.5–33%, respectively. Estimated method detection limits in the low to sub-ng/L. Seven landfill leachates were analyzed by the optimized analytical method for the purposes of method demonstration. Leachates were characterized by a wide variety of PFASs, reporting on 36 previously-unanalyzed PFASs in leachate. Perfluoroalkyl carboxylates were the most abundant class detected while phosphorous-containing PFASs, present in all leachates, were at low concentrations. The 3-perfluoropentyl propanoate (5:3 FTCA) was the most concentrated analyte in most samples and constitutes a previously unreported but significant component of landfill leachate.

Tools used to estimate soil quality in coal combustion waste areas

Soil is a highly complex environmental compartment that has suffered with the contamination of substances of various origins. Among the main activities that affect soil quality are power generation activities that use fossil fuels, such as mineral coal. Environmental protection agencies encourage scientific investigations using tools described in legal devices or standard protocols to evaluate the potential of coal as a pollutant, especially in places that have large reserves of this mineral like the state of Rio Grande do Sul. The aim of this study was to characterize the leached extracts of different soils from an area influenced by coal waste, to classify them according to the guideline values for groundwater described in CONAMA's n. 420/2009, and to estimate the effects of the leachates ingestion in DNA mutation rates. The volume of soil needed to induce a 100% increase in the spontaneous mutation rate varied between 129.3 and 1544.1 mg of soil among the soils studied. Metals such as Mn, Pb, Cd and Ni surpassed the investigation limits for groundwater at least in one soil sample. The results showed that there can be transfer of soil contaminants to groundwater and soil intake in the area could contribute to the increased mutagenic risk.