Subsequent Leaching Research Articles

Gold Leaching with Humic Substances

The study results of gold leaching using the products of humic acids, as well as stage-by-stage fractionation of parent and gold-containing substances of these acids are presented. The gold content in the pregnant solution was up to 14–30 mg/l. Chemical analysis of the supernatant obtained by a stepwise change in pH of the solution and subsequent centrifugation determined that gold-bearing acids contain both organic and dissolved gold, which is stable to precipitation at pH 2. Fractionation of the original humic acids and subsequent leaching of gold by its individual fractions slows down the dissolution kinetics, and the fractions distinguished at different pH vary significantly in their activity. The most active is the fraction obtained by centrifugation at pH value of 4.6. The spectrum is presented, and the kinetics of gold dissolution by these acids modified by the cyanide complex is shown.

Recovery of rare earths from waste cathode ray tube (CRT) phosphor powder with organic and inorganic ligands

Cathode ray tubes (CRTs) have an appreciable amount of rare earth elements (REEs). In this document, the leaching and recovery of the REEs from CRTs, with different organic and inorganic ligands is presented. Among the complexing agents tested, the pyrophosphate ion was found to be the most advantageous for the extraction of REEs from CRTs, as an alternative to the traditional methods that use highly acidic solutions (pH < 1) and elevated temperatures. Thermodynamic analyses predict the formation of soluble REE-pyrophosphate complexes in a pH range of 2–8. Leaching solutions of 0.1 M Na4P2O7 at pH 6 and room temperature were employed. REE dissolution from the untreated CRT powder under these conditions was extremely low, due to the encapsulation by other components in the powders, such as ZnS (26%), and the high content of phosphates (6%), that severely limited the solubility of the REEs. To increase extraction, pretreatments were employed to alter and remove the passivating species: roasting at 800 °C or contact with concentrated solutions of sodium hydroxide at 95 °C. The combination of these pretreatments completely eliminated the Zn and 79% of the phosphate ion, as well as other base metals, resulting in an improved exposure of REEs for subsequent leaching. Extractions for Y, Eu, Sm, and Ce of 58, 90, 90 and 87%, respectively, were achieved with the pyrophosphate solution at ambient temperature. The REEs were later recovered as oxides by adjusting the solution pH to 11. Subsequently, once the pyrophosphate solution pH is reestablished, it may be reused for leaching.

Synthesis of porous resorcinol-formaldehyde resins and study of their sorption characteristics toward Cs in highly mineralized alkaline media

Abstract The present work was devoted to study of sorption parameters of resorcinol-formaldehyde resins synthesized through introduction of an inorganic filler (in amounts of 10 and 25 wt.%) with its subsequent leaching. The surface morphology and composition of ion-exchange resins have been investigated by means of the method of scanning electron microscopy. The effect of internal diffusion on the peculiarities of the ion-exchange process has been determined. It has been revealed that the ion-exchangers destruction upon a prolonged contact with highly alkaline solutions is followed by the decrease of internal diffusion coefficients and selectivity toward Cs-137 micro-quantities. The sorption properties of resins under dynamic conditions at high solution feeding rates have been studied. A sample with the highest efficiency of Cs-137 removal from highly mineralized solutions has been identified.

Mechanistic understanding, gamma phase formation and morphological behaviour of the Reduction−Diffusion processed U-Mo alloy

Reduction−Diffusion (R-D) process has been attempted to synthesize U-Mo alloy powder for the first time, and the mechanism of alloy formation has been investigated. Calciothermic reduction of uranium dioxide in the presence of the alloying element Mo, followed by high temperature soaking; subsequent leaching to remove the calcia slag yields U-Mo alloy in powder form. Experiments were carried out to synthesize U-10 wt%Mo alloy powder. The alloy powder products were characterized by Scanning Electron Microscopy and X-ray Diffraction. Complete stabilization of the metastable isotropic gamma phase has been achieved in U-10 wt%Mo powder synthesized by R-D process, where the final soaking was carried out at 1300 °C and 4 h. Attempts were made to understand the mechanism of formation of U-Mo alloy by R-D process on two fronts, i.e. alloying within a single particle, and particle-to-particle homogenization. The intended application of the alloy powders is in high uranium density dispersion fuels for high flux nuclear research and test reactors.

Improving biocompatibility of cobalt based alloy using chemical etching and mechanical treatment

AbstractBiomedical grade of cobalt based alloy have found a plethora of applications as medical devices especially in dental and articulation joints like in total ankle, knee and hip arthroplasty. However, the long‐term performance of this material is highly dependent on their ability to withstand in harsh aqueous environment effects such as corrosion and wear once they are used inside a human body. Loss of surface integrity and subsequent leaching of toxic metal ions as well as particles to the surrounding tissues may undermine biocompatibility of metallic implants, also potentially causing untimely loss of mechanical function and device failure. In this study, a biomedical grade of Co−Cr−Mo alloy surface was treated with various surface modification techniques such as chemical etching and mechanical roughening in order to improve its biocompatibility. Investigation was done to study which surface modification techniques possesses the positive effect in cell growth and exhibit excellent cell response on Co−Cr−Mo alloy. In‐vitro study showed that human osteoblast cells grown with good adherence and spread out with an intimate contact on the chemical treated surface after 14 days of incubation. It is believed that porous structure with grooves owned by chemical treated surface helps in anchoring the cells to the substrate surface and facilitates cells growth since more protein molecules expected to have more sites on this surface. Whilst on mechanical roughened surface, the cells appeared to show slightly less extended cell membranes and the cells remained retarded.

Microstructure of indica and japonica rice influences their starch digestibility: A study using a human digestion simulator

The aim of this study was to monitor the release of glucose and structural changes in Brazilian indica and Thai japonica rice during digestion in a human digestion simulator capable of simulating both mechanical and chemical food digestion. Chemical composition, cooking time, hardness, thermal properties and morphology of the grains were also investigated. The oral and gastro-small intestinal digestion led to the creation of open structures in the cooked rice endosperm due to hydrolysis by digestive enzymes and subsequent leaching of digested components. Indica cooked rice maintained its compact microstructure until the mid-small intestinal digestion phase, which agrees well with its slower starch hydrolysis. However, both types of rice had similar starch hydrolysis (%) at the end of the digestion period. Higher levels of amylose-lipid complexation and protein content in indica rice may have played a role in slowing down the release of glucose during digestion. The slower release of glucose during digestion of indica rice may reflect prolongation of satiety or the feeling of fullness after its consumption.

Degradation process regulation of waste LCD panel to ensure the remain of indium in solid phase by hydrothermal reaction.

The environmental risks and recycling potential of organic materials and indium of waste LCD panel has produced commercial value. It has been found that hydrothermal reaction can achieve an efficient and clean degradation of organic materials in a closed environment. However, as the degradation process occurs, the glass substrate is gradually exposed to the hydrothermal environment. Whether the metal indium is dissolved into the liquid phase and whether it affects product quality and the subsequent leaching process need to be discussed. In present study, simultaneous organic materials degradation and pretreatment of indium recycling was achieved due to the regulation of parameters. Effects of reaction temperature, reaction time, H2O2 supply and pH of the reaction solution on the transfer of indium in liquid and solid phase were investigated. The results showed that the degradation rate of the organic material reach 90% under the neutral condition of 300℃ of reaction temperature, 36 mL of water and 7.2 mL of H2O2 supply and 11 min of reaction time. This pretreatment method effectively realized the resource recovery of waste LCD panel and the outflow of metal indium was inhibited at the same time, thus further comprehensive recycling of resources could be prepared.

Microbial decomposition of biomass residues mitigated hydrogeochemical dynamics in strongly alkaline bauxite residues

Effective neutralization of strongly alkaline conditions in bauxite residues (BR) is the fundamental step to initiate the process of eco-engineering BR into growth substrate (or soil-like medium) for direct phytostabilization with pioneer plant species. The present study aimed to evaluate the effectiveness of microbial decomposition of organic matter (OM) (i.e., biomass residues) in neutralizing the strong alkalinity of residues under saturated conditions, together with the regulatory role of calcium sulfate (CaSO4) addition. Admixing OM (i.e., sugarcane mulch, Lucerne hay) alone in the BR significantly lowered the porewater pH from 11.4 to around 9.0 by Day 7, which persisted until the end of incubation (Day 28). The pH reduction in the porewater of OM-amended BR coincided with the production of acidic organic compounds (mainly acetic acid). Diverse species of organotrophic bacteria (e.g., Enterobacteriales, Pasteurellales, Lactobacillales, and Streptophyta) were found to have colonized in the OM-amended BR, but which were dominated by haloalkaliphilic bacteria (e.g., Halomonas and Bacillaceae). The CaSO4 addition in the OM-amended BR further lowered pH to 8.3 in the porewater. Besides, the bioneutralization effects resulted in dramatic reduction (>90%) of soluble Al in the porewater, which is a prerequisite to lowering Al toxicity in plants. At the same time, the levels of major cations (i.e., K, Ca, Mg) in the porewater were elevated by the OM + CaSO4 amendment, which would facilitate subsequent leaching of these soluble salts to lower the salinity in the BR, and improve the diversity of organotrophic bacterial communities in the amended BR.

From Electrodes to Electrodes: Building High‐Performance Li‐Ion Capacitors and Batteries from Spent Lithium‐Ion Battery Carbonaceous Materials

AbstractWe report the possibility of recycling carbonaceous materials (GC) from used/spent Li‐ion batteries (LIBs) and re‐using the material again as a negative electrode. In addition to LIB, the possibility of using them in Li‐ion capacitor (LIC) configuration with activated carbon is also explored. First, the carbonaceous materials are recovered from the mechanical treatment and subsequent leaching process. After the successful recovery, the Li‐insertion properties are studied in half‐cell assembly and it exhibits very decent electrochemical activity. While re‐using GC as an anode, large irreversibility is noted compared to fresh usage. Therefore, the elimination of such irreversible capacity is desperately required prior to the fabrication of either LIBs or LICs. Full‐cell LIB is assembled with olivine phase LiFePO4 cathode and the configuration delivers a maximum energy density of ∼313 Wh kg−1. Similarly, the GC is used as an anode in LIC assembly with commercial activated carbon. The LIC displays an energy density of ∼112 Wh kg−1 with decent cycling profiles.

Recycling of rare earth elements from FeNdB-Magnets via solid-state chlorination

Recycling of rare earths from magnetic alloys such as Fe14Nd2B is a widely studied field of research. However, with rare earth metal prices falling, leaching of magnet materials with mineral acids has become economically unfeasible. In order to circumvent high expenditures, solid-state chlorination offers an attractive alternative. Chlorination takes place via partial decomposition of NH4Cl at temperatures between 225 and 325 °C. Subsequently, dry HCl gas reacts with the magnet material in a rotary kiln to form water-soluble metal chlorides, which are dissolved in an acetic acid buffer medium. Here, spent Fe14Nd2B-magnets from a wind turbine served as starting material. For the first time, the solid-state chlorination process was optimised with the aid of statistical experimental design considering binary factor correlations. The global optimum was determined by varying the amount of NH4Cl, temperature, residence time and buffer mass in the subsequent leaching step. The maximum rare earth yield amounted to 84.1%. For dissolving rare earths quantitatively, the unreacted residue requires recirculation. In this respect, solid-state chlorination was compared to an optimised state-of-the-art process employing hydrochloric acid for digestion. The solid-state chlorination process was found to be superior in that consumption of chemicals was reduced by 45%, no costs for neutralisation incur and chemical costs were decreased by at least 51%.

BENCH SCALE TWO STAGE HEAVY METAL LEACHING TEST WITH FLY ASH FROM WOODY BIOMASS COMBUSTION

In this paper a two stage bench scale leaching procedure is used to assess the heavy metals release from a wood-based fly ash of a 5.0 MWth grate-fired boiler. In the first step mostly K was leached with water. In the subsequent acid leaching step heavy metals were leached at a pH of 3. The remaining solids were agglomerated together with the bottom ash and the dried K-concentrate from the first leaching step whereas the filtrate was treated before discharge. In the agglomerates produced the heavy metal concentrations were below the limit concentrations for utilization. The loss of nutrients caused by the treatment was about 10% for Ca and for K 8%. The addition of 15% hydrated lime in the agglomeration step showed a very positive effect on the reduction of the fines contained in the product and on the mechanical stability of the agglomerates. The mass of the precipitate from the waste water treatment was about 10% of the mass of the fly ash. Thus, the mass of residue requiring disposal in landfill sites was reduced substantially. The heavy metal concentrations in the treated discharge water were significantly lower than typical limit values for waste water. This paper also presents the current heavy metal limit values for ash used as a soil conditioner in forestry and agriculture in Austria, Finland, Sweden, Denmark and Lithuania.

Effect of crop residues on interception and activity of prosulfocarb, pyroxasulfone, and trifluralin.

Crop residue retention on the soil surface in no-tillage system can intercept pre-emergent herbicides and reduce their efficacy. Three experiments were conducted to investigate the effect of crop residue amount (0, 1, 2 and 4 t ha–1), moisture (wet versus dry), type (wheat, barley, canola, chickpea and lupin) and age (fresh or aged for one year) on the interception and subsequent leaching of prosulfocarb, pyroxasulfone, and trifluralin from the residue into soil. Bioassays, using cucumber and annual ryegrass as indicator plants, were used to assess herbicide activity/availability in the soil and on the residue. Herbicide interception increased considerably as residue quantity increased from 2 to 4 t ha–1. After simulated rainfall, which washed herbicide into the soil, complete control of ryegrass occurred for trifluralin with 0 t ha–1 residue, for prosulfocarb with 0 and 1 t ha–1 residue, and for pyroxasulfone with all residue rates. Therefore, with rain or irrigation, pyroxasulfone was the herbicide least affected by high residue loads. Less chemical leached from the crop residue into the soil after rainfall, when prosulfocarb and trifluralin were applied to wet residue compared with dry residue, but the initial moisture condition had no effect on the leaching of pyroxasulfone from residue. If practically possible, farmers should minimise spraying prosulfocarb and trifluralin onto wet crop residue. Barley and wheat residues intercepted more herbicide than an equivalent mass of canola, chickpea or lupin residue, which was largely due to the increased ground cover with cereal residues. The effect of residue age on herbicide interception and leaching was relatively small and variable. Overall, more herbicide reached the soil when sprayed on one-year old residue than new residue, which was largely due to reduced ground cover with aged residue. A strong positive linear relationship existed between ground cover percentage and growth of bioassay species (r2 = 0.75). This means that there was little difference in the ability of residue to adsorb and retain herbicide between crop residue types and ages, such that farmers can simply use the ground cover of the crop residue to assess interception.

Depositional, diagenetic and mineralogical controls on porosity development in the Ungani Field, Canning Basin

A 75 m-thick section of Early Carboniferous Tournaisian Ungani Dolomite reservoir was continuously cored in Ungani Far West 1, an appraisal well 3 km west of the Ungani field located on the southern flank of the Fitzroy Tough in the Canning Basin. The objective of this coring program was to better understand the pore systems, mineralogy, and diagenetic history of the reservoir to allow calibration and extrapolation of the petrophysical evaluation of the reservoir at the Ungani field. Petrography, stable isotopic, XRF, hyperspectral logging, grain density and CT scan studies were conducted on the core. The core consists of a 12m overlying sealing shale and 63 m of vuggy, fractured and dolomitised reservoir. The reservoir is commonly bioclastic-rich but pervasive dolomitisation hinders recognition of earlier depositional features. The upper carbonate facies is interpreted as shallow to moderate depth marine ramp-type deposits while the lower carbonate facies is suggestive of shallow platform top settings with ‘reefal’ constructing organisms. Bio-mouldic, vuggy, fracture, cavern and inter-crystalline porosity resulting from multistage brecciation, fracturing, dolomitisation and dissolution events are all present and critical to reservoir development. Based on hyperspectral logging and thin section petrography, the reservoir is predominantly dolomite with late phase cements comprising of quartz, calcite, gypsum, anhydrite, chalcedony, dickite and pyrite. Variable grain densities that correspond with porosity have been noted throughout the core but no obvious relationship between the mineralogy and porosity can be established. Shallow to moderate burial and marine or evaporative reflux fluids are likely responsible for the pervasive dolomitisation. Subsequent leaching of calcite is also key to reservoir development.

Cover Crops and Tillage Influence on Nitrogen Dynamics in Plant‐Soil‐Water Pools

Core Ideas Cereal rye reduced the NO3–N leaching loads during the cover crop season. Nitrate‐N leaching in corn may increase following legume cover crops. Conventional tillage may result in greater N loss compared with no‐tillage. Poor synchronization of N supply‐demand by cash crop can result in higher N losses. Cover crops (CCs) planted after cash crop harvest have the potential to improve vadose zone water quality through scavenging residual soil N. Limited research is available on N release from the biomass after CC termination and its subsequent leaching. This study examined the influence of rotations corn (Zea mays L.)–no cover crop (noCC)–soybean [Glycine max (L.) Merr.]–noCC (CncSnc), corn–cereal rye (Secale cereale L.)–soybean–hairy vetch (Vicia villosa Roth) (CcrShv), corn–cereal rye–soybean–oat+radish (Avena sativa L.+Raphanus sativus L.) (CcrSor) and tillage (conventional‐tillage [CT] and no‐tillage [NT]) on available N in soil, N accumulation in plant biomass, and N leaching to pan lysimeters. The rotations CcrShv and CcrSor with hairy vetch and oat+radish resulted in 89% (37.7 vs. 20.0 kg ha−1) and 68% (33.5 vs. 20.0 kg ha−1) more nitrate N (NO3–N) leaching than CncSnc during cash crop season in fall 2015. Under CT in fall 2017, the rotation CcrShv (19.4 kg ha−1) had higher NO3–N leaching than CncSnc (3.2 kg ha−1) and CcrSor (1.4 kg ha−1). During CC season in spring 2016, cereal rye in CcrShv and CcrSor reduced NO3–N leaching by 84 and 78% compared with the CncSnc, respectively, under CT. Our results indicated that CT had greater N leaching losses than NT. The higher NO3–N leaching during cash crop season with rotations having CCs was due to the mismatched timing of N availability and demand by the cash crop.

A combined compression molding, heating, and leaching process for fabrication of micro-porous poly(ε-caprolactone) scaffolds

Biomaterial scaffolds have been increasingly used for tissue engineering applications as well as three dimensional (3D) cell culture models. Herein, we report a simple procedure combining compression molding, heating, and leaching methods for the fabrication of 3D micro-porous poly(ε-caprolactone) (PCL) biomaterial scaffolds. In this procedure, PCL micro particles are mixed with NaCl of defined sizes and compression molded, followed by heating and subsequent leaching of NaCl particles. This technique eliminates the gas foaming method, which is commonly used in the fabrication of PCL scaffolds. Process and scaffold parameters (i.e., heating time, NaCl concentration, and NaCl particle size) were varied and analyzed to determine their impact on the overall scaffold structural and mechanical properties. An increase in NaCl particle size led to an increase in pore area but did not significantly impact the mechanical properties of the scaffolds. Additionally, NaCl concentration did not show a significant effect on pore area, but considerably impacted the mechanical properties, water absorption capacity and porosity of the scaffolds. Variations in the heating time did not have an effect in the pore area, porosity, water absorption capacity or mechanical properties of the scaffolds. We also demonstrated the ability of these scaffolds to support the proliferation of breast cancer cells. Overall, these results elucidated structure-property relationships in the fabricated micro-porous PCL scaffolds. Further, this procedure could be potentially scaled up for the fabrication of micro-porous PCL scaffolds.

Biochemical methane potential (BMP) of six perennial energy crops cultivated at three different locations in W-Germany

To mitigate the effects of climate change, the emission of greenhouse gases (GHG) should be reduced. In the near future, an increased use of biomass for energy production will be prescribed by law in the European Union (EU) to achieve the target of emission reduction. One possibility to use biomass energetically is its transformation into biogas. The most widely grown crop for this purpose is maize. Although, the increased use of maize as biogas feedstock, due to generous subsidies, is linked to several ecological and (socio)economic problems. The most important are soil erosion, depletion and compaction, high demand and subsequent leaching of fertilizers/biocides, heavy workload, and competition for land between food and energy production. In contrast, the use of second-generation perennial energy crops (PECs) as biogas feedstock can be an auspicious approach to improve the environmental footprint of biomass production. Therefore, we evaluated and compared the biochemical methane potential (BMP) of five different perennial species (cup plant, virginia mallow, tall wheatgrass, giant knotweed, reed canary grass) and a wild plant mix (composite of 25 in parts perennial plants) on three different sites in West-Germany. In terms of methane production per area, tall wheatgrass and reed canary grass exceeded the productivity of maize under favorable conditions. Hence, we recommend both species as biogas feedstock for Central Europe or comparable climates. Additionally, other species might be suitable for biomethanation from an overall perspective, to enhance (agro)biodiversity in rural areas.

Characterization of Al Skeletal Structures Fabricated by Ultrasonic Powder Consolidation

Skeletal aluminum structures were fabricated by ultrasonic powder consolidation (UPC) of NaCl—15 mass pct Al and NaCl—20 mass pct Al composites at 723 K and 773 K (450 °C and 500 °C) for 4 seconds and subsequent leaching of the spacer NaCl from the composites by dissolution in water. Ultrasonically consolidated skeletal specimens withstood ultrasonic washing in water, whereas control specimens fabricated under identical conditions, but without ultrasonic vibration, were severely disintegrated. Scanning electron microscopy and mass analysis indicated full removal of NaCl from the UPC specimens. Scanning transmission electron microscopy confirmed full densification and metallurgical bonding in the cell walls of UPC specimens consolidated at 773 K (500 °C). The mechanisms of rapid densification and bonding in the Al cell walls were elucidated based on microstructural changes during UPC.

Development of a strategy and interpretation of the NIR spectra for application in automated sorting

The Near Infrared (NIR) spectroscopy is a novel technique that can be used for early identification and separation of minerals from unwanted gangue during ore sorting. In this research, the potential of near infrared sensors for application in automated sorting was investigated on a copper-gold ore sample. The ore contains a substantial amount of carbonaceous material which results in excessive acid consumption in the subsequent leaching process during copper extraction. To classify this unwanted gangue material (carbonate) from the valuable metal (copper), a strategy to identify and distinguish the ore according to copper and carbonate content was developed. The near infrared spectra were measured on the surface of ore particles and characteristic absorption features were observed at a longer wavelength ranging from 2000 nm to 2405 nm. The results were then correlated with the chemical and mineralogical composition of the ore determined using X-Ray fluorescence and X-Ray diffraction equipments respectively. The near infrared spectra showed distinct characteristic absorption features for carbonate rich particles that distinguished these from copper bearing particles, which are fairly featureless at longer wavelengths. Combined interpretation of spectral features and chemical and mineralogical data indicates that near infrared-based sorting has potential for this type of ore.

High-performance porous polylactide stereocomplex crystallite scaffolds prepared by solution blending and salt leaching

Biodegradable stereocomplex crystallite polylactide (SC-PLA) porous scaffolds with well-defined pore structures, high heat resistance, mechanical strength, and solvent resistance together with good biocompatibility, were obtained through solution casting of mixed poly(l-lactide) and poly(d-lactide) solution and subsequent leaching of sodium chloride particles. The pore structure of the SC-PLA scaffolds can be perfectly maintained after a high-pressure sterilization treatment at 121 °C, owing to the extensive formation of stereocomplex crystallites in the scaffolds. In vivo pilot study demonstrates that the fibroblasts of rats can infiltrate into the SC-PLA scaffolds well through the open pores. Degradation tests in phosphate-buffered saline solution reveal that the structure of SC-PLA scaffolds was quite stable due to the enhanced hydrolysis-resistance and improved mechanical properties of the scaffolds. These results reveal that SC-PLA scaffolds with good biocompatibility are potentially to be used as implanted biomaterials for the regeneration and restoration of tissues or organs.

Influence of Thermal Treatment on Copper Extraction from Electronic Wastes

The results of studying the influence of the preliminary thermal treatment of crushed electronic waste (EW) at a temperature of 450°C on the copper extraction degree during the subsequent leaching of materials by solutions of nitric acid are presented. The waste of the electronic industry, in particular, automobile microcircuits and computer printed circuit boards, is chosen as a research object. It is experimentally determined that the percentage of the organic phase in the composition of the research object varies within the range of 20–25% of the mass of the crushed raw material. The results of thermogravimetric analysis (TGA) and X-ray fluorescence analysis (XRF) show that the maximum degree of organic removal and formation of oxide forms of metals are observed in the temperature range 400–450oC. A mathematical model of the copper leaching process from EW with nitric acid solutions is obtained. The optimum parameters for the process are found: the temperature in the system is 75°C, the duration of leaching is 150 min, and the concentration of acid is 4 M with the maximum copper extraction to the solution being 98%. A comparative analysis of leaching processes of two types of materials (after thermal treatment and without thermal treatment) was carried out. It is experimentally confirmed that, for materials after preliminary thermal treatment, more completed copper leaching from EW with nitric acid solutions of lower concentration is provided when compared to the leaching of raw materials without thermal treatment. It is proved that, due to the preliminary thermal treatment of the materials, phase changes occur in the composition of the research object, namely, the transition of metals to their oxide forms, which positively affects the degree of copper extraction from EW at the subsequent nitric acid leaching.