Copper Extraction Yield Research Articles

Synergistic catalytic effect of chloride ion and ammonium ion on the leaching of chalcopyrite in sulfuric acid solution

To enhance the leaching of chalcopyrite in sulfuric acid solution at atmospheric temperature, chloride (Cl−) and ammonium (NH4+) were employed in this paper. Action of these additives in chalcopyrite leaching was explored, with an emphasis on the synergistic catalytic effect of Cl− and NH4+. It was demonstrated that the single addition of Cl− and NH4+ could promote the chalcopyrite leaching process respectively. However, the amount of copper ions extracted in the presence of NH4Cl was significantly higher than the sum of that of Cl− and NH4+. With the separate addition of 1 mol/L NaCl, (NH4)2SO4 and NH4Cl, the copper extraction yield of chalcopyrite was 264.1, 138.8 and 598.5 mg/L respectively, while that of the control group was only 69.6 mg/L after 15 days. XRD and SEM-EDS results showed that covellite (CuS) was formed in the control system, while elemental sulfur (S0), atacamite (Cu2Cl(OH)3) and copper ammonium chloride complex (Cu(NH4)6Cl2) were newly formed in the presence of NH4Cl. In addition, chalcopyrite dissolution was controlled by the diffusion model supported by kinetic modelling, while it turned into chemical reaction with NH4Cl addition, indicating that the formed passivation layer was eliminated. This study suggests that the combination of Cl− and NH4+ can provide a novel approach for promoting the chalcopyrite leaching in sulfuric acid media.

Effect of organic and inorganic compounds on dissolution kinetics of chalcopyrite in hydrogen peroxide– Hydrochloric acid system

The addition of 2-Propanol as an organic substance and NaCl as an inorganic compound in hydrochloric acid with hydrogen peroxide as a strong leaching agent of chalcopyrite was investigated. The effects of the leaching parameters on copper extraction, such as stirring speed, H2O2 concentration, temperature, HCl concentration and solid/liquid ratio were studied. The maximum final copper extraction of 54.55% was obtained with 600 rpm stirring speed, 1.5 M H2O2, 0.5 M HCl, 600 rpm, 50 °C, 240 min of the reaction and particle size of −106 +75 µm. Further experiments were performed when the solid-to-liquid ratio (S/L), stirring speed, temperature, HCl, H2O2 and leaching time were kept constant to examine the influence of NaCl and 2-Propanol concentrations in the range of 0–0.5 M and 0–3 M, respectively. The results showed that the copper extraction was increased up to 58.11% with addition of NaCl. While copper extraction yield reached 94.25% in case of addition of 2-propanol with the optimum parameters(0.5 M HCl,50 °C, 1.5 M H2O2, 600 rpm, particle size −106 +75 μm, solid liquid ratio 2g/L, 3 M 2-propanol). The chalcopyrite leaching in hydrogen peroxide– hydrochloric acid system was found to be described by the interface transfer and diffusion across the product layer with activation energy of 77.14 kJ/mol. Addition of 2-propanol suggested that the reaction was under product layer diffusion control and decreased the activation energy of chalcopyrite leaching to 67.98 kJ/mol.

Extraction of copper from chalcopyrite with potassium dichromate in 1-ethyl-3-methylimidazolium hydrogen sulfate ionic liquid aqueous solution

Developing new and sustainable leaching system with limited release of pollutant and low acid and energy consumption is a challenge for copper extraction from chalcopyrite. In this work, a hydrometallurgical process for chalcopyrite dissolution in 1-ethyl-3-methyl-imidazolium hydrogen sulfate ([EMIm]HSO4) media with potassium dichromate (K2Cr2O7) was developed, and the leaching behavior of chalcopyrite with various parameters, such as kinds of ionic liquids (ILs), concentrations of [EMIm]HSO4 and K2Cr2O7, stirring speed, leaching temperature, and particle size were discussed in detail. The result show that the most effective ILs medium for chalcopyrite dissolution was varied with the specific oxidant. The leaching rate of chalcopyrite was significantly enhanced by increasing temperature, concentrations of K2Cr2O7 and [EMIm]HSO4, and decreasing particle size, while it has little to do with the increasing of stirring speed. The maximum copper extraction yield of 90.2% was reached within 90 min under the following optimized conditions: 10 g/L of solid/liquid ratio, 10 vol% of [EMIm]HSO4 concentration, 0.1 M of initial K2Cr2O7 concentration, stirring speed of 200 rpm, the temperature of 70 °C and particle size of −45 µm. The leaching process of chalcopyrite in [EMIm]HSO4-K2Cr2O7 aqueous solution follows an empirical kinetic model 1-2/3x-(1-x)2/3=kdt with the apparent activation energy of 36.26 kJ/mol, which was limited by the diffusion through a protect layer of elemental sulfur and pyrite.

Optimization of nanofiltration for treatment of acid mine drainage and copper recovery by solvent extraction

The high levels of metals and sulfate ions in acid mine drainage (AMD) constitutes a severe risk to the environment. Our study evaluated at pilot-scale the operational conditions of actual AMD nanofiltration (NF) to recover water and subsequent recovery of copper from the concentrated retentate solution by a solvent extraction (SX) process. NF showed a high copper concentration capacity (0.6 to 2.4 g/L) and good total rejection of species (~82%). While NF treatment allowed a high water recovery of 80%, the polarization resistance could limit its performance. A 1.1 g/L copper retentate solution was selected for use in the SX study to prevent membrane fouling in a possible in-series process (NF-SX). Equilibrium isotherms and McCabe-Thiele diagrams obtained using LIX 84-IC as the extractant indicated that using two countercurrent extraction stages and one stripping stage, it could be recovered 97% of the copper. The use of antiscalants and CaSO4 precipitates formed during NF had a negligible effect on the copper extraction yield by SX. The combined NF-SX results showed that a high recovery of water and copper from AMD is possible. This technology can have an impact on the reduction of freshwater consumption and wastewater treatment costs of mining, and its development is the subject of further research work.

Optimizing acid leaching of copper from the wastewater treatment sludge of a printed circuit board industry using factorial experimental design

Heavy metal containing sludge from printed circuit board production (PCB) is not only classified as hazardous waste, but also as a potentially valuable raw material for copper recovery. Since sludge leaching is a significant first step in copper extraction yield via hydrometallurgy, we assessed the optimum copper acid-leaching conditions using a Design of Experiment (DOE) approach (33 full factorial design) and the multiple response method called the desirability (D) function. The effects of acid concentration, the ratio of acid volume to sludge quantity (“L/S ratio”), and leaching time on copper-leaching efficiency were evaluated. The model equation derived using Minitab 17.0 predicts that copper-leaching efficiency can reach 97.0% at optimal values of 0.84 M sulfuric acid, L/S ratio of 100:1, and a leaching time of 80 min. Experiments verified a 96.8% ( $$\sigma = 0.4\% )$$ copper-leaching efficiency. The small discrepancy between predicted and experimental data showed that the DOE approach was a suitable tool for predicting leaching efficiency from PCB sludge by sulfuric acid.

添加 NaCl 提高黄铜矿的铜提取率

The addition of NaCl in the ammonium persulfate-APS (as an oxidant) leaching was investigated. APS has some advantages compared with conventional oxidants and its standard redox potential (E°) is 2.0 V. Effect of six parameters such as NaCl concentration, APS concentration, temperature, time, liquid–solid ration (L/S), and stirring speed on the leaching behavior was studied. Results showed that metals extraction increased with increasing of NaCl concentration, APS concentration, leaching temperature (up to 333 K), and L/S ratio. During oxidative leaching of sulfide minerals, the occurrence of elemental sulfur layer on particle surface is known as primary problem that causes low metal extraction. According to the results, the passivation effect of sulfur layer and low dissolution problems can be eliminated in the presence of chloride ions. Copper and iron extraction yields were obtained as 75% and 80%, respectively under leaching conditions as follows: APS concentration 250 g/L; NaCl concentration 150 g/L; time 180 min; temperature 333 K; stirring speed 400 r/min; and L/S 250 mL/g.

Agitation and column leaching studies of oxidised copper-cobalt ores under reducing conditions

Sulphuric acid agitation and column leaching tests of an oxidised copper-cobalt-bearing ore (1.44% Cu and 1.04% Co) were performed to investigate its amenability to copper and cobalt metals extraction under reducing conditions. Oxidised copper-cobalt-bearing ores from the Congolese Copperbelt contain a large proportion of cobalt in trivalent form, which is readily soluble in solutions of sulphuric acid, provided a reducing agent is also present. Sodium metabisulphite (Na2S2O5) is one of the most commonly recommended reducing agents, but its addition during the leach phase could cause significant environmental problems and could affect copper recovery if present in large amounts. During leaching, sodium metabisulphite reacts with sulphuric acid and dissociates to form SO2 which in fact reduces Co(III). However, SO2 is only partially utilised, and much of it is entrained unreacted in the leach liquor. A large accumulation of SO2 can become uncontrollable and therefore escape to the environment if not consumed by the ore. The paper presents and discusses the effect of recirculation of the leach liquor after pH readjustment to 1.5 on the minimisation of unreacted SO2 entrained in the leach liquor, sulphuric acid consumption; and the overall improvement of copper and cobalt extraction yields. The most important information found is that recirculation of the leach liquor proved to be very useful in reducing the amount unreacted SO2 and significantly increasing recovered metals yields with little acid consumption. Moreover, the injection of Na2S2O5 solution at 75% of the column bed-height considerably reduced the potential risks of SO2 emanation.

Leaching of chalcopyrite with hydrogen peroxide in 1-hexyl-3-methyl-imidazolium hydrogen sulfate ionic liquid aqueous solution

Seeking new solvents for green processing of chalcopyrite at low temperature with low energy and acid consumption as well as low pollutant release is key task in hydrometallurgy of chalcopyrite. In the present study, 1-hexyl-3-methyl-imidazolium hydrogen sulfate ([HMIm]HSO4) aqueous solution was used to leach copper from chalcopyrite at ambient temperature with hydrogen peroxide (H2O2) as oxidant. The effects of particle size, stirring speed, leaching temperatures, the types of ionic liquids, and the concentrations of H2O2 and [HMIm]HSO4 on copper extraction were systematically examined. A high copper extraction yield of 98.3% has been achieved in 10% (v/v) [HMIm]HSO4 aqueous at 45°C after 120min with 25% H2O2, particle size under 45μm, and solid/liquid ratio of 10g/L. It was found that particle size and temperature, as well as the concentrations of H2O2 and [HMIm]HSO4 had a significant influence on the leaching rate of chalcopyrite, while the stirring speed has little effect. The empirical kinetic model, −ln(1−x)=kt was used to describe the kinetics of copper extraction in [HMIm]HSO4 aqueous solution, the results showed that the leaching process was controlled by a surface chemical reaction with an apparent activation energy of 52.06kJ/mol.

Column leaching of low-grade sulfide ore from Zijinshan copper mine

Copper and iron dissolution of Zijinshan low-grade copper sulfide ores was investigated in ore-packed columns. At 60°C and pH1.0, 37.1gFe(III)L−1 permitted effective copper dissolution and inhibited the activity of iron-oxidizing microorganisms. At 30°C, microorganisms stimulated Fe(II) and pyrite oxidation, resulting in 85 and 54% of copper and pyrite extraction yields, respectively. Bacteria belonging to the genera Acidithiobacillus and Leptospirillum were dominant as observed by real-time PCR assay. Aeration and inoculation of columns were not necessary. Solutions had a higher pH of 1.7 in the columns operated without recirculation. Under these conditions, copper extraction was not affected and Fe(III) precipitated as jarosite, indicating a novel method for iron control in Zijinshan copper mine.

The Leaching Behaviours of Chalcopyrite with Distinct Genetic Types

The copper extraction yield from chemical leaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as on the different genetic type of the chalcopyrite used. The chemical leaching characteristics of chalcopyrite from marine volcanic type and porphyry type were studied. It was found that the intermediates of marine volcanic chalcopyrite and porphyry chalcopyrite elucidated from the MLA were elemental sulphur and non-stoichiometric minerals, such as Cu3.5Fe4S2.5, Cu5Fe4S and Cu3.5Fe1.5S5. The results suggested that the main difference between marine volcanic chalcopyrite and porphyry chalcopyrite is the rates of copper and iron ions dissolution from chalcopyrite crystal lattice.

Direct selective leaching of chalcopyrite concentrate

The ammonium persulphate (APS) leaching of chalcopyrite concentrate in the presence of ammonium carbonate was studied. The effects of ammonium carbonate concentration, APS concentration, leaching time, leaching temperature, solid/liquid ratio and stirring speed were investigated. Optimum leaching conditions were found as follows: APS concentration is 200 g L−1; ammonium carbonate concentration is 200 g L−1; leaching time is 180 min; leaching temperature is 60°C; solid/liquid ratio is 0·04 g mL−1; and stirring speed is 400 rev min−1. Under these conditions, copper extraction yield was obtained at about 72%. Furthermore, iron extraction yield decreased with increasing ammonium carbonate concentration and iron did not pass into solution under this condition. X-ray and SEM analysis also supported these results. It was determined that the copper extraction results were satisfactory by way of all experiments were performed under atmospheric conditions (i.e. low temperature and atmospheric pressure) and achieved selective copper leaching from chalcopyrite concentrate.On a étudié la lixiviation au persulfate d’ammonium (APS) du concentré de chalcopyrite en présence de carbonate d’ammonium. On a examiné l’effet de la concentration du carbonate d’ammonium, de la concentration d’APS, de la durée et de la température de lixiviation, du rapport solide-liquide et de la vitesse d’agitation. Les conditions optimales de lixiviation suivent: concentration d’APS = 200 g L−1; concentration de carbonate d’ammonium = 200 g L−1; durée de lixiviation = 180 min; température de lixiviation = 60°C; rapport solide-liquide = 0·04 g mL−1; et vitesse d’agitation = 400 rpm. Avec ces conditions, le rendement d’extraction du cuivre était d’environ 72%. De plus, le rendement d’extraction du fer diminuait avec l’augmentation de la concentration de carbonate d’ammonium, qui empêchait également le fer de passer en solution. L’analyse aux rayons x et au SEM supportait également ces résultats. Grâce à toutes les expériences effectuées en conditions atmosphériques (c’est-à-dire à basse température et à pression atmosphérique), on a déterminé que les résultats d’extraction du cuivre étaient satisfaisants et qu’on obtenait une lixiviation sélective du cuivre à partir du concentré de chalcopyrite.

Bioleaching of low-grade copper sulfide ores by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans

The grown conditions of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were investigated, and then experiments were conducted to research the bioleaching behaviors of crude ore of copper sulfide and hand-picked concentrates of chalcopyrite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The experimental results show that the bacteria grow best when the temperature is (30±1) °C and the pH value is 2.0. The bacteria concentration is 2.24×107 mL−1 in this condition. It is found that the copper extraction yield is affected by the inoculum size and the pulp density and the extraction yield increases as the inoculum size grows. The bioleaching rates reach their highest point in sulfide copper and chalcopyrite with a pulp density of 5% and 10%, respectively. Column flotation experiments of low-grade copper sulfide ores show that the bioleaching recovery reaches nearly 45% after 75 days.

The Bioleaching Characteristics of Chalcopyrite with Different Genetic Types

The copper extraction yield from thermophilic bioleaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), the activity of the thermophile used, as well as on the different genetic type of the chalcopyrite used. The bioleaching characteristics of chalcopyrite from marine volcanic type and porphyry type, and the influence of genetic type on microbial community were studied. The results indicated that the bioleaching of chalcopyrite is controlled by the ORP rather than by the pH. The thermophiles composition of marine volcanic type bioleaching wasMetallosphaeracuprinaandSulfobus spHB59.Metallosphaeracuprinawas the dominate bacteria during porphyry chalcopyrite bioleaching. The different leachability between marine volcanic type and porphyry type is attributed to their nature which caused by genetic type.

Study on the influence of various factors in the hydrometallurgical processing of waste printed circuit boards for copper and gold recovery

The present lab-scale experimental study presents the process of leaching waste printed circuit boards (WPCBs) in order to recover gold by thioureation. Preliminary tests have shown that copper adversely affects gold extraction; therefore an oxidative leaching pre-treatment was performed in order to remove base metals. The effects of sulfuric acid concentration, hydrogen peroxide volume and temperature on the metal extraction yield were studied by analysis of variance (ANOVA). The highest copper extraction yields were 76.12% for sample A and 18.29% for sample D, after leaching with 2M H2SO4, 20ml of 30% H2O2 at 30°C for 3h. In order to improve Cu removal, a second leaching was performed only on sample A, resulting in a Cu extraction yield of 90%. Other experiments have shown the negative effect of the stirring rate on copper dissolution. The conditions used for the process of gold extraction by thiourea were: 20g/L thiourea, 6g/L ferric ion, 10g/L sulfuric acid, 600rpm stirring rate. To study the influence of temperature and particle size, this process was tested on pins manually removed from computer central processing units (CPUs) and on waste CPU for 3½h. A gold extraction yield of 69% was obtained after 75% of Cu was removed by a double oxidative leaching treatment of WPCBs with particle sizes smaller than 2mm.

Effect of surfactant Tween-80 on sulfur oxidation and expression of sulfur metabolism relevant genes of Acidithiobacillus ferrooxidans

The effects of surfactant Tween-80 on the growth, sulfur oxidation, and expression of selected typical sulfur metabolism relevant genes of Acidithiobacillus ferrooxidans ATCC 23270 were investigated. The results showed that in the presence of 10−2 g/L Tween-80, the growth of A. ferrooxidans and its metabolism on the insoluble substrate S0 and CuFeS2 were promoted. After 24 d of bioleaching, the copper extraction yield of chalcopyrite at 10−2 g/L Tween-80 increased by 16% compared with the bioleaching experiment without Tween-80. FT-IR spectra analysis revealed that the result was probably caused by the extracellular polymeric substances whose composition could be changed by the surfactant addition. RT-qPCR was used to analyze the differential expressions of 17 selected sulfur metabolism relevant genes in response to the addition of Tween-80. Down-regulation of the extracellular protein genes indicated the influence of Tween-80 on bacteria-sulfur adsorption. Variation of the expression level of the enzymes provided a supplement to sulfur metabolism investigation.

Metal ion removal by ultrafiltration of colloidal suspensions of organically modified silica

Porous fumed silicas (FS) covalently grafted with 5-phenyl-azo-8-hydroxyquinoline (5Ph8HQ) are considered as extractants for copper(II) and nickel(II) at low concentration levels (10–50μM). The separation of the extracting colloidal functionalized silicas particles from the bulk aqueous phase is achieved by means of the frontal ultrafiltration technique. The stability of the colloidal dispersion of the organically modified silica and of the covalent grafting itself is studied via the loss of silica or of 5Ph8HQ through the ultrafiltration membrane during the separation process. The effects of the anion nature, specific surface area, surface ionization state on the metal ions extraction are assessed. For the sake of comparison, the extraction of copper(II) by 5Ph8HQ solubilized in neutral Triton X-100 (TX-100) micelles has been studied in the most similar experimental conditions, as well as copper(II) extraction by the same ligand in a biphasic water–chloroform system. High copper extraction yields are attained, and taking into account the low volume of extracting phase of the dispersed colloidal silica, high separation factors are obtained. The stoichiometry of the formed complex is the same (1:1) in the two microheterogeneous systems considered here whereas a 2:1 complex is formed in the biphasic liquid–liquid system. The apparent stability constant is greater by a factor 10 in the micelles than for the silica bounded 5Ph8HQ systems but the true affinity of the ligand for copper is 5 times lower in the micelle than on the functionalized systems. Comparing to the literature, it is shown that the type of silica considered (colloidal fumed silica in this work versus silica gel in the literature) greatly influences the affinity of the ligand toward the copper. Finally, the apparent extraction constant in 5Ph8HQ modified silica is ten times higher for copper(II) than for nickel(II).

Elimination of Cu(II) from Aqueous Solutions by Liquid-liquid Extraction. Test of Sodium Diethyldithiocarbamate (SDDT) as an Extracting Agent

The presence of heavy metals in industrial wastewaters, can be an important source of pollution, and may be a severe health hazard, due to their toxicity and to the fact that they are not amenable to biological degradation. Copper is a typical environmental heavy metal pollutant. It is considered in the present study since at high concentration exceeding certain limits, it may cause severe mucosal and a central nervous irritations, necrotic changes in the liver and kidney, etc. So it is necessary to treat wastewaters containing this heavy metal to reduce its concentration before discharge.Different and traditional methods for the removal and recovery of copper from industrial waste streams do exist each having its lacks and shortcomings. One can cite precipitation, ion exchange, electrolysis, adsorption on activated carbon and liquid-liquid extraction which is used in the present work.The main objective of the present experimental work is the determination of the best conditions for the extraction of Cu(II) ions from aqueous solutions, using sodium diethyldithiocarbamate (SDDT) as the extracting agent and different organic solvents, such as chloroform and dichloromethane, as diluents.The analysis of the aqueous phase after separation was performed by means of an atomic absorption spectrophotometer.The obtained experimental results showed that high copper extraction yields are achieved for an added extracting agent mass greater than 7.5mg, fixing the aqueous phase pH at 9. The results showed that the extraction process was more efficient when using dichloromethane rather than chloroform, although this latter is more used in practice.

Influence of indigenous and added iron on copper extraction from soil

Experimental tests of copper leaching from a low permeability soil are presented and discussed. The objective of the experiments was to investigate the influence of indigenous and added iron in the soil towards copper mobilization. Metals’ leaching was performed by flushing (column tests) or washing (batch tests) the soil with an aqueous solution of ethylenediaminetetraacetic acid, EDTA. An excess of EDTA was used in flushing tests (up to a EDTA:Cu molar ratio of about 26.2:1), while, in washing tests, the investigated EDTA vs. copper molar ratios were in the range between 1 (equimolar tests) and 8. Copper extraction yield in flushing tests (up to about 85%) was found to depend upon contact time between the soil and the leaching solution and the characteristics of the conditioning solution. The saturation of the soil with a NaNO 3 solution before the treatment, favoured the flushing process reducing the time of percolation, but resulted in a lower metal extraction during the following percolation of EDTA. The indigenous iron was competitive with copper to form EDTA complexes only when it was present in the organic and oxides–hydroxides fractions. Artificial iron addition to the soil resulted in an increase of both the exchangeable iron and the iron bonded to the organic fraction of the soil, thus increasing the overall amount of iron available to extraction. In both batch and continuous tests, the mechanism of copper extraction was found to involve the former dissolution of metal salts, that lead to an initial high concentration of both copper and selected competitive cations (essentially Ca 2+), and the following EDTA exchange reaction between calcium and copper complexes. The initial metal salts dissolution was found to be pH-dependant.

Bioleaching of chalcopyrite with thermophiles: Temperature–pH–ORP dependence

The copper extraction yield from thermophilic bioleaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as on the activity of the thermophile used. The copper extraction yields obtained with three thermophiles under various pH and temperature conditions and with different initial amounts of Fe 3+ were studied. The results indicated that because of the low ability of Acidianus brierleyi to leach iron as Fe 3+, high biomass concentrations were reflected by ORP close to a critical value (450 mV, Ag 0/AgCl reference), at which copper extractions were highest. By contrast, because of the higher ability of Sulfolobus metallicus and Metallosphaera sedula to leach iron as Fe 3+, high biomass concentrations were reflected by high ORP which in combination with the precipitation of Fe 3+ as jarosite attenuated the leaching rates. Therefore, optimum temperatures for the growth of thermophiles did not always mean high copper extraction yields. Generally, highest copper extractions were obtained at initial pH 1.5. However, higher copper extractions were observed at initial pH 2.5 than at pH 2.0, suggesting that at high pH the bioleaching of chalcopyrite is controlled by the ORP rather than by the pH or temperature. The bioleaching capacity of A. brierleyi was reduced or suppressed when insufficient initial Fe 3+ was provided to trigger the leaching reaction, whereas S. metallicus and M. sedula were less sensitive to the initial availability of Fe 3+. This result confirmed that a direct enzymatic attack on the mineral surface could initiate the leaching reaction, but later ORP governed the leaching rate of chalcopyrite.

Influence of Soil Organic Matter on Copper Extraction from Contaminated Soil

Column experiments of copper extraction from four contaminated soils characterized by a content of Soil Organic Matter (SOM) ranging from 1% to 25% are presented and discussed. The extraction was performed by flushing the soil with an aqueous solution of a sodium salt of ethylene diamminotetraacetic acid (EDTA). Preliminary tests were performed on a soil containing 25% of organic matter, to investigate the influence of pH, concentration and volumes of EDTA on its chelant action and on the dissolution of SOM. Having selected the optimal conditions for the extraction process, a further series of tests was conducted on the four soils to evaluate the influence of organic content on copper extraction yields. EDTA solutions at 0.01 M, 0.05 M, 0.1 and 0.2 M were injected at 0.33 ml/s; copper and organic matter extraction yield were determined. At a pH of 5, 15 pore volume (PV) of a solution containing 0.05M EDTA, extracted about 99% of copper contained by the soil with the higher organic matter content. Under the same conditions, and for soil with > 6% SOM, extraction yields over 80% were achieved, while at lower organic content, copper extraction was dramatically reduced. This was attributed to the formation of highly stable copper-humate complexes and to their increasingly dissolution that occurred in the soils with higher organic matter level. Experimental tests performed at different contamination levels (1200 mg/kg, 2400 mg/kg) showed that EDTA extraction effectiveness also depended upon initial soil Cu concentration.