High-arsenic Copper Research Articles

Hot curing and lime boiling of high-arsenic copper concentrate pressure oxidation product and their effect on precious metals recovery during subsequent cyanidation

Hot curing and lime boiling of high-arsenic copper concentrate pressure oxidation product and their effect on precious metals recovery during subsequent cyanidation

Effect of lime (CaOH+) on chalcopyrite-arsenopyrite separation in high gradient magnetic separation: Experiment and molecular simulation

During the flotation of chalcopyrite from arsenopyrite, the addition of lime (with CaOH+ as the active component) can affect the subsequent high-gradient magnetic separation (HGMS) performance. However, this issue has been overlooked in previous researches. The present study confirms this effect and elucidates its underlying mechanism. Findings demonstrate that CaOH+ could decrease the magnetic moment of Fe atoms in chalcopyrite, deteriorating its separation from arsenopyrite via HGMS method. For a high-arsenic copper ore assaying 0.63 % Cu and 0.78 % As with chalcopyrite and arsenopyrite as the dominant copper-bearing and arsenic-bearing minerals, the HGMS results has confirmed that increasing the lime dosage from 0 kg/t to 14 kg/t reduced the copper grade in the copper concentrate from 0.92 % to 0.61 % and decreased the copper recovery from 67.03 % to 53.95 %. However, the arsenic grade and recovery in the concentrate were improved from 0.35 % to 0.64 % and from 28.27 % to 42.19 %, respectively. The calculations using Density Functional Theory and Crystal-Field Theory revealed that the interaction between Fe ions in chalcopyrite and CaOH+ in lime leads to a considerable change in the single electron occupancy of the d orbitals, that is, it transitions from a high-spin state to a low-spin state; thus, the magnetic susceptibility of the chalcopyrite decreases, reducing the HGMS efficiency for separation of chalcopyrite from arsenopyrite. The findings of this study provide considerable theoretical insights and improved understanding for the effect of lime on the chalcopyrite-arsenopyrite separation efficiency in HGMS process.

Hydrometallurgical technologies of processing arsenic raw materials

Methods presented in Russian and foreign scientific literature sources for processing high-arsenic copper raw materials to convert arsenic into low-soluble and stable compounds are reviewed. Hydrometallurgical processing methods are shown to be applicable for converting environmentally hazardous components into inert solid wastes while avoiding the formation of gaseous emissions. The isolation of arsenic when processing raw materials involves its oxidation and precipitation in the form of low-soluble and stable compounds. Methods for arsenic oxidation using oxygen, hydrogen peroxide, ozone, mixture of oxygen and sulphur dioxide, sodium hypochlorite are compared. Methods of oxidation by iron and permanganate ions, bacteria (biooxidation), as well as by introducing an activated carbon catalyst, are also considered. Precipitation approaches include neutralization by lime, precipitation of sulphides, co-precipitation of arsenic with iron ions, precipitation of scorodite, and encapsulation technology. As a result of the performed analysis, the authors present a promising approach for solving the problem of processing high-arsenic copper concentrates to comply with standards governing arsenic emissions into the environment, including the comprehensive processing of these raw materials using autoclave oxidation. In addition to the ensuring effective precipitation of arsenic in the form of a low-toxic compound (scorodite), this method can be used to isolate valuable components (copper, gold, silver) with their subsequent extraction into individual finished products. The obtained results establish a direction for a further in-depth study of the problem.

Leaching behaviors of copper and arsenic from high-arsenic copper sulfide concentrates by oxygen-rich sulfuric acid leaching at atmospheric pressure

High arsenic copper sulfide concentrates (HACSC) are becoming increasingly common in the world. Copper pyrometallurgy brings a series of problems, such as arsenic-containing dusts and waste acids that are difficult to treat. Hydrometallurgical process is an attractive alternative to treat HACSC. This work dealt with the leaching behaviors and kinetics of copper and arsenic from HACSC by oxygen-rich acid leaching at atmospheric pressure systematically. The leaching temperature, oxygen flux, liquid-solid ratio, sulfuric acid concentration and time have significant effect on the leaching of copper and arsenic. However, the effects on the copper leaching efficiency were much greater than that on the leaching efficiency of arsenic. The experimental optimization conditions were obtained as follows: temperature 80 °C, liquid-solid ratio 20:1, stirring speed 400 r·min-1, oxygen flux 2 L·min-1, sulfuric acid concentration 270 g·L-1. Under these conditions, > 99% copper was leached within 18 h, > 95% arsenic was leached within 36 h. The X-ray diffraction (XRD) and Scanning Electron Microscope/ Energy Dispersive Spectrometer (SEM/EDS) studies confirmed that the changes in the phases and morphologies before and after the leaching processes corroborated the leaching behavior of copper and arsenic. Furthermore, copper leaching kinetic model followed the shrinking core model of the couplings control of diffusion and surface chemical reaction. The activation energy was 36 kJ/mol. The kinetic equations for the effect of leaching temperature, oxygen flux and sulfuric acid concentration were obtained, respectively. The overall kinetic equation which can be applied in solids with particle families of limited size was also developed.

Alkaline sulphide leaching of tennantite in copper flotation concentrates to selectively dissolve arsenic

ABSTRACT High-arsenic copper flotation concentrates, in which the major arsenic-bearing mineral was tennantite, were leached with an alkaline sulphide system. At a pulp density of 5 wt% solids with 100–150 g/L Na2S and 50 g/L NaOH, over 91 wt% As was dissolved within 2 h at 100°C. From concentrates containing 3.4–4.9 wt% As, leach residues containing <0.5 wt% As were obtained making them suitable as a smelter feed without a penalty for arsenic. Copper dissolution ranged from 16 to 22 wt% Cu, with significant amounts of calcium, iron and sulphur also dissolved. In a leach at 34.0 wt% solids, excellent arsenic extraction was obtained (97.9 wt% As), but the levels of copper, calcium, and iron dissolution were 0.5, 1.1, and 0.2 wt%, respectively, meaning excellent selectivity for arsenic was achieved. X-ray diffraction and electron probe microanalyses indicated the mechanism for arsenic dissolution from tennantite, and bornite abundance in the residue.

Separation of arsenic and extraction of zinc and copper from high-arsenic copper smelting dusts by alkali leaching followed by sulfuric acid leaching

Separation of arsenic and extraction of zinc and copper from high-arsenic copper smelting dust (HACSD) is one of the difficulties in the world. A two-stage countercurrent alkali leaching followed by one-stage sulfuric acid leaching for arsenic separation and zinc and copper extraction was developed in this work. The dusts properties, metals leaching behaviors and their phase transformations in the alkali leaching and sulfuric acid leaching were explored systematically. Results indicate that >95.5% of As was successfully separated from HACSD into alkali leachate. Arsenic and metals (Zn, Pb, Bi, Sn) contents were up to 61.50 g·L−1 and as low as 0.001–0.21 g·L−1 in alkali leachate, respectively. >97.2% of Zn and >96.4% of Cu were extracted from the alkali leaching residues into sulfuric acid leachate. The sulfuric acid leaching residues were enriched with 34.16% of Pb, 8.38% of Bi and 11.54% of Sn in oxides and sulfates phases. The metals leaching behaviors, phase transformations and microstructure of metal compounds during the leaching processes were confirmed by X-ray diffraction and scanning electronic microscopy/energy dispersive spectroscopy. The proposed process offered high separation efficiency of arsenic, zinc and copper, as well as low environmental pollution.

Treatment of high-arsenic copper smelting flue dust with high copper sulfate: Arsenic separation by low temperature roasting

Arsenic is the most important hazardous trace element in copper concentrates. In order to separate arsenic from the smelting processes, a pyrometallurgical treatment with additives was developed to deal with high-arsenic copper smelter flue dust high in copper sulfate. Under the optimized conditions of mixing 30 wt% pyrite and roasting at 550 °C under an inert atmosphere for 30 min, more than 92% arsenic was volatilized as a high purity arsenic trioxide by-product while most copper was retained in the calcine to be returned to smelting as a high-copper feed. The high separation of arsenic is due to the transformation from the limited vaporization of arsenate to volatile arsenic trioxide by pyrite at above 460 °C. Two reaction paths of pyrite were identified as follows: one followed the pattern FeS2 → Fe2O3 → FeAsO4 → Fe3O4/Fe2O3 and the other was FeS2 → FeS + S2 (g) → Fe3O4/Fe2O3.

Partial Roasting of High-Arsenic Copper Concentrates

The partial roasting of high-arsenic copper concentrates at 973 K/998 K (700 °C/725 °C) under controlled atmosphere can remove > 95 pct of the arsenic contained in the concentrates, leaving a calcine with 52 to 68 wt pct bornite, 10 to 13 wt pct chalcopyrite and 2 to 5 wt pct magnetite, with 8 to 24 wt pct remnant chalcocite. The mineralogic composition of the calcine obtained is consistent with the calculated mineralogic composition based on the chemical analysis of the calcine and the gaseous phase in equilibrium with the calcine. The formation of the new solid phases present in the calcine (bornite and chalcopyrite) should take place in the emulsion phase of the fluidized bed, while the oxidation of part of the gaseous sulfur generated by thermal decomposition of the sulfides present in the concentrate could occur in the evolving cloud and wake surrounding the air bubbles in the emulsion phase of the fluidized bed.

Thermodynamic and Kinetic Mechanisms of Bornite/Chalcopyrite/Magnetite Formation During Partial Roasting of High-Arsenic Copper Concentrates

A thermodynamic and kinetic model is proposed to explain the formation of bornite, chalcopyrite, and magnetite during partial roasting of enargite-containing copper concentrates. The proposed mechanism involves solid–solid–gas and solid–gas reactions between chalcocite, pyrrhotite, gaseous sulfur, and oxygen. Bornite formation could be explained through a mechanism of simultaneous formation of bornite and chalcopyrite from Cu2S + FeS + gaseous sulfur. After the initial formation of a bornite/chalcopyrite layer, solid-state diffusion appears to control these reactions, with faster diffusion kinetics favoring the formation of chalcopyrite over that of bornite. The newly formed chalcopyrite reacts continuously with additional Cu2S to form bornite up to the complete disappearance of either the available Cu2S or FeS. Although thermodynamically the direct formation of bornite is more favorable than that of chalcopyrite, the lower diffusion kinetics of bornite formation could explain the preferential formation of chalcopyrite prior to the formation of bornite. Without enough chalcocite to form bornite by reaction with chalcopyrite, no bornite can be formed, leaving chalcopyrite as the only reaction product. In the presence of oxygen, chalcocite and pyrrhotite form magnetite, chalcopyrite, and SO2. The proposed model is thermodynamically consistent with the experimental results obtained in the laboratory.

Element Distribution in Oxygen-Enriched Bottom-Blown Smelting of High-Arsenic Copper Dross

An oxygen-enriched bottom-blown smelting process has been proposed to extract valuable metals and remove arsenic from high-arsenic copper dross. PbO, PbS, Cu2S, and Cu5As2 were the main components of the copper dross. Iron scrap, calcium carbonate, coke, and silica were added as flux in the smelting process. Mineralogical analysis revealed that the smelting products were ferrous calcium silicate slag, lead copper matte (PbS and Cu2S), speiss (Cu3As), crude lead (Pb), and dust. Approximately 35% of copper distributed to lead copper matte, while 56% of copper and 75% of arsenic reported to speiss. The Cu concentrated in economical products for further extraction reached 91%, 87% of Pb was directly recovered to crude lead, and the As removed to dust was 4–6%. The technology was first developed and applied in industry by Henan Yuguang Gold and Lead Group Co., LTD, providing an efficient approach and production experience for copper dross recycling.

A Preliminary Study on the Loss of Iron and Arsenic in the Re-Melting of Iron-Bearing Arsenical Copper

Re-melting experiments were conducted with specimens made of high-arsenic copper alloys containing lead, iron and sulphur. The melting treatment at 1000°C in ambient conditions for 5 min was found to cause an almost complete removal of iron and sulphur along with a notable reduction of arsenic levels. Evidence was found that the preferential oxidation of iron and arsenic was responsible for this change in composition. The treatment also brought about perfect dissolution of speiss particles scattered throughout the original specimen, suggesting the possibility of the addition of speiss to molten copper for the production of arsenical copper.

Arsenic-rejection flotation circuit design and selection based on a multiple-objective evaluation

This paper describes the application of a shortcut computational method to analyse and compare alternative flotation circuits developed to treat high-arsenic copper ores. The methodology uses a superstructure that considers the many different available elements of the flotation circuits and compares the results. The circuits were evaluated using radial/spider graphs, and were evaluated based on the metric indices of efficiency, capacity, quality, economics and environmental impact.The simulations were performed for a superstructure that considered 27 flotation circuits for an Australian sulphide ore containing chalcopyrite, tennantite, quartz and pyrite. The starting circuit corresponded to the flotation circuit described in previous work on this ore (Haque et al., 2010; Bruckard et al., 2010), and was used as the basis for comparison of the alternative flotation circuits.The key result of the analysis is that the base condition is one of the best circuits with respect to the copper grade in the concentrates, CO2 emission, and fresh water usage. However, the base condition is one of the most inefficient circuits with respect to the percentage of arsenic in the products, profit, and copper recovery. This study shows that there are more suitable flotation circuits available than the stated base condition for a specific goal and/or multiple goals.

Study on Comprehensive Utilization of Arsenic from High Arsenic-Bearing Copper Sulphide Concentrate

In this paper a new technology for comprehensive utilization of arsenic in high-arsenic copper sulfide concentrate has been studied out. Firstly,the concentrate was bioleached by moderate thermophile Sulfobacillus thermosulfidooxidans, under the suitable leaching conditions, the experiments results show that the concentrate is bioleached 82% of Cu,78% of As and 40% of Fe. Secondly, removal of Fe3+ by solvent extraction with P204 from bacterial leaching solution are presented, and Fe3+ is extracted up to 93％, and the content of Fe3+ in raffinate is under 9 mg/L. The comprehensive utilizations of most of arsenic from leaching liquor after removal Fe3+ has been carried out. When the temperature is 80 to 90°C, pH at 4.0~5.0 and ammonia as a neutralizer, the results of XRD analysis show that the forming process of copper arsenate is complicated, and the formed molecular formulas are in different types, and they are CuAs2O4, Cu5As2O10•5H2O, C4H6As6Cu4O16, Cu5As4O15•9H2O and Cu2AsO4OH•3H2O. The comprehensive utilizations of most of arsenic are in the form of copper arsenate, and the content of arsenic is 9.11~35.82mg/L in solution after its precipitated. This study provides a new treatments and process for the utilization of arsenic in the high-arsenic copper sulfide concentrate.

Comparison of Bioleaching High Arsenic-Bearing Copper Sulphide Concentrate Using Thiobacillus Ferrooxidans and Sulfobacillus Thermosulfidooxidans

The usage of high-arsenic sulfide copper concentrate were limited because the arsenic in the concentrate harms the qualities of copper product and pollutes the environment. In this paper an innovative process for high-arsenic copper sulfide concentrate with with bio-oxidation respectively Thiobacillus ferrooxidans and moderate thermophile Sulfobacillus thermosulfidooxidans has been studied out, and the influencing factors have been comparative studied during the leaching process, such as concentration particle size, leaching methods, pulp concentration, leaching time and the initial concentration of Fe3+, etc. Under the suitable leaching conditions, the experiments results show that the concentrate is leached 47.13% of Cu,50.09% of As and 52.46% of Fe by Thiobacillus ferrooxidans and 82.39% of Cu,78.21% of As and 40.38% of Fe by moderate thermophile Sulfobacillus thermosulfidooxidans. The high concentration initial Fe3+ has speeded leaching process up in the presence of moderate thermophile Sulfobacillus thermosulfidooxidans, and when the pulp initial concentration of Fe3+ is in the range of 0.08~0.32mol/L, the leaching rate of Cu is 86.34~97.06%, As 89.22~94.13%. It is concluded that Sulfobacillus thermosulfidooxidans have a better effect on bioleaching high-arsenic sulfide copper concentrate than Thiobacillus ferrooxidans.

Thermomechanistic model for the processing of a high-arsenic copper concentrate in a duplex fluidized bed reactor

A thermomechanistic model was developed for the thermal decomposition of the enargite contained in a copper concentrate at 650° to 750°C in a fluidized bed with an inert atmosphere. At the particle level, the model permits one to predict the thermal profile inside the reacting enargite particles, as well as their thermal cycle. At the macroscopic level, a population-based model coupled to the bubbling-bed fluidized bed model allows one to predict the fractional conversion (dearsenification) of an enargite-bearing copper concentrate.