Evaluation of coating performance on carbon steel A-36 in copper concentrate environment using electrochemical impedance spectroscopy

The presence of chalcopyrite increases the corrosion rate of carbon steel through a galvanic couple. In this study, five organic coating systems were evaluated for their strength against consequent corrosion in the presence of copper concentrate by electrochemistry impedance spectroscopy (EIS) measurement. The coating system studied are a single application epoxy coating (C1); a three-layer epoxy system with zinc-rich epoxy primer base coat, surface tolerant epoxy middle layer, and a top layer polyurethane (C2); a three-layer epoxy system that has the advantages of fast dry time consist of epoxy zinc phosphate base coat primer, the middle layer of the epoxy primer containing the pigment zinc phosphate and top layer polyurethane (C3); metallic pigmented polyurethane coating (C4), and an epoxy coating which can be applied to wet surfaces or in water (C5). All those systems have been tested by the EIS. The test results showed that C2, C3, C4, and C5 coating systems maintained good barrier properties during the immersion process, the low frequency |Z| is more than 108Ω.cm2 after 30 days of immersion exposure. Epoxy modified coating (C1) had the lowest impedance with resistance under 106 Ω.cm2 provide poor corrosion protection.

The Enhancement of Enargite Dissolution by Sodium Hypochlorite in Ammoniacal Solutions

The dissolution of both copper and arsenic from a copper concentrate was investigated in oxidative ammonia/ammonium solutions at moderate temperatures and atmospheric pressure. The main parameters studied were temperature, pH, concentrations of different ammonia salts, the presence of sodium hypochlorite, pretreatment with sodium chloride, and curing period. In all ammoniacal solutions studied, increasing the temperature enhanced the dissolution of copper, but the dissolution of arsenic remained marginal. Mixing the copper concentrate with sodium chloride and leaving it to rest for 72 h before leaching in ammoniacal solutions significantly increased the dissolution of copper and slightly increased the dissolution of arsenic from the concentrate. A maximum of 35% of Cu and 3.3% of As were extracted when ammonium carbonate was used as the lixiviant. The results show relatively rapid dissolution of the concentrate with the addition of sodium hypochlorite in ammonium carbonate solution, achieving a dissolution of up to 50% and 25% of copper and arsenic, respectively. A copper dissolution with a non-linear regression model was proposed, considering the effect of NaClO and NH4Cl at 25 °C. These findings highlight the importance of using the correct anionic ligands for the ammonium ions and temperature to obtain a high dissolution of copper or arsenic. The results also showed that the curing time of the packed bed before the commencement of leaching appeared to be an important parameter to enhance the dissolution of copper and leave the arsenic in the residues.

Extraction of copper from the mining industry recirculation waters

Acidic recirculation water and effluents generated by the mining industry and bearing heavy metals can have a significant environmental impact on this region. Due to high concentrations of non-ferrous metals (5.2–300 mg/dm3 Cu; 50–450 g/dm3 Zn), such waters can be used as a raw material for producing concentrates for further recovery of metals from them. This study looked at the recirculation water of the Soryinsk tailings pod, the underspoil waters of the Novo-Shemursk deposit and the Urupsky GOK mine waters. The aim of the study is to develop a process for selective extraction of copper into a product that can be further processed into a final product. The most common techniques used to remove ions of heavy non-ferrous metals from industrial wastewater include neutralization techniques. In this case, however, a considerable share of non-ferrous metals get wasted. At the same time, reagent techniques (e.g. sulphidation in the acidic pH region) enable to selectively extract such metals into concentrates that can then be used in the conventional non-ferrous metal production technology. A sulphur solution in sodium hydroxide was used as a sulphidizer for selective extraction of copper from polycomponent wastewater. The sulphur solution was produced at the temperature of 115–120 oC, the mass ratio NaOH:S of 1:1 and the sulphur concentration of 350 g/dm3. Use of sulphur dissolved in sodium hydroxide helped extract copper in the form of sulphides from complex solutions. It resulted in a high recovery of copper (94–99.9%) and a high-concentration copper concentrate (8.9–27.5%). It was found that iron (III) interacts with sulphide ions forming elemental sulphur, which can be reused for conditioning of copper concentrate in sodium hydroxide. Thus, the sulphur can be reused and the concentration of copper can be increased to 24%. The physical properties of particles in copper sulphide concentrates determine the high rate of solid phase precipitation from the slurry. Sulphide particles are characterized with a high negative charge (–80…–100 mV) and the size of the 90% of the particles reaching 68.9 μm. The authors developed a process flow diagram for extracting copper from low-grade complex solutions. The process involves regular addition of sulphidizer to the existing water flow, detention of a solid copper phase and, when necessary, conditioning of copper concentrate.

The Study Of The Selection Of Lead-Copper Concentrate By The Sulfite Method

Currently, sulfoxide methods are of greatest interest for the practice of separation of lead-copper concentrates. The selection processes based on the use of sulfoxides such as sulfuric acid, sulfite salts, etc. should be included in this subgroup.d. Typically, these reagents are used in combination with other depressors [3]. The main advantage of sulfoxide methods is the lack of dissolution of noble metals and higher efficiency compared to many known methods. The subgroup under consideration includes a method using sodium sulfite, iron vitriol and sulfuric acid for halenite depression Currently, about thirty methods of flotation separation of lead-copper concentrates are known.