Chalcopyrite Leaching with Hydrogen Peroxide and Iodine Species in Acidic Chloride Media at Room Temperature: Technical and Economic Evaluation

In Chile, the hydrometallurgical plants are operating below their capacity due to a depletion of copper oxide ores. To obtain suitable pregnant leach solutions (PLSs) for hydrometallurgical plants, leaching solutions combining iodine-based oxidants and hydrogen peroxide in a chloride–acid medium, at room temperature and pressure were studied. Factorial experiments were conducted to evaluate the effects of the different leaching solution reagents (KI, NaIO3, NaCl, H2O2, and H2SO4). The results showed that the most influential variable is the H2O2 concentration; increasing the PLS concentration from 3 g/L to 15 g/L increased the copper extraction percentage by ~25%. In decreasing order of importance, the factorial experimental results showed that the H2O2, H2SO4, NaCl, NaIO3, and KI concentrations affect the copper extraction percentage. The highest copper extraction percentage (i.e., 60.6%) was obtained using a leaching solution containing the highest reagent concentrations. At these conditions, the copper concentration in the PLS was 16.9 g/L. An economic evaluation of the laboratory-scale leaching experiments showed an increase in the unit cost (USD/t Cu) for experiments involving leaching solutions without H2O2 because of poor copper concentration in the PLS. As the concentrations of the reagents NaIO3 and KI, increase, the unit cost increases, because the reagents are relatively expensive and have a limited effect on the copper extraction percentage.

Influence of Laser Treatment on the Corrosion Resistance of Cr3C2-25(Ni20Cr) Cermet Coating

The influence of the laser treatment on the corrosion resistance of the Cr3C2-25(Ni20Cr) cermet coating on the Al7075 (EN, AW-7075) substrate (Cr3C2-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold sprayed (CS) method. The tested coatings were irradiated with a laser spot speed of 600 mm/min, 800 mm/min, and 1000 mm/min. The mechanical properties of the Cr3C2-25(Ni20Cr)/Al7075 were characterized by microhardness (HV) measurements. The surface and microstructure of the specimens were observed by ascanning electron microscope (SEM) and other assistive techniques. The corrosion test of materials wascarried out by using the electrochemical method in the acidic chloride solution. Cermet coatings perfectly protect the Al7075 substrate against contact with an aggressive corrosion environment. The laser remelting process of the Cr3C2-25(Ni20Cr) layer caused the homogenization of the structure cermet coatings. The irradiation with the laser beam eliminates microcracks and pores on the Cr3C2-25(Ni20Cr) surface. However, the best effect of improving the anti-corrosion properties of cermet coating was obtained for the lowest laser spot speed (i.e., 600 mm/min). It was found that the corrosion rate of the Cr3C2-25(Ni20Cr) cermet coating was reduced by more than two times compared to the highest speed of the laser spot.

Corrosion Behavior of Inconel 625 Coating Produced by Laser Cladding

Anti-corrosion properties of Inconel 625 (In) laser cladding coatings onto the (S235JR) steel (S) were investigated. The coatings were produced with the use of wire (WIn/S) or powder (PIn/S). The mechanical properties of the Inconel 625 coatings were characterized by microhardness measurements. The PIn/S shows the highest hardness. The surface and microstructure of the specimens were observed by a scanning electron microscope (SEM). The surface analysis of the laser cladding coatings by energy-dispersive spectroscope (EDS) indicated that the structure of the WIn, and PIn coatings depend on its production technique. The microstructure of the WIn and PIn coatings have a dendritic columnar character. Corrosion test materials were carried out by using electrochemical methods. The corrosive environment was acidic chloride solution. It turned out that the PIn/S coating, which was produced by laser cladding method with the use of Inconel 625 powder, has the best anti-corrosion properties in an aggressive chloride environment.