Bioleaching Process for Copper Extraction from Waste in Alkaline and Acid Medium

Flotation wastes are becoming a valuable secondary raw material and source of many metals and semimetals worldwide with the possibilities of industrial recycling. The flotation tailings contain oxide and sulfide minerals that have not been sufficiently stabilized and form acidic mine waters, which in turn contaminate groundwater, rivers, and reservoi6sediments. An effective way to recycle these mine wastes is to recover the metals through leaching. While the focus is on acid bioleaching by iron- and sulfur-oxidizing bacteria, alkaline leaching, and the removal of iron-containing surface coatings on sulfide minerals contribute significantly to the overall environmental efficiency of leaching. For this study, static and percolate bioleaching of copper from flotation waste at the Bor copper mine in Serbia was investigated in alkaline and then acidic environments. The aim of the study was to verify the effect of alkaline pH and nutrient stimulation on the bioleaching process and element extraction. A sample was taken from a mine waste site, which was characterized by XRF analyses. The concentration of leached copper was increased when copper oxide minerals dissolved during alkaline bioleaching. The highest copper yield during alkaline bioleaching was achieved after 9 days and reached 67%. The addition of nutrients in acidic medium enhanced the degradation of sulfide minerals and increased Cu recovery to 74%, while Fe and Ag recoveries were not significantly affected. Combined bioleaching with alkaline media and iron- and sulfur-oxidizing bacteria in acidic media should be a good reference for ecological Cu recovery from copper oxide and sulfide wastes.

Copper Extraction from Low-Grade Chalcopyrite in a Bioleaching Column Assisted by Bioelectrochemical System

Low-grade ores, tailings and solid wastes contain small amounts of valuable heavy metals. Improper disposal of these results in the waste of resources and contamination of soil or groundwater. Accordingly, the treatment and recycling of low-grade ores, tailings and solid wastes attracted much attention recently. Bioelectrochemical system, an innovative technology for the removal and recovery of heavy metals, has been further developed and applied in recent years. In current study, the low-grade chalcopyrite was bioleached with the assistance of microbial fuel cells. Copper extraction along with electricity generation from the low-grade chalcopyrite were achieved in the column bioleaching process assisted by MFCs. Results showed that after 197 days bioleaching of low-grade chalcopyrite, 423.9 mg copper was extracted from 200 g low-grade chalcopyrite and the average coulomb production reached 1.75 C/d. The introduction of MFCs into bioleaching processes promoted the copper extraction efficiency by 2.7 times (3.62% vs. 1.33%), mainly via promoting ferrous oxidation, reducing ORP and stimulating bacterial growth. This work provides a feasible method for the treatment and recycling of low-grade ores, tailings and solid wastes. But balancing energy consumption of aeration and circulation frequency and chemicals consumption of acid to improve the copper extraction efficiency need further investigation.

Influence of alkaline pre-treatment on acid dissolution of cathode material of 18650 lithium battery

Lithium battery cathodes contain lithium, cobalt, nickel, and manganese. Recycling of spent lithium batteries aims to recover these elements for re-use. Liberation of cathode materials from other metals in the battery such as aluminium, copper, and iron, is essential to obtain a good leaching efficiency in the recovery of valuable metals from end-of-life lithium batteries. This study investigates the behaviour of cathode materials and other metals in spent 18650 lithium batteries during leaching in H2SO4 solution with and without NaOH pre-treatment. Dissolution of aluminium using NaOH is a selective method to separate the metal from other elements. The influence of a 2-hour NaOH pre-treatment on subsequent acid leaching of cathode materials was investigated at both room temperature and 80°C. The extraction of aluminium increased to 75% at a higher temperature. Lithium concentration in the pregnant leach solution from acid leaching also increases with NaOH pre-treatment. The pre-treatment had a negligible effect on nickel, manganese, iron, and copper extraction. However, the cobalt extraction with NaOH pre-treatment was significantly lower. The result was likely due to indirect impact of less hydrogen gas was generated from a lower Al amount. The lattice structure of the leach residue for the sample with NaOH pre-treatment was monoclinic rather than rhombohedral due to stronger delithiation.

Feasibility study and direct extraction of endogenous free metallic cations combining hemodialysis and chelating polymer

In this article, we report the conception and the use of dialysis-based medical device for the extraction of metals. The medical device is obtained by addition in the dialysate of a functionalized chitosan that can chelate endogenous metals like iron or copper. This water-soluble functionalized chitosan is obtained after controlled reacetylation and grafting of DOTAGA. Due to the high mass of chitosan, the polymer cannot cross through the membrane and the metals are trapped in the dialysate during hemodialysis. Copper extraction has been evaluated in vitro using an hemodialysis protocol. Feasibility study has been performed on healthy sheep showing no acute toxicity througout the entire dialysis procedure and first insights of metallic extraction even on healthy animals.

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.

Copper Extraction from Oxide Ore of Almalyk Mine by H2SO4 in Simulated Heap Leaching: Effect of Particle Size and Acid Concentration

In this investigation, a laboratory-scale study to extract copper (Cu) from its oxide ore (0.425–11.2 mm particle size) was conducted using varied sulfuric acid (H2SO4) concentrations (0.05–0.5 M) as a lixiviant. Through a physicochemical and mineralogical analysis of real field ore samples from the Almalyk mine heap site (Tashkent, Uzbekistan), malachite was identified as a Cu-bearing mineral. Extraction rates were analyzed according to the ore particle size and acid concentration. The Cu extraction with the smallest particle size (in 24 h) varied between 76.7% and 94.26% at varied H2SO4 concentrations (0.05–0.5 M). Almost half (50%) of Cu was extracted from the ore within 4 and 72 h of contact time for 0.425–2 mm and 5.6–11.2 mm particle sizes, respectively, using 0.15 M H2SO4. Weeklong leaching experiments with 0.5 M H2SO4 revealed a higher copper extraction rate (≥73%) from coarse ore particles (5.6–11.2 mm). Along with the copper extraction, iron (29.6 wt%), aluminum (70.2 wt%), magnesium (85.4 wt%), and calcium (44.4 wt%) were also leached out considerably through the dissolution of silicate and carbonate gangue minerals. In this study, an 80.0–94.26% copper extraction rate with reduced acid consumption (20%) proved to be a cost-effective approach.

Rapid Atmospheric Leaching of Chalcopyrite Using a Novel Reagent of Trichloroisocyanuric Acid

With the decrease in high-grade chalcopyrite resources, the copper extraction from low-grade chalcopyrite has attracted more and more attention. However, the kinetic rates of chalcopyrite leaching with traditional oxidants are usually very slow due to the formation of the passivation layer. In this study, a novel reagent of chlorinated oxidant, trichloroisocyanuric acid (TCCA), was used to leach chalcopyrite for the first time. The experimental results showed that when the initial oxidant concentration for TCCA was 0.054 mol·L−1, the leaching temperature was kept at 55 °C, and the pH of the pulp was controlled at 1, the oxidation efficiency of Cu can reach above 90% in less than 30 min. Various analyses of chalcopyrite mineral ore and its oxidized residues, such as chemical composition analysis, X-ray diffraction analysis, scanning electron microscopy analysis and X-ray photoelectron spectroscopy, were conducted, respectively. No obvious passivation layer was found on the chalcopyrite surface, though the sulfur product can also be generated during the leaching. Reaction kinetic analysis results showed that the different influence of surface reaction and diffusion process on the dissolution of chalcopyrite is little due to the fast leaching speed. After calculation, the activation energy of the whole leaching reaction is 9.06 kJ·mol−1, much lower than that in other reports. The mechanism was also proposed that TCCA was hydrolyzed in the solution to form hypochlorous acid, which is the strong oxidant, and cyanuric acid, which prevents the formation of a passivation layer. The processing in this study is expected to be applied as a novel method for atmospheric leaching of chalcopyrite.