Browsing by Author "Abdollahzdeh, Ali Akbar"

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Glycine leaching of Sarcheshmeh chalcopyrite concentrate at high pulp densities in a stirred tank reactor
(2020-10-01) Khezri Khabisi, Maryam; Rezai, Bahram; Abdollahzdeh, Ali Akbar; Molaeinasab, Mehdi; Wilson, Benjamin P.; Lundström, Mari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The simplest amino acid, glycine has recently been reported as a safe and environmentally benign reagent for the extraction of copper from both oxide and sulfide minerals. In the current study, leaching of a chalcopyrite concentrate from the Sarcheshmeh Copper Mine (Kerman, Iran) was conducted in stirred tank reactors in the presence of a glycine medium. The effect of some critical leaching parameters including glycine concentration (0.4–2 M), temperature (30–90 °C), stirring rate (250–750 rpm), pH (9–12), oxygen flowrate (0.5–2 L/min) and pulp density (1–20%) was investigated on copper recovery from the chalcopyrite concentrate. Results show that an increase in temperature from 30 to 60 ˚C enhanced the copper extraction, whereas at conditions > 60 ˚C a decrease in copper extraction was observed, probably as a result of the conversion of glycine to glycinate and decrease in oxygen solubility. Moreover, prolonged leaching times at higher pH levels (10.5 and 12) led to a decrease in the extraction of copper, primarily due to the chemical precipitation of copper sulfide and crystallization of copper glycinate. By increasing the pulp density from 1 to 20%, copper extraction declined significantly primarily as a consequence of the partial dissolved copper precipitation at higher copper concentrations. SEM/WDX analyses were subsequently used in order to evaluate the leach residues. Further investigation determined that the activation energy of the glycine leaching of concentrate was 37.4 KJ/mol, thus the kinetics were controlled by diffusion of the reagents through the product layer. From these results, it is evident that due to the high initial rate of glycine leaching and the precipitation of copper-bearing phases (i.e. copper glycinate and covellite) at high pulp densities, glycine leaching processes are recommended for the treatment of low grade chalcopyrite concentrates, ores or tailings.
Investigation into the effect of mechanical activation on the leaching of chalcopyrite in a glycine medium
(2021-08) Khezri Khabisi, Maryam; Rezai, Bahram; Abdollahzdeh, Ali Akbar; Wilson, Benjamin P.; Molaeinasab, Mehdi; Lundström, Mari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The effect of mechanical activation on the leaching and electrochemistry of chalcopyrite was investigated in a glycine medium. Leaching experiments were conducted to evaluate the effect of particle size (with re-ground sample in ball mill) and mechanical activation (with re-ground sample in planetary mill for 4 h) on chalcopyrite dissolution in a stirred tank reactor. Results show that a maximum copper extraction (95.1%) was obtained for mechanically activated chalcopyrite after 12 h leaching in a 0.4 M glycine solution at 60 °C, 2% (w/v) pulp density and an initial solution pH of 10.5. Under these same leaching conditions, a decrease in particle size for conventionally ground chalcopyrite from 106 to 125 μm to <20 μm, led to a substantial increase in the level of copper extraction - from 0.6% to 33.8%. Analysis of solid residue by XRD showed that iron could be precipitated as maghemite and a part of dissolved copper could be removed from the solution as copper glycinate crystals and covellite. Result of the electrochemical analysis showed that the anodic current of the chalcopyrite‑carbon paste electrode was significantly increased for the mechanically activated sample. Nevertheless, anodic current densities were observed to reduce during subsequent voltammetry cycles as a consequence of passivating the surface of chalcopyrite electrode by reaction products and decreasing electroactive cites the electrode surface. A new 2-stage leaching flowsheet was proposed to extract copper from chalcopyrite concentrates in glycine media. Glycine leaching with mechanical activated pretreatment could be a promising method for treating low-grade chalcopyrite concentrates.