查看更多>>摘要：Iron-rich, limonitic laterites may contain economic grades of nickel and cobalt, but efficient extraction of these metals from such ores is still a challenge. In this study, four samples of limonitic laterites originating from the Barro Alto mine in Brazil were subjected to detailed quantitative mineralogical examination followed by bioleaching and chemical leaching tests including mineralogical leaching residue analyses. Bioleaching experiments with pure cultures and addition of elemental sulfur were conducted in 2L bioreactors under aerobic conditions with the sulfur-oxidizing acidophilic bacteria Acidithiobacillus (At.) thiooxidans and At. caldus, and under anaerobic conditions with At. ferrooxidans. Aerobic bioleaching of laterites with At. thiooxidans and At. caldus allowed for a lower pH of 1.0 and 1.1 respectively, and thus a higher Ni and Co extraction than anaerobic bioleaching with At. ferrooxidans at pH 1.5. Extraction of cobalt via bioleaching was in the range of 68-88 %, while extraction of nickel was between 17 % and 56 %. Mineralogical and geochemical analysis (XRD, SEM-MLA, DSC, LA-ICP-TOFMS, XRF) was conducted to (i) identify mineral phases, which are attacked by bioleaching and (ii) estimate the portions of Co and Ni, which are released by bioleaching of different mineral phases. Cobalt was mostly hosted by Mn-rich mineral phases, which were dissolved after reduction with ferrous iron generated by bacterial metabolism during oxidation of sulfur. Nickel was mostly hosted by goethite, the most abundant mineral phase, but nickel was also present in Mn-rich minerals (e.g. asbolane) and magnesium silicates (e.g. serpentine). Mineralogical and geochemical data revealed that goethite was almost unleached in all samples and nickel was mostly released from Mn-rich mineral phases and magnesium silicates. Results of this research were able to confirm reductive bioleaching of Mn-rich phases. Chemical leaching tests performed with different concentrations of sulfuric acid and with hydrochloric acid, and with sulfuric acid plus ferrous iron as a reducing agent supported bioleaching results. The results are not supporting published data on substantial reductive dissolution of goethite via ferric iron reduction activity of acidophilic bacteria.
查看更多>>摘要：In this study, the particle size distribution, fractal dimension, specific energy consumption, and grinding kinetics of chalcopyrite ore under high voltage pulse discharge were systematically discussed. With the increase in voltage and pulse numbers, the undersize content and reduction ratio gradually increased, and the characteristic particle sizes decreased. The dispersion degree of particle size distribution increased and the uniformity became worse. The particle size distribution of breakage products under different voltages and pulse numbers could be described by the Harris three parameter equation. The characteristic particle size D80 gradually decreased and the reduction ratio gradually increased with the increase in specific energy consumption. The specific energy consumption of high voltage pulse discharge breakage was described by the Walker theory (E = 215.13 x (1/ x0.33 - 1/120.33 )). Besides, the high voltage pulse discharge could significantly reduce the mechanical strength of ore and improve its grinding efficiency.
查看更多>>摘要：The recycling of value metals from spent lithium-ion batteries (LIBs) have interesting benefits such as reduction of natural resources exploitation and minimization of energy consumption from mining operations. The aim of this work was to recover lithium, cobalt and manganese from the cathode material present in spent LIBs through a pyrometallurgical process of carboreduction. The method consisted in mixing the cathode material with carbon black and a subsequent heat treatment of the mixture under nitrogen atmosphere. The products obtained were separated by water leaching. To elucidate the reactions and the mechanism involved in the carboreduction process, different studies involving thermodynamic calculations, thermal gravimetric analysis (TGA), differential thermal analysis and X-ray diffraction (XRD) were carried out. The results indicated that Li2CO3, CoO and MnO are produced at temperatures lower than 600 degrees C. The results of atomic absorption spectrometry (AAS) showed that the extraction percentage of lithium was greater than 90% at temperatures between 550 and 600 degrees C. The products obtained through the process presented here could be used in either the manufacture of new batteries or other industrial applications.
查看更多>>摘要：In the one-step bioleaching process of uranium by Aspergillus niger, the formation mechanism and uranium bioleaching model of bio-ore pellets were explored and proposed. The results showed that the formation of bioore pellets could be divided into three phases. In the adaptive-growth phase, a small number of ore particles were adsorbed by mycelia to form flake mycelia with a diameter of 1-2 mm. In the rapid-growth phase, ore particles began to gather and form stable bio-ore pellets (diameter reaching 4.98 mm) owing to the force of electrostatic attraction, secretion of organic acids, and EPS adhesion. In the stationary growth phase, the bio-ore pellets have been stably formed (Zeta potential stable at approx. +/- 2.5 mV), the oxalic acid, citric acid, and tartaric acid secreted by A. niger accumulated and reached a peak of 7625 mg/L, and the uranium recovery achieved a peak of 79.6%. Furthermore, the atomic force microscope (AFM) scanning results indicated that the hyphae and metabolites of A. niger could erode the surface of ore particles. Finally, a uranium dissolution model of the bio-ore pellets was established. It indicates that the globular bio-ore pellets were beneficial to uranium dissolution under the double effects of mycelial mechanical damage and organic acid corrosion.
查看更多>>摘要：Heat-treatment of serpentine minerals generates structural amorphicity and increases reactivity during subsequent mineral carbonation, a strategy for large-scale sequestration of CO2. This study employs thermal analyses (TGA-DSC) in conjunction with in-situ synchrotron powder X-ray diffraction (PXRD) to record concurrent mass loss, heat flow, and mineralogical changes during thermal treatment of antigorite. Isoconversional kinetic modelling demonstrates that thermal decomposition of antigorite is a complex multi-step reaction, with activation energies (E alpha) varying between 290 and 515 kJ mol(-1). We identify three intermediate phases forming during antigorite dehydroxylation, a semi-crystalline chlorite-like phase (gamma-metaserpentine) showing an additional reaction pathway for the decomposition of Al2O3-rich antigorite into pyrope, and two distinct amorphous components (alpha and beta-metaserpentine) which convert into forsterite and enstatite at higher temperature, respectively. The combination of isoconversional kinetics with in-situ synchrotron PXRD illustrates, for the first time, that local crystal structure changes, related to intermediate phase and forsterite formation, are responsible for the steep increase in activation energy above 650 C and only 49% dehydroxylation can be achieved prior to this increase. This suggests that the high thermal stability of Al2O3-rich antigorite would severely limit Mg extraction during application of mineral carbonation under flue gas conditions.
查看更多>>摘要：The current scaleup approaches usually consider the overall metallurgical results, without including the efficiency of flotation machines at different particle size and liberation classes. This approach can limit the prediction of the industrial metallurgical performance, mainly when the mineral feed characteristics change significantly over time. This paper presents a scale-up approach, which allows for estimating scale-up factors per size and liberation class. The plant survey was developed in a copper concentrator in Chile. Plant kinetic testing on three rougher circuits of 130 and 300 m(3) cells, in parallel with batch flotation tests using the same rougher feed samples, allowed the estimation of average scale up factors in the range of 1.8-2.2, which are in good agreement with the typical values observed in flotation scale up. All the samples included sieving, and chemical and mineralogical analysis. Scale up factors, batch-plant, showed a correlation with particle size classes, where the scale up factor increases (1.5-2.5), when particle size increases (20-150 mu m), according to the data. This effect becomes stronger for particle sizes larger than 100 mu m, reaching scale up values around 3-4. This means that the scale up factors are sensitive to the particle size distribution in the plant feed and must be considered. An alternative estimation of scale up factors in terms of the mineral liberation showed a similar trend with those of particle size classes, where the less liberated (mainly coarser sizes) minerals have the largest scale up factors, while decreasing for the highly liberated (mainly finer sizes) minerals.
查看更多>>摘要：In this study, Macadamia-derived activated carbon was utilized for the remediation of selected heavy metals from wastewater samples. The selected heavy metals include Pb (II), Fe (III), Cd (II), and Zn (II). The activated carbon used in the study was modified with KMnO4 and HNO3 to increase the content of the oxygen-containing functional groups on the adsorbent surface. Both the unmodified activated carbon (UAC) and modified activated carbon (MAC) adsorbents were employed throughout the study for comparative purposes in a multi-metallic system. The adsorbents were characterised using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) analysis, and elemental (CHNS) analysis. Elemental analysis revealed an increased oxygen content from UAC to the MAC adsorbent from 8.34 % to 22.87 %. Scanning electron microscopy revealed a morphological contrast in the surfaces of both adsorbents. Optimal conditions for the carbon sorbents were observed at a pH 5, adsorbent mass of 0.2 g, initial concentration of 50 mg L-1, 4 h contact time, and a temperature of 298 K. Overall performance in removal efficiencies were recorded to be 74.74 % for UAC and 87.39 % for MAC. The MAC displayed superior removal efficiencies for Pb (II), and Fe (III) as compared to Cd (II) and Zn (II). Both adsorbents were applied in the treatment of acid mine drainage and leachate samples and the results indicated successful heavy metal remediation using the MAC adsorbent. Twoparameter and three-parameter adsorption isotherm models were fit to the experimental data, and it was found that the Langmuir model was better suited to the equilibrium data as opposed to the other models. The adsorption kinetics were best described using the pseudo-second-order model. Maximum adsorption capacities produced for UAC and MAC were found to be 3.00 and 3.50 mg g-1 respectively.
Sengupta, DiyashaIlankoon, I. M. S. K.Kang, Kai DeanChong, Meng Nan...
11页
查看更多>>摘要：E-waste is considered to be one of the fastest growing solid waste streams in the world. India, the second most populous country in the world, generated more than 3.23 million tonnes of e-waste in 2019 and thus, has become the world's third largest e-waste generating country. However, the documented formal e-waste recycling percentage in India is very low (less than 10%). The existing formal recyclers in India process approximately onethird of the total e-waste generated in the country, though they face e-waste supply chain constraints due to informal e-waste collectors. A significant e-waste fraction is handled by the informal e-waste collectors and value recovery operations. Approximately 1% of the country's population is expected to be currently engaged in informal waste management and value recovery activities and thus, the investigation of the informal e-waste sector in India is of paramount importance. Artisanal value recovery methods pose severe threats to human health and the environment due to toxic and hazardous chemicals in e-waste and their subsequent mobilisation. These drawbacks thus imply that improvements are required in both formal and informal e-waste collection and value recovery operations to establish a more sustainable e-waste industry in the country. Therefore, the aim of this study was to investigate the operational characteristics of both the sectors, including extended producer responsibility (EPR) schemes in India. A modified EPR model pertaining to e-waste was proposed to integrate the informal e-waste collectors to the existing formal industry. The results in this work could be useful to establish a sustainable e-waste industry in India.
查看更多>>摘要：Carbonaceous refractory gold ore has been an important gold ore resource for the sustainable development of the gold industry. Solving the harmful effects of mineral-locking is the first step to increase the gold leaching rate. This study employed vacuum roasting technology in the pretreatment of carbonaceous gold ore. The dissociation efficiency and mechanism of gold in carbonaceous gold ore was investigated using a Mineral Liberation Analyser, thermogravimetric analysis, scanning electron microscopy, and X-ray diffraction analysis. The results showed that the effect of gold-locking could be effectively solved through the thermal decomposition of pyrite during vacuum roasting pretreatment. After vacuum roasting, the content of exposed and semi-exposed gold increased from 43.81% to 78.34%, and 72.37% of the gold locked by pyrite was dissociated. Pyrite was continuously desulfurized and converted into low-sulfur pyrrhotite during vacuum roasting, and desulfurization at 400-700 degrees C was the cause of mass loss and phase transformation of pyrite. The phase transformation of pyrite followed the change pyrite -* monoclinic and hexagonal pyrrhotite -* hexagonal pyrrhotite -* troilite. At 600-700 degrees C, rapid desulfurization produced a well-developed pore structure of the pyrite particles, which loosened the connection between gold and pyrite. Above 700 degrees C, the aggregation of pyrrhotite particles by slow desulfurization improved separation of gold and pyrrhotite. Gold locked by pyrite in the carbonaceous gold ore was dissociated effectively under the combined action of the two stages. The high content of exposed and semi-exposed gold provided necessary conditions for the improvement of gold leaching rate in the later leaching process.
Van Duijvenbode, Jeroen R.Cloete, Louis M.Shishvan, Masoud S.Buxton, Mike W. N....
17页
查看更多>>摘要：Multi-element (ME) datasets provide comprehensive geochemical signatures of an orebody and are commonly used to gain insight into the mineralogy, lithology, alteration patterns and to identify target-pathfinders. However, little effort is made in using these data to explain comminution or recovery characteristics. This paper describes an agglomerative hierarchical clustering approach applied to ME data from the Tropicana Gold Mine, Australia, and investigates the relationship between the resultant classes and run-of-mine comminution and recovery parameters. First, it is demonstrated how an industry scale ME dataset is prepared for clustering. The preparation consists of verifying the absence of interlaboratory and intralaboratory bias between measurements, centred log-ratio transformation (clr), normalisation and principal component analysis (PCA). Afterwards, the first case study indicate that the clustering separation is primarily driven by geochemical differences caused by major rock-forming mineral signatures (felsic vs mafic, alteration vs no alteration, chert or quartz lithologies, unmineralised vs mineralised material). This case study separates the ME dataset into five unmineralised and two Au-mineralised material classes. The second case study continues with the two identified mineralised material classes and further separates these samples into five new classes. These classes are explored geochemically and by using the spatial context (within domains) better matched with metallurgical test results. It is found that domain-related material class proportions assist in interpreting different processing proxies such as the Equotip hardness (Leeb), Bond Work index (BWi), Axb, and processing recovery and reagent consumption. Knowledge of the processing parameters per domain and class composition can be used to infer such characteristics in the absence of standard metallurgical tests. This new approach of gaining insights into comminution and recovery parameters through geochemical analysis demonstrates the benefit of the conceptualised material fingerprinting concept.
NSTL
Elsevier