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Biological column leaching of Ni from low-grade Ni ore was studied, and the effects of ore particle size on leaching rate were investigated. The Ni ore with an average Ni content of 0.23% was crushed into four different particle size fractions: >10 mm, 5–10 mm, 2–5 mm and 10 mm (bioleaching), 5–10 mm (acid leaching), 5–10 mm (bioleaching), and 2–5 mm (bioleaching) were 23.76%, 22.15%, 32.42% and 54.17%, respectively, after 180 d of bioleaching. The ore particle size changed after leaching, compared with the original ore size, the proportion of the same size of 2–5 mm ore decreased to 44.64%. Ore with particle size of 2–5 mm was most suitable for column bioleaching, and effective Ni extraction was achieved with appropriate control of ore granularity.

Heap bioleaching is a microbial technology that catalyzes the decomposition of ore without grinding. The crushed ore is stacked on the liner, and the microbial solution flows through the heap from ...

A process of biooxidation followed by thiosulfate leaching of gold from refractory gold concentrate was investigated. Mineralogical studies on the concentrate showed that very fine gold grains (

To design heap biooxidation process, it is necessary to understand its internal rules. The heap biooxidation of gold ore from Anhui province was researched in this study. The results showed that the main microorganisms in the heap were A. ferrooxidans, F. acidiphilum and L. ferrodiazotrophum. Under their combined action, gold leaching extent rose from 35.62% to 78.08% in 80 d. Boltzmann model matches the actual oxidation effect better and the model equations were obtained. The model predicted that the oxidation extents of arsenic and sulfur are 58.577% and 42.122% after one year, and the gold leaching extent was 80.40%. The arsenic and sulfur oxidation extents, and gold leaching extent were all linearly correlated. It is more reliable to predict gold leaching extent by sulfur oxidation extent. These results provided good guidance for practical application in the actual production.

Microorganisms, one of the key factors affecting the bioleaching process, change the components of extracellular polymeric substance (EPS) and community structure to survive in leaching environments. In this work, Fourier transform infrared (FTIR), X-ray powder diffraction (XRD) and 16S rDna high-throughput sequence analyses were used to reveal the microbial changes in planktonic and sessile phases during bioleaching. The results showed the occupation of sessile cells decreased from 66.2% to (10±3)%. After bioleaching, the planktonic and sessile cells have similar EPS, but they are different from the original cells. Pyrite dissolution mainly occurs at the early and late stages with the decreasing of particle diameter, by 50% and 40%, respectively. The 16S rDna gene based sequence analysis results in total of 1117420 Reads across the six samples, presented among 7 phyla, 9 classes, 17 orders, 23 families and 31 genera. Genera Leptospirillum and Sulfobacillus are the main bacteria at the early and middle stages, and Leptospirillum is the main genus at the end of bioleaching. Aquabacterium and Acidovorax are special genera in sessile cells and Weissella is special in planktonic ones.

Mechanical activation (MA) of malachite was carried out by dry planetary grinding (DPG) and wet Isa grinding (WIG) methods. When the rotational speed was increased to 400 r/min in DPG, the specific surface area of malachite reached the maximum and the particle size reached the minimum of 0.7–100 µm. Agglomeration occurred between mineral particles when the rotational speed was increased to 580 r/min in DPG. However, no agglomeration was observed among particles with sizes 0.4–3 µm in WIG. X-ray diffraction analysis showed that, at a 580 r/min rotational speed in DPG, the amorphization degree of malachite was 53.12%, whereas that in WIG was 71.40%, indicating that MA led to amorphization and distortion of crystal structures. In addition, in the Fourier transform infrared (FT-IR) spectra of activated malachite, the bands associated with −OH, CO 3 2− and metal lattice vibrations of Cu-O and Cu-OH were weakened, and a new H-O-H bending mode and peaks of gaseous CO2 appeared, indicating that MA decreased the band energy, enhanced dihydroxylation, and increased the chemical reactivity of the malachite. Furthermore, the leaching behavior of copper ore was greatly improved by MA.

In this paper, the structures of element carbon and humic acid extracted from carbonaceous gold concentrate were characterized employing a variety of analytical methods. The extracted amounts of ECE (elemental carbon extract) and HAE (humic acid extract) were 14.84&ndash, 38.50 and 11.55&ndash, 28.05 mg g&minus, 1, respectively. SEM and porosity analysis indicated that ECE occurred mostly as irregular blocky particles with a mesoporous surface with the average pore diameter being 31.42 nm. The particle size of ECE was mainly ranged from 5.5 to 42 &mu, m and the specific surface area was 20.35 m2 g&minus, 1. The physicochemical features and structure of ECE were close to activated carbon, and the crystallinity was slightly lower than graphite. The particle size distribution of HAE varied from 40 to 400 nm with the specific surface area of 42.84 m2 g&minus, 1, whereas the average pore diameter of HAE was 2.97 nm. FTIR and UV&ndash, VIS analyses indicated that HAE was a complex organic compound containing the enrichment of oxygen-containing structure. The results showed that the adsorption amounts of ECE and HAE under the acidic conditions were 470.46 and 357.60 mg g&minus, 1, respectively. In an alkaline environment, the amount of ECE was 449.02 mg g&minus, 1 and the value of HAE was 294.72 mg g&minus, 1. ECE mainly utilized the outer surface and mesoporous structure to adsorb gold, while the functional groups&rsquo, complexation or surface site adsorption was the leading approach for HAE to adsorb gold.

Traditional methods of cyanides' (CN

The effect of temperature on leaching behavior of copper minerals with different occurrence states in complex copper oxide ores was carried out by phase analysis means of XRD, optical microscopy and SEM−EDS. The results indicated that at ambient temperature, the easily leached copper oxide minerals were completely dissolved, while the bonded copper minerals were insoluble. At lukewarm temperature of 40 °C, it was mainly the dissolution of copper in isomorphism state. With increasing temperature to 60 °C, the copper leaching rate in the adsorbed state was significantly accelerated. In addition, when the temperature increased to 80 °C, the isomorphic copper was completely leached, leaving 11.2% adsorbed copper un-leached. However, the copper in feldspar−quartz−copper−iron colloid state was not dissolved throughout the leaching process. Overall, the leaching rates of copper in different copper minerals decreased in the order: malachite, pseudo-malachite > chrysocolla > copper-bearing chlorite > copper-bearing muscovite > copper-bearing biotite > copper-bearing limonite > feldspar−quartz−copper−iron colloid.

In this study, a novel α-MnO2 (OMS-2) material with long and uniform nanofibers was synthesized by morphological and phase transitions from δ-MnO2 (OL-1) under a hydrothermal reaction. We systematically investigated the catalytic performances of OMS-2 and OL-1 for the activation of PMS (peroxymonosulfate) to degrade 4-nitrophenol (4-NP) in water. According to the results from Brunauer Emmett Teller (BET), thermo gravimetric analyzer (TGA), H2-temperature programmed reduction (H2-TPR), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and density-functional theory (DFT) calculation, OMS-2 has a larger BET area, more active sites, better adsorption ability, a faster electron transfer rate, and more multiple valence states of Mn than OL-1. These results also well illustrate OMS-2 has much better catalytic performance than OL-1. The results of the electron paramagnetic resonance (EPR) and the radical quantification experiments confirmed that sulfate radicals (SO4 −) and hydroxyl radicals ( OH) were the main oxidants and OMS-2 has better radical generation capability than OL-1. The LC-MS results indicated that there were two routes for the degradation of 4-NP and the degradation mechanism of 4-NP in the OMS-2/PMS system was similar to that in the OL-1/PMS system. Finally, we proposed the PMS activation mechanism, the formation mechanism of radicals, and the degradation mechanism of 4-NP based on the two different kinds of MnO2 with different morphologies.

The XRF, XRD, polarizing microscopy and SEM-EDS were used to study the alteration mechanism of copper-bearing biotite and the leachable property of copper-bearing minerals in Mulyashy Copper Mine, Zambia. It was found that biotite can be divided into copper-bearing biotite and copper-free biotite. Some copper-bearing biotite existed in the form of monomer, and others aggregated with copper-bearing chlorite, malachite or copper-bearing limonite. The main reason for the occurrence of biotite aggregations was that copper-bearing biotite underwent two kinds of alteration mechanisms as follows: altering into copper-bearing chlorite and malachite, and altering into copper-bearing chlorite and copper-bearing limonite. The order of factors effecting the copper leaching rate of the ores in acid leaching experiments was temperature > sample size > H2SO4 concentration > leaching time > stirring speed. In addition, the copper leaching rate of copper-bearing minerals at different temperatures was in the following order: malachite, chrysocolla and pseudomalachite > copper-bearing chlorite > copper-bearing muscovite > copper-bearing biotite > copper-bearing limonite. The leachable property of biotite is closely related to its special structure.

A new and efficient additive, triethanolamine (TEA), was used on pure gold leaching in a thiosulfate-copper-ammonia system. An appropriate TEA concentration enhanced the gold dissolution rate and reduced thiosulfate consumption. The beneficial effect became most pronounced in the case of MTEA:Mcopper = 1:1, where the gold dissolution rate increased by approximately 50% and thiosulfate consumption decreased by approximately 10%. The possible mechanisms of TEA are as follows: TEA combines with cupric and ammonia, which enhances the catalytic oxidation ability of Cu(II). Meanwhile, TEA can reduce the consumption of thiosulfate caused by the oxidation of Cu(II) and hence decreases the formation of passivation layers on the gold surface. Furthermore, the deprotonated ethanolic oxygen atoms of [Cu(NH3)x(TEA)y] act as bridging ligands, which could form an “electronic bridge” that benefits the electron transfer from Au0 to Cu2+. In addition, the actual main reaction complex in the cupric-ammonia-TEA complex ([Cu(NH3)x(TEA)y]) was [Cu(NH3)3TEA]2+.

Bacteria–mineral contact and noncontact leaching models coexist in the bioleaching process. In the present paper, dialysis bags were used to study the bioleaching process by separating the bacteria from the mineral, and the reasons for chalcopyrite surface passivation were discussed. The results show that the copper leaching efficiency of the bacteria–mineral contact model was higher than that of the bacteria–mineral noncontact model. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) were used to discover that the leaching process led to the formation of a sulfur film to inhibit the diffusion of reactive ions. In addition, the deposited jarosite on chalcopyrite surface was crystallized by the hydrolysis of the excess Fe3+ ions. The depositions passivated the chalcopyrite leaching process. The crystallized jarosite in the bacteria EPS layer belonged to bacteria–mineral contact leaching system, while that in the sulfur films belonged to the bacteria–mineral noncontact system.

Traditional methods of cyanides’ (CN−) mineralization cannot overcome the contradiction between the high alkalinity required for the inhibition of hydrogen cyanide evolution and the low alkalinity required for the efficient hydrolysis of cyanate (CNO−) intermediates. Thus, in this study, a novel Electro-Fenton system was constructed, in which the free cyanides released from ferricyanide photolysis can be efficiently mineralized by the synergy of •OH and •O2−. The complex bonds in ferricyanide (100 mL, 0.25 mM) were completely broken within 80 min under ultraviolet radiation, releasing free cyanides. Subsequently, in combination with the heterogeneous Electro-Fenton process, •OH and •O2− were simultaneously generated and 92.9% of free cyanides were transformed into NO3- within 120 min. No low-toxic CNO− intermediates were accumulated during the Electro-Fenton process. A new conversion mechanism was proposed that CN− was activated into electron-deficient cyanide radical (•CN) by •OH, and then the •CN intermediates reacted with •O2− via nucleophilic addition to quickly form NO3-, preventing the formation of CNO− and promoting the mineralization of cyanide. Furthermore, this new strategy was used to treat the actual cyanide residue eluent, achieving rapid recovery of irons and efficient mineralization of cyanides. In conclusion, this study proposes a new approach for the mineralization treatment of cyanide-containing wastewater.

In this study, a high-energy planetary mill was used to perform mechanical activation of chalcopyrite in dry-, moist-, and wet-milling modes. Granulometric and microstructural changes of chalcopyrite were characterized, and their effects on Cu dissolution were distinguished. Although water was added during milling to reduce agglomeration, it led to the inhibition of energy transmission. The maximum Brunauer–Emmett–Teller surface area of 8.382 m2/g was obtained in samples subjected to 7 h of moist milling. Dry milling resulted in considerable microstructural changes; the amorphization degree, grain size, and lattice strain of the chalcopyrite were 66.4%, 10 nm, and 0.427 × 10−2, respectively. Samples that had undergone 7 h of dry milling exhibited the highest copper extraction efficiency of 48.9%, which was 81.5 times higher than that for the nonactivated samples. The results of kinetics analysis revealed that the degree of amorphization exhibited a greater reactivity of chalcopyrite than the surface area did, and the enhancement in the leaching efficiency was highly consistent with the mechanical activation parameter. In addition, because of the selective rupturing of the chalcopyrite lattice, a “sulfur channel” appeared on the surface of the dry- and moist-milling samples, which proved that passivation decreased and leaching was enhanced. The results of this study can provide considerable insight on chalcopyrite leaching.

A hydroxylated xanthate salt (HXS) was synthesized from ethanol, carbon disulfide, and NaOH. The flotation responses of chalcopyrite and molybdenite when HXS was used as a novel depressant were investigated using bench-scale flotation tests. The bench-scale flotation results indicate that HXS strongly influenced the flotation of chalcopyrite and had little effect on the flotation of molybdenite. These results can be attributed to a significant improvement in the molybdenite/chalcopyrite selectivity surface index after the addition of HXS. The synthesized HXS contained both solid-philic and hydrophilic groups. The molybdenum recovery achieved using HXS was 9.91% higher than that obtained using sodium hydrosulfide, and better separation was achieved. Compared with sodium hydrosulfite, the chemical oxygen demand, sulfates and five-day BOD decreased significantly using the alternative depressant. This HXS is therefore a potential depressant for use in copper-molybdenum separation.

The dissolution of pyrite was studied with Phanerochaete chrysosporium (P. chrysosporium). This fungus resulted in the dissolution of 18% iron and 33% sulfur. The oxidization layer was formed on the pyrite surface, which probably consisted of iron oxide, iron oxy-hydroxide, iron sulfate, elemental sulfur and mycelia. The electrochemical characteristics of pyrite were studied in the systems without and with P. chrysosporium. P. chrysosporium could accelerate the dissolution of pyrite by decreasing pitting potential and polarization resistance plus improving polarization current, corrosion potential and corrosion current density. The dissolution of pyrite is the combined effect of enzymes, hydrogen peroxide, ferric iron and organic acids. Enzymes attack the chemical bonds by free radicals. Organic acids dissolve pyrite by acidolysis and complexolysis. Enzymes and hydrogen peroxide play an essential role in this process.

Among cyanide tailings, chalcopyrite is one of the main minerals. However, little study is available regarding the flotation behavior and mechanism of cyanide chalcopyrite, especially the influence of cyanide leaching time on the physical and chemical properties of chalcopyrite surface. In this work, the cyanide adsorption mechanism of the chalcopyrite surface over time and its response to flotation was probed for the first using contact angle, zeta potential, microflotation, X − ray photoelectron spectroscopy (XPS) and time−of−flight secondary ion mass spectrometry (ToF−SIMS). The results of contact angle showed that the surface hydrophobicity of the chalcopyrite surface decreased with increasing cyanidation time, thus preventing the adsorption of xanthate, which was confirmed by zeta potential and microflotation. XPS analysis indicated that with the gradual progress of cyanidation, hydrophilic CN−, CNO−, SO42− and CuCN− were formed on the surface of chalcopyrite. ToF−SIMS investigated the distribution of anion species on the surface of chalcopyrite, showing that with the increasing cyanidation time, more cyanide species formed on the surface of mineral layer, and gradually diffuse from the mineral surface to the bulk phase, finally forming a film with depth of about 20 nm. Thus, the chalcopyrite hydrophobicity was depressed.

Pyrite bio-oxidation can improve the gold leaching extent of refractory gold ores, but it can also cause environmental pollution. In this work, common gangue minerals (feldspar, mica, and quartz) were studied to analyze their solubilization under industrial bio-oxidation condition and their effects on pyrite bio-oxidation. The results show that: They all have certain solubilization under bio-oxidation conditions, and the solubilization sequence is in the reduction order of feldspar, mica, quartz. They all inhibit the pyrite bio-oxidation process, and the order of inhibition is mica, quartz, and feldspar. Reasons for the inhibition include ion toxicity, pulp oppresses, passivation, and changes in microbial communities. The results of response surface analysis indicated that the interaction between feldspar and quartz was the most significant, followed by feldspar and mica, while the interaction between mica and quartz was not obvious. When the weight ratio of pyrite, feldspar, mica and quartz is 10:4:5:11, pyrite dissolves the least, while the weight ratio is 5:9:1:15, pyrite dissolves the most easily. The results provide a reference for related research and provide theoretical support and process optimization guidance for environmental protection and industrial bio-oxidation process.

This work seeks to understand the role of hydrolyzed rice husk in pyrite bio-oxidation. Solution parameters during the bio-oxidation process were monitored, and the bio-oxidation residues were characterized by Scanning Electron Microscopy, Raman Spectroscopy, and Fourier Transform Infrared Spectroscopy. Results showed that rice husk mainly affected pyrite bio-oxidation by promoting microbial reproduction and changing microbial community. It mainly inhibited the reproduction of Sulfobacillus and promoted the reproduction of Leptospirillum. There was a significant positive correlation between pyrite oxidation and the proportion of Leptospirillum. Rice husk had no obvious impact on the adhesion of different microorganisms on the pyrite surface. Quantity and hydrolysis of rice husk are the two factors that affect microbial communities. 1 g·L−1 of fully hydrolyzed rice husk can maximize the pyrite bio-oxidation by about 20% after 14 days. The promoting mechanism of rice husk on pyrite bio-oxidation is summarized based on the results, which provides theoretical support for future industrial applications.

The leaching kinetics of selenium from copper anode slimes was studied in a nitric acid-sulfuric acid mixture. The effects of main parameters on selenium leaching showed that the leaching rate of selenium was practically independent of stirring speed, while dependent on temperature and the concentrations of HNO3 and H2SO4. The leaching of selenium includes two stages. The activation energy in the first stage is 103.5 kJ/mol, and the chemical reaction is the rate controlling step. It was almost independent of H2SO4 concentration and dependent on HNO3 concentration since the empirical reaction order with respect to HNO3 concentration is 0.5613. In the second stage, the activation energy is 30.6 kJ/mol, and the process is controlled by a mixture of diffusion and chemical reaction. The leaching of selenium was almost independent of HNO3 concentration.

A DFT study of H+ effect on CoO(0 1 0) surface was carried out. What could be seen from the inter atomic distance and the density of states (DOS) was: Co-O bonds were broken strongly and H-O bonds formed strongly when one H+ was adsorbed on the O atom, and Co-O bonds were not broken and H-O bond not formed strongly when two H+ were adsorbed on the O atom, so the Skutterudite acid leaching process cannot be described as two H+ were adsorbed on the O atom and formed the H2O molecules to enter the solution. But that can be described as one H+ was adsorbed on the O atom and formed the OH- to enter the solution, the OH- was combined with the H+ in the solution to form the H2O molecule.

In and Ge can be found in Sphalerite crystal which can influence bio-leaching properties of Sphalerite significantly. Occurrence states of In and Ge in Sphalerite crystal and their influence on Sphalerite was calculated by Castep package. The most stable occurrence states are In and Ge substitute for Zn atom in Sphalerite crystal. When In and Ge existed in Sphalerite crystal, the Density of states (DOS) of Sphalerite crystal moved to left, meaning a more reducibility structure. It can explain why In and Ge bearing Sphalerite is easier to bio-leach than the pure sphalerite.

Gradually bio-metallurgy technology is becoming an irreplaceable new technology. The nickel-bearing tailings in Jilin, China contains Ni 0.13 %, Cu 0.03%, Co 0.01%, S 15.20%, Fe 6.30%. A comparative study of the HQ0211 bacteria, indigenous bacteria (after the domestication named ZXJE511 bacteria) and acid pool leaching revealed that the local species ore leaching was preferably the best way. At pH 2.0, room temperature (about 23°C), pulp density 20%,the Ni, Co and Cu leaching rates were 70.08%, 40% and 57.67 % , respectively ,after 38 days of bioleaching, proving the superiority of the bacterial leaching of Ni, Co, Cu from tailings. Biological leaching tailings solved the problem of the conventional methods which could not be addressed by acid leaching. This technology is environmentally friendly and can make maximum use of the resources, thereby avoiding the waste of the resources.

In this study, the important variables of organic acids degradation with Phanerochaete chrysosporium were selected in refractory arsenic-bearing and carbonaceous gold ores. The eight variables of fungal degradation of carbonaceous matter were confirmed by the previous single factor experiments, which were guaiacol concentration, dextrin concentration, tween-80 concentration, oxalic acid concentration, hydrogen peroxide concentration, pulp density, fungal concentration and action time. The most important factors influencing organic acids degradation (p < 0.05), as identified by a two-level Plackett-Burman design with above-mentioned eight variables, were pulp density, oxalic acid concentration and action time. The pulp density could influence the effective contact area between organic acids and fungi, the shear stress and the mass transfer efficiency of degradation system. Oxalic acid could affect the fungal growth and the enzymes activity by adjusting pH value of degradation system. Organic acids could not be fully degraded when the fungal action time was the very short or excessively long. A long action time could lead to the lack of nutrients and the accumulation of toxic and harmful substances.

When dealing with a low-grade complex Zinc ore from Inner Mongolia, problems of low leaching rate, high energy consumption, low economic benefits and pollution were encountered. To treat this low-grade zinc ore economically and effectively, bioleaching was used. This approach produces reliable data for an environmentally friendly and efficient processing of the zinc ore. The results indicate that Zinc occurs in the ore mainly as sphalerite, the latter also containing Indium. The experimental results demonstrated an excellent leaching performance: A leaching rate of nearly 100% is achieved at a temperature of 45°C, a pulp concentration of 10%, an initial pH of 1.8, and an aeration rate of 0.8m3/h. In the initial stage the leaching rate is higher than at the end. It starts with 85% of zinc leaching rate in three days. The Indium in the sphalerite is leached almost completely. This makes a further comprehensive use of such resources possible.

The transformation of selenium-containing phases in copper anode slimes during the leaching process was investigated based on the Eh–pH diagram, leaching efficiencies of metals, and characterization of the residues produced during leaching. The leaching efficiency of selenium increases slowly to 17.7% in the first 50 min and then more rapidly to 98.3% in the next 110 min. The Eh–pH diagram indicates that elemental selenium is an intermediate product of the oxidation of selenide to selenite. The x-ray powder diffraction data and scanning electron microscopy–energy-dispersive x-ray spectroscopy data demonstrate that selenium leaching can be divided into three stages. Ag-Cu selenide first transforms into silver selenide and then converts to elemental selenium. Finally, elemental selenium is dissolved as selenite. The intermediate product, elemental selenium, is the main reason for the slow initial leaching rate of selenium.

A new method was proposed for extracting selenium from copper anode slimes with a low concentration of nitric acid in a sealed sulfuric acid leaching system. It is performed under an atmosphere of oxygen which allowed for a cyclic utilization of nitric acid. The effects of main parameters on selenium leaching were studied. The mineralogical characterizations of the typical samples were investigated by XRD and SEM. The results showed that the optimal conditions of the process are considered to be total gas pressure of 0.1 MPa, leaching temperature of 388 K, solid-liquid ratio of 0.20 g mL–1, H2SO4 concentration of 2 mol L–1, HNO3 concentration of 0.07 mol L–1 and leaching time of 2 h. The high selenium leaching efficiency of 99.23% was obtained under these conditions. According to the results of XRD and SEM-EDS, Cu–Ag selenide in the raw anode slimes is difficult to be leached with sulfuric acid alone; copper can be leached more easily from Cu-Ag selenide than silver; selenide is oxidized into the solution, undergoing the intermediate product of elemental selenium.

Based on the Eh–pH diagram for the Se–H2O system, a new method is proposed for leaching selenium from copper anode slimes using a nitric acid–sulfuric acid mixture. The effects of solid/liquid ratio, HNO3 and H2SO4 concentrations, leaching temperature, and reaction time on the leaching efficiency of selenium were investigated. Samples were mineralogically characterized by x-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy to study the transformation of selenium-containing phases during the leaching process. The results showed that the optimal conditions comprised a solid/liquid ratio of 0.25 g/ml, HNO3 concentration of 0.5 M, H2SO4 concentration of 2 M, leaching temperature of 363 K, and reaction time of 3 h. A selenium leaching efficiency of 97.79% was obtained under these conditions. Mineralogical characterization indicated that selenium occurred as Cu–Ag selenide in the raw copper anode slimes. This was first converted to elemental selenium and then to selenite ions in solution.

An effective process for recycling lead from hazardous waste cathode ray tubes (CRTs) funnel glass through traditional lead smelting has been presented previously. The viscous behavior of the molten high lead slag, which is affected by the addition of funnel glass, plays a critical role in determining the production efficiency. Therefore, the viscosities of the CaO–SiO2–“FeO”–12wt%ZnO–3wt%Al2O3 slags were measured in the current study using the rotating spindle method. The slag viscosity decreases as the CaO/SiO2 mass ratio is increased from 0.8 to 1.2 and also as the FeO content is increased from 8wt% to 20wt%. The breaking temperature of the slag is lowered substantially by the addition of FeO, whereas the influence of the CaO/SiO2 mass ratio on the breaking temperature is complex. The structural analysis of quenched slags using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy reveals that the silicate network structure is depolymerized with increasing CaO/SiO2 mass ratio or increasing FeO content. The [FeO6]-octahedra in the slag melt increase as the CaO/SiO2 mass ratio or the FeO content increases. This increase can further decrease the degree of polymerization (DOP) of the slag. Furthermore, the activation energy for viscous flow decreases both with increasing CaO/SiO2 mass ratio and increasing FeO content.

In recent years, an increasing attention has been paid to the bioleaching of copper from waste computer motherboards. Here, we investigate the effect of humic acid on the bioleaching of waste computer motherboards using the mixed culture HQ0211. For this, the response surface methodology (RSM) is employed to investigate the effect of pulp density, initial pH and humic acid content on copper recovery. Samples leached at optimized experimental conditions according to RSM were analyzed by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The results show that under optimum conditions; the initial pH = 1.53, pulp density = 1.35% (w/v) and humic acid addition = 0.31 g/L, a complete the copper leaching could be achieved. According to the results, the effectiveness of the bacterial and its capability to oxidize humic acid was proved. Overall, the biological leaching was found to be more effective than the chemical leaching. Humic acid can promote the bioleaching of waste computer motherboards, reducing its environmental hazards.

Heap biooxidation method was used to evaluate the availability of Paodaoling gold ore in Anhui province, China. 15,000 tons of gold ores (≤ 10 mm in diameter) were bioxidized under mesophilic conditions. Under the synergistic effect of microbial community, arsenic and sulfur were oxidized by 42% and 38% after 80 days. Relatively, leaching of gold was improved from 36 to 78% after heap biooxidation. The sequencing results showed there were 28 operational taxonomic units identified the microbial community in the heap. The main genera were Acidithiobacillus, Ferroplasma, Acidiferrobacter and Nitrospira. According to stoichiometry, the content of microorganisms with various functions tended to be balanced. The biomass production rate was 10 g/s, the CO2 fixation rate was 18 g/s, and the oxygen consumption rate was 60 g/s. This study provides a good basis for the further design and application of heap biooxidation technology.

Phanerochaete chrysosporium was used to decompose elemental carbon in Carbonaceous gold ore and enhance cyanide recovery of gold. The degradation of elemental carbon amounted to 34% due to fungal treatment for 14 days. A positive correlation between the fungal degradation of elemental carbon and the activity of degradation enzymes was noted. Organic acids and nitrogenous bases, which are generated by the fungi, caused the degradation of elemental carbon indirectly. P. chrysosporium caused a surface exfoliation of elemental carbon in the form of layers and the destruction of the microcrystalline and pore structure. The amount of oxygen-containing groups and of aliphatic groups was increased. The amount of aromatic rings, the specific surface area, the pore volume and the condensation index of aromatic rings were decreased. Also the thermal properties of elemental carbon changed significantly, whereas the amount of the low-stability compounds was increased. P. chrysosporium can reduce the interference of elemental carbon with the cyanide recovery of gold. The amount of gold recovery increased from 44% to 62%. This improvement is ascribed to the combined effect of degradation and passivation of elemental carbon by P. chrysosporium .

In this study, the operating mechanism of a Knelson concentrator (KC) is analyzed by considering the concentration mechanisms of dense minerals obtained based on the feed properties, operating parameters, and design parameters of the KC bowl. The efficiency of the KC is affected by all the studied factors, i.e., the structural parameters of the ring, water flow rate, rotating speed, and gangue size distribution, which further restrict each other and act together. A concentration criterion ( X i ), which is the ratio of the settling velocity to the fluidized water flow velocity, is defined to obtain the correlation between these four key factors. Based on the mechanistic linkage provided by the aforementioned criterion, these factors affect the KC performance because they influence the concentration mechanism. This determination was obtained as follows: as the magnitude of X i increased, the concentration mechanism of the dense mineral transformed from surface plating to substitution and then to elutriation, followed by overload. In case of surface plating, the size distribution of the dense mineral in each ring was similar to that of the feed, and recovery increased gradually from ring R1 to ring R5. In case of substitution, the coarse and dense particles replaced the light particles and formed a thick concentrate layer, with high concentrate grade and tungsten recovery. In case of elutriation, the tungsten particles completely replaced the quartz particles and preferential enrichment could be observed at the bottom of the ring; in this case, the concentrate grade and recovery were the highest and the tungsten particle size was the coarsest. Further, some fine and dense particles were carried into the tailings because of the large water flow velocity.

The Knelson concentrator (KC) is widely used in gold ore and other precious metal ore processing technology because of its excellent separation performance. The development history and types of KCs are reviewed in this paper. Research on the separation mechanism and characteristics of KCs was analyzed and discussed, including the separation characteristics, influencing factors, modification equipment, gravity recoverable gold (GRG) tests, mathematical models, and computer simulations. Two different configurations of a KC for the gold recovery process and the research and application status of KCs in the fields of fine coal, rare earth, platinum group metals, and other minerals were summarized. Based on our review, research trends and development prospects of KCs are proposed.

In the original publication the section heading “Classification of microorganisms” appearing above the sub-section “Air and liquid circulation in the heap” in page four is incorrect. The correct section heading should be read as “Results and discussion". Korrektur zu 10.1007/s00792-020-01160-6

The basic principle of a Knelson Concentrator (KC) is the differential settling velocities of particles in a medium under a centrifugal field. Whether the ore particles remain in the KC bowl depends on the terminal settling velocity ( v ) of the particles and the fluidization water flow velocity ( V ). Both variables are functions of the material properties and the operating parameters. This study reports the relations between the retained mass of quartz in each ring of the KC bowl (obtained by measuring the quartz mass ring by ring) and the rotational speed, fluidization water flow rate, and particle size. The retained mass of quartz in each ring was then modeled by approximating the fluidization water velocity and defining a new ratio v / V . Based on the experimental data, the functional relation between the quartz mass in each ring of the KC bowl and the feed particle properties/operating conditions was fitted by a Weibull model. The model established by the ring-by-ring approach gives more accurate predictions than a previous model, and a model based on the quartz mass in the entire bowl.

A series of novel 1,5-diphenyl-3-spirobifluorenyl pyrazoline derivatives have been synthesized and characterized by 1 H NMR, X-ray crystallography, UV–vis and fluorescence spectroscopy and mass spectrometry. Their maximum UV–vis absorption wavelengths were between 386 and 395 nm, and the fluorescence emission wavelengths were between 459 and 469 nm, which belongs to the typical blue light emission. All compounds exhibited excellent absolute fluorescence quantum efficiency (AFQE) (>90%) in solution. Moreover, at solid phase, compound 4f also displayed good AFQE (54%). The energy gaps of these derivatives were between 2.8 and 3.0 eV, typical for the blue light emission. Molecular orbital calculations revealed that the HOMO and LUMO energy levels were close to 1,3-diphenyl-5-(9-phenanthryl)-4,5-dihydro-1H-pyrazole (DPPhP). The high fluorescence quantum efficiency, appropriate energy gaps and HOMO and LUMO energy levels prove that 1,5-diphenyl- 3-spirobifluorenyl pyrazoline derivatives have the potential to be used as blue light emitting materials.

In this study, the effect ofPhanerochaete chrysosporiumon graphite was investigated, and graphite was used as a substitute of elemental carbon in carbonaceous gold ores. Under the condition of optimum process, the fungal degradation rate of graphite reached to 13.49%, and the carbon content of graphite was decreased by 5.13%. XRD analysis indicated thatPhanerochaete chrysosporiumcould destroy the crystal structure of graphite. FTIR analysis indicated thatPhanerochaete chrysosporiumcould increase the number of aliphatic structures and oxygen-containing groups. The cyanide leaching gold tests showed thatPhanerochaete chrysosporiumcan decrease the preg-robbing capacity of graphite, about 9.52%. It indicated thatPhanerochaete chrysosporiumis an available microorganism, which was employed to pre-treat carbonaceous matter in carbonaceous gold ores to reduce the interference of gold cyanidation leaching.

The function of microorganism and dissolution reaction pathway of carrollite in the bioleaching process were investigated. The results showed that both indirect and contact mechanisms influenced the leaching process. The dissolution of carrollite was significantly accelerated when bacteria were adsorbed on the mineral surface, indicating that the contact mechanism significantly affected the dissolution of carrollite. During bioleaching, the sequence of oxidation state of the sulfur moiety of carrollite was as follows: S−2→S0→S+4→S+6. Elemental sulfur precipitated on the mineral surface, indicating that the dissolution of carrollite occurred via the polysulfide pathway. The surface of carrollite was selectively corroded by bacteria, and oxidation pits with different sizes were observed at various sites. Elemental sulfur, sulfate and sulfite were present on the surface of carrollite during the leaching process, and may have formed a passivation layer on mineral surface.

The effects of activated carbon and/or surfactants on the bioleaching behavior of cobalt ore have been investigated in this paper. It was demonstrated that activated carbon and surfactants (Tween-20 and Tween-80) can significantly promote the dissolution rate of carrollite, either individually or in combination when coupled with ZY101 bacteria strain. The cobalt leaching efficiency increased from 71.3% to 90.8% when 1.0 g/L activated carbon was added, and such an improvement was ascribed to the galvanic interaction between activated carbon and carrollite. In addition, the leaching efficiency of cobalt increased from 71.3% to 92.4% by 0.1 g/L Tween-20 or to 93.2% by 0.1 g/L Tween-80, by changing the surface condition of the mineral and accelerating the bio-oxidation of formed elemental sulfur. When both activated carbon and surfactant were added, the leaching efficiency of cobalt increased by more than 22%, and meanwhile the leaching time decreased by more than 30%. It is shown that the catalytic effect of the combined catalyst was much more significant than that when only using a single catalyst. A similar trend was observed in the case of elemental copper extraction during the bioleaching process.

Intensifying effects of ferrous sulfate and pyrite on bioleaching of low-grade molybdenite concentrate were studied in this paper. The experimental results show that the oxidation dissolution of molybdenite can be accelerated with the addition of either ferrous sulfate or pyrite in bioleaching medium. Pyrite has better enhancing effect than ferrous sulfate, and the highest molybdenum leaching rate in pyrite-added solutions is 20.85 %, increasing by 12.64 % compared with that in 9 K leaching system. Molybdenum leaching rate does not increase linearly with the increase of the addition of either ferrous sulfate or pyrite in each type solution. Great amounts of [NH4Fe3(SO4)2(OH)6] and [KFe3(SO4)2(OH)6] with different morphologies will be deposited on molybdenite ores when the additions of Fe from ferrous sulfate or pyrite exceed that from 9 K leaching system by 0.5 times, and these deposits hinder the oxidation dissolution of molybdenite to some extent.

The efficient extraction of copper as a valuable metal from waste printed circuit boards (WPCBs) is currently attracting growing interest. Here, we systematically investigated the impact of bacteria on the efficiency of copper leaching from WPCBs, and evaluated the effect of graphite on bioleaching performance. The HQ0211 bacteria culture containing Acidithiobacillus ferrooxidans, Ferroplasma acidiphilum, and Leptospirillum ferriphilum enhanced Cu-leaching performance in either ferric sulfate and sulfuric acid leaching, so a final leaching of up to 76.2% was recorded after 5 days. With the addition of graphite, the percentage of copper leaching could be increased to 80.5%. Single-factor experiments confirmed the compatibility of graphite with the HQ0211 culture, and identified the optimal pulp density of WPCBs, the initial pH, and the graphite content to be 2% (w/v), 1.6, and 2.5 g/L, respectively.