Fayalite Research Articles

Water purification from heavy metal ions by nano-sized Fe0/kaolinite composites

We have investigated the physicochemical features of the purification of wastewater that are complex on its content and include a mixture of heavy metal ions (Cu(II), Cd(II), Zn(II), Co(II), Cr(VI)). The phase of a composition and structural-sorption characteristics of synthesized nano-sized Fe0/kaolinite composites were studied. It was found that the obtained materials have much better sorption properties for the extraction of heavy metals from aqueous solutions in comparison with natural kaolinite. Calculations of sorption isotherms according to the Freundlich equation are done. Based on isotherms, the average values of specific sorption per unit of an active surface of the mineral at the content of heavy metal ions in the initial solutions of 300 μmol/dm3 were determined. They range from 0.42 to 17.1 μmol/g for Cr(VI) to Cu(II) ions. It has also been found that similar values for the modified samples are much larger and range from 13.8 to 80.27 μmol/g for ions from Cr(VI) to Cu(II). It is shown that composite sorbents based on nano-sized zero-valent iron and dispersed kaolinite silicate are effective sorbent materials for the purification of water contaminated with toxic heavy metal ions that are commonly found in wastewater of the galvanic and hydrometallurgical industries.

Selective leaching of lead from lead smelter residues using EDTA.

Ethylenediaminetetraacetic acid (EDTA) has been widely used as an effective reagent for removal of lead from soil because of its high lead extraction efficiency caused by the high thermodynamic stability of the Pb(ii)–EDTA complex. In this study, EDTA was used as a lixiviant for recovery of lead from residues (matte and slag) of secondary lead smelter plants. The residues were composed mainly of iron (34–66 wt%) and lead (7–11 wt%). Leaching parameters (EDTA concentration, pH, temperature, liquid-to-solid ratio and leaching time) were optimized. The optimum leaching efficiency was achieved when leached for 1 h at room temperature using 0.05 mol L−1 EDTA at a liquid-to-solid ratio of 5 mL g−1. At such conditions, 72 to 80% of lead and less than 1% of iron were leached from both matte and slag. The high selectivity towards lead with minimal co-dissolution of iron is a major advantage since it reduces the chemical consumption and simplifies the downstream processes. Although the stability constants of the complexes Fe(iii)–EDTA, Fe(ii)–EDTA and Pb–EDTA are all large (log KS 25.1, 14.33 and 18.04, respectively), the leaching of iron was most likely limited by its presence in insoluble phases such as iron oxides, sulfides and silicates in the residues. 100% leaching of lead was achieved by a multi-step leaching process where the leaching residues were contacted three times by a fresh EDTA solution. To recover EDTA, first iron was precipitated as iron hydroxide by raising the pH of pregnant leach solution (PLS) above 12.6 using sodium hydroxide, followed by precipitation of lead as lead sulfide by adding ammonium sulfide. The recovered EDTA was successfully reused two times for leaching without significant changes in leaching yields.

Zinc-iron silicate for heterogeneous catalytic ozonation of acrylic acid: efficiency and mechanism.

This research aimed at researching the degradation of acrylic acid (AA) in aqueous solution, by catalytic and non-catalytic ozonation processes performed in a semi-continuous reactor. Zinc–iron silicate was synthesized and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, Fourier transformation infrared (FT-IR) and energy dispersive spectrometry (EDS). The characterization studies showed that Fe–Si binary oxide, Zn–Si binary oxide, ZnO and Fe2O3 deposits were formed on the surface of poor crystallinity zinc–iron silicate which contained abundant functional groups. Catalytic ozonation test results revealed that zinc–iron silicate exhibited high catalytic activity and stability in catalytic ozonation of AA in aqueous solution. The inclusion of zinc–iron silicate in the ozonation process enhanced AA decomposition by 28.7% and TOC removal by 20%, compared to the ozonation alone. The main AA removal mechanisms involved direct oxidation by ozone and indirect oxidation by hydroxyl radicals generated by the ozone chain reaction accelerated by zinc–iron silicate. The surface characteristics and chemical composition are significant factors determining the catalytic activity of zinc–iron silicate.

From molecules to nanoparticles to functional materials

Functional nanomaterials have held a steady position at the frontier of materials science and engineering in the 21st century. ?Molecular Designing of Nanoparticles with Controlled Morphological and Physicochemical Characteristics and Functional Materials Based on Them? was the title of the research project funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia and performed between 2011 and 2019 in the interdisciplinary area of nanoscience and nanotechnologies. Research activities within this program were divided into five interrelated topics: 1) from molecules to nanoparticles; 2) advanced ceramics with improved functional properties; 3) electrode materials for lithium?ion batteries; 4) nano-calcium phosphate in preventive and regenerative medicine; 5) biodegradable microand nano-particles for the controlled delivery of medicaments. This report gives an insight into this bibliographically most impactful Serbian national project on nanotechnologies executed within the aforementioned nine-year cycle, 2011?2019, focusing here only on the results achieved in the past three years. The project provided an outstanding and internationally recognized contribution to synthesis, characterization and functional design of a number of materials systems, including pure and lanthanide?doped hydroxyapatite, zinc oxides, sodium cobaltates, lithium iron pyrophosphates, lithium iron silicates and a number of polymeric systems.

Flotation separation of specularite from chlorite using propyl gallate as a collector.

Separation of specularite from iron-containing silicate iron ore is challenging due to the similar surface properties of minerals and gangues. In this work, propyl gallate (PG) was applied as a chelating collector to separate specularite from chlorite. The flotation results indicated that collector sodium oleate (NaOL) shows little selectivity for the separation of specularite and chlorite. In contrast, the separation of specularite can be achieved with no depressant required when PG was used as the collector. The optimal separation results were obtained for single mineral flotation with recoveries of 87.11% and 6.98% for specularite and chlorite, respectively, and for mixed mineral flotation with 65.13% TFe grade and 76.28% TFe recovery, when the slurry pH was 8 and PG concentration was 40 mg L−1. FT-IR and XPS analyses indicated that PG could be favorably adsorbed on specularite via phenolic hydroxyl groups, and molecular dynamic simulation results further elucidated the adsorption mechanism. This research suggested that the chelating flotation collector could be effective in the separation of minerals from iron-containing silicate iron ores.

Control of Platinum Loss in WEEE Smelting

In spite of significant economic value, the solubilities of the platinum group and precious metals in metallurgical copper smelting slags are not well known. Recent experimental information on iron-free and low-iron silicate melts indicates that the chemical solubility of platinum is very low, < 1 ppmw (part per million weight). In this study, the concentration of platinum in alumina spinel-saturated iron silicate slags in equilibrium with a solid iron-platinum alloy was measured as a function of oxygen partial pressure at 1300°C. The results were converted to unit activity of platinum by the thermodynamic properties of the iron-platinum alloy formed. This allowed the mechanism of dissolution of platinum in the slag and the forms of platinum species in alumina-rich iron silicate slags in copper scrap smelting and refining conditions to be obtained. Our findings explain some inconsistent results in the geochemical literature by proposing an anionic dissolution mechanism at low oxygen partial pressures in iron-containing silicate slags.

Phase Equilibrium Studies of Iron Silicate Slag Under Direct to Blister Copper-Making Condition

Direct to blister (DTB) accounts for a significant process for copper making due to its simplified process chain and the production of a single stable SO-concentrated off-gas. In this study, the phase equilibria of iron silicate slags in the Cu-Fe-Si-S-O system at controlled atmosphere were, for the first time, experimentally investigated in the spinel primary phase field. The liquidus temperatures were quantified, including the equilibrium “CuO” content as well as the solid solutions in spinel.

Segregation of Na, K, Rb and Cs into the cores of Earth, Mars and Vesta constrained with partitioning experiments

Alkali metals Na, K, Rb and Cs are depleted in planetary mantles and their depletion is commonly attributed to the effect of volatility during the condensation of the first solids in the solar nebula or the high temperatures involved during planetary growth. Most models of planetary differentiation assume that alkalis behave entirely as lithophile elements and do not participate in core segregation. Here, we tested this hypothesis by determining experimentally the partitioning of Na, Cs and Rb between iron sulfide and silicate (Dsulf/sil) and combining it with available data from the literature on K, Na and Cs partitioning. Our experiments were conducted at 1–3.5 GPa, with an additional one at 8 GPa, 1600–1900 °C, and varying FeO contents, which lead to a relatively large range of O content in the sulfide phases (up to 13 wt%). We found maximum Dsulf/sil of 0.8, 0.4, and 0.36 for Na, Cs and Rb respectively. In addition, Dsulf/sil for Na, K, Cs and Rb increases with temperature and O content in the sulfide and decreases with FeO content in the silicate. The degree of polymerization of the silicate melt and the S content of the sulfide additionally increase Dsulf/sil for Na, K and Cs. Since the solubility of O in sulfides is correlated with the FeO content of the silicate and both have opposite effects on Dsulf/sil, varying the oxidation state of equilibrating material does not significantly affect Dsulf/sil, which is more controlled by the temperature of equilibration. We modeled core formation for Earth, Mars and asteroid Vesta, assuming that some of the accreted embryos contained immiscible sulfides, that segregated into planetary cores. Our results show that with such a scenario, significant amounts of Na, K, Cs and Rb were sequestered in planetary cores, leading to core/mantle distribution of alkalis between 4·10−5 and 0.15. The depletion of alkalis in the mantles of Earth, Mars and Vesta could have resulted from combined effects of volatility and core segregation, but are largely due to volatile depletion in the accreting materials.

Impact of MgO and K2O on Slag-Nickel Matte Equilibria

Slag chemistry of the direct nickel matte smelting was studied in typical industrial high-grade nickel matte smelting conditions at 1400 °C and 0.1 atm pSO2. The experimental technique used involved equilibration, quenching and direct elemental phase composition analysis by Electron Probe X-ray Microanalysis. Magnesia and potassia, a typical gangue constituent of sulfidic nickel concentrates and a common impurity of industrial grade silica flux (sand), respectively, were adopted as slag modifiers in concentrations typical to industrial operations. Their effects on oxidation degree of the nickel-copper-iron matte and equilibrium concentrations of Ni and Cu in the slag were studied as a function of oxygen partial pressure. Solubility of silica in the slag increased significantly with additions of MgO and K2O in the constrained case studied, at silica saturation. Equilibrium concentrations of Ni and Cu in the slag containing MgO and K2O were about a quarter lower compared to the pure iron silicate slag, in the entire oxygen partial pressure range studied.

Interaction between iron ore and magnesium additives during induration process of pellets

To eliminate the adverse effect of incompletely mineralized magnesium additive on pellets strength, clarify the interaction between additives and iron ore during the induration process, two types of interaction couples were prepared and scanning electron microscopy-Energy dispersive spectrometer was used to study the diffusion of elements and phase transformation during the induration. Results show that the diffusion of Mg dominates both interactions. The diffusion of Fe from ore to magnesia fines and magnesium olivine are accompanied by the migration of Si, the former generates Magnesioferrite and Forsterite while the latter also generates Fayalite. For the diffusion of Mg from magnesia fines to ore, Mg only reacts with iron oxides and forms Magnesioferrite, but in the ore-olivine couple, Mg both diffuses into iron oxides and silicate, which indicates that the reaction mechanism of two couples is different. The interaction schematic diagrams of each couple are given in this paper.

Investigation of Solid Residues Obtained After Oxidized Nickel Ore Leaching

Leaching residues of oxidized nickel ores is studied. According to the results of chemical analysis, it is found that with 62% extraction of nickel into the solution residues contain, wt.%: 0.58 Ni, 0.016 Co, 14.35 Fe, 9.08 Mg, 1.96 Al, and 21.16 Si. With 89% extraction residues contain, wt.%: 0.26 Ni, 0.001 Co, 6.5 Fe, 9.12 Mg, 1.46 Al, and 26.45 Si. The grain size composition of leaching residues is studied. It is found that the amount of fine fraction (– 2.5 + 0 mm) in the residues with 89% extraction almost doubles compared with the initial ore, and the amount of coarse fraction (– 21.5 + 10 mm) is halved. X-ray phase and X-ray microanalysis methods are used in the work to study residues from leaching oxidized nickel ores (ONO). With extraction of 62% of nickel from ONO nickel is detected predominantly in talc, iron oxides, and siliceous iron oxides. Nickel is not detected in leaching residues with 89% recovery.

Behavior of Ga, In, Sn, and Te in Copper Matte Smelting

The distributions of Ga, In, Sn, and Te between copper-iron mattes and silica-saturated iron silicate slags over a wide range of matte grades 55 to 75 pct Cu were determined at 1300 °C using a gas-phase equilibration-quenching technique and direct phase composition analysis by Electron Probe X-ray Microanalysis and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. Alumina from aluminum, a typical minor element of electric and electronic copper scrap, and lime were adopted as slag modifiers for increasing the trace element recoveries. Gallium and tin were distributed predominantly in the slag, indium preferred sulfide matte at low matte grades and slag at high, whereas tellurium strongly favored the sulfide matte in particular in high matte grades. The slag modifiers alumina and lime had a minor impact on the distribution coefficients of gallium and tin, but for indium and tellurium the distribution coefficients were more strongly affected by the basic oxides. The strong tendencies of tin and tellurium to vaporize at the experimental temperature were confirmed.

Evolution of diamond-forming systems of the mantle transition zone: ringwoodite peritectic reaction (Mg,Fe)2SiO4 (experiment AT 20 GPa)

The peritectic reaction of ringwoodite (Mg,Fe)2SiO4 and silicate-carbonate melt with formation of magnesiowustite (Fe,Mg)O, stishovite SiO2 and Mg, Na, Ca, K-carbonates is revealed by experimental study at 20 GPa of melting relations of the multicomponent MgO-FeO-SiO2-Na2CO3-CaCO3-K2CO3 system of the Earth’s mantle transition zone. A reaction of CaCO3 and SiO2 with the formation of Ca-perovskite CaSiO3 is also detected. It is shown that the peritectic reaction of ringwoodite and melt with the formation of stishovite physic-chemically controls the fractional ultrabasic-basic evolution of both magmatic and diamond-forming systems of the deep horizons of the transition zone up to its boundary with the Earth’s lower mantle.

Pyroxene control of H2 production and carbon storage during water-peridotite-CO2 hydrothermal reactions

Strategies of H2 production and CO2 mineralization were combined through olivine [(Mg,Fe)2SiO4] serpentinization and carbonation in a CO2-rich hydrothermal system. However, natural mantle peridotites commonly contain not only olivine but also orthopyroxene and/or clinopyroxene, which have effects that are not well understood. The present study investigated the reactions in H2O-olivine/orthopyroxene-CO2 systems by performing hydrothermal experiments in 0.5 M NaHCO3 solutions at 300 °C and 10 MPa.The yields of H2 and HCOOH initially were first suppressed in the presence of orthopyroxene; however, after orthopyroxene consumption, the rate of H2 production increased significantly. H2 yield increased to 348.3 mmol/kgmineral in 120 h with the presence of 20 wt% orthopyroxene at the beginning of the reaction. The initial suppression of H2 generation was due to incorporation of more Fe(II) into serpentine [(Mg,Fe)3Si2O5(OH)4] in the high SiO2(aq) concentration system. The presence of orthopyroxene also dramatically accelerated serpentine formation. In contrast, magnesite [(Mg,Fe)CO3] formation was inhibited upon addition of orthopyroxene, which also contributed to the release of Fe(II). Therefore, peridotite containing ≤20 wt% of pyroxenes is more suitable for long-term H2 production than pure olivine. When considering the reaction output of a water-peridotite-CO2 system, controlling the percentage of pyroxenes in the starting mineral may be more important than expected.

Characterization of 3D-printed acrylonitrile-butadiene-styrene with nanoparticles

In addition to being used to produce prototypes rapidly, three-dimensional (3D) printing is now being used in the fabrication of functional materials, such as capsule hotels and energy-saving youth apartments, which can be manufactured through 3D printing at a cost advantage. Due to the small internal space and high-density arrangements of capsule hotels, the antistatic, fireproofing and electromagnetic shielding properties of the construction materials are important. Furthermore, an outdoor-type capsule hotel requires significant toughness (impact strength) to cope with unexpected events. In this study, a natural serpentinite was ground into nanopowder and added into fireproof acrylonitrile-butadiene-styrene (ABS) plastic material to 3D-print test specimens. Then, the hardness, tensile strength, impact strength and antistatic and electromagnetic properties of the mineral particle-reinforced ABS plastic were investigated. The experimental results showed that adding 3 wt.% sintered magnesium silicate–iron nanopowder into the ABS plastic to form ABS materials (ABSM) resulted in a higher degree of hardness and improved wear resistance, tensile strength and impact strength. After 3D printing, the ABSM molecular bonding characteristics showed no significant change (fireproofing was maintained), as examined through Fourier transform infrared spectroscopy. However, the antistatic force and electromagnetic shielding both increased significantly. Accordingly, ABSM can be used to enhance public safety and health.

Role of Fe(II) Content in Olivine Carbonation in Wet Supercritical CO2

Basalt geologic reservoirs are targeted for carbon storage because they are abundant in divalent silicates such as olivine [(Mg,Fe)2SiO4] that can carbonate to permanently trap CO2. Under reservoir...

Evolution of Diamond-Forming Systems of the Mantle Transition Zone: Ringwoodite Peritectic Reaction (Mg,Fe)2SiO4 (Experiment at 20 GPa)

Abstract—The peritectic reaction of ringwoodite (Mg,Fe)2SiO4 and silicate–carbonate melt with formation of magnesiowustite (Fe,Mg)O, stishovite SiO2, and Mg, Na, Ca, K-carbonates is revealed by experimental study at 20 GPa of phase relations in the multicomponent diamond-forming MgO–FeO–SiO2–Na2CO3–CaCO3–K2CO3 system of the Earth mantle transition zone. An interaction of CaCO3 and SiO2 with a formation of Ca-perovskite CaSiO3 is also detected. It is shown that the peritectic reaction of ringwoodite and melt with the formation of stishovite controls physicochemically the fractional ultrabasic-basic evolution of both magmatic and diamond-forming systems of deep horizons of the transition zone up to its boundary with the Earth lower mantle.

Recovery of rare earth elements minerals from iron oxide–silicate rich tailings – Part 2: Froth flotation separation

This study is the second part of an ongoing investigation to recover and upgrade rare earth elements (REE) minerals from iron oxide–silicate rich tailings (IST) generated at a South Australian mining operation. Previous work (Part 1) has shown that REE minerals are preconcentrated in a high-intensity magnetic concentrate and non-magnetic tails along with iron oxides and silicate minerals, respectively. As a part of the overall beneficiation and enhanced REE minerals recovery strategy, complementary studies involving downstream froth flotation of the magnetic preconcentrates were conducted and the results presented in this paper. Froth flotation of the preconcentrates was carried out using sodium oleate and hydroxamic acid as collectors in the presence of sodium silicate and starch as depressants. A comparison of rougher flotation of the preconcentrates indicated that hydroxamic acid produced higher total rare earth oxides (TREO) recoveries (91–93%) with enrichment ratio ranging 1.03–1.30, whereas sodium oleate produced relatively higher upgrade (1.50–1.55 ratios) with significantly lower recoveries (12–36%). Scavenger and cleaner flotation tests were conducted on selected concentrates and tails, where further upgrade was achieved at the expense of recovery. Two process flowsheets for recovering REE minerals were then developed. Flowsheet 1 includes magnetic preconcentration followed by flotation using both collectors, whilst Flowsheet 2 includes magnetic preconcentration prior to hydroxamic acid flotation. Typical metallurgical results indicated Flowsheet 1 produced a final concentrate grade of 1.55% at 55% TREO recovery, whilst rejecting 47% Fe and 74% Si, whereas a final concentrate grade of 1.67% at 72% TREO recovery, with 39% Fe and 59% Si removed using Flowsheet 2. The REE minerals, in combination with mainly silicates in the non-magnetic tails, allows better upgrade, with 2.5 times enrichment through hydroxamic acid flotation, compared to 1.93 times enrichment from the REE–iron oxides magnetic preconcentrate. Florencite, which was not recovered and upgraded by magnetic separation, was successfully recovered and upgraded along with bastnäsite and monazite by froth flotation. The study has revealed that froth flotation can be used to complement the recovery of REE minerals by magnetic separation, suggesting the IST could be exploited for REE beneficiation. However, it is obvious that minerals liberation and particle size distribution are critical in achieving enhanced REE minerals recovery and upgrade.

Slag Cleaning Equilibria in Iron Silicate Slag\u2013Copper Systems

In this study, the equilibrium distributions of selected trace elements between molten iron-saturated copper alloy and selected iron silicate slags were measured, and the effects of silica fluxing on them. In addition to the copper and iron main components of the system, trace elements like antimony, gallium, germanium, gold, indium, and silver were added in experiments that spanned the temperature range of 1473–1573 K (1200–1300 °C). Experimental charges were quenched and prepared in polished mounts. In situ analyses of the resulting phases were made directly on the mounts without the need of phase separation prior to analysis. Electron probe X-ray microanalysis was used for concentrations at or above approximately 100 ppmw, and laser ablation-inductively coupled plasma-mass spectrometry for the lower concentrations in the slags. The very low slag concentrations of germanium, antimony, and indium obtained indicate that these elements can be removed from the slag by reduction, whereas gallium concentrations in the slag were high. Consequently, gallium removal from iron residues, such as zinc smelting jarosite, is difficult without volatilization. Based on the present observations, the industrial reduction processes for the treatment of smelting and refining slags as well as for the processing of iron residues, and extracting the reducible metal oxides and their metal values can be optimized. The target in fluxing should be to maintain the slag compositions with a silica concentration higher than about 28 wt%.

High Temperature Anti-Friction Behaviors of a-Si:H Films and Counterface Material Selection

In the present paper, the influence of self-mated friction materials on the tribological properties of hydrogenated amorphous silicon films (a-Si:H films) is studied systemically at high temperature. The results are obtained by comparing the tribological properties of a-Si:H films under different friction pair materials and temperatures. The a-Si:H films exhibit super-low friction of 0.07 at a temperature of 600 °C, and ceramic materials are appropriate for anti-friction behaviors of a-Si:H films at high temperature. The results of tribotests and observations of the fundamental friction mechanism show that super-low friction of a-Si:H films and ceramic materials of the friction system are involved in high temperature oxidation; this also applies to the tribochemical reactions of a-Si:H films, steel and iron silicate in open air at elevated temperature in the friction process.