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The existence of toxic and carcinogenic pentavalent antimony in water is a great safety problem. In order to remove antimony(V) from water, the purpose of this study was to prepare a novel graphene nano iron zinc (rGO/NZV-FeZn) photocatalyst via hydrothermal method followed by ultrasonication. Herein, weakly magnetic nano-Fe–Zn materials (NZV-FeZn, GACSP/NZV-FeZn, and rGO/NZV-FeZn) capable of rapid and efficient Sb(V) adsorption from water were prepared and characterised. In particular, rGO/NZV-FeZn was shown to comprise franklinite, Fe0, and graphite. Adsorption data were fitted by a quasi-second-order kinetic equation and Langmuir model, revealing that among these materials, NZV-FeZn exhibited the best Sb removal performance (543.9 mgSb gNZV-FeZn−1, R2 = 0.951). In a practical decontamination test, Sb removal efficiency of 99.38% was obtained for a reaction column filled with 3.5 g of rGO/NZV-FeZn. Column regenerability was tested at an initial concentration of 0.8111 mgSb L−1, and the treated water obtained after five consecutive runs complied with the GB5749-2006 requirement for Sb. rGO/NZV-FeZn was suggested to remove Sb(V) through adsorption-photocatalytic reduction and flocculation sedimentation mechanisms and, in view of its high cost performance, stability, and upscalable synthesis, was concluded to hold great promise for source water and wastewater treatment.

In this work, Fe3O4@ZnFe2O4 core/shell nanoparticles were obtained by depositing ZnO by the wet chemistry method on the surface of Fe3O4 nanoparticles seeds obtained by the chemical bath deposition method. Fe3O4 and Fe3O4@ZnFe2O4 were characterized by Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometry, Transmission Electron Microscopy, X-ray Diffraction, Ultraviolet–Visible Spectroscopy, Diffuse Reflectance, and Fourier Transformed Infrared Spectroscopy (FTIR). The Fe3O4@ZnFe2O4 nanoparticles formed an urchin-like spheres morphology (corresponding to Fe3O4) with a homogeneous shell of ZnFe2O4. XRD analysis showed a magnetite crystal structure for Fe3O4 and a franklinite (ZnFe2O4) crystal structure for the shell. Fe3O4@ZnFe2O4 showed higher crystallinity when applying a heat treatment, showing a crystal size of 9.12 nm with heat treatment and 9.43 nm without heat treatment. The diffuse reflectance results suggested an indirect band gap of 1.85 eV for Fe3O4 and two indirect band gaps of 1.85 eV and 2.54 eV for Fe3O4@ZnFe2O4. The FTIR results showed the effect of heat treatment on Fe3O4@ZnFe2O4 core/shell nanoparticles. A simple method was used for the synthesis of Fe3O4@ZnFe2O4.

Recycling of industrial waste has become a process of highly positive impact on the environment, industry and human health. The management of the electric arc furnace dust (EAFD) is a necessary and interesting task due to the possible recovery of its elevated metallic content (Zn, Pb, Cu, etc.). This reduces the environmental pollution generated by the leachability of its heavy metals and produces new revenues for the steel industries. In this work, a hydrometallurgical route was studied to extract the zinc present in EAFD. The research carried out using two carboxylic acids: sodium citrate and oxalic acid at moderate concentrations (≤ 0.5 M). The effect of pH, molar concentration and stirring speed was analyzed. Under pressure and ambient temperature, after 3 h of leaching, the results showed that both agents can leach zinc from waste, reaching metal extractions of approximately 50%. The more stable franklinite (ZnFe2O4) and hematite (Fe2O3) phases were not decomposed under these mild conditions. Citrate was especially promising due to its selectivity for zinc.

The effects of basicity and Al2O3 content on the chemistry of phases in iron ore sinter containing ZnO were investigated by Rietveld analysis of the X-ray diffraction (XRD) patterns. Bulk composition analysis was carried out using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and wet-chemical analysis. The composition of each phase was investigated using a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDX). It was found that ZnO exists in the franklinite and the silicoferrite of calcium and aluminum (SFCA) phases. With increasing ZnO content, the phase fraction of the franklinite increased, while the fraction of SFCA slightly increased. When ZnO content was fixed at 1 wt pct and basicity increased, the fraction of franklinite decreased and that of SFCA increased. Here, the solubility of ZnO in the SFCA increased. As the Al2O3 content increased, the fraction of franklinite decreased and that of SFCA increased, while ZnO content in the SFCA did not change significantly.

Large industrial productions generate large amounts of waste, and researchers are investigating alternatives to reuse them. For instance, these wastes can used to produce ceramic pigments in the ceramic tile industry. Electric-arc furnace dust (EAFD) is waste generated in the steelmaking process through the volatilization of metals from scrap and exhibits great potential for its use as a raw material in the production of ceramic pigments. The aim of this study is to produce glazes containing EAFD for ceramic tiles. The EAFD was characterized via laser diffraction, wavelength-dispersive X-ray fluorescence (WDXRF) spectroscopy, X-ray diffraction (XRD), thermogravimetric (TG), and differential thermogravimetric (DTG) analyses. Two glaze types (BGS and CBT) were produced with 2, 4, 6, and 8 wt.% EAFD and characterized via the Commission Internationale de I´Éclairage (CIE) L*a*b* values, abrasion resistance, and XRD. According to the particle size distribution analysis, the average particle size of the EAFD is 0.770 μm. Further, the chemical WDXRF analysis revealed that 44.60% of the EAFD is iron oxide and 26.24% is zinc oxide. According to the structural XRD analysis, the major crystalline phases of the EAFD are zincite, franklinite, magnetite, and other phases with spinel structures. The EAFD exhibits stability close to the firing temperature of the ceramic tiles (1130 °C). In addition, the ceramic tiles covered with both glazes became darker with increasing EAFD amount. These samples obtained a PEI 3 rating based on the abrasion analysis. Keywords: Glaze, Ceramic tiles, Electric-arc furnace dust (EAFD)

Nowadays, Nexa Resources (ex-Votorantim Metais) operates two zinc mines in Brazil, represented by the Vazante unit in Vazante - MG and the Morro Agudo unit in Paracatu - MG. The present study was carried out at the Vazante unit, where zinc concentrate is produced from a silicate ore called Willemite (Zn2SiO4) through froth flotation processes. The two main objectives of the study were the determination of the maximum zinc recovery that could be obtained in flotation bench tests with specific controlled conditions and the mineral characterization of the tailings generated, using a SEM/EDS (scanning electron microscope with energy dispersive x-ray spectroscopy) with MLA (mineral liberation analyzer). The flotation results showed a maximum recovery of 91.91 % with 1.68 % of zinc in the tailings after an eleven-minute flotation. Considering the mean results of all the tests, the maximum zinc recovery obtained was 91.07 % with 1.75 % zinc grade in the tailings. Mineral characterization analysis showed that zinc minerals besides Willemite, such as Gahnite and Franklinite are present in the zinc tailings. In addition, the analysis demonstrated that the Willemite present in the tailings is very fine (80 % < 0.015 mm) and well liberated. With no liberation problems, it was concluded that the main reason responsible for preventing zinc recovery to increase even more along the flotation tests was the presence of the extremely fine Willemite minerals. The test results showed that, to increase zinc recovery, two main processes needed to be considered. The grinding process, that will need to be improved and carefully revised to reduce Willemite fine grain size generation; and the flotation process, regarding bubble formation, reagent addition, resident time and a redesign of flotation machines, aiming to increase the recovery of extremely fine Willemite ore particles.

This study aims at detailed characteristics and comparison between dusts from various iron and non-ferrous metal production processes in order to identify individual mineral phases, chemical composition, and their influence on the values of magnetic susceptibility. Various analytical methods used include inductively coupled plasma optical emission spectroscopy, X-ray diffraction, scanning electron microscopy, and Mössbauer spectroscopy integrated with magnetic susceptibility measurements and thermomagnetic analysis. Metallurgical wastes that have arisen at different production stages of iron and non-ferrous steel are subjected to investigation. The analyzed dust samples from the iron and non-ferrous metallurgy differ in terms of magnetic susceptibility as well as their mineral and chemical composition. The research confirmed the presence of many very different mineral phases. In particular, interesting phases have been observed in non-ferrous dust, for example challacolloite, which was found for the first time in the dusts of non-ferrous metallurgy. Other characteristic minerals found in non-ferrous metallurgy dusts are zincite, anglesite, and lanarkite, while dusts of iron metallurgy contain mostly metallic iron and iron-bearing minerals (magnetite, hematite, franklinite, jacobsite, and wüstite), but also significant amounts of zincite and calcite.

Millions of tons of bottom ash (BA) is generated from incineration of industrial and municipal solid waste each year within EU. The magnitude of leaching of metals like Cu and Zn is critical for hazard and risk assessment of these ashes. Although speciation of metals is a key factor to understand and predict metal leaching, speciation of Cu and Zn in BA is not well known. In this study six metal separated and carbonized BA were investigated by a combination of X-ray absorption spectroscopy, X-ray diffraction, leaching/extraction tests, and geochemical modelling. Five of the BA were from grate boilers and one from a fluidized bed incinerator. The aims were to identify similarities in Cu and Zn speciation and to identify main species. The combination of several techniques was necessary to draw conclusions about speciation and displayed coherent results. A similar speciation of Cu and Zn was indicated in the five studied grate boiler ashes although the proportions between species may vary. Copper(II) oxide and Cu metal were the main Cu species in all BA. Zinc(II) oxide and willemite (Zn2SiO4) were identified in grate boiler ashes. The fluidized bed ash contained Zn-Si-minerals and possibly franklinite or gahnite, while the Zn(II) oxide content was low, if any. The results have implications for classification and risk assessment of MIBA. (C) 2020 The Authors. Published by Elsevier Ltd.

Microwave (MW) assisted chloride leaching was studied to remove valuable and heavy metals from two zinc plant residues,i.e.goethite sludge and Zn-leach product. For both materials, NaCl leaching parameters, such as temperature, NaCl concentration, leaching time and addition of acid, were optimized. For goethite sludge, the best efficiencies for Cu (45–47 %), Pb (83–90 %), and Zn (47–58 %) extraction, with a minimal dissolution of matrix elements, were obtained at 200 °C, 300 g/L NaCl and L/S 10. At short leaching times (5 min) the maximal leachability of Cu and Zn was reached, while at longer leaching time (60 min) the Pb extraction increased to 90 ± 1%. Zn leaching was limited due to the presence of stable franklinite (ZnFe2O4). NaCl (280 g/L) leaching of Zn-leach product required the addition of 1 M HCl to improve metal leaching to Ag 52 ± 3 %, Bi 83 ± 1 %, Cd 82 ± 4 %, Sb 39 ± 1 %, Zn 71 ± 2 % at 200 °C, L/S 10 for 30 min. Consequently, matrix dissolution was enhanced. Metal associations in Zn-leach product were statistically investigated. The environmental impact of the MW leached materials was evaluated by a one stage leaching test, which showed a significant overall reduction in heavy metal leachability compared to untreated materials.

The sample used for this study was a sulfide flotation concentrate that came from PT Lumbung Mineral Sentosa.The phase changes that occur in the particles of zinc sulfide concentrate during roasting in a muffle furnace were investigated using light microscopy, X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) while its chemical composition was analyzed using atomic absorption spectroscopy (AAS) and X-ray fluorescence (XRF) methods. Characterization also employed DTA-TGA instrument to provide data on the transformations that have occurred while the TGA data presents information about physical and chemical phenomena. Mineral composition of the sample included sphalerite, galena, chalcopyrite, and pyrite. Sphalerite was the most dominant one. Roasting sphalerite samples was intended to release the sulfur from its sulfide, Such a release was made easier for further treatment of the zinc such as a leaching process. Roasting temperature varied from 200 - 1,100 °C. Sphalerite starts to change when the temperature was raised to 650 °C performing the formation of zincite, franklinite, quartz and sphalerite as well. This composition did not change although the temperature increased to 1,100 °C. The Zn content within the original sample was 59.00% and then increased with the increasing of temperature but the improved in line with the increased temperature. The highest Zn was 78.98% achieved at 1,100 °C.

Mill scale is one of the most hazardous waste generated from the steelmaking industry. In 2014, around 16.4–32.8 million t of mill scale was generated all over the world. In this paper, we present recent results about the effect of the structure and microstructure of iron-rich glass-ceramics obtained from mill scale on their electrical behavior. Five iron-rich glass compositions were investigated. The crystalline phases of the crystallized (glass-ceramic) materials were identified by X-ray diffractometry, and phase content quantifications were performed by the Rietveld method. The crystallinity and porosity were also related to the electrical behavior of the glass-ceramics, which was determined by impedance spectroscopy, and the hardness, measured by the Vickers indentation method. Albite, andradite, anorthite, clinopyroxene, franklinite, nepheline, and spinel were shown to be the main crystalline phases present in the investigated compositions. The conductivity showed an increasing trend with the degree of crystallinity. This behavior was attributed to a decrease in porosity, an increase in the concentration of charge carriers in the glass phase (iron, Li+, and Na+), and an increase in the number of conduction paths through the glassy phase/crystalline phase interfaces. The relationship between hardness and crystallinity could not be verified due to the structural complexity of the glass-ceramics studied. However, a nearly linear relationship was found between the effect of porosity and hardness. The G2Z composition exhibited a hardness of 6.1 ± 0.5 GPa at 850 °C, which is a value in very good agreement with other iron-rich glass-ceramics studied.

Utilization of dusts generated from steelmaking industries will avoid disposal of wastes, enhance the use of secondary raw material fines and save costs. Understanding the properties of dust is necessary before determining the suitable recycling method. The present paper describes the chemical, morphological and mineralogical characterization of steelmaking dusts produced in steel plants in Finland. In this paper three different steelmaking dusts: ferrochrome converter (CRC) and electric arc furnace stainless steel (EAFSS) dusts from Outokumpu (Tornio, Finland), and electric arc furnace carbon steel (EAFCS) dust from Ovako (Imatra, Finland) were characterized. The characterization study showed that, the dusts from carbon steelmaking (EAFCS) are rich in zinc, while the dusts from stainless steelmaking (CRC) and (EAFSS) are relatively low in zinc, but richer in chromium. The zinc contents in CRC, EAFSS and EAFCS dusts are 10.83, 19.84 and 35.76 wt%, respectively, while the chromium contents are 20.88, 3.19 and 0.47 wt%, respectively. In the dust from CRC, zinc is found as zinc oxide (zincite, ZnO), while in the dusts from EAFSS & EAFCS zinc is found mostly as zinc ferrite (franklinite, ZnFe2O4). Scanning electron microscopy (SEM) investigations indicated that CRC dust is dominated by non-spherical form and composed mainly of aggregates of irregular particles of chromite, in addition to zincite sphere. EAFSS dust particles are characterized by encapsulation phenomenon, franklinite particles enclosed inside calcium-iron-silicate glass sphere. Manganese (Mn) concentrations show positive correlation with Zn, which suggests the occurrence of Mn mainly with franklinite phase. EAFCS dust is dominated by spherical form, and zinc found as franklinite and zincite. In the large particles > 3 μm of EAFCS dust, franklinite enclosed inside glass sphere, while in finer particles The investigations indicate that steelmaking dusts from CRC, EAFSS, and EAFCS show significant difference in concentration and mode of occurrence of zinc in the dusts, which will influence the determination of suitable processing methods.

Extended milling/mechanical activation properties of zinc plant residue was investigated using two different milling systems, namely, high speed vibrating ball mill and ring mill, comparatively. The zinc plant residue was mixture of gypsum, anglesite, massicot, quartz, maghemite, and franklinite. Zinc plant residue was milled for 1-30 min in high speed vibrating ball mill and ring mill. The obtained samples were characterized using XRD, SEM, particle size distribution, and N-2-BET methods. According to results, it was found that the ring mill caused a further decrease in particle size. Particle size distribution and N-2-BET analyses showed that agglomeration of particles began after 15 min and 5 min milling time for HSBVM and ring mill, respectively.

The nanocomposites of Franklinite (Fe2O4Zn) doped Zincte (ZnO) were synthesized through wet chemical (co-precipitation) technique followed by heat treatment. Metal chlorides and metal oxides are used as precursors for the formation of composites. The asprepared sample composites were subjected to sintering for two hours at the temperature of 300 °C. The detail spectral study and the effect of concentration of precursor salt on the structural parameters were done by using XRD and Rietveld refinement method. The occurrence of two crystalline phases (Fe2O4Zn and ZnO) was estimated from XRD data through Rietveld refinement. It was observed that the Fe2O4Zn have a cubic structure with space group Fd-3m (227), whereas ZnO has hexagonal structure with space group P 63 mc (186). The Wyckoff positions and rietveld refinement parameters like goodness factor, Bragg R factor, Rp value, Rexp were calculated. Effect of varying concentration of precursor on development of complete ferrite phase of structure was discussed.

The current study investigates a novel redox technology based on synthetic franklinite-like zinc-ferrite nanomaterial with magnetic properties and redox nature for potential use in water treatment. Physicochemical characterization revealed the nanoscale size and AB(2)O(4) spinel configuration of the zinc-ferrite nanomaterial. The redox activity of nanoparticles was tested for degradation of diclofenac (DCF) pharmaceutical in water, without any added external oxidants and under dark experimental conditions. Results revealed ~90% degradation in DCF (10 μM) within 2 min of reaction using 0.17 g/L Zn(1.0)Fe(2.0)O(4). Degradation of DCF was due to chemical reduction by surface electrons on zinc-ferrite and oxidation by oxygen-based radicals. Three byproducts from reduction route and eight from oxidation pathways were identified in the reaction system. Reaction pathways were suggested based on the identified byproducts. Results demonstrated the magnetic zinc-ferrite is a standalone technology that has a great promise for rapid degradation of organic contaminants, such as DCF in water.

A novelty process based on acid leaching basic oxygen furnace sludge by means of medium of 2,5M H2SO4 and 1M HCl was proposed. The new medium used in the study leaches franklinite ZnFe2O4 present in the tested sludge, which is hardly soluble in weak sulphuric acid solutions and well soluble in HCl solutions. This allows for 100% zinc extraction from the basic oxygen furnace sludge. The component of the leaching medium in the form of a sulphuric acid solution transforms the calcium compounds contained in the basic oxygen furnace sludge into insoluble calcium sulphate. The study examined the effect of solid to liquid ratio S/L (g/mL), temperature, time and rotational speed of stirrer on zinc and iron extraction from the sludge. Optimal leaching conditions were: t = 120 min, T = 60 °C, n = 500 min−1, S/L: 0.2. The leached solid filtration product obtained after leaching, dried and magnetically processed is separated into pure iron-bearing concentrate, which contains 77% Fe3O4 and 23% Fe2O3 and calcium sulphate waste. Their composition is confirmed by the X-ray diffraction analysis. The use of ethyl alcohol to precipitate sulphate iron compounds is a new alternative to recover and reuse the precipitant. The pure iron sulphate compounds with different hydration are obtained, which is confirmed by the X-ray diffraction analysis. The utilitarian aim of the study was to specify technological guidelines of the presented process and its material balance. Acid leaching of basic oxygen furnace sludge helps solve the problem of lack of selectivity in acid leaching of zinc and iron. This suggests the possibility of comprehensive use of the obtained products.

SARI, Zeynel Abidin/0000-0001-5932-2141, WOS: 000490085200012, Zinc plant residue is a secondary metal source because it has precious metals such as zinc and lead. However, since this residue contains partial ferrite structure, there is no large-scale recovery in metallurgy industry. The aim of this study is to investigate the effect of mechanical activation of zinc plant residue in sodium hydroxide leaching. The results showed that mechanical activation obtained from high-energy mill had positive effect on the leaching of metals under condition of limited grinding time. Mechanical activation over 1 min caused the increase in particle size. It was also determined that specific surface area decreased due to onset of agglomeration of fine particles on the surface. Leaching efficiency of long-time milled residue was lower than short-time milled material's leaching. It was determined that lead dissolution from zinc plant residue was higher than zinc dissolution in all experiments due to the presence of zinc in ferrite structure as franklinite form. Furthermore, sodium hydroxide leaching of this residue could be considered as a selective leach, since no iron was present in the solution., Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [112M285]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK), This work was financially supported by the Scientific and Technological Research Council of Turkey (TUBITAK, No. 112M285). The authors would like to thank TUBITAK for financial support.

This paper is the first description of natural copper-rich oxide spinels. They were found in deposits of oxidizing-type fumaroles related to the Tolbachik volcano, Kamchatka, Russia. This mineralization is represented by nine species with the following maximum contents of CuO (wt.%, given in parentheses): a new mineral thermaerogenite, ideally CuAl2O4 (26.9), cuprospinel, ideally CuFe3+2O4 (28.6), gahnite (21.4), magnesioferrite (14.7), spinel (10.9), magnesiochromite (9.0), franklinite (7.9), chromite (5.9), and zincochromite (4.8). Cuprospinel, formerly known only as a phase of anthropogenic origin, turned out to be the Cu-richest natural spinel-type oxide [sample with the composition (Cu0.831Zn0.100Mg0.043Ni0.022)Σ0.996(Fe3+1.725Al0.219Mn3+0.048Ti0.008)Σ2.000O4 from Tolbachik]. Aluminum and Fe3+-dominant spinels (thermaerogenite, gahnite, spinel, cuprospinel, franklinite, and magnesioferrite) were deposited directly from hot gas as volcanic sublimates. The most probable temperature interval of their crystallization is 600⁻800 °C. They are associated with each other and with tenorite, hematite, orthoclase, fluorophlogopite, langbeinite, calciolangbeinite, aphthitalite, anhydrite, fluoborite, sylvite, halite, pseudobrookite, urusovite, johillerite, ericlaxmanite, tilasite, etc. Cu-bearing spinels are among the latest minerals of this assemblage: they occur in cavities and overgrow even alkaline sulfates. Cu-enriched varieties of chrome-spinels (magnesiochromite, chromite, and zincochromite) were likely formed in the course of the metasomatic replacement of a magmatic chrome-spinel in micro-xenoliths of ultrabasic rock under the influence of volcanic gases. The new mineral thermaerogenite, ideally CuAl2O4, was found in the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption. It forms octahedral crystals up to 0.02 mm typically combined in open-work clusters up to 1 mm across. Thermaerogenite is semitransparent to transparent, with a strong vitreous lustre. Its colour is brown, yellow-brown, red-brown, brown-yellow or brown-red. The mineral is brittle, with the conchoidal fracture, cleavage is none observed. D(calc.) is 4.87 g/cm3. The chemical composition of the holotype (wt.%, electron microprobe) is: CuO 25.01, ZnO 17.45, Al2O3 39.43, Cr2O3 0.27, Fe2O3 17.96, total 100.12 wt.%. The empirical formula calculated on the basis of 4 O apfu is: (Cu0.619Zn0.422)Σ1.041(Al1.523Fe3+0.443Cr0.007)Σ1.973O4. The mineral is cubic, Fd-3m, a = 8.093(9) Å, V = 530.1(10) Å3. Thermaerogenite forms a continuous isomorphous series with gahnite. The strongest lines of the powder X-ray diffraction pattern of thermaerogenite [d, Å (I, %) (hkl)] are: 2.873 (65) (220), 2.451 (100) (311), 2.033 (10) (400), 1.660 (16) (422), 1.565 (28) (511) and 1.438 (30) (440).

Solid waste generation is one of the main problems in the steelmaking process. One of the most problematic waste products is the electric arc furnace dust, which is a by-product rich in iron and zinc and is present as zincite (zinc oxide) or franklinite (zinc ferrite). This work focuses on the reduction kinetics of synthetic zinc ferrite by gases containing hydrogen and carbon monoxide. This process was examined via forced stepwise isothermal analysis. The test was conducted at temperatures ranging from 500 to 950 °C. Reduction of zinc was accomplished using a mixture of hydrogen and carbon monoxide in order to simulate reformed natural gas. The results indicated that reduction of zinc ferrite occurred in two stages (550–750 °C and 800–900 °C). The first stage was characterized by iron oxide reduction, where a mix control between nucleation and diffusion was determined. The apparent activation energy obtained was 71.5 kJ mol−1. The second stage was characterized by zinc oxide reduction, where the controlling mechanism was identified as a mixed control between diffusion and phase boundary reaction. The apparent activation energy was 135.5 kJ mol−1. The formation of a dense layer of metallic iron around the unreacted core may have caused the apparent activation energy to increase.

In this paper, we describe the discovery and characterization of shelled structures that occur inside galleries of Pyrenees mines. The structures are formed by the mineralization of iron and zinc oxides, dominantly franklinite (ZnFe2O4) and poorly ordered goethite (α-FeO(OH)). Subsurface oxidation and hydration of polymetallic sulfide orebodies produce solutions rich in dissolved metal cations including Fe2+/3+ and Zn2+. The microbially precipitated shell-like structure grows by lateral or vertical stacking of thin laminae of iron oxide particles which are accreted mostly by fungal filaments. The resulting structures are composed of randomly oriented aggregates of needle-like, uniform-sized crystals, suggesting some biological control in the structure formation. Such structures are formed by the integration of two separated shells, following a complex process driven likely by different strategies of fungal microorganisms that produced the complex macrostructure.

This paper aims to study the dielectric properties and carbothermic reduction of zinc oxide (zincite, ZnO) and zinc ferrite (franklinite, ZnFe 2 O 4 ) by microwave heating. To achieve this aim, the dielectric properties were measured with an open-ended coaxial method to understand the behaviour of the samples under microwave irradiation. The effects of microwave power, duration time and sample mass on the heating rate, and the effects of the stoichiometric amount of graphite on the reduction of ZnO and decomposition of ZnFe 2 O 4 were investigated. The results show that ZnFe 2 O 4 has significantly higher dielectric properties compared to ZnO. Generally, for both samples, the dielectric values at room temperature were quite low, indicating that both ZnO and ZnFe 2 O 4 are poor microwave absorbers. It was found that the temperatures have a more significant effect on the imaginary permittivities than on the real permittivities. The heating rate showed that the sample temperature increased with increase in microwave power and sample mass. Using 700 W of microwave power and two times the stoichiometric amount of graphite, almost complete reduction of ZnO was achieved in 12 min, while ZnFe 2 O 4 completely decomposed to zincite and wustite in 3 min.

EAF-dust containing metal oxides can be regarded as an important source for zinc and iron. In this study, the reduction behavior of zinc ferrite with CO gas as a reducing agent under different temperatures was investigated to develop a new process for the recovery of zinc and iron from EAF-dust. The results of the phase studies with synthetic franklinite show that zinc substituted wustite, and spinel with low zinc content formed at lower temperatures from 450 to 850 °C due to incomplete zinc-iron-separation. Zinc ferrite was completely reduced to metallic zinc and iron at 950 °C. After evaporation and condensation, metallic zinc was collected in the form of zinc powder while iron, the reduction residue, was obtained in the form of direct reduced iron (DRI). The mass balance indicates a high zinc recovery ratio of over 99%. The new treatment process by thermal reduction with CO gas as a reducing agent achieved higher recovery and metallization grade of both zinc and iron from EAF-dust at lower temperatures than other commercial processes. The metallic products can be used directly as semi-products or as raw materials for refinery.

The Sterling Hill and Franklin zinc-iron-manganese deposits, Sussex County, New Jersey, are sedimentary-exhalative in origin but were highly deformed and metamorphosed to granulite grade during the Mesoproterozoic Ottawan orogeny. They are unique because the major zinc minerals, zincite, franklinite, and willemite, are oxides and silicates rather than sulfides. However, at Sterling Hill minor granular sphalerite occurs in the central black willemite zone associated with loelling and graphite and sparsely elsewhere in the deposit. Based on textural observations and stable isotope geochemistry, sphalerite was present during metamorphism and was most likely part of the protolith mineral assemblage. It likely formed from a fluid containing seawater sulfate that circulated through volcanic rocks and reacted with igneous sulfides; some contribution from biological reduction of sulfate seems likely. This interpretation agrees with the generally accepted model that the protolith formed on the floor of an ...

The present research investigated the removal of zinc from BOF (basic oxygen furnace) sludges in an attempt to reuse the iron content of the sludge in the production of sinter. The study consisted of two main steps: (i) the characterization of fine and coarse fractions of BOF sludges and (ii) the hybrid treatment of sludge to selectively remove zinc from iron. The characterization study showed that the Fe/Zn ratio is 132.6 in the coarse fraction and 11.6 in the fine fraction; the amount of zinc proved to be 8.5 times higher in the later fraction, while the total content of iron ranged between 50 and 60% in both fractions. Zinc could also be identified in the sludge as zincite (ZnO) and franklinite (ZnO.Fe2O3), whose last phase is quite stable and insoluble in NaOH solutions. Other characteristics, including the granulometry, morphology, and toxicity of both fractions of the sludge, were also determined. To improve the zinc removal efficiency, franklinite must be decomposed by a thermal treatment. For this reason, a hybrid route was investigated using the fine fraction of the sludge. The effect of various materials and reagents was evaluated concerning the decomposition of franklinite, in which NaOH was found to be the most effective. Operating variables, such as temperature, time, and NaOH/sludge ratio were studied. The treatment was found to be quite efficient in the selective removal of zinc from the sludge (zinc removal higher than 90% was obtained with practically no iron extraction), thus improving the Fe/Zn ratio in the fine fraction to approximately 200.

Residues from the zinc roast–leach–electrowin process contain zinc mainly as finely dispersed particles of franklinite. Thus, floatation, sulfuric acid leaching, and alkali leaching are ineffective methods for zinc extraction. An efficient technique was used for the extraction of zinc from hydrometallurgical zinc residues by sulfate roasting of a residue–sulfur–oxygen–H2O mixture followed by water leaching. The effects of various parameters, such as roasting temperature/time, the sulfur amount, leaching time/temperature, and liquid/solid ratio on zinc leaching were studied. Systematic studies indicate that high zinc leaching rate can be achieved under the following conditions: sulfur addition, 1.2 times theoretical value; duration, 2 h; temperature, 250 °C at roasting stage; and room temperature, liquid/solid ratio 4, and duration time 0.5 h at leaching. X-ray diffraction analysis indicates that the zinc-containing compounds convert into water-soluble zinc sulfate after roasting.

International audience; Zinc isotopes have been studied along two smelter-impacted soil profiles sampled near one of the largest Pb and Zn processing plants in Europe located in northern France, about 50 km south of Lille. Mean delta(66)Zn values along these two soil profiles range from +0.22 +/- 0.17 parts per thousand (2 sigma) to +0.34 +/- 0.17 parts per thousand (2 sigma) at the lowest horizons and from +0.38 +/- 0.45 parts per thousand (2 sigma) to +0.76 +/- 0.14 parts per thousand (2 sigma) near the surface. The delta(66)Zn values in the lowest horizons of the soils are interpreted as being representative of the local geochemical background (mean value +0.31 +/- 0.38 parts per thousand), whereas heavier delta(66)Zn values near the surface of the two soils are related to anthropogenic Zn. This anthropogenic Zn occurs in the form of franklinite (ZnFe(2)O(4))-bearing slag grains originating from processing wastes at the smelter site and exhibiting delta(66)Zn values of +0.81 +/- 0.20 parts per thousand (2 sigma). The presence of franklinite is indicated by EXAFS analysis of the topsoil samples from both soil profiles as well as by micro-XANES analysis of the surface horizon of a third smelter-impacted soil from a distant site. These results indicate that naturally occurring Zn and smelter-derived Zn exhibit significantly different delta(66)Zn values, which suggests that zinc isotopes can be used to distinguish between geogenic and anthropogenic sources of Zn in smelter-impacted soils. In addition to a possible influence of additional past sources of light Zn (likely Zn-sulfides and Zn-sulfates directly emitted by the smelter), the light delta(66)Zn values in the surface horizons compared to smelter-derived slag materials are interpreted as resulting mainly from fractionation processes associated with biotic and/or abiotic pedological processes (Zn-bearing mineral precipitation, Zn complexation by organic matter, and plant uptake of Zn). This conclusion emphasizes the need for additional Zn isotopic studies before being able to use Zn isotopes to trace sources and pathways of this element in surface environments

Zinc has no particular bearing phases in soils, and it forms very diverse compounds; this complicates zinc’s identification by chemical fractionation. However, Zn-containing particles may be identified using synchrotron X-ray analysis. Franklinite, willemite, hemimorphite, and Zn-containing magnetite are found to be the main technogenic Zn-containing pollutants in the heavy fraction of the contaminated surface soil horizon. Among the secondary zinc compounds, Zn-containing trioctahedral structures and clay minerals (unidentifiable by chemical extraction), as well as zinc fixed by manganese oxides and iron hydroxides, predominate in the soil clay fraction. Being a chalcophile element, zinc precipitates in the form of sulfides and forms complexes with organic substances in organic soils and peats. The degree of affinity to chalcophile metals increases in the following sequence: O-, P-, N-, and S-containing functional groups of organic substances.

In this study, pure ZnO microbullets, ZnO–ZnFe2O4 composite, and ZnO–Fe2O3–ZnFe2O4 composite with micron structured balloons, rods, and particles were prepared by a simple solvent thermal process using methanol or ethanol as solvents. The influence of solvents on the composition and morphology of the products was studied, and their gas-sensing properties were also investigated. The morphology of ZnO microbullets synthesized in ethanol is similar to but more uniform than that of ZnO microbullets synthesized in methanol. The Fe-doped ZnO synthesized in ethanol contains many micron particles homogeneously dispersing on the surface of the microbullets, which is composed of hexagonal wurtzite ZnO and franklinite ZnFe2O4, while Fe-doped ZnO prepared in methanol consists of micron structured balloons, rods, and particles, which is composed of hexagonal wurtzite ZnO, hematite Fe2O3, and franklinite ZnFe2O4. Compared with pure ZnO and ZnO–ZnFe2O4 composite, the ZnO–Fe2O3–ZnFe2O4 composite presented high response, rapid response/recovery characteristics, good selectivity, and excellent stability to acetone at relatively low operating temperature of 190 °C. This sensor could detect acetone in wide range of 1–1000 ppm, which was expected to be a promising gas sensor for detecting acetone.

It is shown that the iron content in zinc silicate concentrates with either high (8–11%) or low (3%) iron does not significantly affect the kinetics or overall recovery of zinc extraction in sulphuric acid. Most of the iron was present as hematite and franklinite with little iron contained in willemite. A small reduction in zinc recovery from 98.5% to 97.5% was observed for silicate ores containing 12% iron. The activation energy determined from high-iron concentrate leaching, 78 ± 12 kJ/mol, is statistically similar to that from low-iron concentrate, 67 ± 10 kJ/mol, suggesting the same rate-controlling step. The leaching of high high-iron concentrates enables a higher mass recovery during flotation. A flowsheet is proposed comprising a magnetic separation step to produce a magnetic and a non-magnetic product so that iron dissolution from the magnetic concentrate acts as a source of soluble iron for impurities removal.

During the production of steel from Electric Arc Furnace (EAF), large amount of by-product called EAF flue dust is generated. The major proportion of flue dust is comprised of Zn (41.5 % wt.). Different phases identified by XRD analysis are zincite, franklinite and magnetite with zincite being dominant. In this study, we have performed flue dust treatment using sodium hydroxide as leaching medium. Different concentrations of alkali were used to optimize maximum recovery of Zn. XRF and Wet Chemical method were used to characterize the dust samples both before and after leaching. The optimum alkali concentration for selective leaching of zinc was found to be 4 M with a zinc recovery of 90 %.

The major geochemical forms of Cr, Ni, Cu, Zn, Pb, and V in a soil from an industrial polluted site in the south of Italy were determined by means of synchrotron X-ray microanalytical techniques such as coupled micro-X-ray fluorescence/micro-X-ray diffraction and micro-X-ray absorption near edge structure spectroscopy in combination with bulk extraction methods (sequential extraction procedures, EDTA extractions, and toxicity leaching characteristic procedure tests). Cr, Ni, Zn, and Cu were found in spinel-type geochemical forms (chromite, trevorite, franklinite, zincochromite, and cuprospinel) and often in association with magnetite and hematite. Vwas mainly present as V(V) associated with iron-oxides or in the form of volborthite [Cu3(OH)2V2O7.2H2O]. Pb was speciated as minium (Pb3O4), lanarkite [Pb2O(SO4)], and, in association with Cr(VI), as crocoite (PbCrO4). In general, despite a high total concentration, metals appear to be speciated for the most part as rather insoluble geochemical forms. However, particular attention should be paid to Zn, Cu, V, and Pb that show non-negligible mobilizable fractions. On the basis of the geochemical forms identified, among others, two major former industrial activities were tentatively ascribed as being responsible for the observed major pollution: polyvinyl chloride and cement-asbestos productions.

Immiscibility in the trevorite (NiFe{sub 2}O{sub 4}) - franklinite (ZnFe{sub 2}O{sub 4}) spinel binary is investigated by reacting 1:1:2 molar ratio mixtures of NiO, ZnO and Fe{sub 2}O{sub 3} in a molten salt solvent at temperatures in the range 400-1000 C. Single phase stability is demonstrated down to about 730 C (the estimated consolute solution temperature, T{sub cs}). A miscibility gap/solvus exists below Tcs. The solvus becomes increasingly asymmetric at lower temperatures and extrapolates to n - values = 0.15, 0.8 at 300 C. A thermodynamic analysis, which accounts for changes in configurational and magnetic ordering entropies during cation mixing, predicts solvus phase compositions at room temperature in reasonable agreement with those determined by extrapolation of experimental results. The delay between disappearance of magnetic ordering above T{sub C} = 590 C (for NiFe{sub 2}O{sub 4}) and disappearance of a miscibility gap at T{sub cs} is explained by the persistence of long-range ordering correlations in a quasi-paramagnetic region above T{sub C}.

Recycling scrap iron and steel in electric arc furnaces (EAFs) generates very fine metal-containing dusts which can present major environmental problems. This paper describes experimental work on a relatively novel, simple, and inexpensive process for decreasing the chloride content and upgrading the zinc level of dust from an Australian plant, to produce saleable products and environmentally safe waste products for disposal. The dust contained about 2.1% Cl as various chlorides, 23.1% Zn as zincite and franklinite, 27.1% Fe as magnetite, franklinite, and hematite, plus small quantities of lead, cadmium, chromium, and other materials. The dust was very fine ( P 80 about 2 μm). Individual particles were commonly aggregates of fine spheres and other shapes. Simple water washing at ambient temperatures and natural pH (12) for 60 min extracted 99% of the chlorides, giving a residue assaying 200 ppm Cl. This residue was strongly coagulated by lime present in the dust and settled rapidly. The wash solution contained low levels of iron, zinc, lead, cadmium, and chromium, most of which could be removed by sulphide precipitation. Wet magnetic separation with a Davis tube was investigated. At the lowest field strength employed (0.6 A), 95% of the zinc was recovered in a non-magnetic product assaying 28% Zn and 24% Fe. At the highest field strength (1.6 A), 91% of the zinc was recovered in a non-magnetic product assaying 29% Zn and 25% Fe. Wet cycloning at a nominal separation size of 2–5 μm gave a cyclone overflow product assaying 31% Zn and 26% Fe, and containing 85% of the zinc. All these results fit a typical zinc grade–recovery relationship. The proposed process of water washing followed by magnetic separation or cycloning would produce a relatively high-zinc, low-iron, low-chloride product suitable for treatment in a lead–zinc smelter or electrolytic zinc plant, a high-iron, low-zinc product suitable for land fill, and a treated waste water for discharge to a sewer.

The para-goethite (PG) iron removal process is one of the several precipitation processes that is utilised today to remove iron from zinc-rich processing solutions. In this paper, the para-goethite process is reviewed and compared with results obtained from a study of similar Zincor Process. The distribution of iron in the Zincor iron residue was found to be as follows: approximately 50% as a combination of schwertmannite and ferrihydrite, 20% as jarosites, 25% as franklinite and trace amounts of pyrite as well as 5% of an unknown phase. This study confirmed that goethite is not present in Zincor's iron residue and that iron is mainly removed in the form of poorly crystalline, intermediate iron phases such as schwertmannite and ferrihydrite. The presence of these intermediate phases in zinc plant iron residues is proposed to be mainly a function of the specific pH profile employed during iron removal and the coprecipitation of silica. Based on these findings, it can be concluded that the Zincor Process in its current form is distinctly different to that historically considered to be the similar patented para-goethite iron removal process, as practiced at the Porto Vesme and the Pasminco Hobart hydrometallurgical zinc plants.

Two new occurrences of willemite coexisting with franklinite are described from the Bergslagen region. At the Garpenberg Norra Pb-Zn mine (Hedemora, Dalarna) willemite and franklinite occur in silicate skarn rocks in association with clino-amphibole, phlogopite, quartz, galena, sphalerite, fluorite and barite. At the Hasselhojden metacarbonate quarry (Hallefors, Orebro) the two minerals appear with mainly sphalerite in talc-bearing dolomite marble. Based on electron-microprobe (EMP) analyses, willemite from Garpenberg Norra contains 0.4–2.1 MnO, 0.2–1.5 MgO and 0.1–1.2 Fe2O3, whereas at Hasselhojden the mineral has 0.4 Fe2O3 as the main impurity (all in wt.%). Mossbauer spectroscopy and EMP data show that Fe is dominantly triva-lent and to some extent substitutes for Si in these willemite samples. Franklinite from Hasselhojden contains up to 7.6 wt.% V2O5, incorporated according to the substitution 2 (Zn, Fe)2+ + V5+ = 3 Fe3+.

The effect of iron oxide content on the crystallisation of a diopside glass–ceramic glaze was investigated using a glass–ceramic frit in the K2O–ZnO–MgO–CaO–Al2O3–SiO2 system and a granite waste glass. Measurements by X-ray diffraction (XRD) combined with scanning electron microscopy (SEM) and EDX microanalysis showed that the distribution of Fe3+ ions among different crystalline phases such as franklinite (ZnFe2O4) and hematite Fe2O3 depends on the iron content in the original diopside mixture. Thus, the original glaze crystallises to franklinite or hematatite when iron content is greater than 2 and 15%, respectively.

A complete characterization was carried out on a jarositic residue from the zinc industry. This residue consists of ammonium jarosite, with some contents of H3O+, Ag+, Pb2+, Na+ and K+ in the alkaline “sites” and, Cu2+ and Zn2+ as a partial substitution of iron. The formula is: [Ag0.001Na0.07K0.02Pb0.007(NH4)0.59(H3O)0.31]Fe3(SO4)2(OH)6. Some contents of franklinite (ZnO·Fe2O3), gunninguite (ZnSO4·H2O) and quartz were also detected. The jarosite is interconnected rhombohedral crystals of 1–2 μm, with a size distribution of particles of 2–100 μm, which could be described by the Rosin–Rammler model. The alkaline decomposition curves exhibit an induction period followed by a progressive conversion period; the experimental data are consistent with the spherical particle with shrinking core model for chemical control. The alkaline decomposition of the ammonium jarosite can be shown by the following stoichiometric formula: NH 4 Fe 3 ( SO 4 ) 2 ( OH ) 6( s ) +3 OH ( aq ) − →( NH ) 4( aq ) + +3 Fe(OH) 3( s ) +2 SO 4( aq ) 2− . The decomposition (NaOH) presents an order of reaction of 1.1 with respect to the [OH−] and an activation energy of 77 kJ mol−1. In NaOH/CN− media, the process is of 0.8 order with respect to the OH− and 0.15 with respect to the CN−. The activation energy was 46 kJ mol−1. Products obtained are amorphous. Franklinite was not affected during the decomposition process. The presence of this phase is indicative that the franklinite acted like a nucleus during the ammonium jarosite precipitation.

High-resolution Fe K-edge XANES spectra of a series of crystalline Fe 2+ - and Fe 3+ -bearing model compounds were measured in an effort to correlate characteristics of the pre-edge feature with oxidation state and local coordination environment of Fe atoms. The model compounds comprise 30 natural minerals and synthetic compounds, with Fe coordination environments ranging from 4 to 12 O atoms for Fe 2+ , including 5-coordinated trigonal bipyramidal Fe 2+ , and from 4 to 6 O atoms for Fe 3+ . Most pre-edge spectra show two components (due to crystal-field splitting) that are located just above the Fermi level. The most useful characteristics of the Fe-K pre-edge for determining Fe oxidation state and coordination number are the position of its centroid and its integrated intensity. The separation between the average pre-edge centroid positions for Fe 2+ and Fe 3+ is 1.4 ± 0.1 eV. Thus, the position of the pre-edge feature can be used as a measure of the average Fe-redox state, with the average pre-edge position for mixed Fe 2+ -Fe 3+ compounds occurring between positions for Fe 2+ and Fe 3+ . The lowest pre-edge normalized heights and integrated intensities are observed for the most centrosymmetric sites of Fe, in agreement with previous studies (see Waychunas et al. 1983). Examination of the pre-edge features of mechanical mixtures of phases containing different proportions of Fe 2+ and Fe 3+ suggests that the pre-edge position and intensity for these mixtures can vary quite non-linearly with the average redox state of Fe. However, distinctly different trends of pre-edge position vs. pre-edge intensity can be observed, depending on the coordination environment of Fe 2+ and Fe 3+ , with an accuracy in redox determination of ±10 mol% provided that the site geometry for each redox state is known. These methods have been used to estimate the Fe 3+ /Fe 2+ ratio in 12 minerals (magnetite, vesuvianite, franklinite, rhodonite, etc.) containing variable/unknown amounts of Fe 2+ /Fe 3+ .

The compositional dependence of the intracrystalline cation distribution was investigated in four synthetic spinels belonging to binary solid solutions. Spinel single crystals were flux-grown in the (Mg,Zn)(Al,Fe 3+ ) 2 O 4 system, and cation distribution was determined by means of single-crystal X-ray structural refinement, electron-microprobe analysis and Mossbauer spectroscopy. Experimental data were processed and a detailed topochemical model was obtained for each sample: IV (Mg 0.76 Al 0.24 ) VI (Al 1.76 Mg 0.24 )O 4 ; IV (Zn 0.65 Mg 0.22 Al 0.13 ) VI (Al 1.87 Mg 0.13 )O 4 ; IV (Mg 0.73 Al 0.18 Fe 3+ 0.09 ) VI (Al 1.62 Mg 0.27 Fe 3+ 0.11 )O 4 and IV (Mg 0.62 Zn 0.15 Al 0.15 Fe 3+ 0.08 ) VI (Al 1.61 Mg 0.23 Fe 3+ 0.16 )O 4 . Zinc was found to occupy only the tetrahedrally coordinated site and its presence strongly influenced intersite cation partitioning. In Zn-bearing crystals both intracrystalline exchanges Mg ⟷ Al and Mg ⟷ Fe 3+ turned out to be limited. Zinc in octahedral coordination, which is rare in natural spinels, was shown to be favoured by high Fe 3+ contents and high equilibration temperatures. The cation distributions determined experimentally were found to be in close agreement with those calculated using the general thermodynamic model for spinel solid solutions by O9Neill & Navrotsky (1984).

More than a century of non-ferrous metallurgical activities have had a severe impact on the natural environment leading, in most heavily contaminated sites, to a complete loss of the vegetation cover (that is, desert-like areas) or to the selection of metal-hyperaccumulator plant species. Identifying the chemical forms of toxic metals is of vital importance for a realistic assessment of the chemical risk posed by their presence in soils and selecting effective remedia- tion technologies. In this study, X-ray diffraction (XRD), X-ray texture goniom- etry, and powder and polarized extended X-ray absorption fine structure (EXAFS, P-EXAFS) have been used to investigate quantitatively the speciation of Zn in soils contaminated by three smelters from northern France and Belgium, and coupled synchrotron-based micro-X-ray radiation fluorescence (SXRF) and mi- cro-EXAFS (EXAFS) were also used for one of these soils. Of these techniques, the application of P-EXAFS and EXAFS to molecular environmental science was unprecedented, and we show that their complementarity greatly improves the sensitivity of powder EXAFS to identify the nature of metal-containing minerals in soils. Franklinite (ZnFe2O4), willemite (Zn2SiO4), hemimorphite (Zn4Si2O7(OH)2 ·H 2O), and Zn-containing magnetite ((Fe,Zn)Fe2O4) were identi- fied in dense soil fractions by XRD and powder EXAFS. These primary minerals originate from atmospheric fallout of Zn dusts emitted during the pyrometallurgi- cal smelting process, and they act as the main source of Zn in contaminated soils. In all soil samples, Zn released in solution during the weathering of these high-temperature minerals is taken up partly by phyllosilicates and, to a lesser extent, by Mn and Fe (oxyhydr) oxides. Zn-containing phyllosilicates were identi- fied by comparing powder EXAFS spectra to a library of model compounds and from the noteworthy angular dependence of EXAFS spectra collected on self- supporting films of clay soil fractions. Analysis of higher correlations in EXAFS spectra suggests that the local structure around Zn in phyllosilicates is trioctahe- dral. The phyllomanganate Zn-sorbed birnessite and Zn-containing Fe grains having a FeOOH-like local structure were unambiguously identified bySXRF— EXAFS. In birnessite Zn is sorbed in the interlayer space above/below vacant sites and can be either 4-fold or 6-fold coordinated depending, presumably, on the anionic stacking of birnessite layers. Based on this micro-mineralogical investiga- tion, a satisfactory fit of the three identified Zn species (that is, phyllosilicate, Mn, and Fe (oxyhydr)oxides) to experimental powder EXAFS spectra of all clay soil fractions was obtained. The significance, origin, and stability of Zn-phyllosilicates are discussed. Specifically, we show that the formation of Zn-containing phyllosili- cates is consistent with calculated thermodynamic solubilities. For the range of measured Zn 2 (D10 ppm), Si(OH)4 (10-20 ppm), and H (5.6 F pH F 7.5) concen- trations, soil solutions are supersaturated (pH G 6) or near saturation (pH F 6) with respect to the trioctahedral Zn phyllosilicate, Zn-kerolite. Finally, the plausi- bility of the formation of (Zn,Al) hydrotalcite-like species contemplated by Julliot (1999) is critically assessed.

Many pyrometallurgical, hydrometallurgical and combined processes have been developed to allow better utilization of steelmaking dusts. The dusts contain metals and compounds that can harm the processes and one of these elements is zinc that is present in the flue dusts as zincite ZnO and franklinite ZnFe2O4. The effect of alkaline roasting on the dissolution of stainless steel flue dusts in acid and alkaline leaching was studied. The extraction of zinc from EAF dust was not significantly improved in alkaline leach (40 – 50 %) but there was indication of better extraction in acid leach (over 90 %). No improvement in extraction from AOD dust was seen either in alkaline (max. 58 %) or acid leach (max. 72 %). The acid leach of synthetic ferrite resulted in less than 32 % Zn recovery, and this must be studied further to find out the effect of franklinite in the dusts.

The pressure dependence of single-crystal elastic moduli of a natural Mn-rich franklinite, (Mn 0.40 Fe 2+ 0.16 Zn 0.37 Mg 0.03 )(Fe 3+ 1.94 Al 0.08 )O 4 , has been determined by GHz-ultrasonic interferometry in a diamond-anvil cell to 9.8 GPa. The room-pressure elastic constants of franklinite are C 11 = 244(3) GPa, C 12 = 142(4) GPa, and C 44 = 77(2) GPa. Linear pressure derivatives of C 11 and C 12 are 4.3(3) and 3.8(3), respectively, whereas the C 44 modulus exhibits softening, fitted in the P ≤ 10 GPa pressure range to C 44 = 77(2) + 0.29(2) P – 0.018(2) P 2 GPa. The average of Hashin-Shtrikman bounds on the adiabatic bulk modulus ( K S0 ) of franklinite is 175(3) GPa, with pressure derivative K S ′ = 4.3(3), and the shear modulus G 0 = 66(2) GPa with G ′ = 0.09(3). The isothermal compressibility of franklinite was determined from a separate high-pressure, single-crystal X-ray diffraction experiment to 7.8 GPa, yielding K T0 = 173.5(7) GPa fitted with a fixed pressure derivative of K T ′ = 4. When K ′ is fixed to the ultrasonic value of 4.3, we obtain K T0 = 172.2(7) GPa. In contrast to iron-free gahnite (ZnAl 2 O 4 ), franklinite exhibits pressure-induced mode softening of C 44 similar to magnetite (Fe 3 O 4 ). Between end-member compositions ZnFe 2 O 4 (franklinite) and MnFe 2 O 4 (jacobsite), the bulk modulus decreases linearly with increasing %Mn, however we observe non-linear behavior in other elastic moduli, especially C 44 , which displays a pronounced negative anomaly for the mid-range Mn composition. Applying Birch’s law to AB 2 O 4 -type spinels reveals that oxide spinels containing transition metals on both A and B sites follow a distinct trend from other spinels.