Recovery of high grade iron compounds from LD slag by enhanced magnetic separation techniques

International audienceA representative sample of LD slag provided from French steel industry was treated by different physical separation techniques especially used in mineral processing. The results of characterisation study show that the LD slag may contain up to 35% of iron compounds. The X-ray diffraction reveals the presence of the following crystallized mineral phases: CaO, MgO, Al2O3, SiO2, MnO, and P2O5. Larnite (Ca2SiO4), di-calcium aluminoferrite (brownmillerite: Ca2Fe2 - xAlxO5 with x = 0.6) and a solid solution (Fe, Mn, Mg)O structurally close to the wustite (FeO) and some residual lime (CaO).The results of grinding tests show that the manner of grinding is very important. Soft Grinding (SG) or sequential grinding is most suitable to reduce the particle size of LD slag avoiding the overproduction of fine particles, which hinder the effectiveness of magnetic separation techniques. The combination of Low and High Intensity Magnetic Separation (LIMS and HIMS) of ground LD slag at 63 mu m in wet process may recover ferromagnetic particles (iron oxides) at LIMS and paramagnetic particles at HIMS, while the non-magnetic fraction contains mostly calcium silicates.From this investigation, two flow-sheets of treatment of LD slag are suggested to recover high grade iron material for recycling in metallurgical processes. Calcium and silicon oxide rich product will be directed to the cement industry

A new approach in the flotation of monazite using a lanthanum salt as a catalyzer of the carboxylate collector adsorption

International audienceIn this study, we developed a new approach of lanthanum chloride and carboxylate collector combination with the aim of improving the selective and effective collector adsorption onto the rare-earth phosphate minerals. Bubble/particle adhesion tests with sodium oleate collector were performed indicating a higher mineral surface hydrophobicity when using lanthanum chloride. Flotation experiments were performed with sodium oleate showing enhanced monazite recovery and flotation rate in presence of lanthanum chloride. The best flotation performance was obtained when the lanthanum chloride was added prior to the collector. With regards to the performed XPS study and the literature data, it was suggested that lanthanum ions or lanthanum species strongly interact with the under-coordinated phosphate groups on the monazite surface playing a role of a bridge between the monazite surface and the carboxylate group of the collector. We also observed that the lanthanum chloride dosage and mode of addition must be strictly controlled to avoid a decrease of the availability of the collector and thus a decrease of the monazite recovery and flotation rate

Effects of atom substitutions and dissolved carbonate species on monazite electrophoretic mobility

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Residual plastics as reducing agents and co-fuel in steel making

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New EAF Slag Characterization Methodology for Strategic Metal Recovery

International audienceThe grown demand of current and future development of new technologies for high added value and strategic metals, such as molybdenum, vanadium, and chromium, and facing to the depletion of basic primary resources of these metals, the metal extraction and recovery from industrial by-products and wastes is a promising choice. Slag from the steelmaking sector contains a significant amount of metals; therefore, it must be considered to be an abundant secondary resource for several strategic materials, especially chromium. In this work, the generated slag from electric arc furnace (EAF) provided by the French steel industry was characterized by using multitude analytical techniques in order to determine the physico-chemical characteristics of the targeted slag. The revealed main crystallized phases are larnite (Ca2SiO4), magnetite (Fe3O4), srebrodolskite (Ca2Fe2O5), wüstite (FeO), maghemite (Fe2.6O3), hematite (Fe2O3), chromite [(Fe,Mg)Cr2O4], and quartz (SiO2). The collected slag sample contains about 34.1% iron (48.5% Fe2O3) and 3.5% chromium, whilst the vanadium contents is around 1500 ppm. The Mössbauer spectroscopy suggested that the non-magnetic fraction represents 42 wt% of the slag, while the remainder (58 wt%) is composed of magnetic components. The thermal treatment of steel slag up to 900 °C indicated that this solid is almost stable and few contained phases change their structure

Thermal treatment of hydrated ferrous sulfate waste under different atmospheres

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Towards the efficient flotation of monazite from silicate-rich tailings with fatty acids collectors using a lanthanum salt as a selective phosphate activator

International audienceThe exploitation of massive rare-earth element (REE) deposits is frequently contested because of the pollution generated by the heavy mining operations and REE extractive metallurgy operations. In an effort to minimise the environmental footprint of the REE production and meet the increasing demand for these elements, mine wastes and extractive metallurgy tailings are attracting attention as alternative primary sources. However, these residues frequently contain small amounts of monazite [(Ce,La,Nd)PO4] in silicate-rich gangues, rendering the efficient and selective recovery via current flotation routes difficult. Herein, we investigated the use of LaCl3 as an activator to promote the selective adsorption of fatty acid collectors on the surface of phosphate minerals, thus improving the monazite flotation performance. Bench-scale flotation tests were performed on a low monazite-grade, silicate-rich residue and revealed that a low LaCl3 dosage (about 1 g t−1) selectively enhanced the floatability of monazite and gangue phosphate minerals. We found that the influence of LaCl3 on the monazite flotation performance depends on the LaCl3 dosage, collector dosage, and method of addition of these reagents to the pulp. The mineral composition of the flotation products was determined by mineral liberation analysis (MLA), which indicated that higher concentrations of lanthanum ions promote the adsorption of the collector on rutile and aluminium-rich minerals, thus reducing the selectivity of the monazite flotation separation. This study is a stepping stone towards the development of a new practice of monazite flotation with environmentally friendly collectors and may render low REE-grade residues a commodity

Evaluating organic acids as alternative leaching reagents for rare earth elements recovery from NdFeB magnets

International audienceThis is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain

Two steps process for the recycling of the tantalum and niobium oxides contained in residual materials

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Process for Enhancing the Valuable Metal Recovery from "Electric Arc Furnace" (EAF) Slags

International audienceGiven the current depletion of the world's natural resources, the strong demand and the induced future deposit of primary mineral resources carrying metals (such as molybdenum, vanadium and chromium), one of the solution to this problem is the recycling of metals from by-products (such as steel slags) containing them. Steel slags are major by-products produced by the steel industry. Although they are considered as industrial waste that may cause public and environmental concerns, slags represent an important potential economic resource because they often contain significant amounts of valuable "Strategic Metals" (SMs). In order to minimize energy costs, environmental impacts and meet the metals demand for new high technologies, it will be more and more necessary to use cleaner and more economical technologies to recover these metals from slags. In this study, steel slags, generated from electrical arc furnace and provided by the Industeel France ArcelorMittal Company located in Châteauneuf (France), were studied. The chemical and mineralogical characterization results show that the investigated slags contain approximately 20–22% Fe, 3–4% Cr, 1 500 ppm V and are constituted of the following main crystalline phases: larnite (Ca2SiO4), magnetite (Fe3O4), wüstite (FeO) and chromite (FeCr2O4). Slag samples underwent different treatment steps before leaching (magnetic separation, grinding at d ≤ 25 μm and roasting). Various alkaline reagents (NaOH, KOH, Na2CO3 and K2CO3) have been studied with a slag/reagent weight ratio of 1, sufficiently high to provide an excess of alkaline reagent and allows the complete modification of the metal species able to be modified with these reagents at different co-grinding residence times. Three temperatures (400, 600 and 800 °C) were tested. The results show that the Cr leaching rate reaches 97.5% for one hour of the slag co-grinding with a NaOH and Na2CO3 mixture followed by roasting at 800 °C, while the V maximum leaching rate of 62.5% of vanadium is obtained after three hours of slag co-grinding with NaOH and Na2CO3 and roasted at 600 °C. The Mo leaching rate, meanwhile, reaches 95.8% using KOH for one hour of co-grinding the slag followed by roasting at 600 °