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The mass production of synthetic plastics began in the last century and today they have become one of the most abundant man-made materials. The disposal or the beneficiation of end-of-life plastics represent a great challenge for society especially in the case of polyvinyl chloride (PVC). This study is focused on the use of PVC waste as a useful agent for the direct reduction of hematite (Fe2O3) after a thermal treatment at 300 °C for removing the chlorine contained in PVC. Thermal reduction tests were conducted from 600 °C to 1100 °C with (Fe2O3 + PVC + clay) pellet mixtures in which clay was used as plasticizing and binder agent of the pellets. The starting samples and treatment residues were analyzed by scanning electron microscopy through energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) to monitor the chemical behavior and reactivity of the pellet constituents during their thermal treatment. The stepwise reduction of hematite up to metallic iron was achieved at temperatures approaching 1000 °C, confirming the capability of using PVC waste for the direct reduction of iron oxides.

International audience; The most economically important iron-chromium bearing minerals is chromite. In natural deposits, iron(II) is frequently substituted by magnesium(II) while chromium(III) is replaced by aluminum(III) and/or iron(III) forming a complex chromium bearing material. The majority of mined chromite is intended for the production of ferrochrome which requires a chromite concentrate with high chromium-to-iron ratio. Found mostly in the spinel chromite structure, iron cannot be removed by physical mineral processing methods. In this frame, the present work deals with the reaction of chlorine and chlorine+oxygen with selected samples of chromite concentrates for assessing the reactivity of their components towards chlorinating atmosphere, allowing the preferential removal of iron, hence meeting the chromite metallurgical grade requirements. Isothermal thermogravimetric analysis was used as a reliable approach for the kinetic reactivity investigation. Results indicated a wide difference in the thermal behavior of chromite constituents in a chlorinating atmosphere when considering their respective values of apparent activation energy oscillating from about 60 to 300 kJ/mol as a function of the sample reacted fraction. During the chromite treatment by chlorine in presence of oxygen, chromium was recovered as liquid chromyl chloride by condensation of the reaction gas phase.

During the treatment of copper anode slime (CAS) under an air atmosphere, several aspects of the interactions of its main components (CuAgSe, Cu2−xSeyS1−y, Ag3AuSe2) with oxygen were described in Part I. As a comparative and complementary study, this work deals with the thermal behavior of CAS under air in the presence of polyvinyl chloride (PVC) between 195 and 770 °C. The preliminary thermal treatment of an e-waste sample containing brominated substances was also performed. The reaction products were systematically analyzed by scanning electron microscopy through energy-dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) to investigate the thermal behaviors of the studied samples in a halogenated medium. At low temperatures, the copper, silver and selenium compounds of the CAS reacted with the HCl, issued from PVC degradation, leading to the formation of their respective chlorides. Bromides of valuable metals (Cu, Pb, Sn…) were synthesized during the e-waste treatment at 500 °C and they were distributed between the solid residue and gaseous phase. The data obtained give an insight into the reactivity of several metals towards halogenated substances, which may be valuable information for conducting the extraction and recycling of targeted elements from industrial by-products and end-of-life materials by a thermochemical route.

The investigation presented here features the design of a cleaner and greener chemical process for the conversion of industrial wastes into super-oxidizing materials. The waste of interest is the iron sulfate heptahydrate (FeSO4·7H2O) mainly generated through the sulfate route used for titanium dioxide industrial production. The products of this transformation process are alkali ferrates (A2FeO4, A = Na, K) containing iron in its hexavalent state and considered as powerful oxidants characterized by properties useful for cleaning waters, wastewaters, and industrial effluents. The proposed process includes two steps: (i) The first step consisting of the pre-mixing of two solids (AOH with FeSO4·xH2O) in a rotary reactor allowing the coating of iron sulfate in the alkali hydroxides through solid–solid reactions; and (ii) the second step involves the synthesis of alkali ferrates in a fluidized bed by oxidation of the single solid obtained in the first step in diluted chlorine. The chemical synthesis of alkali ferrates can be carried out within a timeframe of a few minutes. The usage of a fluidized bed enhanced the energy and mass transfer allowing a quasi-complete control of the ferrate synthesis process. The alkali ferrate synthesis process described here possesses many characteristics aligned with the principles of the “green chemistry”.

Development of our modern society requests a number of critical and strategic elements (platinum group metals, In, Ga, Ge…) and high value added elements (Au, Ag, Se, Te, Ni…) which are often concentrated in by-products during the extraction of base metals (Cu, Pb, Zn…). Further, recycling of end-of-life materials employed in high technology, renewable energy and transport by conventional extractive processes also leads to the concentration of such chemical elements and their compounds in metallurgical by-products and/or co-products. One of these materials, copper anode slime (CAS), derived from a copper electrolytic refining factory, was used for this study. The sample was subjected to isothermal treatment from 225 to 770 °C under air atmosphere and the reaction products were systematically analyzed by scanning electron microscopy through energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) to investigate the thermal behavior of the treated sample. The main components of the anode slime (CuAgSe, Cu2-xSeyS1-y, Ag3AuSe2) react with oxygen, producing mostly copper and selenium oxides as well as Ag-Au alloys as final products at temperatures higher than 500 °C. Selenium dioxide (SeO2) is volatilized and recovered in pure state by cooling the gaseous phase, whilst copper(II) oxide, silver, gold and tellurium remain in the treatment residue.

International audience; The extraction of tin through smelting of cassiterite (SnO 2) has generated considerable amounts of slag in the main production areas of SouthEast Asia, Africa, and South America. Tantalum and niobium naturally occur in cassiterite deposits and are concentrated in the slag during the smelting process. Tin slags have often been disposed as industrial waste despite contents of tantalum and niobium ranging from 2 to 25 %. Conventional hydrometallurgical processes for the concentration of tantalum and niobium oxides utilizing high concentration of strong acids such as HF or H 2 SO 4 are environmentally and economically challenging. This paper describes an original and greener approach for the selective dissolution of the slag amorphous matrix, and the concentration of tantalum and niobium oxides in a solid residue. Starting from a slag containing about 15 % (Ta,Nb) 2 O 5 , sequential alkaline and acid leaching stages resulted in the production of a 63 % (Ta + Nb) oxides concentrate, which is comparable to commercial grade of mineral concentrates.

International audience; This paper is focused on the reactivity of Cl 2 towards MgO in presence of a reducing (CO) and oxidizing (O 2) agent at temperatures up to 1025 °C. Kinetics parameters are determined by thermogravimetry under isothermal conditions. The overviewed results showed that the carbochlorination (Cl 2 +CO) occurred at temperatures lower than oxychlorination (Cl 2 +O 2). The reaction of MgO with Cl 2 +CO from 425 °C to 600 °C proceeds with an activation energy (E a) of about 49 kJ/mol, while the reaction rate does not longer depend on the temperature between 600 and 675 °C. The reaction of MgO with Cl 2 +O 2 at 850-1025 °C was characterized by a value of E a of 214 kJ/mol indicating that the overall rate of the process is controlled by the rate of chemical reaction. Oxychlorination can also be used for removing the impurities contained in the industrial magnesium raw materials. Further, the behavior of the MgO in chlorine atmosphere leads to give an insight about the reaction mechanisms useful for the selective chlorination of complex ores and concentrates containing magnesium oxide.

This work is focused on the preparation of alkali ferrates, especially sodium ferrate, using ferrous sulfate as iron bearing material and chlorine as oxidant. Ferrous sulfate heptahydrate is mainly generated during titanium oxide extraction from ilmenite through the sulfate route; it is considered as a waste for this industry. Obtained alkali ferrates belong to the compounds where iron is in the rare hexavalent state and they are becoming a substance of growing importance for water treatment and industrial effluent cleaning. Two methods are developed for the ferrate synthesis. The first method consists of simultaneous reactions of two solids (iron sulfate and sodium hydroxide) and one gaseous oxidant (diluted chlorine). The second method involves a homogenous premixing of both solids prior to the oxidation by diluted chlorine. The synthesis process is performed in a rotary reactor at room temperature; however, since the overall reaction is exothermic, temperatures as high as 150 degrees C are often recorded. The effects of several parameters such as hydration extent of raw materials, Na/Fe ratio, chlorine content of the reactive gases on the sodium ferrate synthesis are investigated to determine the optimal processing conditions. The conversion efficiency of Fe(II) to Fe(VI) during the sodium ferrate synthesis reaches about 30%. (C) 2013 Elsevier B.V. All rights reserved.

Iron sulfate, in particular FeSO4&middot, 7H2O, is derived from titanium dioxide production and the steel pickling process. Regarding TiO2 manufacturing, the amount of the resultant FeSO4&middot, 7H2O can be as high as 6 tons per ton of produced TiO2, leading to a huge amount of ferrous sulfate heptahydrate, which is considered an environmental and economic concern for the titanium dioxide industry in European countries. The present paper focuses on the thermal treatment of ferrous sulfate (heptahydrate and monohydrate) samples under different conditions. Nonisothermal thermogravimetric (TG) analysis was used to study the behavior of iron sulfate samples at temperatures of up to 1000 &deg, C in Cl2 + O2, O2, and N2 atmospheres. Results showed that the dehydration of iron sulfate heptahydrate in nitrogen started at room temperature and resulted in iron sulfate tetrahydrate (FeSO4&middot, 4H2O). The ferrous sulfate monohydrate (FeSO4&middot, H2O) was formed at temperatures close to 150 &deg, C, while the anhydrous ferrous sulfate (FeSO4) was obtained when the samples were heated in nitrogen at over 225 &deg, C. The kinetic features of FeSO4 decomposition into Fe2O3 were revealed under isothermal conditions at temperatures ranging from 500 to 575 &deg, C. The decomposition of iron sulfate was characterized by an apparent activation energy of around 250 kJ/mol, indicating a significant temperature effect on the decomposition process. The obtained powder iron oxide could be directed to the agglomeration unit of iron and the steelmaking process.

International audience; This work deals with the extraction of phosphorus chlorinated compounds from phosphate materials using chlorination with gaseous chlorine. An industrial sample of dicalcium phosphate dihydrate, after transformation into calcium pyrophosphate (Ca 2 P 2 O 7), is subjected to reactions with Cl 2 +CO+N 2 and Cl 2 +C+N 2 at temperatures ranging from 625 to 950 °C using boat experiments. Gathering results of the thermodynamic predictions and TG/DT analysis with those of SEM and XRD examinations of the chlorinated residues allowed the interpretation of phenomena and reactions mechanism occurring during the calcium pyrophosphate carbochlorination. Reaction rate of Ca 2 P 2 O 7 by Cl 2 +CO+N 2 at 950 °C is slowed down due to the formation of a CaCl 2 liquid layer acting as a barrier for the diffusion of the reactive gases and further reaction progress. While, the carbochlorination with Cl 2 +C+N 2 led to almost full chlorination of Ca 2 P 2 O 7 at 750 °C and the process proceeds with an apparent activation energy of about 104 kJ/mol between 625 and 750 °C. Carbochlorination technique can be considered as an alternative and selective route for the valorization of low grade phosphates and for the phosphorus extraction from its bearing materials. Jo u rn al o f Min in g an d Met allu rgy, S ect ion B: Met a llu rg y

The present paper describes detailed kinetics investigations on some selected chlorine-solid reactions through thermogravimetric measurements. The solids studied in this article include chemical pure oxides and sulfides as well as their natural bearing materials. The chlorinating agents employed are gaseous mixtures of Cl2+N2 (chlorination), Cl2+O2 (oxychlorination), and Cl2+CO (carbochlorination). Results are presented as effects of various parameters on the reaction rate of these solids with these chlorinating agents. It was observed that the reactivity of these solids towards different chlorinating agents varied widely. Sulfides could be chlorinated at room temperature, while carbochlorination of chromium (III) oxide was possible only above 500 °C. The variation of the chlorination rate of these complex materials with respect to gas velocity, composition and temperature enabled us to focus some light on the plausible reaction mechanisms and stoichiometries. The obtained results were used for selective removal of iron from chromite concentrates, extraction of valuable metals from sulfide materials, purification of MgO samples, etc.Este trabajo describe detalladas investigaciones cinéticas en algunas reacciones seleccionadas de cloro-sólido a través de medidas termogravimétricas. Los sólidos estudiados en este artículo incluyen óxidos químicos puros y sulfuros, así como sus materiales naturales de soporte. Los agentes de cloración empleados son mezclas de gases de Cl2+N2 (cloración), Cl2+O2 (oxicloración) y Cl2+O2 (carbocloración). Los resultados se presentan como efecto de varios parámetros en el porcentaje de reacción de estos sólidos con los agentes de cloración. Se ha observado que la reactividad de estos sólidos a través de diferentes agentes de cloración varía ampliamente. Los sulfuros se pudieron clorar a temperatura ambiente mientras que la carbocloración del óxido de cromo (III) sólo fue posible por encima de los 500 °C. La variación del porcentaje de cloración de estos materiales complejos con respecto a la velocidad del gas, composición y temperatura permitió arrojar alguna luz en los posibles mecanismos de reacción y estequiometrías. Los resultados obtenidos se han usado para la eliminación selectiva del hierro de concentrados de cromo, extracción de metales valiosos de materiales sulfhídricos, purificación de muestras de MgO, etc.

The effects of Cl2/O2 ratio, P(Cl2+O2), PCl2, and PO2 on the oxychlorination rate of the chromite mineral were determined between 750 and 1000°C using isothermal TGA measurements. The effect of the gases’ composition on the oxychlorination rate of chromite were compared with those resulting from the oxychlorination of simple oxides of the chromite (Cr2O3, Fe2O3 and MgO). The apparent reaction orders with respect to Cl2+O2, Cl2, and O2 for the chromite oxychlorination at 750°C were about 0.94, 1.24, and −0.30, respectively. At 1000°C, apparent reaction orders with respect to the reactive gases changed significantly as the reaction progressed. Boat experiments were carried out to oxychlorinate a chromite concentrate between 600 and 1000°C. The reaction products were analyzed by SEM, XRD and chemical analysis. The oxychlorination of a chromite concentrate at about 800°C led to the partial elimination of iron increasing the Cr/Fe ratio in the treated concentrate. A part of chromium was also oxychlorinated and it was recovered as chromium oxychloride (CrO2Cl2).

The effect of temperature on the oxychlorination of Cr 2 O 3 and MgO using Cl 2 +O 2 was evaluated using non-isothermal conditions. A mathematical treatment of the experimental data was performed. Results were compared with those obtained using isothermal conditions. The oxychlorination of Cr 2 O 3 up to 650°C was characterized by an apparent activation energy ‘ E a ’ of ca. 83 kJ/mol. Beyond 650°C, the reaction proceeded with an E a of ca. 51 kJ/mol. Between 850 and 1025°C, the reaction of MgO with Cl 2 +O 2 was strongly dependent on temperature and its E a was equal to ca. 215 kJ/mol. The values of the apparent activation energies, found for the oxychlorination of both oxides using non-isothermal conditions, were comparable to those obtained during isothermal treatment.

The chlorination behaviors of two chalcopyrite concentrates and their pure constituents in Cl2+N2 were investigated by thermogravimetric analysis (TGA) in nonisothermal conditions up to 1000 °C. The effect of temperature on the reaction of chlorine with both concentrates was studied between 170 °C and 300 °C under isothermal conditions. The effects of gas flow rate, chlorine content of the gas mixture, and reaction time on the reaction rate were also investigated. The reaction products were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that the kinetics of chlorination of chalcopyrite concentrates generating chlorides of Cu, Pb, Zn, Fe, and S was rapid at about 300 °C. The iron and sulfur chlorides were volatilized, leading to a residue containing valuable metal chlorides.

International audience; The carbochlorination of a chromite concentrate was studied between 500 °C and 1000 °C using boat experiments. The reaction products were analyzed by scanning electron microscopy (SEM), x-ray diffraction (XRD), and chemical analysis. The carbochlorination of a chromite concentrate at about 600 °C led to the partial selective elimination of iron, thus increasing the Cr/Fe ratio in the treated concentrate. Total carbochlorination of the chromite concentrates and volatilization of the reaction products was achieved at temperatures higher than 800 °C. The kinetics of the chromite carbochlorination was studied between 750 °C and 1050 °C using thermogravimetric analysis (TGA). The results were discussed in terms of the effects of gas flow rate, temperature, partial pressure of Cl2+CO, and Cl2/CO ratio on the carbochlorination process. It was observed that the temperature effect changed significantly with the progress of the reaction. The initial stage of the carbochlorination was characterized by an apparent activation energy of about 135 and 74 kJ/mol below and above 925 °C, respectively, while a value of about of 195 kJ/mol was found for the remainder of the carbochlorination process.

Characterization of industrial incinerating wastes have been conducted by Thermogravimetric Analysis (TGA), Scanning Electron Microprobe (SEMP), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). During the treatment of incinerating residues with free temperature increase (20-1.000 °C) in air, some weight losses determinations have been observed, indicating an incompleted incineration. XRD characterization reveáis the presence of poorly crystallized phases in these slags. Data from SEMP were statistically treated with the purpose to determine the pseudostructure of these solids. This allows estimation of the possible association of elements in the amorphous solid, and, consequently, to forsee their adequated treatment.La caracterización de los residuos de incineración industriales se ha hecho por análisis termogravimétrico (ATG), microsonda electrónica (MSE), difracción de rayos X (DRX) y microscopio electrónico de barrido (MEB). Durante el tratamiento de los residuos de incineración con subida libre de temperatura (20-1.000 °C) en atmósfera de aire, se han observado diversos valores de pérdida de peso, que testimonian una incineración incompleta. La DRX revela la presencia de fases mal cristalizadas en estas escorias. Los datos de la MSE se han tratado estadísticamente con el fin de determinar la "pseudo-estructura" de estos sólidos. Todo ello permite hacer una estimación de la posible proximidad de los elementos en el sólido amorfo y, en consecuencia, prever el tratamiento necesario de estos sólidos.

Plastic materials have been associated with electric and electronic applications since the early days of the electrical industry. Plastics can amount up to 30% of the scrap mass. Generally, they contains flame retardants such as halogenated compounds which can lead to the formation of different toxic products. Recycling, incineration and landfilling are the current methods used to treat these plastics. They also can be used as combustibles in some metallurgical processes. However, during their combustion, halogenated flame retardants can produce dibenzop-dioxins and dibenzo-furans.

International audience; Synthesis of potassium ferrate using residual ferrous sulfate as iron bearing material To cite this article: N Kanari et al 2013 J. Phys.: Conf. Ser. 416 012013 View the article online for updates and enhancements. Related content Integrated transformations of plant biomass to valuable chemicals, biodegradable polymers and nanoporous carbons B N Kuznetsov, N V Chesnokov, V E Taraban'ko et al.-Synthesis of Li 5 AlO 4 involving a repulpation mixing in a Li 2 CO 3 saturated solution Ol'ga N Krivolapova and Vadim P Tarasov-Oxygen Compounds of Iron(VI, V, IV) I G Kokarovtseva, I N Belyaev and L V Semenyakova-Abstract. This paper summarizes the results obtained during potassium ferrate (K 2 Fe VI O 4) synthesis which is a high added value material. This compound that contains iron in the rare hexavalent state is becoming a substance of growing importance for the water and effluent treatment industries. This is due to its multi-functional nature (oxidation, flocculation, elimination of heavy metals, decomposition of organic matter, etc.). The most well known synthesis methods for potassium ferrate synthesis are those involving the chemical and/or electrochemical oxidation of iron (II) and (III) from aqueous solutions having a high alkali concentration. These methods are generally characterized by a low Fe VI efficiency due to the reaction of the potassium ferrate with water, leading to the reduction of Fe VI into Fe III. Concerning the work pertinent to this paper, the synthesis of K 2 Fe VI O 4 was achieved by a simultaneous reaction of two solids (iron sulfate and KOH) and one gaseous oxidant (chlorine). The synthesis process is performed in a rotary reactor at room temperature and the global synthesis reaction is exothermic. The effects of different experimental parameters on the potassium ferrate synthesis are investigated to determine the optimal conditions for the process.

The main purpose of this paper is to describe the results of different thermal treatments of metallurgical wastes, under controlled atmospheres, in order to concentrate their valuable metals. All the results show the metallic concentration yield obtained for the different treatments.Se describen los resultados de diferentes tratamientos térmicos bajo atmósferas controladas, de tres residuos procedentes de la metalurgia no férrea, con el fin de concentrar los valores metálicos que contienen (Cu, Pb, Zn,...). Los valores metálicos, así como sus rendimientos de concentración en los residuos de tratamiento, se consignan en todos los casos.

Tin slag may contain up to 25% of (Nb+Ta)2O5. Tantalum and niobium are used in advanced technologies. Classical methods for the extraction of these elements are based on the full dissolution of these slags by HF or (HF+H2SO4). This leads to high reagent consumption, due to presence of Si, Fe, Mn, Ca, Al oxides, and the production of toxic wastes. This paper describes a new approach for the characterization and extraction of these metals based on a combined hydro- and pyrometallurgical process. The planning of successive alkaline and acid leaching of this slag based on the “pseudo-structure” of these amorphous materials permits a selective dissolution of the economic metals, a lower consumption of chemical reagents, especially HF, less toxic residues and a high grade concentrate (up to 60% of pentoxide of tantalum and niobium) with a satisfactory recovery rate (about 85%). These concentrates are subjected to a subsequent selective carbochlorination, at temperatures lower than 500°C, leading to full extraction of niobium compounds at 300°C and that of tantalum at 500°C.

The thermal treatment of natural sulfidic minerals such as sphalerite, galena, chalcopyrite, and pyrite in an N2 or H2 atmosphere was studied to examine the nature of reactions taking place. Such treatments have the potential of avoiding sulfur dioxide production which is associated with the roasting of complex sulfide ores (CSOs). The thermal treatment of CSO concentrates at temperatures less than 1000 °C in a nitrogen atmosphere leads to the decomposition of the pyritic matrix to pyrrhotite and the volatilization of sulfur, galena, and some of the CSOs’ trace elements. Treating the CSO in a reducing atmosphere converted sphalerite to zinc and produced a solid containing Cuo, Feo, and silicoaluminates. Selective dissolution of copper may be achieved by a hydrometallurgical process. Hydrogen sulfide could be reacted with pyrrhotite to form pyrite and hydrogen. A flow sheet is proposed.

As X-ray, neutron scattering, and vibrational spectroscopy are not useful for amorphous solids characterization, microprobe analysis is used in determining the composition of these materials. The correlation coefficient matrix between the slag’s elements is obtained by a simple computer program which is commercially available. This matrix is employed for the constitution of the neighborhood of an element, which may be called the “pseudo-structure” (PS). The proposed method is a statistical view of the probable associations between the elements. It gives an insight into the amorphous solids' structure. The lixiviation of tin slags in order to recover the refractory metals they contain is used to illustrate the importance of the PS. A multistage acid-basic (AB) leaching leads to the dissolution of the matrix composed of Ca, Al, Fe, Mn, Si, ... oxides and the concentration of refractory metal oxides in the residues. The optimum tantalum and niobium recovery rates are 93 and 78 pct, respectively. The results of this research indicate that the leaching of the amorphous tin slag is a structure-sensitive operation. However, one may emphasize that the PS of amorphous solids is a simplification of the real neighborhood of ele-ments. It may be considered as a complement to other methods of investigation of the amorphous solids and may facilitate the hydrometallurgical process planning.

International audience; Preliminary tests of the chlorination of two iron oxides (wüstite and hematite) in various chlorinating gas mixtures were performed by thermogravimetric analysis (TGA) under non-isothermal conditions. Wüstite started to react with chlorine from about 200 °C generating ferric chloride and hematite as the final reaction products. The presence of a reducing and oxidizing agent in the chlorinating gas mixtures influenced the chlorination reactions of both iron oxides, during non-isothermal treatment, only at temperatures higher than 500 °C.The chlorination kinetics of hematite with Cl2 have been studied in details between 600 and 1025 °C under isothermal chlorination. The values of the apparent activation energy (Ea) were about 180 and 75 kJ/mol in the temperature ranges of 600–875 and 875–1025 °C, respectively. The apparent reaction order with respect to Cl2 was found to be 0.67 at 750 °C. Mathematical model fitting of the kinetics data was carried out to determine the most probable reaction mechanisms.

International audience; Chlorination of two chalcopyrite concentrates with Cl2+N2 was investigated under isothermal conditions in the temperature range of 20–750°C using boat experiments. The effects of gas flow rate, chlorine content of the gas mixture and residence time on the reaction rate were also investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and chemical analysis are used for the physico-chemical characterization of the reaction products.The chlorination of chalcopyrite concentrates started at room temperature generating chlorides of Cu, Pb, Zn, Fe, and S. The reaction of chlorine with sulfides is almost complete at about 300°C and the overall reaction is exothermic. At this temperature, the valuable metal chlorides were concentrated in the chlorination residues, while those of iron and sulfur were volatilized.A flow sheet is proposed for the selective chlorination of chalcopyrite concentrates at low temperatures. Such flow sheet could be considered as an attractive route for the sulfide concentrates’ treatment without SOx emissions. It could be also regarded as energy saving with respect to the classical pyrometallurgical routes.

International audience; The chlorination of a chromite concentrate was studied between 600 and 1000°C. The reaction products were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and chemical analyses. Chlorination of a chromite concentrate at about 700°C allowed the extraction of about 50% of the iron, thus doubling the Cr/Fe ratio in the treated concentrate. Aluminum chloride was tested as a chlorinating agent in the presence of a reducing atmosphere.The effect of temperature on the kinetics of chromite chlorination was studied between 900 and 1040°C using thermogravimetric analysis (TGA). Temperature effects changed significantly with reaction extent. The initial stage of the chlorination was characterized by an apparent activation energy of about 112 kJ/mol, while a value of about of 269 kJ/mol was found for reaction extents greater than 0.4.

International audience; Thermal treatments of five different types of non-ferrous metallurgical wastes, under a controlled atmosphere, were carried out at temperatures lower than 800 degrees C for the separation of their toxic compounds and the concentration of valuable metals in the treatments residues. The best results were obtained by the treatments in air or hydrogen, or both successively. Simple treatments, using air or hydrogen, of three samples allowed the elimination of more than 95% of their toxic elements and almost doubled their valuable metals concentration. For the rest of the samples, a combined treatment was necessary for their efficient decontamination. In this case, the valuable metals content in the treatment's residue was increased to a reasonable value. Most of the solids issuing from these treatments can be recycled in current non-ferrous metallurgical processes.

The carbochlorination kinetics of pure Nb2O5 and Ta2O5 by gas mixture (C12 + CO + N2) between 380 and 1,000 °C is studied. A calculation of the standard free energy of the carbochlorination reactions is made. A diagram of the phases stability is drawn. The influence of the gas flow, temperature and the pardal pressure of Cl2 and CO at temperatures below 650 °C on the reaction rate is studied. The apparent activation energy is approximately 75 and 110 kJ/mol for Nb2Os and Ta2O5, respectively. At temperatures above 650°C the Arrhenius diagram presents an anomaly which may be attributed to the decomposition of the COCl2 formed in situ. The apparent reaction order of the carbochlorination of these oxides against Cl2+CO is approximately 2. The carbochlorination rates of these oxides are much greater than those of chlorination by Cl2 + N2. The carbochlorination kinetics of tin furnace slag leaching concentrates containing tantalum and niobium compounds are also studied and compared with the carbochlorination kinetics of the pure oxides.En este trabajo se estudia la cinética de carbocloruración del Nb2O5 y del Ta2O5 por la mezcla de gases (Cl2 + CO + N2) entre 380 y 1000°C. Se hace un cálculo de la energía libre estándar de carbocloruración y se dibujan los diagramas de equilibrio de fases. Se estudia la influencia del flujo de gas, la temperatura y la presión parcial de Cl2 y CO a temperaturas por debajo de 650°C sobre la velocidad de reacción. La energía de activación es aproximadamente 75 y 110 kJ/mol para el Nb2O5 y el Ta2O5, respectivamente. A temperaturas por encima de 650°C, el diagrama de Arrhenius presenta una anomalía que puede ser atribuida a la descomposición del COCl2 formado in situ. El orden aparente de reacción de la carbocloruración de estos óxidos frente a Cl2 + CO es aproximadamente 2. La velocidad de carbocloruración de estos óxidos es mucho más grande que la que se conseguía con una mezcla de Cl2 y N2. Se ha comparado la cinética de carboclururación de los compuestos de niobio y tantalio contenidos en los concentrados de lixiviación de las escorias de hornos de estaño con la cinética de carbocloruración de los óxidos puros.

International audience; The kinetics of oxychlorination of MgO by Cl2+O2 was studied in the temperature range of 850 degrees C - 1025 degrees C, using thermogravimetric analysis. The effects of Cl2/O2 ratio, gas velocity, temperature and partial pressure of reactive gases on the reaction rate were investigated. The oxychlorination process was characterized by an apparent activation energy of about 214 kJ/mol. The reaction orders with respect to Cl2+O2 , Cl2 and O2 at 950 degrees C were about 0.65, 0.98, and -0.37, respectively.Some data about oxychlorination kinetics of MgO, Cr2O3, and MgCr2O4 contained in chromite were compared. Efficiency of using oxychlorination for the removal of iron oxides contained in magnesia was demonstrated.

International audience; Chlorination of wüstite (Fe(1−x)O) and hematite (Fe2O3) with Cl2 + CO and Cl2 + N2 was studied by thermogravimetric analysis using non-isothermal conditions up to about 1000°C. The wüstite started to react with the carbochlorinating gas mixtures at low temperatures producing FeCl3 and Fe2O3 as final reaction products. The presence of carbon monoxide, during non-isothermal tests, enhanced the chlorination of wüstite at temperatures higher than 550°C when the produced hematite started to react with carbochlorinating gas mixture. The separate treatment of the two oxides under isothermal conditions in Cl2 + CO for 2 h led to their full reaction at about 550°C. An apparent activation energy of about 53 kJ/mol was obtained for the carbochlorination of hematite between 350°C and 550°C.Reaction of wüstite with FeCl3 was also studied by thermogravimetric analysis using non-isothermal conditions. Higher oxides of iron and ferrous chloride were the main reaction products at 600°C, even in the presence of carbon monoxide.