La eliminación de metales tóxicos presentes en efluentes líquidos mediante resinas de cambio iónico. Parte III: cobre(ll)/sulfato/Amberlite 200

5 pages, 5 figures, 6 tables.[EN] Copper(II) adsorption from aqueous sulphate media on Amberlite 200 was investigated. The influence of operating variables such as aqueous pH, temperature and copper concentration on the metal adsorption kinetics was measured. The copper{II) uptake is best fitted to the film-diffusion controlled process. The resin has been used in minicolumns to investigate its performance under dynamics conditions. Copper(II) desorption from the resin is accomplished using sulphuric acid solutions.[ES] Se estudia la adsorción de cobre(II), de disoluciones en medio sulfato, en la resina Amberlite 200. La cinética de adsorción del metal se ha estudiado en función de una serie de variables experimentales: pH de la fase acuosa, temperatura y concentración del metal en el medio acuoso. La adsorción de cobre(II) se puede correlacionar como controlada por un proceso de difusión en capa límite. Se ha utilizado la resina en minicolumnas para estudiar su comportamiento bajo condiciones dinámicas. La desorción del cobre(II) se lleva a cabo con disoluciones de ácido sulfúrico.To the CSIC for support.Peer reviewe

Recent trends in metals extraction

After near 70 years of practical usage, solvent extraction is a perfectly mastered technique of separation, widely used on an industrial scale for the separation of metals mainly from raw materials. However, currently, in the era of depleting natural resources and increasingly less accessible deposits, environmental restrictions, etc., an increasing interest, both from social and economical constrains, is being directed at the extraction of metals from the secondary sources (such as batteries, electronic scrap). In many cases, solvent extraction, due to its operational characteristics, can be considered as the Best Available Technology for the purpose of separating multielemental metal solutions. This paper provides a brief overview of past achievements and present scenario of solvent extraction investigations and developments, describing some recently commissioned solvent extraction plants, whereas the Skorpion Zinc plant (Namibia) for zinc extraction from raw materials and caesium removal from radioactive High Level Wastes (HLWs) are told over in detail as case studies. The paper also presents some proposals for the use of liquid-liquid extraction to separate metal ions from secondary sources (e.g. cobalt from industrial waste streams). The review highlights the emerging use of ionic liquids as new extractants for metals, providing an insight into this exciting research field. Despite its detractors, solvent extraction has entered in force into XXI century as a leading separation technology for metals.Peer Reviewe

Acid leaching of scheelite concentrates

4 páginas, 6 figuras.[ES] Se estudió la lixiviación acida, en medio clorhídrico, de un concentrado de wolframio (scheelita, CaW04). De lo anterior, se obtuvo un sólido insoluble (H2WO4), que se trató con una solución alcalina de hidróxido de sodio, lográndose la completa solubilización del wolframio como ion wolframato (WO4 ). La fracción transformada de wolframio aumenta con la temperatura, como también con una granulometría más fina. Se logró una disolución máxima de 88,5 % (400 g/1 HCl, 363 K y 20 j^lm de tamaño de partícula) para 3 h de proceso, disolución que se interpretó a través del modelo de núcleo recesivo con formación de capa de producto sólido para todo el rango de variación de los parámetros en estudio. El valor de energía de activación encontrado fue de 28,0 k]/mol.[EN] The acid leaching in hydrochloric media of a tungsten concentrate (scheelite, CaWO^) was studied. Of the above-mentioned, an insoluble solid (H2WO4) was obtained which were treated with an alkaline solution of sodium hydroxide, achieving the complete solubilization of the tungsten as wolframate ion (WO4 ). The transformed fraction of tungsten increases with the temperature, as well as with a finer grain. A maximum dissolution of 88.5 % (400 g/1 HCl, 363 K and 20 jLim of particle size) was achieved for a 3 h process, of the disolution process was interpreted by the recessive core model with formation of a layer of solid product for the whole range of variation of the parameters in study. The activation energy value was found to be 28.0 kj/mol.Los autores agradecen a la Universidad de Santiago de Chile y al CSIC (España) por la ayuda prestada para la realización de este estudio.Peer reviewe

Proposal of an index to evaluate the ‘dewaterization’ of the urban water cycle and a practical application

Analyses of the relationship between water and energy do not account for the fact that the energy used in the urban water cycle is a consumer of water. To ensure the efficient use of water resources, the operator must know the raw water use associated with the energy input of the urban water infrastructure. The main contribution of this research is the proposal of an index that measures how much raw water is consumed by the energy used to produce 1 cubic m of water. The resulting index is a decision-making tool that enables the sustainable use of water resources. This article first explains the index, which is called the Water Footprint of the Urban Water Cycle. It then provides examples of how to apply the proposed method; among other applications, it can be used to establish a classification of energy sources based on their relative consumption of raw water, according to the electricity generation mix in each service area. The proposed method is useful for operators, policymakers and other stakeholders, enabling them to make decisions that contribute to the ‘dewaterization’ of the urban water cycle.European CommissionSpanish State Research AgencyRegional Government of AndalusiaEuropean Regional Development Fun

The adsorption of gold on activated carbon from thiosulfate-ammoniacal solutions

The adsorption of gold on activated carbon in ammoniacal thiosulfate solution was studied. The variables affecting the adsorption of gold on the carbon included, among others, temperature, concentrations of ammonium hydroxide and thiosulfate, and those of accompanying cations and anions. The apparent activation energy for the adsorption process was estimated to be 19.4 kJ/mol, and this value indicates that the gold adsorption is film diffusion-controlled. It was also found that the rate of initial adsorption rate was fast, when compared to that of the overall adsorption processPeer reviewe

Gold cementation with zinc powder from leaching solutions with ammonia-thiosulphate

9 páginas, 11 figuras, 7 tablas.[ES] Se estudió la cementación de oro con polvo de cinc desde soluciones con tiosulfato y amoniaco, evaluando la influencia de las siguientes variables: concentración de tiosulfato, concentración de amoniaco, pH, concentración de cobre y concentración de cinc. Los resultados han permitido establecer la gran importancia que tiene, en este proceso, la relación amoniaco/tiosulfato y cómo la presencia de impurezas como cobre y cinc inhiben el proceso de cementación.[EN] The cementation of gold with powder of zinc, from solutions with thiosulphate and ammonia, was studied. The variables evaluated were: thiosulphate concentration, ammonia concentration, pH, copper concentration and zinc concentration. The results have revealed the great importance of ammonia/thiosulphate relationship in this process and that the impurities presence like copper and zinc will to inhibit the cementation process.Los autores expresan sus agradecimientos por el patrocinio recibido de la Comisión Nacional de Investigación Científica y Tecnológica a través del proyecto FONDECYT 1020017.Peer reviewe

Revisión de algoritmos para modelización de equilibrios de distribución de metales en procesos de extracción líquido-líquido

10 pages, 5 figures, 2 tables, 1 appendix.[EN] This work focuses on general guidelines to be considered for application of least-squares routines and artificial neural networks (ANN) in the estimation of metal distribution equilibria in liquid-liquid extraction process. The goal of the procedure in the statistical method is to find the values of the equilibrium constants (K¡) for the reactions involved in the metal extraction which minimizes the differences between experimental distribution coefficient (Dgxp) and theoretical distribution coefficients according to the mechanism proposed (Dt^^gor)- Iri the first part of the article, results obtained with the most frequently routine reported in the bibliography are compared with those obtained using the algorithms previously discussed. In the second part, the main features of a single back-propagation neural network for the same purpose are discussed, and the results obtained are compared with those obtained with the classical methods.[ES] El trabajo presenta las líneas generales a considerar para la estimación del equilibrio de distribución de metales en procesos de extracción líquido-líquido, según dos métodos: algoritmo clásico de mínimos cuadrados y redes neuronales artificiales. El objetivo del procedimiento, en el caso del método estadístico, es encontrar los valores de las constantes de equilibrio (KJ para las reacciones involucradas en la extracción del metal, que minimizan las diferencias entre el coeficiente de distribución experimental y el coeficiente de distribución teórico, de acuerdo al mecanismo propuesto. En la primera parte del artículo se comparan los resultados obtenidos a partir de los algoritmos usados más habitualmente en la bibliografía, con los datos obtenidos mediante el algoritmo previamente descrito. En la segunda parte, se presentan las características fundamentales para aplicar una red neuronal sencilla con algoritmo hack-propagatioriy y los resultados obtenidos se comparan con los de los métodos clásicos.Peer reviewe

Thermal dehydration kinetics of phosphogypsum

© 2015 CSIC. Phsophogypsum is a by-product from the processing phosphate rock. Before the use of it in cement industry such as setting regulator is necessary a study of dehydration reaction of phosphogypsum to avoid the false setting during the milling. The aim is to study the thermal behavior of two different phosphogypsum sources (Spain and Tunisia) under non-isothermal conditions in argon atmosphere by using Thermo-Gravimetriy, Differential Thermal Analysis (TG-DTA) and Differential Scanning Calorimetry (DSC). DSC experiments were carried out at temperatures ranging from ambient to 350 °C at different heating rates. The temperatures of conversion from gypsum to hemihydrate and anhydrite states and heat of dehydration were determined. Various methods were used to analyze the DSC data for reaction kinetics determination. The activation energy and frequency factor were calculated for dehydration of phosphogypsum. Activation energy values of the main dehydration reaction of phosphogypsum were calculated to be approximately 61-118 kJ/mol.The authors are grateful to the Spanish National R&D&I Plan and FEDER (Project CTQ200802012/PPQ) for the financial support of this study.Peer Reviewe

Zinc and iron removal from chromium(III) passivation baths by solvent extraction with Cyanex 272

The use of Cyanex 272 for extraction of zinc and iron from industrial wastes like chromium(III) passivation baths is investigated. The extraction of the metals is studied, in batch conditions, as a function of equilibration time, temperature, diluent of the organic solution, metals and extractant concentrations and pH values of the aqueous solutions. Also the stripping of the metals from loaded organic phases had been investigated using sulphuric acid solutions as strippant

Carbon-based nanomaterials for gold (III) recovery: kinetics and loading investigations

Currently, the development of different smart technology to recover or eliminate strategic or toxic metals from liquid effluent is constant. Among the different process developed to the treatment of liquid effluents bearing these types of metallic elements, include chemical or electrochemical precipitation, membrane based technology, ion exchange and adsorption. Adsorption is a high efficiency, cost-effectiveness and easily handing method to recover pollutants or strategic metals. Nowadays a research challenge is the development of new adsorbents. Among nanomaterials, carbon nanomaterials have adequate properties to be used as metal adsorbent. On the other hand gold is one of the most precious elements in the world. The price in 2015 of this strategic metal is 1.376 $/kg. Besides its uses in jewellery it is highly used in different industries, so it is important the gold recovery from liquid effluents generated from these various industries. The adsorption method is a way to treat these types of effluents, characterized for their low gold concentration. The aim of this research was to optimize various operational parameters, and thus obtain efficient carbon nanotubes processing for gold (III)-bearing effluents. The adsorption of gold (III) by carbon nanofibers (CNF), carbon multiwalled (MWCN) and carbon multiwalled with carboxyl group (MWCN_ox) systems were investigated. The experimental parameters which may influence gold adsorption were investigated, i.e. stirring speed of the aqueous solutions, adsorbent dosage, acid concentration, temperature etc. Figure 1 shows the effect of the acid concentration on the Au(III) adsorption to the three adsorbent. It can be seen that the adsorption Au(III) decreases with the increase of HCl concentration. Probalby it is due the existence of other gold species, such as HAuCl4, at the higher hydrochloric solution against the presence of the predominant AuCl4- species in the more dilute HCl solutions which are more adsorbable than the gold-acid form. SEM studies of gold loaded carbon nanomaterials show on the surface dark particles, Figure 2. The EDS of the dark particles show two peaks for Lα(9.7 keV) and Mα (2.1 keV) characteristic of metallic gold. Probably this reduction occurs on the carbon surface, related with the metal reduction. The isotherm and kinetic studies of the carbon nanomaterial-Au(III) system show a different behavior in function of the carbon nanomaterial used as adsorbent. The experimental data obtained using the MWCNT and CNF fit better to a pseudo second order equation and an isotherm Freundlich model. The three carbon nanomaterials, appeared to be a promising material for recovery of Au(III) from this type of acid solutions in the optimal experimental for each one of them condition.Peer reviewe