M. Sanchez

Influence of mechanical activation on the alkaline leaching of enargite concentrate

Abstract In this study the alkaline leaching of enargite Cu3AsS4 (El Indio, Chile) in the medium of sodium sulphide was investigated. The rate of leaching can be influenced by the pre-treatment consisting of mechanical activation of the concentrate in a stirring ball mill (attritor). The XRD and XPS methods used to characterise the bulk and surface properties of the solid phase after leaching have shown that arsenic extraction from enargite leads to its transformation to covellite CuS. On the basis of the value of experimental activation energy (62 kJmol−1) we can conclude that a chemical reaction is the rate-determining process of the reaction between Cu3AsS4 and Na2S. The applied procedure represents a potentionality of de-arsenification of sulphidic concentrates and preparation of a charge convenient for further processing, e.g., by pyro-treatment.

Environmental viewpoint on small-scale copper, gold and silver mining in Chile

Abstract This paper analyses the importance and environmental impacts of metallic small-scale mining in Chile. This sector is characterized by the exploitation of primarily artisanal copper (Cu), gold (Au), and silver (Ag) deposits, which are dispersed throughout (Chilean) Regions I through VI, with heaviest concentrations in Regions III and IV. In 2000, Chilean small-scale mines employed some 1700 workers (5.1% of total mining workers), and plants with a production capacity of less than 50 tpd accounted for 0.97% (44,603 t) of Cu; 6.5% (3,484) of Au; and 1.1% (13,665 kg) of Ag output in the country. High-grade ore extraction, flotation, gravity concentration, acid leaching–cementation, and mercury amalgamation, are the main metallurgical technologies employed. Following an overview of Chilean small-scale mining, the paper examines the environmental impacts of its production processes, and discusses the legal support and regulatory framework in place for operations.

The Copper Losses in the Slags From the El Teniente Process

Abstract The current El Teniente Pyrometallurgical Process for copper concentrate was commissioned at Caletones Smelter during the period 1988 - 1991 following an intensive research and development program that led to several improvements to the original process developed during the seventies. The Caletones Smelter production capacity is 370,000 tons of cast copper annually related to a concentrate smelting capacity of 1,250,000 tons per year. Several industrial applications of the process, in Chile and abroad, have shown its capability to treat copper concentrates in a wide range of chemical and mineralogical compositions. The main operational parameters that determine the performance of the process are oxygen enriched air flow rate, degree of oxygen enrichment, moisture content of the solid materials processed, molten material levels inside the vessel, frequency of molten materials tapping, bath temperature and copper losses in slags. The copper losses in the slags from the El Teniente Pyrometallurgical Process, predicted by calculation from thermodynamic data, have been compared with those determined by microscopic examination and quantitative electron microprobe analysis of the slag samples and by flotation tests of finely ground slag. Au cours de la periode 1988-1991, on a mis en service a la fonderie Caletones le procede pyrometallurgique actuel El Teniente pour le concentre de cuivre, suite a un programme intensif de R & D qui a conduit a plusieurs ameliorations du procede original developpe dans les annees 70’s. La capacite de production de la fonderie Caletones est de 370,000 t de cuivre coule annuellement, en relation avec une capacite de fonte de concentre de 1,250,000 t par année.Plusieurs applications industrielles du procede, au Chili et a l’etranger, ont montre sa capacite a traiter des concentres de cuivre couvrant une grande gamme de compositions chimiques et mineralogiques. Les principaux parametres operationnels, qui determinent la performance du procede, incluent le taux d’ecoulement d’air enrichi a l’oxygene, le degre d’enrichissement en oxygene, le contenu en humidite des materiaux solides traites, le niveau de materiel fondu a l’interieur du reacteur, la frequence de recolte des materiaux fondus, la temperature du bain et la perte de cuivre dans les scories. On a compare les pertes de cuivre dans les scories par le procede pyrometallurgique El Teniente, predites par les calculs a partir des donnees thermodynamiques, avec celles determinees par examen microscopique et par analyse quantitative par microsonde electronique des echantillons de scories ainsi que par des tests de flottation de scories pulverisees finement.

Copper losses to slags obtained from the El Teniente process

Abstract The smelting and converting El Teniente process for copper concentrates as well as slag cleaning furnace technologies to treat slags coming out from the El Teniente furnaces are widely applied today in Chile and around the world. Several industrial applications of this process have shown their ability to treat copper concentrates in a wide range of chemical and mineralogical compositions. Main operational parameters determining performance of the process are: oxygen enriched air flow rate; degree of oxygen enrichment; moisture content of the solid materials processed; molten material levels inside the vessel; frequency of molten materials tapping; bath temperature; and copper losses in slags. In this work, the copper losses in the slags from the El Teniente pyrometallurgical process are predicted by calculation from thermodynamic data and compared with those determined by microscopic examination and slag industrial data. Results obtained show that the main part of copper losses in the slag from the El Teniente furnace are mechanically entrapped or floated unsettled droplets of the co-existing matte phase. Conversely, the very low copper losses in the slag from the slag cleaning furnace are limited by the physicochemical form.

Wastes as resources: update on recovery of valuable metals from copper slags

Abstract Copper production from sulphide minerals generates massive amounts of slag as final waste of the pyrometallurgical processes. Dumping the slag nearby the smelter plant has been the common practice and, currently it is produced in a proportion of 2·2 ton of slag per ton of blister copper and is granulated to facilitate the transportation and final disposal. Thus, it is relevant to improve sustainability by recycling this waste to minimise the environmental impact generated during pyrometallurgical treatment of copper sulphides concentrates. Laboratory tests were run in order to concentrate and separate metals and materials for obtaining results that could be scaled up to pilot and industrial level. The results of pyrometallurgical and hydrometallurgical experiments are presented in order to show the importance of the oxidation of the slag at high temperatures that could liberate those metals molecularly entrapped during processing sulphide concentrate in the smelter plant. Therefore, the present work shows experimental work done in Chile in order to add value to this waste by recovering contained metals and materials such as copper, molybdenum, and iron and silica, with iron and silica being more than half of the total content of the slag, which has an important effect on the volume of the stocked material.

Two families of Xenopus tropicalis skeletal genes display well‐conserved expression patterns with mammals in spite of their highly divergent regulatory regions

SUMMARY The origin of bone and cartilage, and their subsequent diversification in specific vertebrate lineages, is intimately linked to the precise transcriptional control of genes involved in matrix mineralization. It is not yet clear, however, to which extent the osteoblasts, osteocytes, and chondrocytes of each of the major vertebrate groups express similar sets of genes. In this study we have focused on the evolution of two independent families of genes that code for extracellular matrix components of the skeleton and that include secreted protein, acidic, cysteine‐rich (SPARC), bone sialoprotein (BSP) and dentin matrix protein 1 (DMP1) paralogues, and the osteocalcin (OC) and matrix gla protein (MGP) paralogues. Analyzing developing Xenopus tropicalis skeletal elements, we show that the expression patterns of these genes are well conserved with mammals. The fact that only a few osteoblasts express DMP1, while only some osteocytes express SPARC and BSP, reveals a significant degree of molecular heterogeneity for these two populations of X. tropicalis cells, similarly to what has been described in mouse. Although the cis‐regulatory modules (CRM) of the mammalian OC, DMP1, and BSP orthologs have been functionally characterized, we found no evidence of sequence similarity between these regions and the X. tropicalis genome. Furthermore, these regulatory elements evolve rapidly, as they are only poorly conserved between human and rodents. Therefore, the SPARC/DMP1/BSP and the OC/MGP families provide a good paradigm to study how transcriptional output can be maintained in skeletal cells despite extensive sequence divergence of CRM.

Recovery of molybdenum from roasted copper slags

Abstract Recycling copper slag to recover metals has been focused on copper, which is contained in the range of 0·77 to 1·32%; however some slags also contains molybdenum in amount up to 0·4% transforming the copper smelting slags into a potential raw material for the development of new processes to obtain new products. In this regard, copper slags were treated using roasting–leaching process in order to recover the molybdenum content in the slag. Oxidative roasting is used to convert the iron oxide into insoluble hematite, and copper and molybdenum into the soluble form in acidic solution. Since molybdenum is associated to iron oxide spinel type phase, its recovery was influenced by the magnetite content in the slag during the leaching process. Sulphuric acid was used for leaching the slag, and molybdenum shows recovery higher than 80%. Thus, the obtained results show the feasibility for recovering molybdenum using two-step processes, oxidative roasting followed by an acidic leaching.

Comparative analysis of slag systems Cu–Fe–O–SiO2 and Cu–Fe–O–CaO between 1100 and 1300°C

Abstract The present work reviews the state of the art of the quaternary systems Cu–Fe–O–SiO2 and Cu–Fe–O–CaO during copper pyrometallurgy processes, mainly, matte converting and blister copper fire refining. Both systems are particularly important to be considered in physicochemical understanding and modelling of pyrometallurgical processes today, then their knowledge become of particular interest for fundamental research and its applications to the copper industry. This analysis includes Cu losses, behaviour of impurities, and the interaction of MgO/Cr2O3 refractories with Cu2O both in fayalite and calcium ferrite slags.