Different strategies for recovering metals from CARON process residue

http://dx.doi.org/10.1016/j.jhazmat.2011.03.048The capacity of Acidithiobacillus thiooxidans DMS 11478 to recover the heavy metals contained in the residue obtained from the CARON process has been evaluated. Different bioreactor configurations were studied: a two-stage batch system and two semi-continuous systems (stirred-tank reactor leaching and column leaching). In the two-stage system, 46.8% Co, 36.0% Mg, 26.3% Mn and 22.3% Ni were solubilised after 6 h of contact between the residue and the bacteria-free bioacid. The results obtained with the stirred-tank reactor and the column were similar: 50% of the Mg and Co and 40% of the Mn and Ni were solubilised after thirty one days. The operation in the column reactor allowed the solid–liquid ratio to be increased and the pH to be kept at low values (<1.0). Recirculation of the leachate in the column had a positive effect on metal removal; at sixty five days (optimum time) the solubilisation levels were as follows: 86% Co, 83% Mg, 72% Mn and Ni, 62% Fe and 23% Cr. The results corroborate the feasibility of the systems studied for the leaching of metals from CARON process residue and these methodologies can be considered viable for the recovery of valuable metals

Manganese and cobalt redox cycling in laterites; Biogeochemical and bioprocessing implications

This research was developed during the PhD studies of Agustín Solano Arguedas in the University of Manchester, United Kingdom. PhD scholarship was funded by the Ministerio de Ciencia, Tecnología y Telecomunicaciones (MICITT) of the Government of Costa Rica and the Universidad de Costa Rica (UCR). Agustín Solano Arguedas is a researcher at the Unidad de Recursos Forestales (Reforesta, Unit of Forest Resources) of the Instituto de Investigaciones en Ingeniería (INII, Engineering Research Institute), UCR.Cobalt is essential for the modern technology that underpins the decarbonisation of our economies, but its supply is limited leading to its designation as a critical metal. Cobalt biogeochemistry is poorly understood, yet knowledge of how biogeochemical cycling impacts cobalt behaviour could assist the development of new techniques to recover cobalt from ores, and so improve the security of supply. Laterites are an important source of cobalt, they are primarily processed for nickel using energy or chemical intensive processes, with cobalt recovered as a by-product. Metal-reducing conditions were stimulated in laterite sediment microcosms by the addition of simple and cheaply available organic substrates (acetate or glucose). At the end of the experiment the amount of easily recoverable cobalt (aqueous or extractable with acetic acid) increased from < 1% to up to 64%, which closely mirrored the behaviour of manganese, while only a small proportion of iron was transformed into an easily recoverable phase. Sequencing of the microbial community showed that the addition of organic substrates stimulated the growth of indigenous prokaryotes closely related to known manganese(IV)/iron(III)-reducers, particularly from the Clostridiales, and that fungi assigned to Penicillium, known to produce organic acids beneficial for leaching cobalt and nickel from laterites, were identified. Overall, the results indicate that the environmental behaviour of cobalt in laterites is likely to be controlled by manganese biogeochemical cycling by microorganisms. These results are compelling given that similar behaviour was observed in four laterites (Acoje, Çaldağ, Piauí and Shevchenko) from different continents. A new bioprocessing strategy is proposed whereby laterites are treated with an organic substrate to generate metal-reducing conditions, then rinsed with acetic acid to remove the cobalt. Not only are organic substrates environmentally-friendly and potentially sourced from waste carbon substrates, a minimal amount of iron oxides was mobilised and consequently less waste generated.Natural Environment Research Council/[CoG3 NE/M011518/1]/NERC/Reino UnidoDiamond Light Source/[SP16735]//Reino UnidoDiamond Light Source/[SP17313]//Reino UnidoOffice of Science User Facility/[DE-AC02-05CH11231]//Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII

ΤΑ ΜΑΡΜΑΡΑ ΤΗΣ ΜΑΝΗΣ: Θέσεις εμφάνισης/εξόρυξης, πετρογραφική και ισοτοπική αναγνώριση

Στην παρούσα εργασία καταγράφονται οι θέσεις εξόρυξης (πάνω από 90, αρχαίες αλλά και νεότερες) αλλά και οι εμφανίσεις μαρμάρου της περιοχής της χερσονήσου Μάνης, Λακωνικής και Μεσσηνιακής. Καταρτίζεται πλήρης κατάλογος και διαμορφώνεται λεπτομερής χάρτης με γεωγραφικές συντεταγμένες, φωτογραφικό υλικό αλλά και τεκμηρίωση περί της εξορυκτικής δραστηριότητας αλλά και της διαχρονικής χρήσης του μαρμάρου Μάνης σε διάφορα έργα τέχνης και τεχνουργήματα . Ειδικότερα αποτυπώνεται η περιοχή του Προφήτη Ηλία Δημαρίστικων Ανατολικής Μάνης για την εξόρυξη-αποκομιδή του ερυθρού μαρμάρου. Η καταγραφή των χώρων εξόρυξης επιτρέπει την άρση αμφισβητήσεων στην ιστορική διαδρομή των μαρμάρων Μάνης, ειδικότερα αναφορικά με την προέλευση του Nero Antico. Επίσης γίνεται ορυκτολογική, πετρογραφική και ισοτοπική αναγνώριση 27 αντιπροσωπευτικών δειγμάτων με την οποία ταυτοποιήθηκε γεωχημικά το μάρμαρο Μάνης εκτιμώντας το είδος και το μέγεθος των περιεχομένων ορυκτών, τον ιστό, την υφή, την κατάσταση εξαλλοίωσης αλλά και τους ισοτοπικούς λόγους δ18O και δ13C. Η συμπλήρωση και με άλλα κρίσιμα δεδομένα, κυρίως η εξέταση του υφιστάμενου θεσμικού πλαισίου, επιτρέπει την εξαγωγή συμπερασμάτων και προτάσεων ως προς την δυνατότητα προοπτικών αξιοποίησής τους. Τέλος, γίνονται και ορισμένες προτάσεις που αφορούν την εκλεκτική εξόρυξη με ανάπτυξη μικρής κλίμακος μονάδων με σκοπούς καθαρά πολιτιστικούς, οι οποίες θα μπορούσαν να επεκταθούν και σε άλλα ιστορικά μάρμαρα του τόπου μας.This dissertation investigates the marbles, quarries and outcrops of Mani peninsula in the southern central part of the Peloponnesus, Greece, which is very rich in white-grey, black and red marbles, exploited since the antiquity. In particular, the aim is to provide a de-tailed breakdown of all quarries/main outcrops and then a petrographic characterization of specific samples from several outcrops as well as ancient quarries within the Mani penin-sula. An isotopic (δ18O and δ13C) analysis is also employed to provide a database to a broader perspective, in view of the trustworthy identification of archaeological pieces made out of these marbles (provenance determination).The definition of both petrographic and isotopic features obtained from this work to-gether with the “sample database” can be used for future archaeometric research in the region as the identification of the Mani marble provenance remains an issue of interest for archaeologists and art historians and continues to engage scientists of various specialties. Finally, a number of suggestions are made, with the examination of the existing institu-tional framework, regarding future selective mining with the development of small-scale units for purely cultural purposes, which could be extended to other historical marbles of Greece