Search

Mineral carbonation is considered to be the most stable mechanism for the sequestration of CO2. This study comprises a comparative review of the effect of ball milling on the CO2 uptake of ultramafic/mafic lithologies, which are the most promising rocks for the mineralization of CO2. Samples of dunite, pyroxenite, olivine basalt and of a dolerite quarry waste material were previously subjected to ball milling to produce ultrafine powders with enhanced CO2 uptake. The optimum milling conditions were determined through selective CO2 chemisorption followed by temperature-programmed desorption (TPD) experiments, revealing that the CO2 uptake of the studied lithologies can be substantially enhanced via mechanical activation. Here, all these data are compared, demonstrating that the behavior of each rock under the effect of ball milling is predominantly controlled by the mineralogical composition of the starting rock materials. The ball-milled rock with the highest CO2 uptake is the dunite, followed by the olivine basalt, the pyroxenite and the dolerite. The increased CO2 uptake after ball milling is mainly attributed to the reduction of particle size to the nanoscale range, thus creating more adsorption sites per gram basis, as well as to the structural disordering of the constituent silicate minerals.

Mineral carbonation has been suggested as a safe carbon capture and storage (CCS) strategy for the mitigation of climate change. This study investigates the effect of ball milling on the CO2 sequestration capacity of peridotites, which are among the most promising readily available lithologies for CCS on the Earth's surface. A partially serpentinized harzburgite from the Troodos ophiolite (Cyprus) was subjected to different degrees of ball milling to produce nanoscale ultramafic powders with enhanced CO2 uptake. The optimum ball milling conditions were found (16 h of wet ball milling with 50 wt% ethanol as process control agent) through CO2 chemisorption followed by temperature-programmed desorption (CO2-TPD) experiments. The results clearly showed that the CO2 uptake of the initial rock material was increased by a factor of 4.5 after ball milling. Detailed characterization of the unmilled and ball-milled samples indicated that this enhancement is mainly attributed to (i) the reduction of particle size down to the nanoscale range and (ii) the structural disordering of the constituent Mg-silicate minerals due to mechanical deformation. © 2018 Elsevier Ltd 120 66 74 66-74

Investigation of new efficient pathways for CO2 sequestration is of great significance for the mitigation of climate change. Ultramafic rocks are considered among the most promising lithotypes for the safe storage of CO2 via mineral carbonation. This paper investigates a powerful method for the optimization of the ex situ carbonation of pyroxenitic rocks, which comprise part of ultramafic lithologies occurring in ophiolite complexes. The ball milling process was applied to a sample of pyroxenite from the Troodos ophiolite (Cyprus) for the first time, in order to create novel nanomaterials with enhanced CO2 storage capacity. The goal was to accelerate the kinetics of rock-fluid reactions during the carbonation process. The starting rock material and the ball-milled samples were characterized using a variety of methodologies. The experimental results imply that only a few hours of wet ball milling with ethanol as process control agent can substantially increase the CO2 storage capacity of pyroxenites. Through temperature-programmed desorption of CO2 (CO2-TPD) experiments, we show that the optimum milling conditions are 4 h of ball milling with 50 wt% ethanol, leading to an increase of the CO2 uptake of the studied rock material by 41 times. This notable increase designates that pyroxenites are very promising lithologies for CO2 storage via ex situ carbonation, and that ball milling can be an effective preparation technique for this process, providing an efficient and secure carbon storage solution. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd. 5 5 577 591 Cited By :2

The goal of this study is to propose a cost-effective method for the optimization of the ex situ carbonation of basaltic rocks. The ball milling process was applied to a sample of olivine basalt from the Troodos ophiolite complex (Cyprus) for the first time, in order to fabricate novel nanomaterials for CO2 storage. The purpose was to accelerate the kinetics of rock–fluid reactions during the carbonation procedure. Various methodologies were used for the characterization of the starting rock material and the ball-milled samples. Preliminary results reveal that only a few hours of wet ball milling with ethanol as process control agent can induce significant changes to olivine basalt towards improvement of its performance for CO2 storage. Specifically, CO2 uptake measurements via the use of the temperature-programmed desorption (TPD) technique indicate that 4h of ball milling with 50wt.% ethanol can lead to an enhancement of the carbonation of olivine basalt by 295%. The experimental results strongly suggest that (i) olivine basalts have important CO2-storage capacity and are very promising lithotypes for ex situ carbonation, and (ii) the ball milling process provides hopes for its use at an industrial scale as a preparation technique for the safe and permanent ex situ storage of CO2. •The ball milling process was used to create novel nanomaterials for CO2 capture.•The experiments were carried out using a sample of olivine basalt.•Olivine basalt shows higher CO2 uptake compared to the reference forsterite.•The pore volume principally controls the extent of carbonation.•Ball milling results in an enhancement of the carbonation of olivine basalt by 295%. 273 220 229 220-229

•Dunitic materials with enhanced CO2 uptake were created via ball milling (BM).•The optimum conditions are 12h of BM with 50wt% ethanol as process control agent.•The BM process increased the CO2 uptake of dunites by a factor of 6.9.•The presence of H2O has a substantial positive effect on CO2 uptake.•The positive effect of H2O on CO2 uptake is more evident after the BM process. The investigation of potential options for CO2 sequestration is of vital importance for alleviating the ongoing climate problem. This paper presents an efficient method for enhancing the ex situ carbonation of dunites. The ball milling process was applied to a dunite from the Troodos ophiolite (Cyprus), in order to create a new type of material with enhanced CO2 uptake. Through CO2 chemisorption followed by temperature-programmed desorption (CO2-TPD) experiments, optimum ball milling conditions were found (12h of wet ball milling with 50wt% ethanol as process control agent), leading to an increase of CO2 uptake of dunite by a factor of 6.9. A further increase of CO2 uptake by 10% was accomplished after 4h of additional ball milling with smaller balls. Additionally, CO2-TPD along with in situ DRIFTS studies indicated that the CO2 uptake of the dunitic materials can be substantially enhanced by the presence of H2O during CO2 chemisorption. The positive effect of H2O on CO2 chemisorption becomes much more evident after the ball milling process. Specifically, the CO2 uptake of the ball-milled sample (BM45) was enhanced by a factor of 5.8 (from 181.9 to 1047.5μmolg−1), when CO2 chemisorption was performed in the presence of 20vol% H2O. 27 360 371 360-371

•Novel nanomaterials were produced via ball milling (BM) of quarry waste material.•Various morphological and structural modifications occurred after the BM process.•The optimum conditions are 20h of BM with 50wt% ethanol as process control agent.•The BM process increased the CO2 uptake of mafic quarry wastes by a factor of ∼120.•The presence of augite nanocrystals after BM is linked to the increased CO2 uptake. The use of solid wastes rich in Ca2+, Mg2+ and Fe2+ for the ex situ sequestration of CO2 could provide an economically and technologically viable option for the reduction of anthropogenic CO2 emissions. Here, we investigate for the first time the potential use of waste materials from mafic rock quarries as a feedstock for the sequestration of CO2 by ex situ mineral carbonation. The experimental procedure was performed on a waste material from a dolerite quarry operating in the Troodos ophiolite (Cyprus). The ball milling process was applied to this quarry waste in order to create nanomaterials with enhanced CO2 adsorption capacity. Through CO2 chemisorption followed by temperature-programmed desorption (CO2-TPD) experiments, the optimum ball milling conditions were found (20h of wet ball milling with 50wt% ethanol as process control agent), leading to an enhancement of the CO2-storage capacity of the waste material by a factor of ∼120. This enhancement of CO2 uptake is closely related to (i) the reduction of particle size to the nanoscale, (ii) the structural disordering of the constituent silicate minerals, and (iii) the presence of augite nanocrystals after ball milling. The experimental results suggest that waste materials from dolerite quarries may indeed be used as feedstock for the ex situ mineralization of CO2. They also strongly demonstrate that ball milling is a very promising technique for optimizing the ex situ carbonation of this waste material thus the proposed methodology could be a fundamental part of a future carbon sequestration strategy. 16 361 370 361-370

Η παρούσα διατριβή διερευνά την επίδραση των πετρογραφικών παραμέτρων στις φυσικομηχανικές ιδιότητες των οφιολιθικών πετρωμάτων Πίνδου και Βούρινου. Επιπρόσθετα, μελετώνται ορισμένα δείγματα από τα οφιολιθικά συμπλέγματα του Κόζιακα και της ανατολικής Όθρυος και ορισμένα Τριαδικά ηφαιστειακά πετρώματα από την περιοχή του Δομοκού. Tα συλλεχθέντα δείγματα αξιολογούνται για την καταλληλότητά τους ως αδρανή υλικά. Επιπλέον, διερευνάται η καταλληλότητα υγιών υπερβασικών δειγμάτων στη βιομηχανία πυρίμαχων. Στις υπό μελέτη εμφανίσεις πραγματοποιήθηκε λεπτομερής γεωλογική χαρτογράφηση. Ακολούθησε πετρογραφική εξέταση των επιμέρους λιθότυπων και ποσοτικοποίηση των ορυκτολογικών συστατικών τους. Εφαρμόστηκαν σύγχρονες τεχνικές με ηλεκτρονικό μικροσκόπιο σάρωσης, μικροσκόπιο φθορισμού και λογισμικό ψηφιακής επεξεργασίας εικόνας. Διερευνήθηκε επίσης ο τρόπος διάδοσης των μικρορωγμών κατά τη μοναξονική φόρτιση των πετρωμάτων και δόθηκε έμφαση στην πιθανή συμμετοχή αμιαντούχων ορυκτών σε αυτά. Προσδιορίστηκαν οι γεωμετρικές, φυσικομηχανικές, φυσικοχημικές και χημικές ιδιότητες των δειγμάτων και διαπιστώθηκε ότι οι βασικοί λιθότυποι παρουσιάζουν υψηλότερη μηχανική αντοχή από τους υπερβασικούς, ενώ οι τραχίτες έχουν συνήθως μεταβατικά χαρακτηριστικά μεταξύ των δύο παραπάνω κατηγοριών πετρωμάτων. Οι συσχετίσεις μεταξύ των προσδιορισθέντων ιδιοτήτων διερευνήθηκαν με ανάλυση παλινδρόμησης και παραγοντική ανάλυση. Οι ιδιότητες των βασικών και υπερβασικών λιθότυπων τείνουν να βελτιώνονται όσο μειώνεται ο βαθμός εξαλλοίωσης. Εξαίρεση αποτελεί ο δείκτης αντίστασης σε στίλβωση, ο οποίος τείνει να βελτιώνεται αυξανομένου του βαθμού υδροθερμικής μεταμόρφωσης. Για τους δολερίτες διατυπώθηκαν δύο νέοι μικροπετρογραφικοί δείκτες, ο δείκτης αντοχής (Ips) και ο δείκτης αντικατάστασης (Irep), οι οποίοι αποτελούν ποσοτική έκφραση των πετρογραφικών μεταβολών που λαμβάνουν χώρα κατά την εξαλλοίωση. Για τους υπερβασικούς λιθότυπους εισήχθηκε ο λόγος OOS, ο οποίος εκφράζει το βαθμό διατήρησης των πρωτογενών ορυκτών κατά τη σερπεντινίωση. Για τον προσδιορισμό του βαθμού εξαλλοίωσης των υπερβασικών πετρωμάτων εισήχθηκε ο δείκτης ευκίνητων στοιχείων (Im). Οι υπό μελέτη λιθότυποι είναι κατάλληλοι για χρήση ως αδρανή σκυροδεμάτων, κονιαμάτων, οδοποιίας, σκύρων σιδηροτροχιών, φίλτρων και βράχων θωράκισης, με εξαίρεση τους έντονα σερπεντινιωμένους και τεκτονισμένους χαρτσβουργίτες και τους τραχίτες. Ακόμη, τα υγιή υπερβασικά δείγματα είναι κατάλληλα για χρήση ως πρώτες ύλες στη βιομηχανία πυρίμαχων. The present thesis aims at investigating the influence of petrographic factors on the physicomechanical properties of the Pindos and Vourinos ophiolitic rocks. Samples were also collected from the Koziakas and eastern Othrys ophiolitic complexes, as well as from an exposure of Triassic volcanic rocks near the Domokos locality. The evaluation of the collected samples for their suitability as aggregates is attempted. In addition, selected ultrabasic samples are evaluated for their suitability in refractory industry. The studied areas were thoroughly mapped. The petrographic characteristics of each lithotype were examined and their mineralogical composition was quantified. Modern techniques were also applied, using scanning electron microscopy and fluorescent microscopy, in combination with digital image analysis. Additionally, the microcrack propagation during uniaxial compression was investigated, as well as the potential existence of asbestiform minerals in each sample. The geometrical, physicomechanical, physicochemical and chemical properties were determined for each rock sample. The basic lithotypes have higher strength than the ultrabasic. The trachytes usually have characteristics transitional between the basic and ultrabasic lithotypes. The interrelationships between the various properties were examined using regression and factor analysis. The properties of the basic and ultrabasic lithotypes tend to improve when the degree of alteration decreases. Exceptionally, the polishing resistance tends to increase with an increasing degree of hydrothermal metamorphism. Two new micropetrographic indices were proposed for the dolerites, the micropetrographic strength index (Ips) and the replacement index (Irep). These indices reflect and quantify petrographic transformations which take place during alteration. The ratio OOS was introduced for the ultrabasic samples, which reflects the degree of preservation of the primary mineral phases during serpentinization. Additionally, the index of mobile elements (Im) was introduced in order to quantify the degree of alteration of ultrabasic rocks. The studied rock types are suitable for the production of aggregates for concretes, mortars, road construction, railway track ballast, filters and armourstone. The only unsuitable samples are the intense serpentinized and tectonized harzburgites and the trachytes. In addition, the fresh ultrabasic samples can be used as raw materials in the refractory industry.