Experimental determination of trace element concentrations in copper-slag equilibria with laser ablation technique

Sekundääriset kuparin lähteet, kuten sähkö- ja elektroniikkaromu (lyhenne SER, engl. WEEE), ovat nousseet tärkeään rooliin kuparin tuotannossa. WEEE-romun määrä kasvaa jatkuvasti sähkö- ja elektroniikkalaitteiden käyttöiän lyhentyessä ja elintason noustessa. Erilaisten säädösten ja kiertotalouteen pyrkimisen myötä tämän romun käsittelyyn on kiinnitettävä erityistä huomiota, jotta sen sisältämät metallit ja muut aineet saadaan talteen mahdollisimman tehokkaasti. Tämä on haastavaa, sillä WEEE-romussa on kymmeniä eri metalleja vaihtelevina pitoisuuksina. Yhtenä varteenotettavana prosessointireittinä ovat pyrometallurgiset prosessit, joissa kupari toimii perusmetallina ja muut (hivenaine)metallit jakautuvat sulatuksen aikana kuparin, kuonan ja kaasufaasin välille metallien ominaisuuksista riippuvassa suhteessa. Tämän työn tarkoituksena oli tutkia lyijyn, molybdeenin, reniumin ja iridiumin jakautumista sekundäärisessä kuparin sulatusprosessissa sekä pohtia erityisesti LA-ICP-MS-menetelmän etuja ja haasteita näiden metallien faasikohtaisten pitoisuuksien määrityksessä. Koemenetelmän päävaiheina olivat tasapainotus, nopea sammutus ja suora faasikoostumu-sanalyysi EPMA- ja LA-ICP-MS-menetelmillä. Kokeet suoritettiin 1300 °C lämpötilassa 16 tunnin tasapainotusajalla, hapen osapainealueella 10-10 – 10-5 atm. Metallien jakaumia tutkittiin kuparin, FeOx-SiO2-Al2O3 ja FeOx-SiO2-Al2O3-CaO kuonien sekä osittain myös spinellien välillä. Kuonien alumiinioksidi liukeni kokonaisuudessaan kokeissa käytetyistä reagoivista alumiinioksidiupokkaista, jotka muodostivat systeemiin alumiini-rautaspinellikyllästyksen. Haluttu hapen osapaine muodostettiin CO-CO2-kaasuseoksella. Työssä tutkituista metalleista vain iridiumin pitoisuus ylitti EPMA:n määritysrajan kuparifaasissa. Tätä faasia ei voitu analysoida laserilla soveltuvan ulkoisen standardin puutteen vuoksi. Kuonapitoisuudet määritettiin luotettavasti kaikille tutkituille metalleille, ja laseranalyysisignaaleista voitiin todeta metallien liukenevan kuonaan hyvin homogeenisesti. Spinellipitoisuuksista saatiin laseranalyysilla alustavia tuloksia, joiden mukaan liukoisuus spinelleihin on mahdollisesti heterogeenisempaa. Määritettyjen faasikohtaisten pitoisuuksien perusteella iridiumin jakaumakerroin kuparin ja kuonan välillä on noin 106.2 hapen osapainealueella 10-10 – 10-6 atm. Tällä alueella jakaumakertoimen arvo ei näytä juurikaan riippuvan hapen osapaineesta, mikä viittaa iridiumin liukenemiseen metallina. 10-5 atm hapen osapaineessa kuonaliukoisuus kasvaa huomattavasti, jolloin jakaumakertoimen arvo laskee. Tällöin iridium vaikuttaa liukenevan kuonaan oksidimuodossa Ir2O3. Lyijy jakautuu selkeästi kuonaan hapen osapaineen noustessa yli 10-7 atm, kun taas molybdeeni jakautuu voimakkaasti kuonaan kaikilla tutkituilla hapen osapaineilla. Reniumin pitoisuus kuonassa on hyvin matala kaikilla hapen osapaineilla, ja suurin osa siitä vaikuttaa höyrystyvän kaasufaasiin. Reniumia havaittiin kuitenkin kuparifaasin sekaan pelkistävämmissä olosuhteissa muodostuneissa erkaumissa, jotka sisältävät myös iridiumia ja molybdeenia. Jakaumakertoimen todellisesta arvosta tai liukoisuusmuodosta ei voida lyijyn, molybdeenin ja reniumin osalta sanoa mitään varmaa kuparipitoisuuksien puuttuessa. Tulosten perusteella voidaan varmasti sanoa, että jakaumakerroin kuparin ja kuonan välillä on lyijylle < 105 (pO2 10-10 atm) ja < 0.35 (pO2 10-5 atm), molybdeenille < 0.062 ja reniumille < 104.3 koko tutkitulla hapen osapainealueella. Iridium- ja reniumpitoisuudet kuonan sekaan muodostuneissa kiinteissä spinelleissä vaikuttivat olevan moninkertaiset näiden metallien kuonapitoisuuksiin verrattuna.Secondary copper sources, such as WEEE, have become increasingly important in the overall production of copper. The amount of WEEE is rapidly increasing due to the decrease in lifetime of electronic appliances and increase in living standards. Proper processing of this waste for efficient recovery of metals and other substances is key in reaching a true circular economy. The composition of WEEE is extremely heterogeneous, containing dozens of different metals, which makes it difficult to find the most suitable processing route for maximum overall efficiency. One potential route is smelting, where copper acts as the base metal and trace elements distribute between copper, slag and gas phases in ratios that depend on the properties of these elements. The aim of this work was to investigate the distribution of lead, molybdenum, iridium and rhenium during secondary copper smelting and to present the advantages and challenges of LA-ICP-MS technique in determining the concentrations of these trace elements in different phases of the system. The experimental method consisted of equilibration, fast quenching, and direct phase composition analysis with EPMA and LA-ICP-MS. Experiments were carried out at 1300 °C with an equilibration time of 16 hours and oxygen partial pressures varying from 10-10 atm to 10-5 atm. Distributions between copper, FeOx-SiO2-Al2O3 and FeOx-SiO2-Al2O3-CaO slags, and spinel were investigated. All of the alumina in the system was dissolved from reactive alumina crucibles, which ensured iron-alumina spinel saturation to the system. Desired oxygen partial pressures were achieved by using a mixture of CO and CO2 gases. Of the four trace metals investigated, only iridium concentration in copper phase was reliably determined by EPMA. Copper phase could not be analysed using LA-ICP-MS, since a suitable external standard does not yet exist. Slag concentrations were reliably determined for all metals, and based on the laser signals, the investigated metals were quite homogenously dissolved into the slag phase. Preliminary results for spinel concentrations were obtained using LA-ICP-MS, and they indicate possibly a more heterogeneous dissolution into the spinel phase. Based on the results, the distribution coefficient of iridium between copper and slag is approximately 106.2 in oxygen partial pressure range 10-10 to 10-6 atm, where the value is relatively independent of pO2, which indicates dissolution as a metallic species. At pO2 10-5 atm, iridium concentration in slag increases quite rapidly, which lowers the distribution coefficient value. Dissolution into slag as Ir2O3 is suggested in oxidizing conditions. Lead is strongly distributed into the slag phase when pO2 rises above 10-7 atm, whereas molybdenum strongly favours the slag phase in the whole pO2 range investigated. Rhenium concentration in slag is very low in the whole pO2 range, and most of it appears to volatilize into the gas phase. However, significant rhenium concentrations were detected in precipitates, which formed in the copper phase in reducing conditions. These precipitates contained also iridium and molybdenum. The true values of distribution coefficients and the form of dissolution could not be determined for lead, molybdenum and rhenium, as their concentrations in copper phase were not determined. Based on the results obtained, it can only be concluded that the distribution coefficient between copper and slag for lead is < 105 at pO2 10-10 atm and < 0.35 at pO2 10-5 atm, for molybdenum < 0.062 and for rhenium < 104.3 in the whole pO2 range investigated. Iridium and rhenium concentrations in the solid spinels surrounded by slag seemed to be considerably higher than concentrations in the slags

Hivenaineiden käyttäytyminen kuparinsulatusprosesseissa - LA-ICP-MS työkaluna näytteiden analysoimisessa

Defence is held on 10.12.2021 10:00 – 13:00 https://aalto.zoom.us/j/64655585892The rapidly increasing demand for metals used for instance in batteries, electronics and renewable energy production cannot be satisfied merely by increasing mining and primary production capacities. In order to better secure the metal supply and achieve a circular economy, metal recycling and recovery from End-of-Life (EoL) products must be significantly increased. One viable option for recycling several metals is to utilise existing primary or secondary copper smelters. Many of these smelters have been optimised for handling primary ores, which means that more research is needed in order to understand and quantify the effects of introducing secondary raw materials into the process circuits. In this thesis, the behaviour of several trace elements present in secondary raw materials (Ir, Mo, Pb, Re, Sn, Sb, Te, Ga, In, La, Nd, Li, Co, Mn) was investigated in laboratory-scale primary and secondary copper smelting experiments. The experiments were conducted in equilibrium conditions or as a function of time at 1300 °C. Different gas atmospheres were utilised for simulating the process conditions in different stages of industrial smelting operations. The phase-by-phase elemental concentrations were analysed using scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), electron probe micro-analysis (EPMA), as well as the state-of-the-art laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) technique. A convenient way of presenting and comparing the behaviour of different trace elements is via distribution coefficients (L = wt.% metal in alloy or matte / wt.% metal in slag). Some of the obtained distribution coefficient data represents the first reported values in the literature, whereas some provide significantly more accurate results compared to earlier results. For the distributions of gallium, indium and lanthanum between copper sulphide mattes and iron silicate slags, no previous data was found in the literature. This also applies to the experimentally verified distribution coefficients of lithium and lanthanum between copper-rich alloy and high-alumina iron silicate slags. Regarding manganese, the new data indicates significantly lower distribution coefficients compared to previous data, i.e. manganese deports extremely heavily to slag. The improved accuracy and reliability in distribution data is due to the use of direct phase-by-phase analysis techniques without the need of manual phase separation, as well as the extremely low detection limits obtained with the LA-ICP-MS. The results of this thesis can be applied to industrial processes in designing, optimising, modelling and evaluating processes for industrial-scale recycling of electronic scrap and EoL batteries, for example.Nopeasti kasvavaa tarvetta metalleille, joita käytetään akuissa, elektroniikassa sekä uusiutuvan energian tuotannossa, ei voida kattaa pelkästään louhimista ja primäärituotantoa lisäämällä. Jotta metallien riittävyys voidaan paremmin turvata ja päästä lähemmäs kiertotaloutta, elinkaarensa päässä olevien tuotteiden kierrätystä ja metallien talteenottoa niistä tulee lisätä merkittävästi. Yksi varteenotettava vaihtoehto useiden metallien kierrätykselle on käyttää olemassa olevia primääri- ja sekundäärikuparisulattoja. Monet näistä on optimoitu primääririkasteiden käsittelemiseen, minkä vuoksi tarvitaan enemmän tutkimusta ymmärtääksemme sekundääristen raaka-aineiden lisäämisen vaikutukset prosesseihin. Tämän väitöstutkimuksen tavoitteena oli selvittää usean, sekundääriraaka-aineissa läsnä olevan hivenainemetallin (Ir, Mo, Pb, Re, Sn, Sb, Te, Ga, In, La, Nd, Li, Co, Mn) käyttäytymistä laboratoriomittakaavan kokeissa. Näiden metallien jakautumista tutkittiin termodynaamisessa tasapainossa tai ajan funktiona 1300 °C:ssa, ja teollisten kuparinsulatusprosessien olosuhteita simuloitiin käyttämällä useaa eri kaasuatmosfääriä. Faasikohtaiset alkuaineiden pitoisuudet analysoitiin käyttäen kolmea suoraa faasi-analyysitekniikkaa: pyyhkäisyelektronimikroskooppi–energiadispersiivinen röntgenspektroskopia (SEM-EDS), elektronisäde–mikroanalyysi (EPMA) sekä laserablaatio–induktiivisesti kytketty plasma–massaspektrometria (LA-ICP-MS). Näistä viimeisimmällä voidaan analysoida erittäin pieniä hivenainepitoisuuksia tarkasti eri faaseista. Jakaumakerroin (L = m.% alkuainetta metalliseoksessa tai kivessä / m.% alkuainetta kuonassa) on kätevä tapa esittää ja vertailla eri hivenaineiden käyttäytymistä. Osa työn jakaumakerrointuloksista edustaa ensimmäisiä kirjallisuudesta löytyviä arvoja, ja osa parantaa huomattavasti aiemmin raportoitujen tulosten tarkkuutta. Galliumin, indiumin ja lantaanin jakaumakertoimille kuparikivien ja rautasilikaattikuonien välillä ei löytynyt vertailuarvoja aiemmin julkaistusta kirjallisuudesta, kuten ei myöskään litiumin ja lantaanin jakaumakertoimille kupariseoksen ja korkea-alumiinioksidisen rautasilikaattikuonan välillä. Mangaanin osalta uudet tulokset osoittavat selvästi aiemmin raportoiduista tuloksista pienempiä jakaumakertoimia eli mangaani jakautuu erittäin vahvasti kuonaan. Tulosten parempi tarkkuus ja luotettavuus johtuvat suorien faasianalyysitekniikoiden käytöstä sekä LA-ICP-MS tekniikan alhaisista määritysrajoista. Tässä väitöskirjassa raportoituja tuloksia voidaan soveltaa teollisuudessa, kun suunnitellaan, optimoidaan, mallinnetaan ja arvioidaan prosesseja esimerkiksi elektroniikkaromun ja käytettyjen akkujen kierrätykseen teollisessa mittakaavassa

Time-Dependent Behavior of Waste Lithium-Ion Batteries in Secondary Copper Smelting

Publisher Copyright: © 2022 by the authors.As the electrification sector expands rapidly, the demand for metals used in batteries is increasing significantly. New approaches for lithium-ion battery (LIB) recycling have to be investigated and new technologies developed in order to secure the future supply of battery metals (i.e., lithium, cobalt, nickel). In this work, the possibility of integrating LIB recycling with secondary copper smelting was further investigated. The time-dependent behavior of battery metals (Li, Co, Ni, Mn) in simulated secondary copper smelting conditions was investigated for the first time. In the study, copper alloy was used as a medium for collecting valuable metals and the distribution coefficients of these metals between copper alloy and slag were used for evaluating the recycling efficiencies. The determined distribution coefficients follow the order Ni >> Co >> Mn > Li throughout the time range investigated. In our study, the evolution of phases and their chemical composition were investigated in laboratory-scale experiments under reducing conditions of oxygen partial pressure p(O2) = 10−10 atm, at 1300 °C. The results showed that already after 1 h holding time, the major elements were in equilibrium. However, based on the microstructural observations and trace elements distributions, the required full equilibration time for the system was determined to be 16 h.Peer reviewe

Urban mining of precious metals via oxidizing copper smelting

Recycling of precious metals from end-of-life electronics is a key factor for sustainable and efficient raw material usage. Simultaneously with the depletion of natural ore resources, the urban mines are storing increasing amounts of valuable and, more importantly, rare metals. To fulfill the targets of sustainability and move towards circular economy, the liberation of these valuables from wastes back to production and use needs to be improved. This study investigates the recoveries and behavior of gold, silver, palladium and platinum in copper smelting conditions at 1300 °C and pO2 = 10−5–10−7 atm. The investigated system includes a copper alloy with three different type of slags in silica saturation: pure iron silicate, iron silicate with 10 wt% alumina and iron silicate with 10 wt% alumina and 5 wt% lime, providing information on the influence of alumina and lime on precious metal recovery possibilities. A highly advanced equilibration-quenching technique, followed by EPMA and sensitive LA-ICP-MS analyses, has been adopted to execute the experiments. Results show that gold, platinum and palladium are recovered very efficiently in copper, as their distribution coefficients between copper and slag, LCu/s, were greater than 104 under every experimental condition studied and with all slag compositions. Silver distributed 30–60 times more in copper phase than was lost to slag. The addition of alumina into the slag somewhat decreased the distribution coefficient of silver, whereas gold and palladium distribution coefficients were increased. Lime addition improved the recovery of every precious metal (Pt unclear) into the copper phase. The concentrations of platinum in the slags were mainly below the detection limit of the used LA-ICP-MS, providing a minimum distribution coefficient of 106.Peer reviewe

Iron activity measurements and spinel-slag equilibria in alumina-bearing iron silicate slags

Alumina is a common substance deporting in copper smelting slags when various secondary copper fractions, e.g. e-scrap or WEEE, are used as feedstock as such or along with primary sulphide concentrates. Properties of iron-silicate slags at high alumina concentrations, in the iron-alumina spinel saturation, have been studied at 1300 °C by a high temperature equilibration-quenching method combined with EPMA (electron probe microanalysis) phase composition data from the polished sections. The equilibrations were performed in fixed oxygen activity with platinum or palladium powder, which dissolved iron from the slag and generated a heterogeneous equilibrium system, characterised by the general equilibrium criterium in isothermal and isobaric conditions, as. μalloy(Fe) = μslag(Fe) = μspinel(Fe). This criterium was used for measuring experimentally iron activities of molten silicate slags. The locations of the spinel-liquid slag tie-lines were also determined in the oxygen partial pressure range of 10−6–10−10 atm. A comparison with the recent critical thermodynamic assessments of the Fe–O–Al2O3 system indicates that the iron-alumina spinel-corundum phase boundary in silica-containing systems as a function of oxygen partial pressure is too steep and thus the assessed databases do not match with the experimental data of this study. The liquid slag domain from silica to iron oxide saturation is also smaller than expected earlier, as the spinel primary phase boundary locates at higher silica concentrations than e.g. obtained in the assessments of the Mtox database.Peer reviewe

Feasibility study of producing multi-metal parts by Fused Filament Fabrication (FFF) technique

This study was partly funded by Business Finland (Grant 632/31/2018), and also utilized the RawMatTERS Finland infrastructure (RAMI, Academy of Finland) based jointly at Aalto University, GTK, and VTT, Espoo.Additive manufacturing, or more commonly 3D printing, has been recently established as one of the most advanced technologies for fabricating multi-material parts. In this work, the possibility of manufacturing multi-metal parts by material extrusion process was studied for the first time. Three types of samples, named mixed, coupled and graded, resulting from deposition of two ferrous alloys: high carbon iron and stainless steel 316 L filaments, were successfully printed. After de-binding with different heating rates, they were isothermally sintered in the range of 1310−1400 °C for various holding times in argon atmosphere. Finally, some properties of the final parts, such as relative density, shrinkage, microstructural evolution, and hardness were analyzed. In conclusion, the relative density was measured up to 92 %, and the shrinkage recorded for the samples ranged between 10 % and 40 %. Based on the performed analyses, a relatively homogeneous microstructure was observed in the mixed sample, which indicates that the affordable metal extrusion technique could replace the conventional methods for metallic alloying.Peer reviewe

Recovering value from end-of-life batteries by integrating froth flotation and pyrometallurgical copper-slag cleaning

Funding Information: Funding: This research was funded by Business Finland BATCircle2.0 project, grant number 44886/31/ 2020, and SYMMET project, grant number 3891/31/2018. 26 of 30 Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.In this study, industrial lithium-ion battery (LIB) waste was treated by a froth flotation process, which allowed selective separation of electrode particles from metallic-rich fractions containing Cu and Al. In the flotation experiments, recovery rates of ~80 and 98.8% for the cathode active elements (Co, Ni, Mn) and graphite were achieved, respectively. The recovered metals from the flotation fraction were subsequently used in high-temperature Cu-slag reduction. In this manner, the possibility of using metallothermic reduction for Cu-slag reduction using Al-wires from LIB waste as the main reductant was studied. The behavior of valuable (Cu, Ni, Co, Li) and hazardous metals (Zn, As, Sb, Pb), as a function of time as well as the influence of Cu-slag-to-spent battery (SB) ratio, were investigated. The results showcase a suitable process to recover copper from spent batteries and industrial Cu-slag. Cu-concentration decreased to approximately 0.3 wt.% after 60 min reduction time in all samples where Cu/Al-richLIB waste fraction was added. It was also showed that aluminothermic reduction is effective for removing hazardous metals from the slag. The proposed process is also capable of recovering Cu, Co, and Ni from both Cu-slag and LIB waste, resulting in a secondary Cu slag that can be used in various applications.Peer reviewe

Behavior of tin and antimony in secondary copper smelting process

Different types of metal-bearing wastes, such as WEEE (Waste Electrical and Electronic Equipment), are important urban minerals in modern society, and the efficient recycling and reuse of their metal values is of key interest. Pyrometallurgical copper smelting is one of the most prominent ways of treating WEEE, however, more accurate experimental data is needed regarding the behavior of different elements during each process stage. This article investigates the behavior of tin and antimony, both commonly present as trace elements in electrical and electronic waste, in secondary (i.e., sulfur-free) copper smelting conditions. The experiments were conducted in oxygen partial pressure range of 10 −10 –10 −5 atm, covering the different process steps in copper smelting. The basis of the equilibrium system was metallic copper–iron silicate slag, with the addition of alumina and potassium oxide to account for the presence of these compounds in the actual industrial process. The results showed that the distribution coefficients of both trace metals, L Cu/slag = [wt % Me] copper /(wt % Me) slag , increased significantly as a function of decreasing oxygen pressure, and the addition of basic potassium oxide also had an increasing effect on the distribution coefficient. A brief comparison between EPMA and LA-ICP-MS (electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry), the two in situ analytical techniques used, was also presented and discussed.Peer reviewe

Reaction mechanisms of waste printed circuit board recycling in copper smelting : The impurity elements

Feeding Waste Printed Circuit Boards (WPCBs) into existing pyrometallurgical processes is developing as an easy-to-adapt and efficient way to recycle them. To fulfill sustainability and circular economy targets, kinetics and distributions are the key factors when recovering metals and trace elements from WPCBs. We investigated the reaction mechanisms and distribution behavior of impurity elements Sb, As and Bi between copper matte and slag at a typical smelting temperature of 1300 °C both in air and argon atmospheres. Laboratory-scale heat-quench experiments indicated that vaporization can effectively eliminate arsenic in the matte phase, but not antimony or bismuth either in air or in an argon atmosphere. Sufficient contact time between the gas and matte phase is also needed to transfer the trace elements into gas and slag. In this work, kinetic data and distribution ratios of these impurity elements in the matte and slag phase were calculated. They can be used in process development for WPCB recycling and, equally, when using complex copper concentrates with high As, Sb, and Bi contents. The results also complement CFD models to simulate flash smelting processes more precisely.Peer reviewe