A study on recovery strategies of graphite from mixed lithium-ion battery chemistries using froth flotation.

The growing electric vehicle industry has increased the demand for raw materials used in lithium-ion batteries (LIBs), raising concerns about material availability. Froth flotation has gained attention as a LIB recycling method, allowing the recovery of low value materials while preserving the chemical integrity of electrode materials. Furthermore, as new battery chemistries such as lithium titanate (LTO) are introduced into the market, strategies to treat mixed battery streams are needed. In this work, laboratory-scale flotation separation experiments were conducted on two model black mass samples: i) a mixture containing a single cathode (i.e., NMC811) and two anode species (i.e., LTO and graphite), simulating a mixed feedstock prior to hydrometallurgical treatment; and ii) a graphite-TiO2 mixture to reflect the expected products after leaching. The results indicate that graphite can be recovered with > 98 % grade from NMC811-LTO-graphite mixtures. Additionally, it was found that flotation kinetics are dependent on the electrode particle species present in the suspension. In contrast, the flotation of graphite from TiO2 resulted in a low grade product (<96 %) attributed to the significant entrainment of ultrafine TiO2 particles. These results suggest that flotation of graphite should be preferably carried out before hydrometallurgical treatment of black mass.

Analogical environmental cost assessment of silicon flows used in solar panels by the US and China.

Achieving carbon neutrality requires deployment of large-scale renewable energy technologies like solar photovoltaic (PV) panels. Nevertheless, methods to ascertain the overall environmental impacts PVs and further improve their sustainability are under-investigated. In an effort to provide more understanding of this crucial topic, this research focuses on silicon flows-a key element for manufacturing crystalline silicon PVs. Using system dynamics modeling, we conduct a comprehensive environmental cost assessment of the silicon flows used in PVs based on a comparative analysis between the United States and China as the leading global PV manufacturers. Despite the advancement in wafer quality, material usage reductions and overall price decreases achieved in recent decades, our results project a substantial increase in energy and water consumption in China related to Metallurgical Grade Si (MG-Si), Solar Grade Si (SoG-Si) and cell manufacturing by 2030. An approximate 6.5 times increase of energy and water consumption is observed for c-Si cell manufacturing in China between 2010 and 2020. In 2030, increases of 70% in energy consumption and 69% in water use are estimated for Chinese MG-Si and SoG-Si production. The most significant environmental impact is observed in silicon cell and module manufacturing in both countries, particularly concerning GHG, SOx and NOx emissions. This study provides valuable insights into the environmental impacts of these two major solar panel manufacturing countries by examining the silicon life cycle, from production to end-of-life.

Sweet Side Streams: Sugar Beet Pulp as Source for High-Performance Supercapacitor Electrodes.

Valorization of the lignocellulosic side and waste streams is key to making industrial processes more efficient from both an economic and ecological perspective. Currently, the production of sugars from beets results in pulps in large quantities. However, there is a lack of promising opportunities for upcycling these materials despite their promising properties. Here, we investigate beet pulps from two different stages of the sugar manufacturing process as raw materials for supercapacitor electrodes. We demonstrate that these materials can be efficiently converted to activated, highly porous carbons. The carbons exhibit pore dimensions approaching the size of the desolvated K+ and SO42- ions with surface areas up to 2600 m2 g-1. These carbons were subsequently manufactured into electrodes, assembled in supercapacitors, and tested with environmentally friendly aqueous electrolytes (6 M KOH and 1 M H2SO4). Further analysis demonstrated the presence of capacitance-enhancing functionalities, and up to 193 and 177 F g-1 in H2SO4 and KOH, respectively, were achieved, which outperformed supercapacitors prepared from commercial YP80 F. Overall, our study suggests that side streams from sugar manufacturing offer a hidden potential for use in high-performance energy storage devices.

A New Hydrometallurgical Process for Metal Extraction from Electric Arc Furnace Dust Using Ionic Liquids.

This research proposes a new hydrometallurgical method for Zn, In, and Ga extraction, along with Fe as a common impurity, from electric arc furnace dust (EAFD), using ionic liquids. EAFD is a metal-containing waste fraction generated in significant amounts during the process of steelmaking from scrap material in an electric arc furnace. With valuable metal recovery as the main goal, two ionic liquids, [Bmim+HSO4-] and [Bmim+Cl-], were studied in conjunction with three oxidants: Fe2(SO4)3, KMnO4, and H2O2. The results indicated that the best combination was [Bmim+HSO4-] with [Fe2(SO4)3]. An experimental series subsequently demonstrated that the combination of 30% v/v [Bmim+HSO4-], 1 g of [Fe2(SO4)3], S/L ratio = 1/20, a 240 min leaching time, and a temperature of 85 °C was optimal, resulting in maximum extractions of 92.7% Zn, 97.4% In, and 17.03% Ga. In addition, 80.2% of the impurity metal Fe was dissolved. The dissolution kinetics of these four elements over a temperature range of 55-85 °C was found to be diffusion controlled. The remaining phases present in the leached residue were low amounts of ZnO, Fe3O4, ZnFe2O4, and traces of Ca(OH)2 and MnO2, and additional sharp peaks indicative of PbSO4 and CaSO4 appeared within the XRD pattern. The intensity of the peaks related to ZnO and Fe3O4 were observed to have decreased considerably during leaching, whereas some of the refractory ZnFe2O4 phase remained. SEM-EDS analysis revealed that the initial EAFD morphology was composed of spherical-shaped fine-grained particle agglomerates, whereas the leached residue was dominated by calcium sulphate (Ca(SO4))-rich needle-shaped crystals. The results clearly demonstrate that [Bmim+HSO4-] is able to extract the target metals due to its acidic properties.

Study on valuable metal incorporation in the Fe-Al precipitate during neutralization of LIB leach solution.

The role of aluminum concentration and pH in the purification of waste Li-ion battery leach solution was investigated using NaOH and LiOH as neutralization agents ([H2SO4] = 0.313 M, t = 6 h). Solution was prepared from synthetic chemicals to mimic real battery leach solution. Results demonstrate that pH (3.5-5.5) has a significant effect on the precipitation of metals (Fe, Al, Ni, Cu, Co, Mn, and Li), whereas higher temperature (T = 30 and 60 °C) decreases the precipitation pH of metals. Iron and aluminum were both found to precipitate at ca. pH 4 and the presence of aluminum in PLS clearly decreased the separation efficiency of Fe vs. active material metals (Ni, Co, Li). In the absence of dissolved aluminum, Fe precipitated already at pH 3.5 and did not result in the co-precipitation of other metals. Additionally, the Al-free slurry had a superior filtration performance. However, aluminum concentrations of 2 and 4 g/L were found to cause loss of Ni (2-10%), Co (1-2%) and Li (2-10%) to the Fe-Al hydroxide cake at pH 4. The use of LiOH (vs. NaOH) resulted in 50% lower co-precipitation of Ni, Co and Li. Overall, these results demonstrate that hydroxide precipitation can be an effective method to remove iron from battery waste leach solutions at aluminum concentrations of < 2 g/L only. Although the highest level of lithium loss in the cake was found at pH 4, the loss was shown to decrease with increasing pH.

Biopolymeric Anticorrosion Coatings from Cellulose Nanofibrils and Colloidal Lignin Particles.

This study presents a process for preparation of cellulose-lignin barrier coatings for hot-dip galvanized (HDG) steel by aqueous electrophoretic deposition. Initially, a solution of softwood kraft lignin and diethylene glycol monobutyl ether was used to prepare an aqueous dispersion of colloidal lignin particles (CLPs) via solvent exchange. Analysis of the dispersion showed that it comprised submicron particles (D = 146 nm) with spherical morphologies and colloidal stability (ζ-potential = -40 mV). Following successful formation, the CLP dispersion was mixed with a suspension of TEMPO-oxidized cellulose nanofibers (TOCN, 1 and 2 g·L-1) at a fixed volumetric ratio (1:1, TOCN-CLPs), and biopolymers were deposited onto HDG steel surfaces at different potentials (0.5 and 3 V). The effects of these variables on coating formation, dry adhesion, and electrochemical properties (3.5% NaCl) were investigated. The scanning electron microscopy results showed that coalescence of CLPs occurs during the drying of composite coatings, resulting in formation of a barrier layer on HDG steel. The scanning vibrating electrode technique results demonstrated that the TOCN-CLP layers reduced the penetration of the electrolyte (3.5% NaCl) to the metal-coating interface for at least 48 h of immersion, with a more prolonged barrier performance for 3 V-deposited coatings. Additional electrochemical impedance spectroscopy studies showed that all four coatings provided increased levels of charge transfer resistance (Rct)-compared to bare HDG steel-although coatings deposited at a higher potential (3 V) and a higher TOCN concentration provided the maximum charge transfer resistance after 15 days of immersion (13.7 cf. 0.2 kΩ·cm2 for HDG steel). Overall, these results highlight the potential of TOCN-CLP biopolymeric composites as a basis for sustainable corrosion protection coatings.

Hazard-free treatment of electrolytic manganese residue and recovery of manganese using low temperature roasting-water washing process.

A combined low-temperature-roasting and water-washing process is investigated as a hazard-free method to treat electrolytic manganese residue (EMR) and recover manganese. In this study, the phase transformation characteristics and a thermodynamics analysis of the low temperature roasting process of EMR are evaluated. In addition, the effects of temperature and time on the phase transformation of EMR in the roasting process and the washing characteristics of roasted EMR samples are also investigated. Results reveal that some unstable phases within EMR are transformed into more stable phases depending on the treatment time/temperature conditions used and EMR roasted for 60 min at 600 °C (R60min/600°C) exhibit the highest rate of manganese recovery, 67.12 %. After 25 min of deionized water washing, the concentration of manganese in solution from R60min/600°C material become stable, whereas after 6 washing cycles the concentration of manganese in the solution is < 0.005 g/L. The R60min/600°C material with three wash cycles results in a manganese-water solution concentration that is suitable for use in electrolytic manganese metal production. Finally, toxicity leaching tests show that the concentrations of ions present in the leaching solution are all lower than the regulatory limits mandated by the Chinese Integrated Wastewater Discharge Standard GB 8978-1996.

Extraction of Li and Co from industrially produced Li-ion battery waste - Using the reductive power of waste itself.

Industrially produced spent lithium-ion batteries (LIBs) waste contain not only strategic metals such as cobalt and lithium but also impurity elements like copper, aluminum and iron. The current work investigates the distribution of the metallic impurity elements in LIBs waste, and their influence on the acid dissolution of target active materials. The results demonstrate that the presence of these, naturally reductive, impurity elements (e.g. Cu, Al, and Fe) can substantially promote the dissolution of active materials. Through the addition of Cu and Al-rich larger size fractions, the extraction efficiencies of Co and Li increased up to over 99%, to leave a leach residue that is rich in graphite. By this method, the use of high cost reductants like hydrogen peroxide or ascorbic acid could be avoided. More importantly, additional Co and Li associated with the Cu and Al electrode materials could be also recovered. This novel approach contributes not only to improved reduction efficiency in LIBs waste leaching, but also to improved total recovery of Co and Li from LIBs waste, even from the larger particle size fractions, which are typically lost from circulation.

Electro-hydraulic fragmentation vs conventional crushing of photovoltaic panels - Impact on recycling.

Currently, the first generation of solar panels are reaching their end-of-life, however so far, there is no best available technology (BAT) to deal with solar panel waste in terms of the optimized circular economy of metals. In this brief communication, electro-hydraulic fragmentation (EHF) is explored as an initial conditioning stage of photovoltaic (PV) modules to facilitate the recovery of valuable metals with the main goal to produce liberated fractions that are suitable for the retrieval of materials like Si, Ag, Cu, Sn, Pb, and Al. When compared to traditional crushing, the results suggest that dismantling of PV panels using EHF shows more selectivity by concentrating metals among well-defined particle size fractions. Using this method, the subsequent recovery of metals from PV panels can be achieved in a straightforward manner by simple means like sieving. The fragmentation achievable with EHF technology allowed approximately 99% Cu, 60% Ag, 80% of Pb, Sn and Al total elemental weight within the solar panels to be concentrated solely within the >4 mm size range, whereas high purity (>99%) Si could be found in the fractions between >0.50 mm and <2 mm. To the best of the authors' knowledge, this paper presents for the first time a comparative analysis on the use of EHF technique and conventional crushing for the processing of PV solar panel waste.

Platinum Recovery from Industrial Process Solutions by Electrodeposition-Redox Replacement.

In the current study, platinum-present as a negligible component (below 1 ppb, the detection limit of the HR-ICP-MS at the dilutions used) in real industrial hydrometallurgical process solutions-was recovered by an electrodeposition-redox replacement (EDRR) method on pyrolyzed carbon (PyC) electrode, a method not earlier applied to metal recovery. The recovery parameters of the EDRR process were initially investigated using a synthetic nickel electrolyte solution ([Ni] = 60 g/L, [Ag] = 10 ppm, [Pt] = 20 ppm, [H2SO4] = 10 g/L), and the results demonstrated an extraordinary increase of 3 × 105 in the [Pt]/[Ni] on the electrode surface cf. synthetic solution. EDRR recovery of platinum on PyC was also tested with two real industrial process solutions that contained a complex multimetal solution matrix: Ni as the major component (>140 g/L) and very low contents of Pt, Pd, and Ag (i.e., <1 ppb, 117 and 4 ppb, respectively). The selectivity of Pt recovery by EDRR on the PyC electrode was found to be significant-nanoparticles deposited on the electrode surface comprised on average of 90 wt % platinum and a [Pt]/[Ni] enrichment ratio of 1011 compared to the industrial hydrometallurgical solution. Furthermore, other precious metallic elements like Pd and Ag could also be enriched on the PyC electrode surface using the same methodology. This paper demonstrates a remarkable advancement in the recovery of trace amounts of platinum from real industrial solutions that are not currently considered as a source of Pt metal.

Selective reductive leaching of cobalt and lithium from industrially crushed waste Li-ion batteries in sulfuric acid system.

Recycling of valuable metals from secondary resources such as waste Li-ion batteries (LIBs) has recently attracted significant attention due to the depletion of high-grade natural resources and increasing interest in the circular economy of metals. In this article, the sulfuric acid leaching of industrially produced waste LIBs scraps with 23.6% cobalt (Co), 3.6% lithium (Li) and 6.2% copper (Cu) was investigated. The industrially produced LIBs scraps were shown to provide higher Li and Co leaching extractions compared to dissolution of corresponding amount of pure LiCoO2. In addition, with the addition of ascorbic acid as reducing agent, copper extraction showed decrease, opposite to Co and Li. Based on this, we propose a new method for the selective leaching of battery metals Co and Li from the industrially crushed LIBs waste at high solid/liquid ratio (S/L) that leaves impurities like Cu in the solid residue. Using ascorbic acid (C6H8O6) as reductant, the optimum conditions for LIBs leaching were found to be T = 80 °C, t = 90 min, [H2SO4] = 2 M, [C6H8O6] = 0.11 M and S/L = 200 g/L. This resulted in leaching efficiencies of 95.7% for Li and 93.8% for Co, whereas in contrast, Cu extraction was only 0.7%. Consequently, the proposed leaching method produces a pregnant leach solution (PLS) with high Li (7.0 g/L) and Co (44.4 g/L) concentration as well as a leach residue rich in Cu (up to 12 wt%) that is suitable as a feed fraction for primary or secondary copper production.

Lanthanide-alkali double sulfate precipitation from strong sulfuric acid NiMH battery waste leachate.

In NiMH battery leaching, rare earth element (REE) precipitation from sulfate media is often reported as being a result of increasing pH of the pregnant leach solution (PLS). Here we demonstrate that this precipitation is a phenomenon that depends on both Na+ and SO42- concentrations and not solely on pH. A two-stage leaching for industrially crushed NiMH waste is performed: The first stage consists of H2SO4 leaching (2 M H2SO4, L/S = 10.4, V = 104 ml, T = 30 °C) and the second stage of H2O leaching (V = 100 ml, T = 25 °C). Moreover, precipitation experiments are separately performed as a function of added Na2SO4 and H2SO4. During the precipitation, higher than stoichiometric quantities of Na to REE are utilized and this increase in both precipitation reagent concentrations results in an improved double sulfate precipitation efficiency. The best REE precipitation efficiencies (98-99%) - achieved by increasing concentrations of H2SO4 and Na2SO4 by 1.59 M and 0.35 M, respectively - results in a 21.8 times Na (as Na2SO4) and 58.3 times SO4 change in stoichiometric ratio to REE. Results strongly indicate a straightforward approach for REE recovery from NiMH battery waste without the need to increase the pH of PLS.

Noncovalent Surface Modification of Cellulose Nanopapers by Adsorption of Polymers from Aprotic Solvents.

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF3E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.

Dissolution control of Mg by cellulose acetate-polyelectrolyte membranes.

Cellulose acetate (CA)-based membranes are used for Mg dissolution control: the permeability of the membrane is adjusted by additions of the polyelectrolyte, poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). Spin-coated films were characterized with FT-IR, and once exposed to an aqueous solution the film distends and starts acting as a membrane which controls the flow of ions and H2 gas. Electrochemical measurements (linear sweep voltammograms, open-circuit potential, and polarization) show that by altering the CA:PDMAEMA ratio the dissolution rate of Mg can be controlled. Such a control over Mg dissolution is crucial if Mg is to be considered as a viable, temporary biomedical implant material. Furthermore, the accumulation of corrosion products between the membrane and the sample diminishes the undesirable effects of high local pH and H2 formation which takes place during the corrosion process.

QCM study of the adsorption of polyelectrolyte covered mesoporous TiO2 nanocontainers on SAM modified Au surfaces.

Mesoporous TiO(2) nanocontainers (NCs) covered with polyelectrolyte multilayers were adsorbed on self-assembled monolayer (SAM) modified gold substrates at different values of pH and ionic strength. The adsorption process was followed in situ by means of a quartz crystal microbalance (QCM) and the morphology of the adsorbate was investigated by means of FE-SEM images taken of the substrates after each adsorption process. Deposition could be achieved if either the particles and the surface had opposite charge, or if the salt concentration was sufficiently high, reducing the repulsion between the spheres and the surface. In the latter case the adsorption kinetics could be explained in the context of the DLVO-theory. Using conditions of like charges, one has a means to control the speed of deposition by means of ionic strength. However, interparticle aggregation and cluster deposition on the surface were observed at high ionic strength. Such conditions have to be avoided to obtain a uniform deposition of separated nanocontainers on the surface.