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.

Circular And Sustainable: Evaluating Lithium-Ion Battery Recycling using a Combined Statistical Entropy and Life Cycle Assessment Methodology.

While there has been a growing interest on the concept of Circular Economy (CE), its correlation with sustainability remains controversial. In this work, the combination of Statistical Entropy Analysis (SEA) and Life Cycle Assessment (LCA) is proposed as a new methodology to evaluate recycling processes from the perspective of materials circularity and environmental impacts using a Li-ion battery recycling process as a case study. This work addresses the need of quantitative circularity indicators, as SEA evaluates the concentration of materials at a systems level, while LCA measures the environmental impact of recycling processes in comparison with virgin raw materials production. It was found that process optimization points can be found by simultaneously accounting for materials recovery and the LCA categories of global warming potential, ozone depletion and mineral resource scarcity. Furthermore, a strong correlation was found for the first time between the recovery of critical elements and the environmental impact of raw materials production. The proposed methodology thus offers a robust analysis of a product lifecycle that aids in its design and optimization from the CE perspective.

A multi-dimensional indicator for material and energy circularity: Proof-of-concept of exentropy in Li-ion battery recycling.

Recycling processes are an important stage in the raw material life cycle, as it enables the transition from a linear economy into a circular one. However, the currently available indicators of productivity in recycling technologies respond to the needs of a linear economy. In this work, a parameter called "exentropy" is proposed, offering the possibility to simultaneously account for mass preservation and the energy efficiency of transformative stages. As a proof-of-concept of this indicator, the analysis of a lithium-ion battery recycling process under various concentrations of a leaching reagent (i.e., 0.1M, 1M, and 2M) is presented. It is shown that, when the energy or mass dimensions are considered independently, the processes considered optimal may have conflicting characteristics. In contrast, the multi-dimensional analysis identified the process option offering the best compromise for both material and energy preservation, an aspect closer to the goals of the circular economy.

A simple methodology for the quantification of graphite in end-of-life lithium-ion batteries using thermogravimetric analysis.

A new method based on thermogravimetric analysis was developed to measure the graphite content in battery material mixture. This approach exploits the thermochemical reduction of cathodic Li-transition metal oxides with anodic graphite at elevated temperatures under an inert atmosphere. Using known composition artificial mixtures, a linear correlation between cathode mass loss and sample graphite content was observed. The method was validated using industrial black mass samples and characterized traditionally to estimate and rationalize potential error sources. Thermal degradation profiles of industrial battery waste reflected those in the artificial system, demonstrating its applicability. This work also demonstrates that thermogravimetric degradation profiles can distinguish between a cathode consisting of single or multiple Li-metal oxides. Although accuracy depends on active component mixture content and impurities, it is demonstrated that the method is useful for a fast graphite content estimation. Unlike other graphite characterization techniques, the method proposed is simple and inexpensive.

N-Alkylated Chitin Nanocrystals as a Collector in Malachite Flotation.

The majority of reagents currently used in mineral flotation processes are fossil-based and potentially harmful to the environment. Therefore, it is necessary to find environmentally-friendly alternatives to reduce the impact of mineral processing activities. Chitin nanocrystals are a renewable resource that, due to the natural presence of amino groups on its surface, represents a promising collector for various minerals of economic relevance. This study examines the one-pot functionalization of chitin nanocrystals with aldehyde structures to obtain hydrophobized colloids suitable for mineral flotation. The chemical properties of these nano-colloids were investigated by nuclear magnetic resonance spectroscopy, their colloidal behavior and structure by electrophoretic light scattering and atomic force microscopy, and their wettability through water contact angle measurements. The functionalized N-alkylated chitin nanocrystals possessed a hydrophobic character, were able to dress mineral particles and featured a performance in the flotation of malachite similar to commercial collectors, which proves the high potential of chitin nanocrystals in this field of application.

On the Colloidal Behavior of Cellulose Nanocrystals as a Hydrophobization Reagent for Mineral Particles.

In the search for more sustainable alternatives to the chemical reagents currently used in froth flotation, the present work offers further insights into the behavior of functionalized cellulose nanocrystals as mineral hydrophobization agents. The study corroborates that hexylamine cellulose nanocrystals (HACs) are an efficient collector for the flotation of quartz and also identifies some particular characteristics as a result of their colloidal nature, as opposed to the water-soluble reagents conventionally used. To investigate the individual and collective effects of the frother and HACs on the attachment of particles and air bubbles, an automated contact timer apparatus was used. This induction timer measures particle-bubble attachment probabilities (Patt) without the influence of macroscopic factors present in typical flotation experiments. This allowed the study of the combined influence of nanocellulose and frother concentration on Patt for the first time. While HACs readily adsorb on quartz modifying its wettability, the presence of a frother leads to a drastic reduction in Patt up to 70%. The improved recovery of quartz in flotation cells might thus be attributed to froth stabilization by HACs, perhaps acting as a Pickering foam stabilizer. Among the main findings, a tendency of HACs to form mineral agglomerates was identified and further explained using the extended DLVO theory in combination with measured adsorption rates in a quartz crystal microbalance. Therefore, this study distinguishes for the first time the antagonistic effect of frothers on Patt and their synergies with HACs on the stabilization of orthokinetic froths through the hydrophobization mechanism unlike those of typical water-soluble collectors.

Novel laser surface texturing for improved primary stability of titanium implants.

Recently, the production of well-defined patterned surfaces with random or regular micro and nano-features has brought new opportunities for research and development in the field of tissue engineering and regenerative medicine. Among advanced micro and nano processing technologies, laser surface texturing (LST) stands out due to its simplicity, flexibility, precision, reproducibility and relatively low cost. This work studies the development of patterned surfaces controlled by of LST into biomedical grade V titanium, Ti-6Al-4V-alloy. We present different cross-hatched micropatterns followed by the characterisation of surface morphology and topography. Structural integrity of the produced patterns is evaluated by friction tests against bone, mimicking the insertion of an implant. Wettability is studied as it is crucial for protein adsorption and cell adhesion. The results show that the surface topography obtained using different patterning plans influences the wetting behaviour and the coefficient of friction against bone.

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.

Environmental remediation of sulfidic tailings with froth flotation: Reducing the consumption of additional resources by optimization of conditioning parameters and water recycling.

The removal of sulfidic species in tailings using froth flotation is a promising approach to prevent phenomena such as acid mine drainage. However, flotation requires the consumption of reagents and water that represent additional expenses. Despite the strong interest of scientists and industry alike on tailings remediation, there is no study on the minimization of resource consumption to promote the implementation of desulfurization with froth flotation. Following a systematic analysis based on Design of Experiments (DoE), this work aims to determine the implications of a decrease in the consumption of flotation reagents and fresh water. It was found that: i) recovery of sulfidic species is strongly influenced by collector concentration and the use of a preliminary re-dispersion step; ii) higher frother concentrations have a negative impact on sulfur grade in the concentrate; and iii) the interactions between the conditioning variables hereby explored have no significant impact on flotation performance. Composition analysis showed that flotation further aids in the removal of hazardous species, such as As, Co and Zn. Finally, the use of recycled water appears possible since flotation performance remained unchanged over 10 flotation cycles, despite the observed accumulation of metallic ions and organic species in the process water.

Challenging the concept of electrochemical discharge using salt solutions for lithium-ion batteries recycling.

The use of lithium-ion batteries (LIB) has grown significantly in recent years, making them a promising source of secondary raw materials due to their rich composition of valuable materials such as Co, Ni and Al. However, the high voltage and reactive components of LIBs pose safety hazards during crushing stages in recycling processes, and during storage and transportation. Electrochemical discharge by immersion of spent batteries in salt solutions has been generally accepted as a robust and straightforward discharging step to address these potential hazards. Nonetheless, there is no clear evidence in the literature to support the use of electrochemical discharge in real systems, neither are there clear indications of the real-world limitations of this practice. To that aim, this work presents a series of experiments systematically conducted to study the behavior of LIBs during electrochemical discharge in salt solutions. In the first part of this study, a LIB sample was discharged ex-situ using Pt wires connected to the battery poles and submerged into the electrolyte solution on the opposite end. The evolution of voltage in the battery was measured for solutions of NaCl, NaSO4, FeSO4, and ZnSO4. The results indicate that, among the electrolytes used in the present study, NaCl solution is the most effective for LIBs discharge. The discharge of LIB using sulfate salts is however only possible with the aid of stirring, as deposition of solid precipitated on the electrodes hinder the electrochemical discharge. Furthermore, it was found that the addition of particulates of Fe or Zn as sacrificial metal further enhances the discharging rate, likely due to an increased contact area with the electrolyte solution. While these findings support the idea of using electrochemical discharge as a pre-treatment of LIBs, severe corrosion of the battery poles was observed upon direct immersion of batteries into electrolyte solutions. Prevention of such corrosion requires further research efforts, perhaps focused on a new design-for-recycling approach of LIBs.

Applications of pore-expanded mesoporous silica. 7. Adsorption of volatile organic compounds.

Three different varieties of mesoporous silicas were synthesized by varying the postsynthesis treatment of an as-synthesized ordered mesoporous material type MCM-41. The resulting materials consisted of a purely siliceous MCM-41, a pore-expanded MCM-41 (PE-MCM-41C), and a surfactant-laden pore-expanded MCM-41 (PE-MCM-41E) and were evaluated as adsorbents for two types of volatile organic compounds, i.e., chlorinated and aromatic hydrocarbons. Values of heat of adsorption and Henry's law constant were determined by pulse chromatography. Additionally, adsorption capacities were calculated with a dynamic method using breakthrough curves for single components in dry and humid environments. The surfactant-containing material exhibited good compatibility with chlorinated compounds in terms of heat of adsorption and efficiency in gaseous streams containing moisture. Purely siliceous mesoporous materials, i.e., MCM-41 and PE-MCM-41C, were more selective toward aromatic hydrocarbons but also gave rise to exceptionally strong adsorption.