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Open research questions in Extraction and Separation Processes

97 unresolved questions extracted from the limitations and future-work sections of 1,148 Extraction and Separation Processes papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • neutralizing agents, as well as reduce the amount of resi- due produced. In systems where there is a structural con- straint of lithium and the liberation of the lithium cannot be decoupled from the disruption of the framework, thermal Sustainable exploitation of lithium in the alumi- activation or step-by-step hybrid strategies may provide a na-rich ores requires accepting that these feedstocks are es- viable route by decoupling the lithium recovery and uncon- sentially geometallurgical systems, and not homogeneous trollable disruption of the gangue, although at the penalty feedstocks. Compared to traditional brines and spodumene of increased energy requirements and inevitable emissions. concentrates, lithium is usually present in alumina-rich The gel propensity and strong buffering capacity, the high ores as fine-grained aluminosilicates that determine both levels of alkaline earths, or the high levels of halide/sulfate lithium release and dissolution of both alumina and silica, loads also put further constraints on the routes which are formation of gelation and rheology issues, as well as the possible at any rate, particularly when realistic pulp den- 1141 Journal of Environmental & Earth Sciences | Volume 08 | Issue 08 | August 2026 sities and steady-state recycle water chemistry are used. valorization ought to be addressed along with regulatory Domaining in this sense is not simply an exercise of char- and market reality, with a focus on being consistently se- acterization, but a form of decision logic which ensures curable and verifiably life-cycle advantageous. flowsheets do not optimize to behave in the laboratory but Overall, lithium ores with high alumina content have fail when put in the industrial environment. the potential to play an important role in the future of lith- Another important point made in the review is that ium, although, because of the generic flowsheet approach, in alumina-rich systems, operability and sustainability are they cannot be developed sustainably without transitioning closely intertwined. Not only are aluminum dissolution to a geometallurgy-based paradigm where the domains of and silica polymerization chemical obstacles, but they also ore determine the viable processing window and the sus- cause water demand, separation capacity, reagent intensity, tainability profile. The strongest pathways will be the ones and volume, as well as long-term risk of residues. Similar- that relate deposit knowledge and domain classification ly, water, particularly the drive to recycle water, which is with flowsheet design to closed-loop resource management one of the key sustainability goals, can add to salt and clay and responsible residue outcomes. Through the use of do- deposits, altering the behavior of clay dispersion and in- main-sensitive decision models and enhanced comparabil- creasing the risk of scaling or gelation, unless purge, treat- ity via standardized data sets, the community will be able ment, and circuit chemistry are specified. The management to speed up the process of moving out of the laboratory of the residue and tailings cannot thus be handled as a sec- demonstrations to trustworthy industrial practice that ful- ondary design variable, and the principles of design to clo- fills economic and environmental demands. sure need to be incorporated into the route choice, reagent design, and solid–liquid separation decisions. Circularity can somehow be supported through valorization of alumi- nosilicate residues, but only in certain situations, and only as an addition, not an alternative to, careful storage and closure planning. In the future, some priorities become apparent to scale ESG-prepared lithium production out of lithium-rich alumina ores. In the first place, the field should be provid- ed with standardized, domain-relevant reporting compris- ing quantitative mineralogy, characterization of particle size and fines, lithium and impurity deportment, complete mass balances, considerations of steady-state recycle wa- ter, and residue properties associated with long-term stabil- ity. Second, selectivity, as recovering lithium and reducing the dissolution of aluminum and silica, should be maxi- mized by innovating selective activation, shut windows, and powerful selective separations that are still effective in complex liquors. Third, electrification of energy-intensive processes, such as electrified or even low-carbon heat, and increased heat integration where activation is necessary, will be necessary. Fourth, the water and salt management solutions should be prepared and tested in the conditions of closed circuits under realistic conditions, and the design of the purges, treatment alternatives, and scaling regulation

    Sustainable Utilization of Lithium in Alumina-Rich Ores: Insights from Geology, Processing, and Environmental Management Xiaokun Dong · 2026 · DOI

  • The study identifies the potential influence of service life, operating history, degree of degradation, and confirmed reason for decommissioning on the leaching behavior of the recovered cathode active material as a limitation. The study notes that residual PVDF may affect subsequent leaching by promoting the agglomeration and encapsulation of recoverable particles. The study identifies the need for further research to optimize the leaching conditions and improve the selectivity of lithium recovery.

    Selective Lithium Recovery from Spent Lithium Iron Phosphate Batteries Used in Solar Energy Storage · 2026 · DOI

  • Investigating the effect of service life, operating history, degree of degradation, and confirmed reason for decommissioning on the leaching behavior of the recovered CAM, - Evaluating the scalability of the optimized leaching conditions, - Assessing the economic viability of the proposed process

    Selective Lithium Recovery from Spent Lithium Iron Phosphate Batteries Used in Solar Energy Storage · 2026 · DOI

  • The paper identifies challenges related to the implementation of the circular economy concept, including mismanaged flows of people and materials. It notes the tension between economic development and environmental protection. The paper highlights the need to consider the social and political implications of the circular economy.

    Spiraling out in the Circular Economy: Movement and Belonging at a Malaysian Rare Earth Elements Refinery · 2026 · DOI

  • The paper identifies a gap in the understanding of the circular economy concept and its effects on human movement and belonging. It highlights the need to consider the social and political implications of the circular economy. The paper notes that prior research has focused on the environmental and technological aspects of the circular economy.

    Spiraling out in the Circular Economy: Movement and Belonging at a Malaysian Rare Earth Elements Refinery · 2026 · DOI

  • investigation of the long-term stability of the adsorbent, - exploration of other potential applications of Zr-SBA-15-30

    Selective Adsorption Separation of Sc(III) and Zr(IV) from Acidic Solutions via Zr-SBA-15 with Rich Oxygen-Vacancy Defective · 2026 · DOI

  • The similar ionic radii and hydrolysis behavior of Sc(III) and Zr(IV) make their separation a challenging issue. Current methods for Sc/Zr separation have limitations. There is a need for a viable material design strategy for efficient separation under strongly acidic conditions.

    Selective Adsorption Separation of Sc(III) and Zr(IV) from Acidic Solutions via Zr-SBA-15 with Rich Oxygen-Vacancy Defective · 2026 · DOI

  • To efficiently rise to this occasion, advanced technology should be explored to address these challenges.

    Ultrafast Thermal Engineering in Energy Materials: Design, Recycling, and Future Directions · 2025 · DOI

  • However, the traditional solid-phase repair technology is limited by the heterogeneous contact between the lithium source and spent LFP.

    Constructing a Homogeneous Medium Layer To Promote the Direct Regeneration of Spent Lithium Iron Phosphate · 2025 · DOI

  • Methods for recycling key components such as hard carbon (HC), a negative electrode material, remain underexplored.

    Sustainable Recovery and Reuse of Hard Carbon From Scrap and End‐of‐Life Sodium‐Ion Batteries · 2025 · DOI

  • Hard-rock Li mining from Li-pegmatites is rapidly expanding to support the clean energy transition, yet associated water-quality impacts remain understudied.

    The Water Quality Impacts of Legacy Hard-Rock Lithium Mining and Processing · 2025 · DOI

  • This review presents a contemporary analysis of PM recovery with focus on underexplored and emergent avenues, such as bio-based leaching, mechanochemistry, photocatalysis, ionic liquids and deep eutectic solvents, and computationally driven ligand design, in addition to reviewing conventional procedures.

    Recent advances in the recycling of precious metals using sustainable chemistry · 2025 · DOI

  • This study emphasizes the need for improved recycling of REE-containing waste, better monitoring of impacts, and further research on REE ecotoxicology and bioavailability.

    A review of rare earth elements in waste disposal: Release mechanisms, environmental behaviors and risks · 2025 · DOI

  • However, the release behaviors and migration pathways of REEs during waste disposal remain insufficiently explored.

    A review of rare earth elements in waste disposal: Release mechanisms, environmental behaviors and risks · 2025 · DOI

  • However, a comprehensive analysis of the carbon footprint (CF) of lithium has not yet been reported, posing a challenge to promoting battery sustainability.

    Carbon Footprint of Battery-Grade Lithium Chemicals in China · 2025 · DOI

  • However, most studies are limited to single-site analyses, and a global, system-level understanding remains scarce.

    Environmental Impacts of Lithium Brines Across the World: Brine Quality, Technology Choices and Regional Disparities · 2025 · DOI

  • However, the corrosion behavior of citric acid under hydrothermal conditions has not yet been thoroughly investigated, limiting the further development of a leaching apparatus.

    Evaluation of the Corrosion Behavior of Various Metallic Materials for Material Selection of Citric Acid Hydrothermal Leaching Apparatus for Lithium-Ion Battery Recycling · 2025 · DOI

  • Yet limited research explores their impact on trade stability or how technological progress mitigates diffusion.

    Technological risks disrupting trade stability in the global lithium supply chain network · 2025 · DOI

  • These findings demonstrate the strong potential of CPO-27(Ni) and other underexplored MOFs as efficient, regenerable materials for lithium recovery from aqueous solutions.

    Metal organic framework materials for efficient lithium adsorption from aqueous solution – comparative study · 2025 · DOI

  • Among these, five materials, MOF-801, MOF-303, MIL-53(Al), aluminium fumarate, and CPO-27(Ni), have not been previously reported for lithium adsorption.

    Metal organic framework materials for efficient lithium adsorption from aqueous solution – comparative study · 2025 · DOI

  • However, the underlying dissociation mechanism of the cathode is poorly understood.

    Dissociation Mechanism on Spent Ternary Lithium-Ion Battery Cathode via Carbothermal Reduction Reaction with Biomass Components · 2025 · DOI

  • Sodium-ion batteries are considered a promising substitute for Li-ion, but the timeline and conditions for achieving cost-competitiveness remain uncertain.

    Critically assessing sodium-ion technology roadmaps and scenarios for techno-economic competitiveness against lithium-ion batteries · 2025 · DOI

  • However, the future demand and production of batteries remain uncertain, while the ambition to strengthen national capabilities and self-sufficiency is gaining momentum.

    Feasibility of meeting future battery demand via domestic cell production in Europe · 2025 · DOI

  • Nevertheless, they have rarely been reported to have lithium selectivity over divalent cations due to the well-known flexibility of MOF framework and the similar physiochemical properties of Li + and Mg 2+ .

    Sustainable lithium extraction enabled by responsive metal-organic frameworks with ion-sieving adsorption effects · 2024 · DOI

  • While the importance of impurity analysis is acknowledged by suppliers and manufacturers of battery materials, reports on elemental analysis of trace impurities in Li 2 CO 3 salt are scarce.

    Analysis of Trace Impurities in Lithium Carbonate · 2024 · DOI

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