Separation Technologies

Summary

Membrane, adsorption, chromatographic and ion-exchange methods underpin modern separation science, offering routes to isolate, purify and concentrate target species from complex mixtures. Membrane processes span microfiltration, ultrafiltration and nanofiltration, harnessing pore-size selectivity to fractionate macromolecules, ions and small organics under modest pressures. Adsorption utilises high-surface-area solids—such as activated carbon, metal-organic frameworks or bio-inspired polymers—to bind solutes via ionic, covalent or van der Waals interactions, with subsequent regeneration by pH shift or solvent wash. Chromatographic techniques, particularly gas and liquid chromatography, achieve high resolution through selective partitioning between mobile and stationary phases, guided by differences in volatility or polarity. In ion-exchange and reactive extraction, tailored ligands distinguish closely related ions by coordinating selectively and enabling their transfer into an immiscible phase. Advances in material design—from two-dimensional nanosheets and mixed-matrix membranes to polymer inclusion membranes and deep eutectic solvents—continue to extend the scope and efficiency of separations. Across water treatment, pharmaceutical purification, nuclear fuel reprocessing and biorefining, these technologies address challenges of scale-up, energy use and fouling by integrating process intensification, hybrid architectures and real-time sensing.

Research from Nature Portfolio

Ion desorption from graphene-based adsorbents has long been limited by harsh chemical regenerants but a recent report demonstrates rapid, efficient release of a range of cations (Co(II), Mn(II), Sr(II)) from magnetite-graphene oxide composites using trace levels of Al³⁺ at ambient pH. Desorption exceeds 97 % within one minute, preserving magnetic recovery and enabling repeated reuse without loss of performance. A complementary study exploits ion sieving in a task-specific graphene oxide membrane under oxidising acidic conditions. High-valent linear actinyl ions are effectively excluded from subnanometre interlayer channels, while spherical lanthanide cations permeate freely. Separation factors of up to 400 for actinides over lanthanides under 4 M HNO₃ underscore the power of nanochannel architecture for group-specific separations in advanced fuel-cycle applications. In nuclear-waste partitioning, ultrafiltration of hexavalent americium–polyoxometalate clusters achieves organic-free, energy-efficient fractionation of Am(VI) from trivalent lanthanides. The robust cluster remains soluble in high-acid media and is retained by fine-pored membranes, delivering rapid, once-through americium/lanthanide group separation without conventional solvent extraction.

Research from all publishers

Amyloid fibril-derived carbon aerogels, produced from food-industry proteins, exhibit exceptional adsorption of precious and toxic metal ions (Au, Pt, Fe, Ag) with capacities up to 650 mg·g⁻¹ and stable performance over multiple regeneration cycles. Soy-protein-based microsponge structures self-assembled under varied pH form β-sheet–rich, porous networks that selectively sequester lead(II) with high capacity, tunable binding and minimal loss of efficiency over repeated use, highlighting plant proteins as sustainable biosorbents. Hybrid adsorbents combining coconut-shell biochar with Ti₃C₂Tₓ MXene nanosheets via electrostatic self-assembly integrate ion-exchange and electrostatic interactions to immobilise U(VI) and Cs(I) with maximal capacities of 240 and 40 mg·g⁻¹, respectively, and maintain performance through several desorption–regeneration cycles.

Separation Technologies publication trend

The graph below shows the total number of articles in separation technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Nanofiltration (NF): Membrane filtration with molecular-weight cut-offs of 200–1000 Da, separating small organics and multivalent ions from water.

Carrier‐mediated transport: Selective ion movement across a membrane facilitated by binding to a mobile carrier molecule within the membrane matrix.

Ion sieving: Size‐ and shape‐based exclusion of ions by subnanometre channels, enabling group‐specific separations based on ionic radii and geometry.

Mixed‐matrix membrane (MMM): Composite membrane combining a polymer matrix with dispersed inorganic or organic porous fillers to enhance selectivity and permeability.

Polymer inclusion membrane (PIM): A polymeric membrane plasticised and doped with selective carriers for facilitated diffusion of specific ions or molecules.

Reactive extraction: Liquid–liquid separation that combines reversible chemical reaction and phase transfer to enhance solute partitioning into an organic phase.

Magnetite–graphene oxide (M–GO): A composite adsorbent integrating magnetic nanoparticles with graphene oxide for rapid, magnetically assisted separation of bound ions.

References

  1. Unexpectedly efficient ion desorption of graphene-based materials. Nature Communications (2022).
  2. Ion sieving in graphene oxide membrane enables efficient actinides/lanthanides separation. Nature Communications (2023).
  3. Ultrafiltration separation of Am(VI)-polyoxometalate from lanthanides. Nature (2023).
  4. Amyloid-based carbon aerogels for water purification. Chemical Engineering Journal (2022).
  5. Sustainable soy protein microsponges for efficient removal of lead (II) from aqueous environments. International Journal of Biological Macromolecules (2023).
  6. Constructing coconut shell biochar/MXenes composites through self-assembly strategy to enhance U(VI) and Cs(I) immobilization capability. Biochar (2023).

About these summaries

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