Metal Ion Separation Techniques in Liquid and Aqueous Systems

Metal ion separation in liquid and aqueous matrices encompasses a diverse array of physicochemical methods designed to isolate and recover valuable or hazardous ions from complex mixtures. Conventional approaches include solvent extraction, in which metal ions partition between immiscible liquid phases; adsorption and ion-exchange processes that exploit tailored solid sorbents; and chromatographic techniques for high-resolution fractionation. Recent advances have expanded the repertoire to incorporate biosorption by biomaterials, task-specific ionic liquids immobilised on solid supports, crown-ether functionalised media and nanostructured materials such as porous polymers or nanocellulose. These strategies are underpinned by detailed characterisation of thermodynamic parameters and kinetic profiles, often modelled by Langmuir and Freundlich isotherms or pseudo-second-order kinetics, to optimise uptake capacity, selectivity and recyclability. Emerging work also integrates mathematical modelling of breakthrough behaviour in fixed-bed systems and the design of solvent systems that harness entropy-driven complexation. Collectively, these innovations address global challenges in nuclear waste management, environmental remediation and critical-metal recovery, delivering scalable solutions that balance performance, cost and sustainability.

Research from Nature Portfolio

Recent studies have demonstrated the potential of biomass-derived sorbents for selective radionuclide and heavy-metal removal under mild conditions. In one report, immobilised protonated orange peel was employed in batch experiments to capture thorium(IV) from acidic solutions. The biosorbent achieved a maximal uptake of nearly 19 mg g⁻¹ at optimal pH and contact time, with equilibrium reached after 10 hours. Data fitting to Langmuir and Freundlich models indicated monolayer adsorption, while pseudo-second-order kinetics pointed to chemisorption as the rate-limiting step. In parallel, algal biomass of Sargassum sp. was treated and assessed for strontium(II) biosorption using response surface methodology to tune pH, ion concentration, biomass dosage and pretreatment. The optimised system exhibited a capacity exceeding 100 mg g⁻¹ and conformed to Freundlich isotherms, reflecting heterogeneous binding sites. Both investigations highlight the applicability of biosorption in large-scale liquid waste treatment and resource recovery, emphasising ease of sorbent regeneration and minimal chemical footprint.

Metal Ion Separation Techniques in Liquid and Aqueous Systems publication trend

The graph below shows the total number of articles in metal ion separation techniques in liquid and aqueous systems across all publications each year (not limited to Nature Index journals).

Technical terms

Adsorption isotherm: Mathematical relationship describing how the amount of adsorbate on a sorbent varies with solute concentration at constant temperature.

Langmuir isotherm: Model assuming monolayer adsorption on a homogeneous surface with finite binding sites.

Freundlich isotherm: Empirical model describing adsorption on heterogeneous surfaces with variable affinities.

Pseudo-second-order kinetics: Rate expression indicating that adsorption rate is proportional to the square of the number of unoccupied sites, often implying chemisorption.

Ionic liquid: Salt in liquid form at ambient temperature, used as a designer solvent or immobilised phase for metal extraction due to tunable solvation properties.

Crown ether: Macrocyclic ligand that selectively complexes metal cations based on cavity size and coordination chemistry.

Biosorption: Passive binding of metal ions onto biological materials, typically via functional groups on cell walls or extracellular polymers.

Solvent extraction: Separation technique in which solutes distribute between two immiscible liquids, often driven by specific ligand–metal interactions.

References

1. Study on Dynamic Column Behavior and Complexation Mechanism of DBS-Modified Crown Ether-Based Silica to 90Sr. Toxics (2023).
2. Investigation of kinetic, isotherm and adsorption efficacy of thorium by orange peel immobilized on calcium alginate. Scientific Reports (2023).
3. Intensification of strontium (II) ion biosorption on Sargassum sp via response surface methodology. Scientific Reports (2023).
4. Novel ionic liquid-modified polymers for highly effective adsorption of heavy metals ions. Separation and Purification Technology (2020).
5. Sr( ii ) extraction by crown ether in HFC: entropy driven mechanism through H 2 PFTOUD. RSC Advances (2022).
6. Preparation of Two Novel Stable Silica-Based Adsorbents for Selective Separation of Sr from Concentrated Nitric Acid Solution. Metals (2024).
7. A Mathematical Simulation of Copper and Nickel Ions Separation Using Prepared Nanocellulose Material. Membranes (2023).