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From Fundamentals to Industrial Prospects: Ion-Imprinted Polymers for Metal Ion Separation: History
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Please note this is an old version of this entry, which may differ significantly from the current revision.
Contributor: Heru Agung Saputra , Muhammad Hanif Amrulloh ,
Nadiya Ayu Astarini
, Fathan Bahfie ,
David Candra Birawidha
, Kyeong-Deok Seo ,
Yuanhui Huang
, Widi Astuti , Yeni Wahyuni Hartati

Ion-imprinted polymers (IIPs) are advanced adsorbents featuring selective recognition cavities for targeted metal ion capture, offering a promising route to high-efficiency separation in extractive metallurgy. In the present work, the evolution, design principles, synthesis strategies, separation mechanisms, and practical applicability of IIPs for metal recovery from complex aqueous matrices are overviewed. Key material components, including functional monomers, crosslinkers, template ions, initiators, solvents, and support materials, are discussed in relation to adsorption capacity, selectivity, kinetics, stability, and recyclability. Major preparation routes, such as surface imprinting, bulk polymerization, in situ polymerization, and sol–gel methods, are critically compared to clarify their advantages and limitations. Recent applications for base metals, precious metals, and rare-earth elements demonstrate that IIPs can achieve high specificity and rapid equilibrium under optimized conditions. However, their translation from simulated solutions to real leachates remains constrained by interfering ions, organic contaminants, mass transfer resistance, incomplete template removal, and matrix complexity. Mitigation strategies, including sample pretreatment, improved polymer architecture, and hybrid supports, are therefore emphasized. Additionally, chemometric modelling, machine learning, or artificial intelligence-assisted design may be implemented to advance the prospects of IIPs in industry. Conclusively, IIPs represent a strong separation platform, yet industrial deployment requires robust validation with real feed streams and scalable regeneration protocols during column operation, as well as under chemically aggressive conditions at scale.

  • advanced material
  • adsorption
  • ion-imprinted polymer
  • metal ion
  • rare earth element
  • separation
Various methods have been employed in extractive metallurgy, which are primarily categorized by physical and chemical techniques, such as pyrometallurgy, hydrometallurgy, and electrometallurgy [1][2][3][4][5][6][7]. Pyrometallurgy has been reported to be the most widely used method in extractive metallurgy. Perhaps its high throughput, speed, simplicity, and mature operations become the reasons [4][7][8][9][10]. Hydrometallurgy is valued for its selectivity and lower energy consumption and is increasingly used for low-grade and complex ores, as well as in the recycling industry. With the advantages of hydrometallurgy, the industry is gradually shifting toward hybrid approaches that integrate this technique for lower-grade deposits and to improve environmental compliance [5][7][11][12][13][14][15][16]. On the other hand, electrometallurgy is generally used for final refining to produce high-purity metals [6][7][17][18][19].
Hydrometallurgy is a rapidly evolving, multidisciplinary field that offers more sustainable solutions to meet future metal demand than traditional, energy-intensive smelting methods [5][7][12][20][21][22][23][24][25]. First, hydrometallurgy operates at relatively low temperatures, making it energy-efficient and implying lower greenhouse gas emissions. Surely, this is ideal for modern sustainability goals. Second, hydrometallurgy allows for precise selectivity and purity, often without the need for further refining. This advantage enables the extraction of metals from lean-grade and complex ores that are uneconomical to smelt. Third, hydrometallurgy is the most efficient technique for recovering critical metals from end-of-life electronics, making it a core technology for recycling and the circular economy. Last but not least, hydrometallurgy constantly introduces exciting, innovative technologies.
The hydrometallurgical process, which includes solvent extraction [26][27][28], ion exchange [29][30][31], cementation [32][33], precipitation [34][35][36][37], adsorption [38][39][40], and liquid membrane [41][42][43], is generally employed to concentrate the desired metal from the leach solution. The step is crucial because the initial leaching process often yields a pregnant leach solution with too many impurities to directly produce high-purity metal. Among the various methods available, adsorption is economical, highly efficient, and environmentally friendly [39][40][44][45]. A few decades ago, ion-imprinted polymers (IIPs) were first introduced as smart adsorbents with specific adsorption sites and used to recover various metal ions from aqueous solutions [46]. Today, IIP technology is expected to deliver a major breakthrough in separating critical elements from complex matrices in the extractive metallurgy industry. On this basis, the present work introduces IIPs as advanced adsorbent materials and seeks to determine the extent to which IIPs are applicable in separation technology.
Although many studies have reported the development of IIPs in the hydrometallurgical separation of metal ions, most focus on specific aspects or narrow topics [47][48][49][50][51]. As a few examples, Majalis et al. (2026) provided a theoretical and practical basis for developing advanced Li-IIPs to support future industrial-scale Li recovery [47]. Wu et al. (2022) provided the historical progress of IIPs in the removal of heavy metal ions from wastewater [48]. Keçili et al. (2025) reviewed recent advances in the production of environmentally friendly IIPs for the selective removal of metal pollutants in environmental samples [49]. Liang et al. (2025) reported development in IIP technology for rare-earth separation [50]. Similarly, Chen et al. (2026) systematically outlined recent advancements in ion-imprinting technology and its immense potential for the selective separation of rare-earth metals [51]. Unlike these works, our review provides a comprehensive overview of the current state of research on IIPs for metal ion separation. The discussion starts from the IIP evolution, the basic principles of IIPs, strategies in the IIP preparation, superiority of IIPs over other adsorbent materials, mechanism in the IIP-based metal ion separation, eluent-dependent behaviour towards template ion release, cutting-edge developments of IIPs in the extractive separation of metal ions, mitigation strategies in IIP practical applications, to IIP prospects in the extractive metallurgy industry.

This entry is adapted from the peer-reviewed paper 10.3390/encyclopedia6080167

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