## 1 Introduction  
Nowadays, the problem of developing really effective sorbents has become a key issue for industry. In hydrometallurgy, sorption methods are widely used to extract metals from solutions (e.g., gold, copper, heavy metals, rare earth elements). So, the extraction of target metals is presented by a wide range of sorbents, such as inorganic sorbents, chelating polymers, ion-exchange resins/membranes, polymer hydrogels, interpolymer systems, and carbon-based sorbents [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. However, these technologies have a number of significant problems that limit their effectiveness and economic feasibility. Such issues can be named as follows: low selectivity of sorbents; sensitivity to solution composition; limited capacity and kinetics of sorption; regeneration and disposal problems; high cost of modern sorbents; technological difficulties [13, 14, 15, 16, 17, 18, 19]. Regarding this, the extraction of target metals from water media (such as environmental lakes or technological solutions) requires a new approach to the development of sorbents. The use of polymers with molecular imprints has wide potential for solving various tasks related to the recognition and isolation of target molecules from complex mixtures, as well as wastewater treatment. Molecular imprinting,as well as an ionic imprinting technique, was successfully used for recognition and sorption of different metals [20; 21; 22; 23]. Polymers with molecular imprints (MIPs) are synthetic materials engineered with highly selective binding sites that mimic natural molecular recognition systems. These polymers contain tailor-made cavities, functionalized with specific chemical groups designed to adsorb target molecules with high specificity [24; 25; 26]. MIP is proposed to be used in different application fields: medicine [27; 28], pharmacy [29], water purification [30], catalysis [31; 32], etc. MIPs are used effectively to detect and recognize a wide spectrum of tiny chemical compounds, metal ions, and large-structured molecules such as viruses, proteins, and cells. For example, molecularly imprinted polymers were efficiently applied in the separation of various active components from plants, including flavonoids, organic acids, alkaloids, phenylpropanoids, anthraquinones, phenolics, terpenes, steroids, and diketones [33]. For biomedical purposes, MIPs are used for separation and recognition of biological small molecules and biomacromolecules [34], as well as microorganisms [35] and biologically active substrates--in particular, steroidal systems [36] and proteins [37]. Based on the recognition of biomolecules, the imprinting technique has been widely used in biomarker detection, i.e., biosensors [38; 39]. In comparison with general biosensors, imprinted biosensors are characterized by fewer non-specific recognition sites. The idea of using the imprinting approach for creating sensors is described in a variety of works [40; 41; 42; 43; 44]. Detection in such sensors is based on different physical signals, e.g., colorimetric [45], electrochemical [46; 47; 48], and electrochemiluminescence [49]. Authors mention the high sensitivity and selectivity of such systems as the main advantages of imprinted polymers. This makes MIPs relevant and promising materials for use in various fields of science and technology. As mentioned above, the imprinting technique was used for selective recognition and separation of different metals. Among them, several works were devoted to the sorption of rare earth metals [50; 51; 52; 53; 54; 55; 56], which could be found in industrial wastewaters. Filtration, chemical precipitation, neutralization, chelating ion exchange, and adsorption have all been used to remove such ions [57; 58; 59; 60; 61]. The latter method is often selected because of its efficiency, controllability, selectivity, and low cost. Imprinted polymers show more efficiency in comparison with other traditional ion exchange resins.