## 2 Synthetic Protocols for Hydrometallurgy  
Traditionally, most of the IX and chelating resins for applications in industrial processes are based on styrene (St) and divinylbenzene (DVB) copolymers (St-co-DVB). Due to the presence of strong covalent bonds, these materials are chemically inactive. Bearing this in mind, it is necessary to introduce chloromethyl groups (-CH\({}_{2}\)Cl) into their structure. The process of such activation is highly undesirable as the alkylating agents, such as bis-chloromethyl ether (BCME), are highly carcinogenic. Consequently, the processes of synthesis require extra measures undertaken to protect the environment, as well as the staff [11; 12]. For these reasons, an alternative route involves application of vinylbenzyl chloride (VBC), instead of St, as a functional monomer. Direct copolymerization of VBC with DVB leads to the VBC-co-DVB copolymer production, already possessing -CH\({}_{2}\)Cl groups ready for direct modification. Then, as displayed in Figure 1, the so-obtained copolymer can be further modified to an IX resin by a nucleophilic attack on Cl by, for example, amine or carboxylic acid, resulting in the synthesis of an anion- or cat-ion exchange resin, respectively [11]. As can be seen in Figure 1, the modification process using amines results in the changing of the color of an initial VBC-co-DVB copolymer, from white/transparent to yellow, attributed to the presence of amino-m moieties. Amino functionalities are able to dissociate in solutions of HCl. As a result, the N atom becomes protonated, and Cl- anion is held on an anion exchange resin (see Figure 1C). Another one that functionality reveals an affinity with can easily exchange this excessive anion. This simply defines  
Figure 1: Modification of (**A**) VBC-co-DVB copolymer, using (**B**) an amine (here example for 1,2-diamonoethane), followed by (**C**) an anion exchange (here example for Au(III) ions). mechanism of separation of noble metals, as they exist in solutions of electrolytes mainly in anionic forms, such as AuCl4\({}^{-}\), PtCl6\({}^{-}\), PdCl4\({}^{-}\), and ReO4\({}^{-}\)[13; 14; 15; 16]. The main drawbacks of applying VBC as a starting monomer for the synthesis of polymeric matrices are related to the reactivity of -CH2 Cl groups. Conditions of free-radical suspension polymerization (elevated temperature and water-based suspension) make the reactive groups susceptible to hydrolyze, resulting in mers originating from vinyl benzyl alcohol in the formed VBC-co-DVB copolymer or to additionally crosslink thereof through methylene-brides [17]. Both of these undesired side reactions result in decreasing the capacity of a final IX resin, by limiting the number of functionalities or by increasing hydrophobicity of the material, respectively. Although there are examples exploiting the secondary crosslinking of VBC aimed to increase its affinity toward organic adsorbates, its hydrolysis is highly undesirable, as it simply wastes the possible IX capacity a functional resin can achieve. In the past several years, different factors have been investigated in the view of possible limiting of VBC hydrolysis [18; 19]; however, due to the elevated temperatures and prolonged residence of the monomer in water, the issue had not been resolved [20]. To address this problem, our research group decided to take an alternative approach toward the synthesis of VBC-co-DVB copolymers. The research hypothesis was associated with limiting undesired hydrolysis of VBC, which should involve reducing residence of the monomer in water phase first. The influence of the elevated temperature was considered as a secondary factor that could be difficult to avoid, as the benzoyl peroxide (BPO) used as an initiator of polymerization needed 90 \({}^{\circ}\)C to generate free radicals. Because of this, microwave (MV) heating was applied for synthesis of starting VBC-co-DVB copolymer.