**8. Ion exchangers of functional imidazole groups**

ions from nitric(V) acid solutions (0.1–4 M). High values of partition coefficients (particularly in diluted HNO3 (0.1 M) solutions) decreased with the increasing concentration of nitric(V) acid for the ion exchangers Tulsion CH-95, Tulsion CH-96 and Tulsion CH-97. The values of partition coefficients (particularly in diluted HNO3 (0.1 M) solutions) which were >10 000 cm3

decreased with the increasing nitric acid(V) concentration. The selectivity series of the Tulsion ion exchangers towards Pd(II) ions is as follows: *Tulsion CH-95 > Tulsion CH-97 > Tulsion CH-96.* The ion exchangers of the functional thiourea and isothiourea groups, commercially known as Srafion NMRR, Lewatit TP-214 and Purolite S-920, are widely used for the concentration of platinum metal ions [53-61]. Srafion NMRR (Ionac SR-3) exhibits great affinity for Au(III) and Ag(I) as well as Pd(II), Pt(IV), Rh(III), Ru(III), Ir(III) and Os(VI) ions [53-61]. It is applied in the separation of noble metal ions [57], similar to the ion exchangers Monivex which develop high sorption capacity values particularly in the largely acidic solutions (2–6 M HCl) [67]. Lewatit TP-214 was used for the removal Pd(II) ions from two component Pd(II)–Zn(II); Pd(II)–Cu(II)) and multicomponent (Pd(II)–Cu(II)–Zn(II)) chloride solutions [61] and for the removal of Pd(II) ions from chloride solutions (0.1–8.0 – 0,001 M Pd(II)) and chloride–nitrate ones (0.1÷0.9 M HCl – 0.9÷0.1 M HNO3– 0,0011 M Pd(II)) ) [55]. The total ion exchange capacity of Lewatit TP-214 towards Pd(II) ions was from 0.97 mmol/g–3 M HCl to 1.16 mmol/g–0.1 M HCl [55]. Zuo and Muhammed prepared a large number of ion exchangers of the functional thiourea groups by modification of macroporous polystyrene matrices of Bonopore, Amberlite XAD-2, Amberlite XAD-4 as well as the weakly basic anion exchanger Amberlite IR-45 [62]. Newly prepared ion exchangers were used in sorption of Au(III), Ag(I), Cu(II) and Fe(III) ions from one-component chlorides solutions (2 M HCl) and their mixtures (Au(III), Ag(I), Fe(III), Cu(II)), as well as in sorption of platinum metal ions e.g. Pd(II), Pt(IV), Rh(III), etc. The studied ion exchangers are characterized by high selectivity towards noble metal ion, particularly gold

Separation of Pd(II), Cu(II) and Zn(II) ions using the melamine-formaldehyde-thiourea (MFT) resin was presented in [63]. There was proved high selectivity of this resin towards Pd(II) ions, and the obtained values of sorption capacity were 15.29 mg Pd(II)/g (static method) and 1580 μg Pd(II)/g resin (dynamic method). Desorption of ions with studied resin was conducted using 0.5 M thiourea, 0.5 M HCl solutions and the acidified thiourea (0.5 M (NH2)2CS–0.5 M

The chelating ion exchangers of functional thiol and methylene thiol groups with the com‐ mercial names: Chelite S, Duolite GT-73, Imac GT-73, Duolite GT-74, Purolite S-924, Spheron Thiol 1000 and Tulsion CH-97 are widely applied in sorption and separation of noble metal ions [55, 56, 64-69]. Introducing 8-hydroxchinoline (HOxn) and sodium salicylate groups to the methacrylate polymer matrix generates two new chelating ion exchangers Spheron Oxine 1000 and Spheron Salicyl 1000, respectively, which similar to Spheron Thiol 1000 are applied

/g for Tulsion CH-95, Tulsion CH-96 and Tulsion CH-97, respectively,

g, 1650 cm3

HCl).

/g, 5210 cm3

10 Ion Exchange - Studies and Applications

and silver in the presence of Cu(II) and Fe(III).

**7. Ion exchangers of functional thiol groups**

/

Many authors prove high reactivity of imidazole groups and their derivatives towards metal ions, particularly noble metals ions. For example, VBC-DVB (VBC – vinylbenzene chloride, DVB – divinylbenzene) – recovery of Pd(II) and Pt(IV) ions from chloride solutions (1–2 M HCl) and their separation from Cu(II), Zn(II) and Ni(II); sorption capacity, 1.6–1.7; 1.4–1.5 and 1 mmol of metal/g for the 0.1 M HCl, 1 M HCl and 2 M HCl solutions, respectively; desorption of Pd(II) and Pt(IV) ions, 0.1–0.3 M thiourea solution (desorption effectiveness >98% for Pd(II); 85% for Pt(IV)) [71, 72]; epoxide resin of the functional imidazole groups concentration of trace (20 ng/dm3 ) amounts of Au(III), Pd(IV) and Ru(III) ions. Noble metal ions can be enriched in a quantitative way (recovery 94.5–100%, pH = 4), desorption: acidified thiourea solutions (16 cm3 6 M HCl, 0.2 g thiourea), recovery 96–99.5% [73], polystyrene-divinylbenzene resin of functional benzimidazole group – separation of heavy metal ions that is Pd(II), Ag(I) and Hg(II) from medical alloys, geological materials, different kinds of waste waters and sludges; sorption capacity: 1 mmol/g for Ag(I) (pH = 4–6), 0.62 mmol/g for Pd(II) (pH = 5–6) and 0.83 mmol/g for Hg(II) (pH = 4–6); desorption: 5% thiourea solution in 0.1 M HClO4 (recovery: Ag(I) and Hg (II) – 100%, Pd(II) – 60%) and 12 M hydrochloric acid solution (recovery: Ag(I) – 45 %, Pd(II) – 100 %, Hg(II) – 65 %) [74]; polystyrene-divinylbenzene resin of Im-NO3 (Im-imidazole) groups – removal of Pd(II) (0.00062 M) form nitric(V) acid solutions (1–5 M HNO3); sorption capacity depends, among others, on the molar ration of initial reagents of chloromethylated resin (I) and 1-methylimidazole (II) at the reagents ratio I:II = 1:1.5 this capacity is the highest (4.06 mmol/g), the total capacity determined form the Langmuir 88 mg/g (3 M HNO3) [75]; resin of functional aminoethylene imidazole (IEA) – concentration of trace amounts of Au(III), Pt(IV), Ir(IV), Pd(II) ions and their separation from Cu(II), Fe(III), Zn(II), Ni(II), Mn(II), Cr(III), Ca(II) and Mg(II) ions; sorption capacity in 2 M HCl solution: 4.0 mmol/g – Au(III), 1.57 mmol/ g – Pt(IV), 2.26 mmol/g – Pd(II) and 1.85 mmol/g – Ir(IV) [76].
