**5. Chelating ion exchangers of functional dithizone groups**

Chelating ion exchangers of functional dithizone (diphenyl carbamate) groups are widely applied in concentration, separation and recovery of noble metal ions [44–54].

Grote and Kettrup [45–48], by conversion of the ion exchanger of functional dehydrodithizone groups, prepared a chelating resin containing dithizone groups. It was used on both sorption and separation of 27 noble and non-noble ions from acids (HCl, HNO3).They showed very high values of partition coefficients of noble metal ions of the order 104 –106 (Pd(II)–7.7×105 ; Pt(IV)–3.4×105 ; Au(III)–2.1×105 (0.01 M HCl)) in the whole range of hydrochloric acid (0.01–6 M) as well as Ag(I) (1.1×103 ) and Hg(II) (5.8×104 ) ions in diluted nitric(V) acid solutions compared to the values of partition coefficients for non-noble metal ions. Also high values of ion exchange capacities of platinum metals and gold (Au(III) 0.74; Pd(II) 0.68; Pt(II) 0.39; Pt(IV) 0.31; Os(IV) 0.12; Ir(IV) 0.14; Ir(III) 0.02; Ru(III) 0.14; Rh(III) 0.16 mmol/g of the dithizone resin) indicate large selectivity of the resin with dithizone functional groups towards noble metal ions as well as possibility of their application in separation from other non-noble metals. Satisfactory results were obtained using the chelating ion exchanger with dithizone functional group in concentration and recovery of Au(III), Pt(IV) and Pd(II) ions originating from the extraction of sulfide ores, stones and enriched ores. Elution of the above-mentioned ions was conducted by means of 2 M chloric(VII) acid and 5% thiourea solution [44]. There was also made a thorough analysis of desorption of single noble metal ions and their mixtures from the resin with the dithizone functional groups using the following eluents: HCl, HClO4, NH4NO3, NaSCN, (NH2)2CS. Palladium(II) and platinum(IV) ions retained on this resin can be qualita‐ tively desorbed using the thiourea solution [46].

nitrate one. Before the separation of platinum(IV) and rhodium(III) ions on the polystyrenesulfone cation exchanger Varion KS in the hydrogen form, the chloride complexes were in contact with sodium hydroxide at pH 13 for four hours. Then the obtained solution was acidified with 4 M HNO3 to pH 2. Under such conditions, rhodium(III) ions occur in the cation form and platinum(IV) ions in the anion form. Platinum(IV) ions are not retained by the cation exchanger. Rhodium(III) ions can be eluted with 1 M hydrochloric acid from the cation

**4. Application of chelating ion exchangers for concentration and removal**

Chelating ion exchangers also called complexing ion exchangers are formed by building organic reagents containing organic groups into the ion exchange resin skeleton. Owing to that they possess active chemical groups capable of selective/specific interactions with metal ions in the solution forming chelating complexes when a metal ion can bind with two or a larger number of donor atoms of their functional groups. These ion exchangers are characterized by high selectivity and their sorption capacities depend, among others, on the kind of functional groups, their reciprocal position and spatial configuration (steric effects) and also on physi‐

On the huge number of chelating ion exchangers, on a large laboratory and industrial scale, there are produced ion exchangers of functional dithizone, thiourea, isothiourea, aminophos‐ phonic, phosphonic, thiol, amidooxime, aminoacetate, dithiocarbamate, iminodiacetate, thiosemicarbamate groups as well as chelating ion exchangers containing triisobutylphos‐

Chelating ion exchangers of functional dithizone (diphenyl carbamate) groups are widely

Grote and Kettrup [45–48], by conversion of the ion exchanger of functional dehydrodithizone groups, prepared a chelating resin containing dithizone groups. It was used on both sorption and separation of 27 noble and non-noble ions from acids (HCl, HNO3).They showed very

compared to the values of partition coefficients for non-noble metal ions. Also high values of ion exchange capacities of platinum metals and gold (Au(III) 0.74; Pd(II) 0.68; Pt(II) 0.39; Pt(IV) 0.31; Os(IV) 0.12; Ir(IV) 0.14; Ir(III) 0.02; Ru(III) 0.14; Rh(III) 0.16 mmol/g of the dithizone resin) indicate large selectivity of the resin with dithizone functional groups towards noble metal

; Au(III)–2.1×105 (0.01 M HCl)) in the whole range of hydrochloric acid (0.01–6

–106 (Pd(II)–7.7×105

) ions in diluted nitric(V) acid solutions

;

**5. Chelating ion exchangers of functional dithizone groups**

applied in concentration, separation and recovery of noble metal ions [44–54].

high values of partition coefficients of noble metal ions of the order 104

) and Hg(II) (5.8×104

exchanger [41].

**of platinum metal ions**

8 Ion Exchange - Studies and Applications

phine sulfides [44-64].

Pt(IV)–3.4×105

M) as well as Ag(I) (1.1×103

cochemical properties of the polymer matrix [42, 43].

Similar investigations using polyvinylpyridine resin of functional dithizone groups in Pd(II) and Pt(IV) ions concentration in the presence of Au(III), Ni(II) i Hg(II) ions were carried out by Shah and Devi [49]. The values of maximal ion exchange capacities towards palladium and platinum ions were 100 and 250 mg/g of resin, respectively. Separation of the above-mentioned ions from nickel, gold and mercury ions (Pd(II)-Ni(II); Pt(IV)-Au(III); Pt(IV)-Ni(II); Pd(II)- Pt(IV)-Ni(II); Pt(IV)- Au(III)-Hg(II)) was conducted using various eluants 0.1 M HCl + 1% (NH2)2CS (elution of Pd(II)), 0.1 M HCl + 5 % (NH2)2CS (elution of Pt(IV)), 0.2 M CH3COOH (elution of Ni(II)), 5 M HCl + 1 M HNO3 (elution of Au(III)) and 0.5 M HNO3 + 2 % NH4NO3 (elution of Hg(II)).

Modification of the commercially available polyacrylate matrix Diaion HP-2MG with dithi‐ zone resulted in the preparation of the selective sorbent towards Pd(II) and Pt(IV) ions. Chwastowska et al. [51] used the above-mentioned sorbent for removal of Pd(II) and Pt(IV) ions from the environmental samples, among others, from road dusts, soil and grass collected from fast traffic routes. After proper preparation, among others, drying (673 K, 1 h) and digestion in *aqua regia*, the geological samples were analyzed using the GF AAS technique. The detection limit (LOD) for the determined metal ions was 1 ng/g for Pt(IV) and 0.2 ng/g for Pd(II). Metal ions desorption was run in two ways: using thiourea solution (possibility of determination of both elements in the eluant by the GFAAS technique) and concentrated HNO3 solution (possibility of directed determination of only Pd(II) ions in the eluant). The obtained ion exchange capacity towards both metal ions was about 0.16 mmol/g of resin.

Chelating resin formed by immobilization of sulfonated dithizone on the anion exchanger Amberlite IRA-400 was applied in concentration of heavy metal ions, i.e. Pd(II), Ni(II), Co(II), Cu(II) and Pb(II) in the water samples collected in Japan. The first four elements were deter‐ mined by the GFAAS technique but Pb(II) by HGAAS. The affinity series of the studied ions towards the present resin is as follows: Pd(II) > Cu(II) > Co(II) > Pb(II) > Ni(II) [52].
