**12. Ion exchangers of functional hydrazone and hydrazine groups**

Modification of the macroporous copolymer ACR/ST/DVB (where ACR – acrolein, ST – styrene, DVB – divinylobenzene) using isonicotinic acid hydrazide and hydrazine hydrate results in preparation of new chelating ion exchangers: P-NHZ and P-THZN, respectively [85– 87]. These resins exhibited high selectivity towards noble metal ions which allows their separation from common metal ions. The maximal values of sorption capacities obtained in 0.1 M HCl are 3.77 mmol Au(III)/g, 1 mmol Pt(IV)/g, 0.79 mmol Pd(II)/g, 0.72 mmol Ir(III)/g, 0.51 mmol Ru(III)/g, 0.39 mmol Rh(III)/g for the resin P-NHZ and 4.2 mmol Au(III)/g, 1.36 mmol Pd(II)/g, 0.5 mmol Pt(IV)/g, 0.4 mmol Ir(III)/g, 0.31 mmol Rh(III)/g, 0.29 mmol Ru(III)/g for the resin P-THZN, whereas the sorption capacities for common metal ions (Cu(II), Fe(III), Co(II), Ni(II), Cr(III), Zn(II), Mn(II) and Al(III)) are small, in the range 0–0.13 mmol/g for the resin P-NHZ and 0.03–0.32 mmol/g for the resin P-THZD. Desorption of the above-mentioned ions from the P-NHZ and P-THZN was achieved using a 5% thiourea solution in 0.1 M HCl. Quantitative desorption was possible only in the case of Au(III) and Pd(II) from the resin P-NHZ. Another advantage of the ion exchanger P-NHZ over P-THZN is fast kinetics of sorption and easy elution of adsorbed ions [87].

Ge et al. [86] proved high selectivity of the P-NHZ resin towards noble metal ions and possibility of its exploitation for separation and concentration of trace amounts of Pd(II) and Pt(IV) contained in road dust samples. Sorption of the above-mentioned ions on the P-NHZ resin can be conducted also from the HNO3, HF and H3BO3 solutions of the concentration 0.08-1.2 M.
