**18. Copolymers modified with triisobutylphosphine sulfide**

Of special importance are the studies by Sanchez et al. [106–109] of building triisobutylphos‐ phine sulfide (TIBPS, Cyanex 471X) into the styrene-divinylbezene (4% DVB) copolymer in order to obtain a resin concentrating noble metal ions. Polymers are characterized by high selectivity towards Au(III) and Pd(II) ions (sorption from chloride solutions) as well as a lack of selectivity towards Ir(IV), Rh(III), Pt(IV) and Fe(III), Cu(II) or Ni(II) [106]. Based on the obtained values of sorption capacities (mmol/g) towards Pd(II) ions, the affinity series of the studied resins is as follows: Pd(II): Polymer 2 (0.07 mmol/g) < Polymer 1 (0.11 mmol/g) < Polymer 5 (0.17 mmol/g) < Polymer 3 (0.51 mmol/g) < Polymer 4 (0.72 mmol/g) [106].

With the temperature increase in the range 298–333K, there is observed the increase in Au(III) ions sorption compared to that of Pd(II) ions. The sodium nitrate(III) and thiourea solutions were used as eluents. Sodium nitrate(III) (2 M, pH 4.7) desorbs 75% of Pd(II) practically not washing out Au(III) from the ion exchanger, whereas thiourea (0.5 M, [H+ ] 0.1 M) enables almost quantitative recovery of gold(III) containing trace amounts of palladium (II) ions.
