Selective Extraction of Precious Metal from Automotive Catalyst Residue by Thiacalix[6]arene Derivatives

Two new thiacalix [6] arene (TC6A) derivatives modified at the lower rims, which are TC6A-COOCH3 (1) and TC6A-COOC2H5 (2), respectively, were synthesized. The metal extraction properties of TC4A, TC6A, 1 and 2 from automotive catalyst residue solution containing platinum-group metal cations have been investigated. TC6A shows the highest extraction capability for Pd cation with higher selectivity. On the other hand, 1 shows the remarkable higher extraction ability for Zr cation between metal cations examined.