Application of a Newly Synthesized Calixarene in Metal Ions Extraction

A new ligand, 25,27‐bis (3‐(4′‐biphenyl‐4‐hydroxy carboxylic acid) propoxy)‐26,28‐dihydroxy‐5,11,17‐tetra(tert‐butyl)calix[4]arene (CBiPh), a derivative of p‐tert‐butylcalix[4]arene (Cax) that was functionalized at the lower rim with biphenyl carboxylic acid has been synthesized. The compound was characterized by using NMR, FT‐IR, and elemental analysis. The 1H and 13C NMR studies indicate that this new macrocycle (CBiPh) preferably adopts a cone structure. Sorbent materials prepared by immobilizing the ligands into silica sol–gel matrix (referred to as calixarene immobilized with sorbent (Cax‐SG) and CBiPh immobilized with sorbent (CBiPh‐SG)) were studied for their competitive sorption characteristic of a mixture of twelve metal ions (Mg2+, Li+, Cd2+, Co2+, Pb2+, Ca2+, Ba2+, Rb+, Ag+, Cs+, Sr2+, and Hg2+). Under the adopted conditions, both sorbents exhibited highest selectivity toward Ag+ (70% for Cax‐SG and 85% CBiPh‐SG), followed by Hg2+ (60% for Cax‐SG and 65% CBiPh‐SG) while the other metal ions were negligibly extracted (