Calixarene-Composited Host–Guest Membranes Applied for Heavy Metal Ion Adsorbents

Abstract

Calixarene host–guest membranes were prepared with hybridization of calixarene and poly(ethersulfone) (PES) by phase inversion process. Herein, the calixarene, 2,18,14,20-tetra(3-hydroxy-4-methoxybenzyl)calix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, was successfully synthesized from resorcinol and vanillin. The phase inversion process was carried out in phase change of the solution of N-methyl-2-pyrrolidone containing both PES and the vanillin calixarene to solid membrane in water coagulation. The composited membranes having different loading amounts of the vanillin calixarene were prepared with 10, 25, 50 and 60 wt% loading. The observation of SEM pictures indicated porous morphology in the PES scaffold. The porous morphology in the cross section of the membrane caused high water content in the range of 371–375 %, meaning easy accessibility of aqueous solution in the membrane. The adsorption behavior of aqueous heavy metal ions: Pb(II), Ni(II), Cu(II) and Cd(II), was examined for the composited membranes containing 10, 25, 50 and 60 wt% of the calixarene host. It was evidenced that each composited membrane adsorbed effectively Pb2+ ion, as the solution was permeated at 4.0 × 104 Pa applied pressure. When the calixarene was loaded at 50 and 60 wt% in the membranes, the Pb2+ capacity was 13 and 15 μmol/g−membrane, respectively, for the batch experiment. In addition, when the quarterly mixture of the aqueous heavy metal ions was permeated through the membrane, the composited membrane having 50 and 60 wt% of the calixarene loading maintained high retention of the Pb2+ ion.