SYNTHESIS AND APPLICATION OF LONG-CHAIN CARBOXYLATE CROWN-ETHER IONOPHORES FOR TRANSPORT OF METAL-CATIONS

Alkyl-substituted sym-dibenzo-16-crown-5-oxyacetic acid and sym-dibenzo-16-crown-5-oxydodecanic acid were synthesized and applied as ion transport carriers in liquid and film membranes. Increasing crown-ether lipophilicity decreased acid dissociation constants and solubilities of crown-ether carboxylic acids in water but enhanced the solubility and transport ability of the carboxylic anion-K+ complex through a liquid organic (CH2Cl2) membrane. Transport phenomena of the cations alkali-metal ions, alkaline-earth metal ions and transition-metal ions through liquid membranes based on these crown-ether carriers were investigated. Effects of anions, crown-ethers and pH on ion transport are discussed. A mechanism of ion transport through a crown-ether membrane is proposed to include [OH-] and [H+] in both source and target layers. Ion transport through a polymer/crown-ether film membrane was more efficient than through a liquid membrane.