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Faculty of Technology, University of Tuzla , Tuzla , Bosnia and Herzegovina
Faculty of Technology, University of Tuzla , Tuzla , Bosnia and Herzegovina
Faculty of Natural Sciences and Mathematics, University of Tuzla , Tuzla , Bosnia and Herzegovina
Considering the toxic properties of heavy metals and their effects on the environment, there is an
increasing interest in studying their interactions with different ligands and searching for
possibilities to remove those ions from the environment. Compared to other ligands, crown ethers
possess the highest selectivity as ligands for metal cations, due to their “macrocyclic effect”. In
this paper, interactions between Pb(II), Cd(II) ions and various crown ethers (18 crown-6, benzo-
18-crown-6, dibenzo-18-crown-6, dicyclohexane-18-crown-6 ether), were analyzed. The UV/VIS
spectrometric method was used to record absorption diagrams of "model systems" of varying
complexity. Cd(II) and Pb(II) ions were monitored using flame atomic absorption spectrometry.
In different organic solvents used (chloroform, dichloromethane), UV/VIS and FAAS
measurements showed that higher absorption intensity caused more stable complexes in the
membrane, complicating the release of ions. With the benzo-18-crown-6 ether as ligand, Pb(II)
ions released into the aqueous phase at a rate higher than 60%, compared with Cd(II) ions
released at a rate of 49%. In a model system containing a nonionic surfactant (TX-100), metal
ions interact more intensely with the membrane, and cation release is reduced in the aqueous
phase, indicating that the reverse micellar aggregates incorporate metal ions that result in higher
absorption intensities. According to the macrocycle selected, the presence of benzo- and
cyclohexyl groups (B18C6, DB18C6, DCH18C6) probably reduces interactions between
substituted macrocyclic ligands and metal cations, resulting in lower values of Pb(II) and Cd(II)
ions measured in the aqueous phase compared with a model system with 18 crown-6 ether.
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