Use of polymer-free calixarene nanofibers in heavy metal extractions

Polymer free calix[4]arene nanofibers were prepared via new electrospinning method with metal ion adsorption capacity. Two different calix[4]arene derivatives (compound 2 and 3) containing amide functionalities were used in this study, which were fully characterized by HNMR, FTIR and elemental analysis. Calix[4]arene nanofibers were analyzed with different surface characterization techniques such as SEM, TEM and AFM. SEM images of compound 2 and 3 nanofibers reveals there are non-bonded randomly grown fibers with average fiber diameter (AFD) was in the range of 237 to 307 nm for compoud 2 and 203–280 nm for compound. Adsorption study show the SEM-EDX mapping show adsorption of different metal ions (Hg⁺², Pb⁺², Cu⁺², Co⁺², Cd⁺², Ni⁺²) on nanofibers. The the adsorption study show Hg⁺², Pb⁺² and Cu⁺² adsorbed on nanofibers particularly at high pH. The maximum adsorption (98 %) was observed at pH 2 for Hg⁺².