Bentonite-decorated calix [4] arene: A new, promising hybrid material for heavy-metal removal

Abstract

There is global concern about the contamination of ground, river, and tap waters as well as soil contamination with heavy metal ions; these chemical species are known to not degrade and to cause severe health problems if ingested by humans and animals. Such environmental and health concerns necessitate the development of ultrasensitive sensors and high-capacity adsorbents. This study demonstrates for the first time the potential of organophilic bentonite combined with tetra(2-pyridylmethyl)amide calix [4] arene as a high-performance hybrid material for the removal of toxic heavy metals. After consecutive synthesis steps, the modified bentonites were thoroughly characterized by FT-IR, XRD, UV spectroscopy, and TEM. In particular, the XRD analysis showed strong supporting evidence for intercalation in the clay following each modification step. The salient feature of the newly prepared hybrid material is its high extraction capacity for Cd(II) and Zn(II) metals, as determined by atomic absorption spectrometry and UV spectrometry. Different preparation methods, with respect to the quantity of the added cationic surfactant, were investigated to determine the optimal conditions for synthesis. The extraction percentage for the as-prepared hybrid material was measured to be as high as 97.4% and 94.2% for Cd(II) and Zn(II), respectively.