Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Research paper Bentonite-decorated calix [4] arene: A new, promising hybrid material for heavy-metal removal Khouloud Jlassi a, ⁎ , Rym Abidi b , Memia Benna c , Mohamed M. Chehimi d, ⁎ , Peter Kasak a , Igor Krupa e, ⁎ a Center for Advanced Materials, Qatar University, PO Box 2713, Doha, Qatar b Laboratory of Applied Chemistry and Natural Substances Resources and Environment (LACReSNE), Faculty of Sciences at Bizerte, 7021 Zarzouna-Bizerte, Tunisia c ISSTE, Higher Institute of Environmental Science and Technology, 2050 Borj Cedria, Tunisia d Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086, CNRS, F-75013 Paris, France e QAPCO Polymer Chair, Center for Advanced Materials, Qatar University, PO Box 2713, Doha, Qatar ARTICLE INFO Keywords: Bentonite Calixarene Surfactant New hybrid adsorptive materials Cd (II) and Zn(II) extraction 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 ul- trasensitive 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 hy- brid 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 con- ditions 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. 1. Introduction Heavy metals can cause serious environmental problems due to their abundant use and toxicity. Indeed, high amounts of heavy metals are used in many industries, including tanneries, electroplating, pesti- cides, phosphate fertilizers, mining, and batteries(Halim et al., 2003; Liu et al., 2018). Once introduced into the environment, heavy metal pollution of both surface and ground waters poses a serious threat be- cause of the metal motility and solubility, which can represent serious risks to the environment and human health (Balasubramanian et al., 2009; Chen et al., 2018). Among all heavy metal water pollutants, cadmium and zinc heavy metals have received increased attention be- cause of their hazardous effect on humans. Cadmium may cause kidney damage and renal disorder (Godt et al., 2006), while zinc can cause abnormal pregnancy and retardation of children's growth(Galbeiro et al., 2014). To remove zinc and cadmium from aqueous solutions, several methods and techniques have been proposed(Uddin, 2017); chemical precipitation, evaporation, adsorption, ion exchange, elec- trochemical treatment, and membrane filtration technologies(Uddin, 2017). Among all these techniques, adsorption is considered as the most efficient and most cost-effective method to remove low metal con- centrations(Khan et al., 2014; Rao et al., 2015). Many types of ad- sorbent materials have been tested for zinc and cadmium ion uptake, such as clay(Hamid et al., 2017; Refaey et al., 2017), carbon nanotubes (Tofighy and Mohammadi, 2012), calixarenes(Sliwa and Deska, 2008), polymers(Liu et al., 2017), and zeolites (Adinehvand et al., 2016). Bentonite can be used as advantageous absorbent for water treat- ment(Mo et al., 2017), compared to commercial adsorbents; because of their abundance(Bergaya and Lagaly, 2006; Bouazizi et al., 2016), low cost(Hamid et al., 2017) and high cation exchange capacity(Heller- Kallai, 2006), which is responsible for the hydration and swelling of the absorbent(Sidhoum et al., 2013). The uptake of trace heavy metals by bentonite requires complex adsorption mechanisms involving direct bonding between metal cations and the surface of the clay, surface https://doi.org/10.1016/j.clay.2018.04.005 Received 12 December 2017; Received in revised form 3 April 2018; Accepted 4 April 2018 ⁎ Corresponding authors. E-mail addresses: Khouloud.jlassi@qu.edu.qa (K. Jlassi), chehimi@icmpe.cnrs.fr (M.M. Chehimi), igor.krupa@qu.edu.qa (I. Krupa). Applied Clay Science 161 (2018) 15–22 0169-1317/ © 2018 Published by Elsevier B.V. T