Synthesis of a new chitosan-p-tert-butylcalix[4]arene polymer as adsorbent for toxic mercury ion

In this paper, we have synthesized a novel chitosan-p-tert-butylcalix[4]arene polymer (CCP) as a highly efficient adsorbent for mercury ion (Hg(2+)) removal from water. In fact, a lower rim diamine derivative of p-tert-butylcalix[4]arene has been cross-linked with chitosan chain by carbonyl diimidazole (CDI) as the linker. CDI forms a urea linkage between calix[4]arene diamine derivative and amine groups of the chitosan polymeric chain. The structure and properties of the new polymer were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscope. Also, the adsorption capacity of CCP was studied towards Hg(2+) in aqueous medium by inductively coupled plasma-optical emission spectrometry. Interestingly, the results showed a considerable adsorption capacity for CCP in comparison with chitosan. Therefore, CCP can be introduced as a promising adsorbent for the elimination of Hg(2+) from wastewaters. Moreover, because of the conformity of adsorption kinetic with pseudo-second-order kinetic models, it can be concluded that chemical adsorption has an important role between functional groups on CCP polymer and Hg(2+) ions. In addition, according to Freundlich isotherm, the CCP surface was heterogeneous with different functional groups.