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

In this paper, we have synthesized a novel chitosan--butylcalix[4]arene polymer (CCP) as a highly efficient adsorbent for mercury ion (Hg) removal from water. In fact, a lower rim diamine derivative of -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 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 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 ions. In addition, according to Freundlich isotherm, the CCP surface was heterogeneous with different functional groups.