Novel thiourea-modified magnetic ion-imprinted chitosan/TiO2 composite for simultaneous removal of cadmium and 2,4-dichlorophenol

In the present study, a novel type of adsorbent called thiourea-modified magnetic ion-imprinted chitosan/TiO2 (MICT) was prepared with the purpose of improving its feature as a composite adsorbent. The simultaneous cadmium ion adsorption and 2,4-dichlorophenol (2,4-DCP) degradation by this novel composite adsorbent were investigated. The obtained results showed that the optimum pH values for adsorption of cadmium and degradation of 2,4-DCP were approximately 6.0-7.0. The kinetics study demonstrated that the adsorption process proceeded according to the pseudo-second-order model. The maximum adsorption capacity for cadmium was 256.41 mg/g according to the Langmuir model. The intermediate products of the reaction consisted of 4-chlorophenol, 1,4-benzoquinone, phenol, cyclohexanol, and some other trace substances, as identified by gas chromatography/mass spectroscopy (GC/MS) technique. The sequential degradation process was proposed, including reductive dechlorination or reaction with hydroxyl radicals based on the products identified. The used sorbent was reusable after regenerated through desorption, and the adsorption and degradation capacities were barely affected after five cycles. (C) 2012 Published by Elsevier B.V.