Experimental andmodeling of cadmiumions removal by chelating resins

摘要

Nowadays, the concerns regarding cadmium pollution increased steadily, due to its serious damages to the environment and human health. Consequently, stringent limits have been set for this heavymetal ion both in industrial and drinking water. Numerous traditional and unconventional methods were applied to reach these limits. In this paper, two phosphine oxide/phosphine oxide and thiourea chelating resins MPX-310 and MPX-317 produced by Magpie Polymers - Italmatch Chemicals, Italy were comparatively evaluated with a commercial thiourea chelating resin Lewatit (R) MonoPlus TP 214 produced by Lanxess regarding Cd(II) removal from aqueous synthetic solutions. The physicochemical properties of the resins were studied by FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TG-DSC) and X-ray Photoelectron Spectroscopy (XPS). Batch tests have been performed to assess the performance of these resins in Cd(II) removal. A value of 3-4 for pH and 600 min of contact time were determined as optimal parameters for the removal process. The experimental results also showed that the Lewatit (R) MonoPlus TP 214 has a higher removal capacity than MPX-317 and MPX-310 due to the presence of the thiourea and ion-exchange functional groups on the Lewatit (R) MonoPlus TP 214 backbone, compared with the presence of the phosphine oxide functional groups on the MPX-310 and thiourea and phosphine oxide on MPX-317. A monolayer adsorption on the homogenous adsorbent surface mechanism involved in Cd(II) removal was pointed out by the results regarding adsorption isotherms. The best fit of the pseudo-second kinetic model indicates that the sorption process goes through a mechanism that involves chemical reaction between Cd(II) and functional groups grafted on the resin's backbone. The chelating capacity of the tested resins showed that they are suitable for Cd(II) removal from aqueous synthetic solutions and industrial wastewater. (C) 2020 Elsevier B.V. All rights reserved.