Cu-BTC derived CuO and CuO/Cu2O composite: an efficient adsorption material to iodide ions

The copper benzene tricarboxylic acid (Cu-BTC) cannot be used as an adsorbent in water due to hydrophilicity. However, the calcination process can destroy the benzene ring structure to lose hydrophilicity and retains carbon structure skeleton. The CuO composite and CuO/Cu2O composite based on cubical Cu-BTC (C-Cu-BTC) and dodecahedral Cu-BTC (D-Cu-BTC) are successfully manufactured to absorb radioactive iodine ion from water. Before and after calcination, the SEM and XRD were used to characterize the changes of morphology and material structure. The adsorption experiment for iodine ion showed that their saturated adsorption capacities can reach 28.64 mg g(-1) (for C-CuO), 49.63 mg g(-1) (for D-CuO), 49.84 mg g(-1) (for C-CuO/Cu2O) and 91.91 mg g(-1) (for D-CuO/Cu2O), respectively. The iodine ion adsorption of adsorbent is an exothermic reaction as shown thermodynamic curves. Through results of adsorption kinetics it is proved that the iodide ion adsorption of CuO composite is physical adsorption and the iodide ion adsorption of CuO/Cu2O composite is chemical adsorption. Compared with CuO composite, CuO/Cu2O composite had better absorption capacity for iodide ions. Furthermore, the interference of common ion on iodide absorption has also been studied. The different types of ion, such as Cl-, SO4 (2-) and CO3 (2-), have effects on the iodine ions absorption capacity for two types of adsorbent. These ions have a slightly effect on iodine ions adsorption of CuO composite. However, these ions have greater influences on iodine ions absorption capacity of the CuO/Cu2O composite. The biggest influence is CO3 (2-), and the CO3 (2-) reduces the adsorption capacity by 44% iodine ion absorption capacity for the CuO/Cu2O composite.