Synergistic effect and interaction of nano zero-valent iron and Al13 in carbamazepine removal

Abstract

In this study, a multi-functional coagulant with both coagulation and oxidation function was obtained by pre-doped nano zero-valent iron (nZVI) with Al13 for the removal of the typical emerging contaminants Carbamazepine (CBZ). At the optimal doped dosage of nZVI, the pre-doped agent (Al13@nZVI) showed 23% improvement of the maximum removal rate of Carbamazepine compared with Al13 under pH 7. It was found that Al13@nZVI could produce H2O2 in situ at pH 2 to pH 8, especially under acid conditions. By the analysis of FT-IR, it could be found that the groups of C-N, benzene, and CO were disappeared after treatment. Instead, -NO2 was found in treated water which indicated the breakage and oxidation of amine group. Thus, the effects of pH on Al13 and Al13@nZVI were different. Al13 will undergo depolymerization and decompose into small polymers with low positive charge density with the increasing of pH, while, because of Al13@nZVI having oxidation ability, effect of pH on Al13@nZVI was not that significant. The influence of Humic acid (HA) with different concentration on CBZ removal were analyzed. The system with 2 mg/L HA showed better removal performance of both CBZ and total dissolved organic carbon (DOC) compared to the system with 1 mg/L HA, which may because of the increase of the necessary nuclei for the flocs formation, as well as the bridging function by the long chain structure of HA. Moreover, Al13@nZVI was found improved the removal efficiency of organic matters with molecular weight about 1500–2000 Da compared to Al13.