Preparation of novel ZnO-NP@Zn-MOF-74 composites for simultaneous removal of copper and tetracycline from aqueous solution

Abstract

• ZnO-NP@Zn-MOF-74 was prepared using layered porous ZnO as the zinc sources. • ZnO-NP@Zn-MOF-74 showed a smaller framework structure and stronger affinities. • The loaded ZnO nanoparticles on ZnO-NP@Zn-MOF-74 provided more function groups. • The formation of ZnO-NP@Zn-MOF-74-Cu-TC improved the removal of both TC and Cu. • ZnO-NP@Zn-MOF-74 had good ability for the simultaneous removal of Cu and TC. In this study, layered porous ZnO microspheres, instead of traditional zinc ions, were used to obtain a composite of nano-ZnO and a metal organic framework (Zn-MOF-74), namely ZnO-NP@Zn-MOF-74. Compared with the traditional Zn-MOF-74, the ZnO-NP@Zn-MOF-74 showed better removal performances for both copper (Cu) and tetracycline (TC) due to its smaller size and good affinities of the loaded nano-ZnO. Batch experiments showed that the simultaneous removal of Cu and TC by the ZnO-NP@Zn-MOF-74 was rapid and pH-dependent. The removal efficiencies of both Cu and TC increased rapidly during the first 10 min and could reach equilibriums within 2 h. The maximum sorption capacities of Cu and TC on the ZnO-NP@Zn-MOF-74 derived from the Langmuir model were 106.27 and 137.17 mg·g −1 , respectively. The removal mechanisms for Cu and TC involved surface complexation, π-π stacking, ion exchange, and electrostatic interaction. In addition, the formation of the ZnO-NP@Zn-MOF-74-Cu-TC complex on the surface of the ZnO-NP@Zn-MOF-74 improved the removal of both TC and Cu. Given the above results, the ZnO-NP@Zn-MOF-74 has great application prospects for the treatment of Cu and TC polluted water.