Removal of low Sb(V) concentrations from mining wastewater using zeolitic imidazolate framework-8

Abstract

Wastewater generated during mining remains a significant source of antimony pollution, because techniques to quickly and efficiently remove antimony from wastewater do not exist. In this study, zeolitic imidazolate framework-8 (ZIF-8), a specific type of Metal Organic Frameworks (MOFs), was successfully used to remove trace levels (1 mg L−1) of Sb(V) with a high removal efficiency when the ZIF-8 dose was 0.5 g L−1. Scanning electron microscopy-X-ray energy dispersive spectrometry (SEM-EDS) indicated that Sb(V) was adsorbed onto the ZIF-8surface. The powder X-ray diffraction (XRD) pattern of ZIF-8 before and after adsorption of Sb(V) indicated that ZIF-8 was successfully synthesized, and remained structurally stable after Sb(V) was adsorbed. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) both suggested complexation of zinc on ZIF-8 with Sb(V), where removal of Sb(V) by ZIF-8 followed the Langmuir adsorption isotherm with pseudo second-order kinetics. Thus, a possible removal mechanism was proposed which involved Sb(V) complexing with the zinc hydroxyl groups on ZIF-8 (Zn–OH–Sb). Practically, ZIF-8, could remove 78.6% of Sb(V) from a mining wastewater containing 20 μg L−1 Sb(V). Furthermore, ZIF-8 could be remain active after repeated uses and could still remove and 42.3% of Sb(V) from wastewater containing 1 mg L−1) Sb(V) even when the ZIF-8 was reused five time. This indicated that ZIF-8 had potential for practical removal of Sb(V) from mining wastewaters.