Magnetic zeolitic imidazolate frameworks composite as an efficient adsorbent for arsenic removal from aqueous solution.

In this study, magnetic zeolitic imidazolate frameworks (ZIF-8) was prepared by a one-step method, where its evolution involved the coprecipitation reactions concomitant with the self-assembly reactions. Structural characterizations indicated that magnetic ZIF-8 showed irregular polyhedral morphology with a large specific surface area (696.5 m/g) and saturation magnetization (4.31 emu/g). The as-prepared magnetic ZIF-8 enhanced the adsorption performance of As(III) and As(V), compared with bare FeO. The pseudo second-order kinetic model (R = 0.9627 and 0.9893 for As(III) and As(V), respectively) and the Langmuir model (R = 0.9441 for As(III) and 0.9851 for As(V)) can fit the adsorption process well, confirming the nature of single-layer homogeneous chemisorption. The adsorption capacity was 30.87 and 17.51 mg/g, and their corresponding values of PC were 2.664 and 1.286 L/g, for As(III) and As(V), respectively. Solution pH showed an adverse effect on As(V) adsorption whereas no obvious effect on As(III). The ionic strength and coexisting ions had not obvious influence on adsorption of As(III) and As(V). The adsorption mechanism was explored and discussed based on the detailed spectroscopy analysis. This adsorbent can be recovered magnetically after use, which is promising for the practical application.