Magnetic Fe3O4/MIL-101 composite as a robust adsorbent for removal of p-arsanilic acid and roxarsenic in the aqueous solution

Abstract

The p-arsanilic acid (p-ASA) and roxarsenic (ROX) are typical organic arsenic compounds (OACs), which can be evolved into highly poisonous inorganic arsenic species in the aqueous solution. Herein, a magnetic MOFs-based composite of Fe3O4/MIL-101 was successfully obtained by a stepwise solvothermal method and further used in the adsorption of p-ASA and ROX. The structural and physicochemical characteristics of Fe3O4/MIL-101 were firstly investigated in detail. It was found that Fe3O4 microspheres were evenly embedded on the polyhedral MIL-101 surface after the solvothermal process and exhibited a strong superparamagnetic property. After adsorption, a simple external magnetic field can be used to quickly separate the composite from the aqueous solution. The adsorption experiments indicated that the composite is an excellent adsorbent with maximum adsorption capacities of 683.44 and 946.57 mg·g−1 for p-ASA and ROX, respectively. In addition, the effects of composite dosage, initial pH and co-existing anions on the adsorption efficiency were investigated. The main adsorption mechanism consists of the existence of hydrogen bonding, π-π stacking and As-O-Fe coordination between Fe3O4/MIL-101 composite and OACs. We believe that this study would be very meaningful to promote the application of magnetic MOFs based composites for effective adsorption for OACs in the environmental remediation.