Rapid oxidation and deep As(III) purification from water using gelatin-supported iron-based metal-organic framework aerogel coupled with H2O2: Preparation, performance and mechanism

Abstract

Metal-organic frameworks (MOFs) are considered a reliable adsorbent for controlling arsenic contamination. However, developing rapid and efficient MOF adsorbents with the capability of easy recovery is still challenging. Herein, we prepared a three-dimensional porous MIL-88A-Fe/gelatin aerogel (PMGA) with macroscopic size and coupled it with H2O2 to fabricate a heterogeneous catalytic oxidation adsorption system to remove As(III) in water. The green synthesis strategy of this catalyst by foaming and low-temperature carbonization not only avoided the use of toxic chemical crosslinkers but also endowed PMGA with a rich hierarchical porous structure and exposed more active sites. Thus, the PMGA/H2O2 system was able to reduce the concentration of As(III) from 1106 to below 10 µg/L and simultaneously realize the complete oxidation of As(III) to As(V) in only 120 min. Meanwhile, the system exhibited an excellent saturation adsorption capacity (24.863 mg/g) for As(III), superior to most similar bio-based or iron-based materials. Quenching experiments, EPR and DFT calculations showed that the active species (surface •OOH and surface •OH) generated by the Fenton-like interaction between the exposed (100) facet of MIL-88A-Fe in PMGA and H2O2 played an essential role in promoting the oxidative removal of As(III). Moreover, the reaction system could work efficiently for As(III) in a wide pH range and was hardly affected by other substances such as chlorides, sulfates, carbonates, silicates, and humic acids. Simultaneously, the fixed bed column filled with PMGA could stably and continuously treat As(III) in groundwater. Therefore, this study not only broadens the horizon for the development and design of 3D functional materials but also provides a new strategy in water purification to eliminate arsenic pollutants using Fe-MOF aerogels.