Efficient adsorption H3AsO4 and Cr(VI) from strongly acidic solutions by La-Zr bimetallic MOFs: Crystallinity role and mechanism

Abstract

Due to the non-degradable of heavy metal, adsorption has been extensively applied to abatement it. Most studies were focused on uptake metal ions via electrostatic attraction and ion exchange, and load molecule H3AsO4 from strongly acidic wastewater was still challenging. To solve the problem, bimetallic La–Zr MOFs was facilely fabricated in this work, and the fcu topology structure of La-Zr MOFs was remained well under the investigate crystallization time and crystallization temperature. However, the crystallinity of the obtained La-Zr MOFs was influenced by the synthesized factors. The obtained La–Zr MOFs was employed as adsorbent to removal Cr(VI) and As(V), and the performance was evaluated by the batch experiment. The result indicated that the adsorption performance of Cr(VI) and As(V) was positively correlated with the crystallinity, and the optimal sample was 1LaUN12. From the XPS characterization, it was found that H3AsO4 was successfully uptake over 1LaUN12 surface, and the maximum monolayer adsorption capacity was 83.40 mgH3AsO4/g via ligand exchange and coordination reactions with La−OH and Zr−OH. In addition, the sample 1LaUN12 also exhibited the excellent Cr(VI) load performance, and the maximum monolayer adsorption capacity of Cr(VI) was 222.5 mg/g. Above 40% Cr(VI) was reduced to Cr(III) by amino groups, and immobilized over the surface of 1LaUN12. Eventually, 1LaUN12 displayed a good structural stability in the acidic medium, which was in favor of removing Cr(VI) and As(V) efficiently from strongly acidic solutions.