Bifunctional Co3O4-La2O2CO3@C derived from MOFs for peroxymonosulfate activation to degrade roxarsone and simultaneous removal of released inorganic arsenic from water

In this study, a novel Co3O4-La2O2CO3@C composite was fabricated via the calcination of Co-La bimetallic MOFs at 500 °C, and was employed to efficiently activate peroxymonosulfate (PMS) for simultaneous oxidation of roxarsone (ROX) and adsorption of concomitant inorganic arsenic. Approximately 100% of ROX (50 μmol L−1) was degraded by PMS (0.5 mmol L−1) activated with Co3O4-La2O2CO3@C (0.2 g L−1) at initial pH 6 within 10 min. Meanwhile, the produced inorganic arsenic was almost completely adsorbed within 90 min. The maximum adsorption capacity of As(V) by Co3O4-La2O2CO3@C was determined to be high up to 275.4 mg g−1. Co3O4-La2O2CO3@C also exhibited superior stability. During 6 rounds, the degradation efficiency of ROX and the removal efficiency of the total As maintained almost 100% and more than 97%, respectively. SO4− and OH were confirmed to be the reactive oxygen species (ROS) in charge of the degradation of ROX and the conversion of As(III) to As(V). The investigation of the adsorption mechanism revealed that the As species were combined with La species via ligand and anion exchange, resulting in the formation of La-O-As bond. Furthermore, the practical application potential of Co3O4-La2O2CO3@C in the ROX degradation and the in-situ adsorption of the released arsenic were further evaluated in a continuous flow column reactor. The Co3O4-La2O2CO3@C composite as catalyst and adsorbent may offer a feasible strategy for the implementation of organoarsenic degradation and produced inorganic arsenic adsorption.