3D sponge-based cobalt-lanthanum difunctional composite (3D sponge@Co-La) promotes peroxymonosulfate activation for efficient removal of roxarsone and released arsenic: An easy-to-use and highly recyclable catalyst for wastewater remediation

Abstract

Cobalt-lanthanum bimetallic oxide (tricobalt tetraoxide-lanthanum oxocarbonate (Co3O4-La2O2CO3)) is a promising environmental functional material for the remediation of organic-arsenic wastewater via simultaneous degradation and adsorption. However, the existing nanomaterials are mostly powder-like, which are prone to reunion and inactivation and difficult to separate and recycle. To solve the awkward problems, in this study, an efficient, easy-to-use and highly recyclable 3D sponge-based cobalt-lanthanum composite (3D sponge@Co-La) was fabricated for the first time by coating powder-like Co3O4-La2O2CO3 onto a blocky sponge with the assistance of chitosan. The results demonstrated that over 97% degradation of 50 μmol L−1 roxarsone (ROX) and almost complete adsorption of the released inorganic arsenic were achieved in the system of 3D sponge@Co-La/peroxymonosulfate (PMS) within 20 and 45 min, respectively. The maximum adsorption capacity of 3D sponge@Co-La toward As(V) was up to 158.73 mg g−1. Besides, the removal efficiencies of ROX in well water and lake water were 100% and 92.8%, respectively. The mechanism investigation revealed that the generated sulfate radicals (SO4•−), hydroxyl radicals (•OH) and singlet oxygen (1O2) were responsible for the oxidation of ROX and the conversion of As(III) to As(V). 3D sponge@Co-La also exhibited excellent reusability and stability, and even in the fourth cycle test, the removal efficiencies of ROX and secondary inorganic arsenic maintained almost 100% after regeneration. In short, this study not only provides an easy-to-use and highly recyclable catalyst for eliminating organic-arsenic from water, but also addresses the disadvantages of existing powder-like catalysts, exhibiting an important practical application potential.