A heterogeneous Co3O4–Bi2O3 composite catalyst for oxidative degradation of organic pollutants in the presence of peroxymonosulfate

Abstract

By using cobalt nitrate and bismuth nitrate as precursor salts and NaOH as a precipitation agent, Co₃O₄–Bi₂O₃ nanocomposite oxides (CBO) were prepared as a heterogeneous catalyst for the activation of peroxymonosulfate (PMS) by a conventional reverse co-precipitation method and post-calcination. The characterization with transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy and Raman spectroscopy demonstrated that there was a strong interaction between Bi and Co components in CBO. The presence of Bi increased the content of surface hydroxyl oxygen, which favored the formation of Co(II)–OH complexes that were vital for heterogeneous activation of PMS. CBO showed strong catalytic activity in the heterogeneous activation of PMS for degradation of organic pollutants such as methylene blue (MB), rhodamine B, phenol and 2,4-dichlorophenol. With the addition of 0.5 mmol L⁻¹ PMS, CBO produced fast and full degradation of MB (20 μmol L⁻¹) with the apparent rate constant of 0.36 min⁻¹, being 8.6 fold of that (0.042 min⁻¹) over nano-Co₃O₄. It decreased the cobalt leaching to 43 μg L⁻¹, being much less than that (158 μg L⁻¹) from Co₃O₄ under the same conditions. The effects of CBO loading, PMS concentration and calcination temperature on the degradation of MB and cobalt leaching were also investigated.