Enhanced degradation of rhodamine B by UV/Co3O4@BC/PMS system: Performance and mechanism

Abstract

The degradation of rhodamine B (RhB), a commonly used dye in the textile industry, is a concern in dye wastewater treatment. Advanced oxidation technology using Peroxymonosulfate (PMS) shows promise due to its highly asymmetry molecular structure. To enhance RhB removal efficiency, a novel catalyst, called Co₃O₄@BC, was developed. This catalyst consists of cobalt oxide (Co₃O₄) loaded onto biochar (BC). Additionally, a UV/Co₃O₄@BC/PMS system was developed. The photocatalytic degradation performance of RhB by this system was investigated. With the addition of only 20 mg·L⁻¹ of Co₃O₄@BC, a degradation rate of 99.8 % for RhB was achieved in the system within 25 min, a 56 % improvement compared to the system without Co₃O₄@BC. Additionally, when the concentration of peroxymonosulfate (PMS) was increased from 0.02 g·L⁻¹ to 0.4 g·L⁻¹, the degradation rate increased by 42.5 %. As the concentration of Co₃O₄@BC increased from 5 mg·L⁻¹ to 20 mg·L⁻¹, the degradation rate improved by 15.6 %. When the UV radiation intensity increased from 10 W·m⁻² to 120 W·m⁻², the degradation rate increased by only 3.3 %. It was found that Co₃O₄@BC had an excellent ability to activate PMS to generate active species, with the contribution of reactive oxygen species in the order of ¹O₂>SO₄^•->•OH. The leaching concentration of cobalt ions in UV/Co₃O₄@BC/PMS system was 121.1 μg·L⁻¹, which still meets the specified limit by the Environmental Quality Standard for Surface Water (Gb3838-2022). It well below the specified limit of 1.0 mg·L⁻¹. Therefore, the use of the UV/Co₃O₄@BC/PMS system is practical and economically feasible from both economic and environmental perspectives.