Co-Mn layered double hydroxide as an effective heterogeneous catalyst for degradation of organic dyes by activation of peroxymonosulfate.

In this study, Co-Mn layered double hydroxide (Co-Mn LDH) was synthesized, characterized, and tested as heterogeneous catalyst to activate peroxymonosulfate (PMS) for degradation of organic dyes. The results of characterization showed that Co-Mn LDH had high purity, uniform morphology and large specific surface area (49.9379 m2 /g). The degradation experiments demonstrated that five different dyes with the concentration of 50 mg/L could be decomposed completely within 240 s using only 0.025 g/L of Co-Mn LDH and 0.1 g/L of PMS. Moreover, Co-Mn LDH/PMS system presented the highest decomposition efficiency for acid orange G (AOG) compared with other related materials under the same condition. Further investigation found that Co-Mn LDH/PMS system had an excellent adaptability in a wide pH range (from 3 to 10), and the best efficiency was achieved when the solution was natural (pH = 6.87). The mineralization of AOG was assessed by Total Organic Carbon (TOC), and 52.2% of TOC was removed. Meanwhile, the good reusability and high stability of Co-Mn LDH were demonstrated by recycle tests and ion-leaching tests. The catalytic mechanism was explored through quenching tests as well as X-ray photoelectron spectroscopy (XPS) analysis. Finally, all of the results suggested that Co-Mn LDH/PMS system with high stability and decomposition efficiency was suitable for the remediation of organic dyes in wastewater.