Cobalt-doped MIL-88A anchored on a cellulose filter paper: a recyclable flow-through catalyst for peroxymonosulfate activation during the degradation of organic dyes†

To demonstrate the effective use of a heterogeneous catalyst for the treatment of wastewater in a flowing state, we synthesized a metal–organic framework, MIL-88A, in situ on a filter paper. A cobalt doping modification yielded a composite catalyst, Co-doped MIL-88A, on a filter paper (Co-M88A-FP), which was then used to activate peroxymonosulfate (PMS). Characterizations of Co-M88A-FP catalyst revealed that the morphology and structure of MIL-88A did not change when synthesized on the filter paper; however, the surface of MIL-88A became rough and amorphous after Co doping. The Co-M88A-FP/PMS catalytic system exhibited highly efficient degradation of rhodamine B (a test pollutant dye) and appeared to be adaptable to continuous flow conditions. XPS, EPR and radical scavenging test results indicated that singlet oxygen was the reactive species that mainly contributed to the degradation of the test pollutant dye. Therefore, it was revealed that electron-rich substances with low steric hindrance would be degraded more quickly by the Co-M88A-FP/PMS system.