Recognizing the relevance of non-radical peroxymonosulfate activation by co-doped Fe metal-organic framework for the high-efficient degradation of acetaminophen: Role of singlet oxygen and the enhancement of redox cycle

Abstract

A bimetallic MOF derivative consisting of Fe and Co (Fe/Co2-MOF) by Co-doping MIL-101(Fe) was successfully synthesized for peroxymonosulfate (PMS) activation in acetaminophen (N-Acetyl-Para-Amino-Phenol, APAP) degradation. The presence of Co significantly accelerated the transfer of electrons due to the synergistic effect between Fe and Co bimetallic sites. Specifically, the reaction rate constant of APAP in the Fe/Co2-MOF + PMS system was three orders of magnitude higher than that of MIL-101(Fe) alone and 90 times higher than that of the MIL-101(Fe) + PMS system, respectively. At room temperature, 100 % of the APAP was degraded in 15 min with a Fe/Co2-MOF concentration of 0.05 g/L and a PMS concentration of 0.8 mmol/L across a wide pH range from 3 to 9. High-valence metal species (CoIV and FeIV) and electron transfer-dominated nonradical processes were responsible for the APAP degradation. Although singlet oxygen (1O2) was identified as the main active species in our study, the relative contribution of 1O2 was negligible. The catalytic performance was particularly notable in the practical implementation of hospital sewage treatment. However, it is still urgent to seek ways to relieve cobalt leaching of Fe/Co2-MOF. This strategy of Co-doping provides a clear illustration of modulating MIL-101(Fe) ultimately maximize their catalytic efficiency in PMS activation for water purification.