Degradation of 4-chlorophenol using MnOOH and γ-MnOOH nanomaterials as porous catalyst: Performance, synergistic mechanism, and effect of co-existing anions
School of Engineering
Isfahan University of Medical Sciences (Project No.: 1400410 Ethic code: IR.MUI.RESEARCH.REC.1400.444 and Project No.: 1400476; Ethic code: IR.MUI.RESEARCH.REC.1400.522)
Transition metal catalysts have been proven to be a highly-potent catalyst for peroxymonosulfate (PMS) activation. The present work aimed to synthesizes the γ-MnOOH and MnOOH based on the one-pot hydrothermal method as PMS activators for efficient degradation of 4-chlorophenol (4 - CP). The effect of operational parameters including solution pH, γ-MnOOH and MnOOH dose, PMS dose, 4 - CP concentration, and also mixture media composition was elaborated. The results showed that the combination of MnOOH and γ-MnOOH with PMS noticeably creates a synergistic effect (SF) in 4 - CP degradation by both PMS/MnOOH and PMS/γ-MnOOH process, with a SF value of 48.14 and 97.42, respectively. In both systems, the removal of 4 -CP decreased in severely alkaline and acidic conditions, while no significant changes were observed in pH 5 to 9. Also, coexisting PO43ˉ significantly reduced the removal efficiency of both systems. In addition, the effect of humic acid (HA) as a classical scavenger was investigated and showed that presence of 4 mg/L HA reduced the removal efficiency of 4 - CP in the PMS/MnOOH process from 97.44 % to 79.3 %. The three consecutive use of both catalysts turned out that MnOOH has better stability than γ-MnOOH with lower Mn ions leaching. More importantly, quenching experiment showed that both non-radical (1O2 and [rad]O2 − ) and radical ([rad]SO4 − and [rad]OH) pathways are involved in 4-CP degradation and non-radical pathway was the dominant one in both systems.