An α-MnO₂nanotube used as a novel catalyst in ozonation: performance and the mechanism

Abstract

As a common monocomponent metal oxide, an a-MnO 2 nanotube was synthesized by a simple hydrothermal method and developed as an ozonation catalyst for the first time. a-MnO 2 nanotubes revealed excellent catalytic activity and stability for degradation of phenol in water. The strong interaction between ozone and a-MnO 2 in water was observed and confirmed as a critical step of catalysis. The IR analysis and the influence of phosphate showed that the surface hydroxyl groups and chemisorbed water acted as the active sites in promoting active oxygen species, while Lewis acid sites were confirmed as reactive centers for catalytic ozonation in the aqueous phase. The OH, O 2 À , *O 2 and *O were not mainly involved in the catalytic ozonation of phenol based on the corresponding experimental results. According to the X-ray photoelectron spectroscopy (XPS) results, in the presence of a-MnO 2 , electrons from the surface Mn(III) were responsible for the catalysis and the oxidation of lattice oxygen enhanced the reversion of Mn(IV) to Mn(III). The balance between Mn(III)/Mn(IV) and O(-II)/O(0) was the primary factor for the catalytic performance of a-MnO 2 .

Catalytic ozonation of 4-nitrophenol over an mesoporous α-MnO2 with resistance to leaching

“…It was reported that ozone molecule attached with ␣-MnO 2 on its active sites detaches with another ozone molecule to produce oxygen and superoxide free radicals [37,38]. The ozone decomposed to oxygenated species, and superoxide radicals formed in this process was responsible for the efficient degradation of 4-NP [35,36].…”

“…8). It was already reported that in the catalytic ozonation of phenols, hydroxyl radical is not the main active oxidant in 4-NP degradation [35]. Moreover, p-benzoquinone (p-BQ) was widely applied to quench superoxide radicals (O 2 −• ) to study its influence to the organics degradation [36,37].…”

Efficient Catalytic Ozonation over Reduced Graphene Oxide for p-Hydroxylbenzoic Acid (PHBA) Destruction: Active Site and Mechanism

“…6). Owing to the instantaneous reaction with hydroxyl radicals (3.8×10 8 -7.6×10 8 M -1 s -1 ) and the stagnated reaction with ozone (3 ×10 -5 M -1 s -1 ), tert-butanol (t-BA) was suggested to be the effective scavenger for •OH in the catalytic ozonation process 41. Addition of 12 mM t-BA brought no inhibition effect to the catalytic ozonation reaction, indicating •OH were not the reactive species for this catalytic ozonation system, which confirms the ESR results.The contribution of •O 2 -for PHBA degradation was determined using p-benzoquinone (p-BQ) as the quenching agent [42][43].…”

Facile one pot synthesis and Li-cycling properties of MnO2

“…In contrast, MnO 2 prepared by MnSO 4 The low capacity value of the compound could mainly be attributed to its agglomerated spherical particle morphology.…”