Evolution of Singlet Oxygen by Activating Peroxydisulfate and Peroxymonosulfate: A Review

Abstract

Advanced oxidation processes (AOPs) based on peroxydisulfate (PDS) or peroxymonosulfate (PMS) activation have attracted much research attention in the last decade for the degradation of recalcitrant organic contaminants. Sulfate (SO4•−) and hydroxyl (•OH) radicals are most frequently generated from catalytic PDS/PMS decomposition by thermal, base, irradiation, transition metals and carbon materials. In addition, increasingly more recent studies have reported the involvement of singlet oxygen (1O2) during PDS/PMS-based AOPs. Typically, 1O2 can be produced either along with SO4•− and •OH or discovered as the dominant reactive oxygen species (ROSs) for pollutants degradation. This paper reviews recent advances in 1O2 generation during PDS/PMS activation. First, it introduces the basic chemistry of 1O2, its oxidation properties and detection methodologies. Furthermore, it elaborates different activation strategies/techniques, including homogeneous and heterogeneous systems, and discusses the possible reaction mechanisms to give an overview of the principle of 1O2 production by activating PDS/PMS. Moreover, although 1O2 has shown promising features such as high degradation selectivity and anti-interference capability, its production pathways and mechanisms remain controversial in the present literatures. Therefore, this study identifies the research gaps and proposes future perspectives in the aspects of novel catalysts and related mechanisms.

Effective hole conductivity in nitrogen-doped CVD-graphene by singlet oxygen treatment under photoactivation conditions

“…Thus, from a chemical standpoint, N-doped graphene is an appealing graphene type, because nitrogenous functionalities and, in particular, pyridine nitrogen can be a reactive center as well as activate a reactive center at the adjacent carbon atoms in the functionalized C-N bonds for additional post reaction like oxidation 26 , 27 . In addition, the presence of these N-functionalities in the graphene structure, besides changing the carrier density (i.e., doping), gives an interesting catalytic activity of the graphene surface, such as the well investigated activated generation of reactive oxygen species (ROS) 28 – 31 . Among these new “catalytic” capabilities, the production of singlet oxygen ( 1 O 2 ) by both (i) activating the dissociation of peroxydisulfate 28 and (ii) the photosensitize excitation of molecular oxygen 30 is of particular interest.…”

“…In addition, the presence of these N-functionalities in the graphene structure, besides changing the carrier density (i.e., doping), gives an interesting catalytic activity of the graphene surface, such as the well investigated activated generation of reactive oxygen species (ROS) 28 – 31 . Among these new “catalytic” capabilities, the production of singlet oxygen ( 1 O 2 ) by both (i) activating the dissociation of peroxydisulfate 28 and (ii) the photosensitize excitation of molecular oxygen 30 is of particular interest. In fact, singlet oxygen (also known as singlet delta oxygen 1 O 2 ( 1 Δg)), being a non-radical reactive oxidizing specie, does not intervene on the conjugated double bond as it happens for radical species (oxygen atoms, OH radicals, ozone) and shows higher reactive selectivity also because of its electrophilic nature.…”

Systematic Performance Comparison of Fe3+/Fe0/Peroxymonosulfate and Fe3+/Fe0/Peroxydisulfate Systems for Organics Removal

“…It should be noted that the results are strictly pH-dependent since the distribution of ROS can change with pH. For instance, SO 4 •− can be converted to • OH in the presence of H 2 O and HO − [ 9 , 28 ].…”

Clay-Supported Metal Oxide Nanoparticles in Catalytic Advanced Oxidation Processes: A Review

“…The mechanism involves peroxydisulfate (PDS, S 2 O 8 2− ) and peroxymonosulfate anions (PMS, HSO 5 − ) as the radical precursors for producing sulfate radicals through the presence of UV, heat, metal ions, ozone, alkaline solution, metal ions, and metal oxide semiconductors. Various transition metal ions, such as Fe(II), Fe(III), Co(II), Ru(III), Mn(II), Ni(I), Ag(I), and V(III), have been reported as effective PDS/PMS initiators, or as catalysts for catalytic oxidation [ 29 , 30 ]. It was noted that Co(II), Ag(I), and Ru(III) are the most effective catalysts for PDS activation; however, their high prices make them not applicable in practical water treatments.…”