Peracetic
acid (PAA) is increasingly used as an alternative disinfectant
and its advanced oxidation processes (AOPs) could be useful for pollutant
degradation. Co(II) or Co(III) can activate PAA to produce acetyloxyl
(CH3C(O)O•) and acetylperoxyl (CH3C(O)OO•) radicals with little •OH radical formation, and Co(II)/Co(III) is cycled. For the first
time, this study determined the reaction rates of PAA with Co(II)
(k
PAA,Co(II) = 1.70 × 101 to 6.67 × 102 M–1·s–1) and Co(III) (k
PAA,Co(III) = 3.91 ×
100 to 4.57 × 102 M–1·s–1) ions over the initial pH 3.0–8.2
and evaluated 30 different aromatic organic compounds for degradation
by Co/PAA. In-depth investigation confirmed that CH3C(O)OO• is the key reactive species under Co/PAA for compound
degradation. Assessing the structure–activity relationship
between compounds’ molecular descriptors and pseudo-first-order
degradation rate constants (k′PAA•
in s–1) by Co/PAA showed the
number of ring atoms, E
HOMO, softness,
and ionization potential to be the most influential, strongly suggesting
the electron transfer mechanism from aromatic compounds to the acetylperoxyl
radical. The radical production and compound degradation in Co/PAA
are most efficient in the intermediate pH range and can be influenced
by water matrix constituents of bicarbonate, phosphate, and humic
acids. These results significantly improve the knowledge regarding
the acetylperoxyl radical from PAA and will be useful for further
development and applications of PAA-based AOPs.