Peroxymonosulfate (PMS) alkaline activation has gained considerable interest in advanced oxidation processes for wastewater

treatment due to its reduced secondary pollution, high economic effi ciency, and strong degradation capability. 

This study hypothesized that a gradual increase in pH would improve and maintain the alkaline activation of PMS more 

than rapid pH shift. Magnesium peroxide (MgO 2 )-based PMS system was proposed to control the alkaline activation of 

PMS. Under equal molar dosage, the MgO 2 /PMS system removed 60.7% of acetaminophen (ACT), while NaOH/PMS 

and CaO 2 /PMS systems oxidized 43.3% and 18.2% of ACT, respectively. Although the initial reaction rate in CaO 2 /PMS 

system was faster than that in the MgO 2 /PMS system, the MgO 2 /PMS system ultimately demonstrated greater overall 

ACT removal, even with higher PMS consumption. These results indicate that MgO 2 -based gradual activation enhances 

pollutant removal and prolongs the persistence of reaction. Furthermore, the MgO 2 -PMS system showed less interference 

by co-existing anions, including Cl − , SO 42− , NO 3− , HCO 3− , and HPO 42− . In the system, singlet oxygen ( 1 O 2 ) and superoxide

radical (O 2˙) were the dominant reactive species responsible for degradation of ACT. In conclusion, the MgO 2 /PMS 

system proposed in this study is a promising alternative for wastewater treatment due to its simple process, effi cient PMS 

utilization, high adaptability, and signifi cantly enhanced pollutant removal via gradual alkaline activation.