Elimination of acetaminophen in sodium carbonate-enhanced thermal/peroxymonosulfate process: Performances, influencing factors and mechanism

Abstract

Peroxymonosulfate (PMS) is commonly poor for degrading organic contaminants through thermal activation because of the high O-O bond dissociation energy. This work is the first to demonstrate that sodium carbonate (Na2CO3) significantly promoted the degradation of acetaminophen with thermal/PMS process, and Na2CO3/thermal/PMS process exhibited faster removal rate of acetaminophen and a lower formation potential of BrO3− than Na2CO3/thermal/peroxydisulfate process. The increase of Na2CO3 dosage, PMS dosage and reaction temperature were favorable for acetaminophen degradation with Na2CO3/thermal/PMS process. Na2CO3/thermal/PMS process could generate multiple reactive species including 1O2 and the radicals of ·OH, SO4·− and CO3·−. 1O2 was dominant in acetaminophen removal regardless of the dosage of Na2CO3, while the radicals of ·OH, SO4·− and CO3·− also participated in the removal of acetaminophen. Three different degradation pathways of acetaminophen were proposed based on UPLC-Q-TOF-MS detection, and the toxicity towards luminescent bacteria and green algae significantly decreased. Humic acid slightly inhibited the removal of acetaminophen, sulfate ion and nitrate ion presented negligible effect on acetaminophen removal, while chloride ion and bromide ion greatly accelerated the elimination of acetaminophen. Na2CO3/thermal/PMS process exhibited wide suitability in eliminating acetaminophen in ground water and degrading other organic contaminants, including bisphenol A, naproxen, diclofenac, rhodamine B and acid orange 7. This work provided a promising method to enhance the oxidizing ability of thermal/PMS process and might promote its application in the remediation of contaminated water and soil.