Nanobubbles improve peroxymonosulfate-based advanced oxidation: High efficiency, low toxicity/cost, and novel collaborative mechanism

Abstract

Cl- activated peroxymonosulfate (PMS) oxidation technology can effectively degrade pollutants, but the generation of chlorinated disinfection byproducts (DBPs) limits the application of this technology in water treatment. In this study, a method of nanobubbles (NBs) synergistic Cl-/PMS system was designed to try to improve this technology. The results showed the synergistic effects of NBs/Cl-/PMS were significant and universal while its upgrade rate was from 12.89% to 34.97%. Moreover, the synergistic effects can be further improved by increasing the concentration and Zeta potential of NBs. The main synergistic effects of NBs/Cl-/PMS system were due to the electrostatic attraction of negatively charged NBs to Na+ from NaCl, K+ from PMS, and H+ from phenol, which acted as a "bridge" between Cl- and HSO5- as well as phenol and Cl-/HSO5-, increasing active substance concentration. In addition, the addition of NBs completely changed the oxidation system of Cl-/PMS from one that increases environmental toxicity to one that reduces it. The reason was that the electrostatic attraction of NBs changed the active sites and degradation pathway of phenol, greatly reducing the production of highly toxic DBPs. This study developed a novel environmentally friendly oxidation technology, which provides an effective strategy to reduce the generation of DBPs in the Cl-/PMS system. Environmental ImplicationCl- activated peroxymonosulfate (PMS) oxidation technology results in the formation of chlorinated disinfection byproducts (DBPs), limiting its application in water treatment. In this study, the nanobubbles (NBs) synergistic Cl-/PMS system was designed to enhance the degradation and mineralization rates of ionizable pollutants. Based on luminescent bacterial toxicity tests, the inhibition rate of the NBs/Cl-/PMS system was (9.35%) much lower than that of the control (only phenol, 30.96%) or Cl-/PMS system (100%). This study developed a novel environmentally friendly oxidation technology, which provides an effective strategy to reduce the generation of DBPs in the Cl-/PMS system.