Overlooked interaction between redox-mediator and bisphenol-A in permanganate oxidation

Honglong Zhang; Qiaoqiao Zhao; Kangbao Zhong; Ruopeng Bai; Jiaojiao Dong; Jun Ma; Jing Zhang; Timothy J Strathmann

doi:10.1016/j.ese.2024.100421

Overlooked interaction between redox-mediator and bisphenol-A in permanganate oxidation

Environ Sci Ecotechnol. 2024 Apr 20:21:100421. doi: 10.1016/j.ese.2024.100421. eCollection 2024 Sep.

Authors

Honglong Zhang^{1

2}, Qiaoqiao Zhao³, Kangbao Zhong³, Ruopeng Bai³, Jiaojiao Dong⁴, Jun Ma¹, Jing Zhang¹, Timothy J Strathmann⁵

Affiliations

¹ School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China.
² Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, PR China.
³ School of Chemistry and Chemical Engineering, Chongqing Key Laboratory of Chemical Theory and Mechanism, Chongqing University, Chongqing, 401331, PR China.
⁴ College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China.
⁵ Department of Civil and Environmental Engineering, Colorado School of Mines, 1500 Illinois Street, Golden, CO, 80401, United States.

Abstract

Research efforts on permanganate (Mn(VII)) combined with redox-mediator (RM), have received increasing attention due to their significant performance for bisphenol-A (BPA) removal. However, the mechanisms underpinning BPA degradation remain underexplored. Here we show the overlooked interactions between RM and BPA during permanganate oxidation by introducing an RM-N-hydroxyphthalimide (NHPI). We discovered that the concurrent generation of MnO₂ and phthalimide-N-oxyl (PINO) radical significantly enhances BPA oxidation within the pH range of 5.0-6.0. The detection of radical cross-coupling products between PINO radicals and BPA or its derivatives corroborates the pivotal role of radical cross-coupling in BPA oxidation. Intriguingly, we observed the formation of an NHPI-BPA complex, which undergoes preferential oxidation by Mn(VII), marked by the emergence of an electron-rich domain in NHPI. These findings unveil the underlying mechanisms in the Mn(VII)/RM system and bridge the knowledge gap concerning BPA transformation via complexation. This research paves the way for further exploration into optimizing complexation sites and RM dosage, significantly enhancing the system's efficiency in water treatment applications.

Keywords: Bisphenol-A; Complexation; Permanganate; Radical cross-coupling; Redox-mediator.