Enhanced removal of recalcitrant naphthenic acids through electro-cocatalytic activation of peracetic acid: Synergistic effects of multiple factors

Abstract

Herein, a peracetic acid (PAA)-based electro-cocatalytic system (EC/PAA/Fe(III)) has been established for efficient degradation of 1-adamantanecarboxylic acid (ACA), which is a typical model chemical for naphthenic acids (NAs) that are abundantly present in petroleum industrial wastewater. The electric field greatly boosted the regeneration of Fe(II) to activate PAA in the system, resulting in 99.8 % removal for ACA within 20-min reaction time, with kobs of 0.3451 min−1. Results of quenching and chemical probe experiments verified the production of •CH3, CH3C(O)O•, •OH and FeIVO2+, in the EC/PAA/Fe(III) system with the FeIVO2+ identified as the primary contributor to ACA removal. The H2O2 present in the PAA solution enhanced the activation of PAA by promoting Fe(II) generation, thereby significantly improving ACA degradation efficiency. The ACA degradation byproducts and pathways were identified using the results of high resolution mass spectrometry analysis and density functional theory (DFT) calculations. Decarboxylation, hydroxy substitution, and carbonyl substitution reactions were predominant oxidation pathways of ACA decontamination. The EC/PAA/Fe(III) system demonstrated resilient degradation performance under the influence of anions and the natural water matrix for effective degradation of the commercial NAs mixture. Overall, the EC/PAA/Fe(III) system has been established with effectiveness and reliability for future remediation of NAs in petroleum industrial wastewater.