Enhanced dimethyl phthalate degradation via mild heat-assisted Bi2Fe4O9 catalyst: Properties and mechanism

[Display omitted] •Study on mild heat-assisted Bi2Fe4O9 for PMS activation.•Detailed investigation of thermal assistance mechanism promoting DMP degradation.•DMP degradation pathway was studied using detected and calculated intermediates.•Reduced toxicity was confirmed using T.E.S.T. and the growth of wheat seedlings. In this study, a thermally-assisted Bi2Fe4O9 activated permonosulfate (PMS) system was deemed the optimal solution for achieving efficient degradation of dimethyl phthalate (DMP) in water, after compared with the efficaciousness of other auxiliary methods. The degradation efficiency of this system (96.6%) markedly surpasses that of other BixFeyOz materials or a homogeneous activation system of iron ion. Optimal conditions and influencing factors for this novel approach were systematically determined. Electron paramagnetic resonance and scavenging experiments of free radicals identified the predominant reactive species. The mechanism of PMS activation by Fe and Bi sites was speculated by XPS, PMS decomposition rate and electrochemical test. Mild thermal assistance (50°C) was found to expedite the decomposition of PMS and facilitate generation of active species, which appears to be a pivotal factor in enhancing the degradation of DMP. Twelve degradation intermediates including monomethyl phthalate were detected by liquid chromatography-mass spectrometry, and plausible degradation pathways were postulated and corroborated through density functional theory calculations. The Bi2Fe4O9 exhibited commendable stability and recyclability under thermal conditions, with negligible metal leaching (0.19 mg/L). Finally, the toxicity of the degradation solution was preliminarily studied by using the actual growth index of wheat seedlings. Collectively, this study furnishes robust data supporting the efficacy of heat-assisted transition metal-activated PMS systems for pollutant degradation.