Mechanism Of Heterogeneous Fenton-like Reactions With Pyrite For The Degradation Of Diethyl Phthalate

Phthalates?PAEs? are widely used environmental organic pollutants that have carcinogenic effects.Human exposure to PAEs may have adverse effects on the reproductive,liver and kidney systems.Therefore,it has great environmental significance to study how to efficiently degrade PAEs.Fenton-like reactions based on catalytic decomposition of hydrogen peroxide?H₂O₂? to produce hydroxyl groups are widely used in the degradation of pollutants.However,as an oxidant,H₂O₂ has some disadvantages such as excessive consumption and severe reaction in practical applications.Compared with H₂O₂,peroxymonosulfate?PMS? and calcium peroxide?CaO₂? are more stable in the soil environment and are more suitable for large-scale repair applications.Based on this,diethyl phthalate?DEP? was chosen as representative of PAEs,the microscopic mechanism of the catalytic decomposition of PMS and CaO₂ by typical sulfur minerals pyrite?FeS₂? to decompose DEP was studied systematically in this paper.The process and mechanism of DEP degradation were investigated from two perspectives of free radicals and sulfate radicals.The main research contents and results are as follows:?1?PMS was found to be efficiently activated by FeS₂ for DEP degradation and mineralization,achieving 58.9% total organic carbon removal using 0.5 g/L FeS₂ and 2.0 mmol/L PMS.The mechanism of catalytic decomposition of PMS by FeS₂ to generate free radicals was analyzed.It was found that ferrous?Fe???? on the surface of FeS₂ is the main active site for catalytic decomposition of PMS,and sulfur as an electron donor promotes the regeneration cycle of Fe??? on the solid surface.Meanwhile,different sulfur conversion intermediates,such as S₅^2-,S₈⁰,S₂O₃^2- and SO₃^2-,were formed from the oxidation of sulfides by Fe??? and PMS,and determined by X-ray photoelectron spectroscopy and in-situ attenuated total reflectance Fourier transform infrared spectroscopy analysis.SO₃^2- was the dominant sulfur species responsible for sulfate radicals?SO₄·^-? generation by activating PMS directly or activating Fe??? to initiate a radical chain reaction,which was supported by the electron paramagnetic resonance results.This study highlights the important role of sulfur conversion in PMS activation by pyrite and provides new insights into the mechanism of oxidant activation by sulfur-containing minerals.It also provides a new method for the repair of PAEs pollutants.?2?CaO₂ was found to be efficiently activated by FeS₂ for DEP degradation,achieving 100% removal?10 mg/L? using 0.1 g/L FeS₂ and 1.0 mmol/L CaO₂ within 2 hours.The mechanism of catalytic decomposition of CaO₂ by FeS₂ for DEP degradation was elucidated.If the amount of FeS₂ is increased by 3 times,10 mg/L of DEP will be completely removed in a few minutes.The H₂O₂ produced by the decomposition of CaO₂ in water can be activated by the dissolved Fe²⁺,thereby producing ·OH to degrade DEP.Cl^-,HCO₃^-,and NO₃^- all inhibit the degradation of DEP.This study provides a theoretical basis for the practical use of pyrite and CaO₂ for in situ remediation.