Effect And Kinetic Model Study On The Degradation Of Acetaminophen Using Fe²⁺/Persulfate Process

In recent years,the water environmental pollution caused by pharmaceutical and personal care products（PPCPs）has become the focus of more and more water treatment workers.The advanced oxidation processes based on SO₄^·-is an effective water treatment technology to remove PPCPs in water,which can generally generate SO₄^·-by activating persulfate（PS）.In this paper,acetaminophen（ACT）,a typical anti-inflammatory painkiller,was used as the target pollutant to study the treatment effects of Fe²⁺/PS and Fe²⁺/PS/NH₂OH systems,and a kinetic model for ACT degradation in Fe²⁺/PS system was established.It provides a theoretical reference for the application of advanced oxidation processes based on SO₄^·-.The main research contents and results are as follows:Fe²⁺/PS system could effectively degrade ACT in water.The second-order reaction rate constants of ACT with SO₄^·-and HO^·were measured,and the results were 1.8×10⁹ M^-1s^-1 and 3.26×10⁹ M^-1 s^-1,respectively.Moderate increase of Fe²⁺or PS concentration could improve the removal rate of ACT,but a high concentration of Fe²⁺could inhibit the degradation of ACT,and high concentration of PS not further increased the removal rate of ACT,methanol and tert-butyl alcohol could significantly inhibit the degradation of ACT,initial pH value had little impact on the degradation of ACT,an increase of the initial concentration of ACT caused a decline in the degradation of the ACT effect,Low concentration Cl^-could inhibit the degradation of ACT and high concentration of Cl^-would accelerate the degradation of ACT.Matlab software was used to establish the unsteady state kinetic model for ACT degradation in Fe²⁺/PS system,and the model could well simulate the degradation of ACT under various conditions.The simulation results showed that SO₄^·-was the main free radical that account for ACT degradation.Eight intermediates in the ACT degradation process were detected and the possible degradation pathway of ACT was speculated.Hydroxylamine could greatly enhance the degradation of ACT in Fe²⁺/PS system,but Fe²⁺/PS/NH₂OH system had poor mineralization effect on ACT.An appropriate increase in Fe²⁺or NH₂OH concentration could improve the degradation rate of ACT,but excessive Fe²⁺and NH₂OH concentration would inhibit ACT degradation.When PS concentration reached 1.2 mM,ACT could be almost completely degraded within 30 min,and the degradation rate of ACT decreased with the increase of pH.The EPR experiment showed that the major free radicals in Fe²⁺/PS/NH₂OH system were SO₄^·-and HO^·.Some common reducing agents such as Na₂SO₃,NaNO₂ and Na₂S₂O₃ could enhance the degradation of ACT in Fe²⁺/PS system,but their enhancement effect is lower than that of hydroxylamine.