Degradation of Ibuprofen by the Electro/Fe3+/Peroxydisulfate Process: Reactive Kinetics, Degradation Products and Mechanism

Na Qiu,Yongxia Liu,Chanchan Shen,Xinglei Wang,Guangyin Jia,Xiuqing Li,Jingping Qin

doi:10.3390/catal12030329

Abstract

Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is one of the most widely used and frequently detected pharmaceuticals and personal care products in water bodies. This study examined the IBU degradation in aquatic solutions via ferric ion activated peroxydisulfate (PDS) coupled with electro-oxidation (EC/Fe3+/PDS). The degradation mechanisms involved three synergistic reactions in the EC/Fe3+/PDS system, including: (1) the electro-oxidation; (2) SO4•− generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) SO4•− generated from the electron transfer reaction. The radical scavenging experiments indicated that SO4•− and •OH dominated the oxidation process. The effects of the applied current density, PDS concentration, Fe3+ dosage, initial IBU concentration and initial pH as well as inorganic anions and humic acid on the degradation efficiency, were studied, and the degradation process of IBU followed the pseudo-first-order kinetic model. About 99.37% of IBU was removed in 60 min ((Fe3+ concentration) = 2.0 mM, (PDS concentration) = 12 mM, (initial IBU concentration) = 30 mg/L, current density = 15 mA/cm2, initial pH = 3). Finally, seven intermediate compounds were identified and probable IBU degradation pathways in the EC/Fe3+/PDS system were speculated.

Highlights

By raising the current density from 5 mA/cm2 to 15 mA/cm2, the IBU removal increased from 67.33% to 99.37%, and the k value increased progressively from 0.0193 min−1 to 0.0851 min−1
The synergistic effect was attributed to the following aspects: (1) the electro-oxidation; (2) sulfate radicals generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) sulfate radicals generated from the electron transfer reaction
Free radicals quenching experiments revealed that both SO4− and OH contributed to the excellent removal of IBU

Summary

Introduction

Ibuprofen (IBU), a non-steroidal anti-inflammatory drug, is extensively used to treat fever and pain, including muscle aches, tooth aches, headache pain and arthritis pain [1,2]. IBU has been frequently found in municipal and hospital wastewater with concentrations of up to 83 μg/L [4]. Constant discharge of IBU into the aquatic environment may pose threat to human health and affect the safety and balance of the aquatic ecosystem [8,9]. Apoptosis and a decrease in proliferating cells of humans might occur after exposure to 10–100 μmol/L of IBU [12]. IBU may pose acute toxicity to the reproduction of some aquatic organisms, for example, Japanese medaka and zebrafish [10,13]. IBU could promote cyanobacteria and reduce the eukaryotic algae biomass, resulting in algal blooms in freshwaters [14]. IBU had an adverse impact on the reproduction and the survival of Oryzias latipes as well as the growth of algae

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