Degradation of sunscreen agent p-aminobenzoic acid using a combination system of UV irradiation, persulphate and iron(II)
2016
Xue, Yicen | Dong, Wenbo | Wang, Xiaoning | Bi, Wenlong | Zhai, Pingping | Li, Hongjing | Nie, Minghua
Increased usage and discharge of sunscreens have led to ecological safety crisis, and people are developing the advanced oxidation processes (AOPs) to treat them. The present study aimed to determine the degradation efficiency and mechanism of the sunscreen agent p-aminobenzoic acid (PABA) using the UV/Fe²⁺/persulphate (PS) method. A series of irradiation experiments were conducted to optimise the system conditions and to study the impacts of the natural anion. Free radicals and degradation products were identified in order to clarify the degradation mechanism. Initial PS and Fe²⁺ concentrations showed significant impacts on PABA degradation. Natural anions, such as Cl⁻, NO₃ ⁻, H₂PO₄ ⁻ and HCO₃ ⁻, impeded PABA degradation because of ion (Fe²⁺) capture, radical scavenging or pH effects. Hydroxyl (HO·) and sulphate (SO₄ ·⁻) radicals were two main radicals observed in the UV/Fe²⁺/PS system; of these, SO₄ ·⁻ showed greater effects on PABA degradation. Over 99 % of the available PABA was completely degraded into carbon dioxide (CO₂) and water (H₂O) by the UV/Fe²⁺/PS system, and the remaining PABA participated in complex radical reactions. By-products were identified by total ion chromatography and mass spectrometry. Our research provides a treatment process for PABA with high degradation efficiency and environmental safety and introduces a new strategy for sunscreen degradation.
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