Affiliations: School of Life Science, Sun Yat-sen University,
Guangzhou 510275, China | Guangdong Key Laboratory of Agricultural Environment
Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil
Science, Guangzhou 510650, China | Zhongshan Institute, University of Electronic Science
and Technology of China, Zhongshan 528402, China
Abstract: To understand the degradation of endocrine disrupting chemicals
(EDCs) in natural environment with existence of iron oxides and carboxylic
acids, the dependence ofbisphenol A (BPA) photodegradation on the initial
concentration ofoxalate (C_{ox}) in lepidocrocite
(γ-FeOOH) aqueous suspension was investigated under both UV and visible
lights in this study. Lepidocrocite powder was home-prepared by a hydrothermal
process. It was found that BPA degradation was promoted greatly in the presence
of oxalate owing to the formation of lepidocrocite-oxalate complex. And there
was an optimal C_{ox}, which was 2.0 and 2.4 mmol/L, under
UV and visible lights, respectively. The first-order kinetic constant, k value
increased 38 times from 0.17 × 10^{-2}
min^{-1} in the absence of oxalate to 6.39 ×
10^{-2} min^{-1} in the presence
ofoxalate with an optimal C_{ox} (2.0 mmol/L) under UV
irradiation, and almost 306 times from 0.02 × 10^{-2}
min^{-1} in the absence ofoxalate to 6.11 ×
10^{-2} min^{-1} in the presence of
oxalate with an optimal C_{ox} (2.4 mmol/L) under visible
irradiation. The BPA degradation rate increased and the first-order kinetic
constants decreased with the increase in BPA initial concentration. The
dependence of the variation of pH value, total-Fe and
Fe^{2+} during the photoreaction on
C_{ox} was also investigated. The pH value increased
obviously with the reaction time. Total-Fe increased dramatically at the first
5 min and then decreased quickly under UV irradiation and slowly under visible
irradiation. The initial concentration of oxalate is a main factor to affect
BPA photodegradation in aqueous suspension under both UV and visible
lights.
Keywords: bisphenol A, lepidocrocite, oxalate, photodegradation
