The individual and Co-exposure degradation of benzophenone derivatives by UV/H₂O₂ and UV/PDS in different water matrices

Highlights

• The degradation of UV filter for individual and co-exposure pattern were studied.

• CO₃.^•− made a contribution for UV filter degradation in surface water.

• Reactivity of RNS and molecular structure are responsible for BP3 inhibition in hydrolyzed urine.

• The sink for HO.• and SO₄^•- in seawater is Br⁻ and Br⁻&Cl⁻, respectively.

Abstract

Benzophenone derivatives, including benzophenone-1 (C₁₃H₁₀O₃, BP1), benzophenone-3 (C₁₄H₁₂O₃, BP3) and benzophenone-8 (C₁₄H₁₂O₄, BP8), that used as UV filters are currently viewed as emerging contaminants. Degradation behaviors on co-exposure benzophenone derivatives using UV-driven advanced oxidation processes under different aqueous environments are still unknown. In this study, the degradation behavior of mixed benzophenone derivatives via UV/H₂O₂ and UV/peroxydisulfate (PDS), in different water matrices (surface water, hydrolyzed urine and seawater) were systematically examined. In surface water, the attack of BP3 by hydroxyl radicals (HO∙) or carbonate radicals (CO₃^∙-) in UV/H₂O₂ can generate BP8, which was responsible for the relatively high degradation rate of BP3. Intermediates from BP3 and BP8 in UV/PDS were susceptible to CO₃^∙-, bringing inhibition of BP1 degradation. In hydrolyzed urine, Cl⁻ was shown the negligible effect for benzophenone derivatives degradation due to low concentration of reactive chlorine species (RCS). Meanwhile, BP3 abatement was excessively inhibited during co-exposure pattern. In seawater, non-first-order kinetic behavior for BP3 and BP8 was found during UV/PDS treatment. Based on modeling, Br⁻ was the sink for HO∙, and the co-existence of Br⁻ and Cl⁻ was the sink for SO₄^∙-. The cost-effective treatment toward target compounds removal in different water matrices was further evaluated using EE/O. In most cases, UV/H₂O₂ process is more economically competitive than UV/PDS process.

Introduction

To protect humans from the harmful effects of ultraviolet radiation, UV filters are used in a diverse range of personal care products (PCPs), including sunscreens, cosmetics and shampoo (Fent et al., 2010; Jansen et al., 2013). UV filters are used in combinations and can exceed 10% of the product's mass (Brausch and Rand, 2011; Schreurs et al., 2002). Among UV filters, benzophenone derivatives are commonly used due to their high photo/biostability, resulting in their general occurrence in environment media, especially aqueous environments (Brausch and Rand, 2011; Kasprzyk-Hordern et al., 2008; Poiger et al., 2004; Tsui et al., 2017). Due to their endocrine disrupting potential and carcinogenic effects, benzophenone derivatives are considered to the emerging contaminants in recent decades (Schlumpf et al., 2001; Schreurs et al., 2005; Suzuki et al., 2005; Tang et al., 2013). The most detected UV filters families in surface water were benzophenone derivatives with concentrations up to 0.4 mg/L (Kasprzyk-Hordern et al., 2009). Meanwhile, benzophenone-1 (C₁₃H₁₀O₃, BP1) and benzophenone-8 (C₁₄H₁₂O₄, BP8) in the influent of urban sewage treatment plants have reached maximum concentrations of 245 and 10 ng/L, respectively (Negreira et al., 2009; Wu et al., 2013). Benzophenone-3 (C₁₄H₁₂O₃, BP3) has been reported to occur in surface waters in Switzerland, at a concentration range of <2–35 ng/L (Balmer et al., 2005), and in wastewater from China, at concentration ranging from 68 to 722 ng/L (Li et al., 2007). Besides, UV filters were also detected in seawater (Tsui et al., 2017; Manasfi et al., 2017), even in human urine because of dermal exposure (Kunisue et al., 2012; Wang et al., 2013). Hence, an efficient and economical approach to removing these pollutants from aquatic environments is highly needed.

Advanced oxidation processes (AOPs), which can generate reactive species, are becoming increasingly popular technologies for contaminants degradation in water (Oller et al., 2011; Oturan and Aaron, 2014). Radical-based AOPs, in particular those with hydroxyl radical (HO∙) or sulfate radical (SO₄^∙-), have been successfully applied to decompose micropollutants (Keen and Linden, 2013; Luo et al., 2015, 2017; Nfodzo and Choi, 2011; Yang et al., 2019; Liu et al., 2018). Meanwhile, AOPs were also used in human urine and seawater to obtain the pharmaceuticals removal, toxicity elimination and disinfection (Zhang et al., 2015, 2016b; Rubio et al., 2013). Reports have shown that many micropollutants can react rapidly with HO∙ (10⁸ ≤ k ≤ 10¹⁰ M⁻¹ s⁻¹) (Wols and Hofman-Caris, 2012), whereas the reaction rates of PCPs with HO∙ and SO₄^∙- have not been extensively studied, especially for secondary reactive species (i.e., carbonate radical-CO₃^∙-). Additionally, one critical issue is that micropollutants, such as PCPs, normally occur in a co-exposure pattern rather than individual existence in aqueous environments. The degradation behaviors of PCPs in co-exposure pattern are likely different from individual pattern using AOPs. However, the specific difference of degradation behaviors and its related factors for triggering are still unknown. Furthermore, constituents in various water matrices make micropollutants degradation even more complex because of conversions of reactive species (Yang et al., 2014; Zhang et al., 2015). To the best of our knowledge, degradation behaviors of multiple PCPs (i.e., UV filters) by AOPs in various aqueous environments have not been investigated.

In this study, the degradation of benzophenone derivatives in both individual and co-exposure patterns by UV/H₂O₂ and UV/PDS in the presence of different water matrices (surface water, hydrolyzed urine and seawater) was comprehensively investigated. The degradation kinetics were also experimentally and mathematically determined. For the first time, the reaction rate constants of benzophenone derivatives toward HO∙, SO₄^∙- and CO₃^∙- were determined, which can largely benefit the future work regarding on the kinetic simulation of radical-based degradation in other water matrices. An energy-cost evaluation (i.e., electrical efficiency per log order (EE/O)) was also conducted to compare the energy cost of UV-based AOPs in different water matrices.