Insight into the Degradation of Two Benzophenone-Type UV Filters by the UV/H2O2 Advanced Oxidation Process

Abstract

Environmental problems caused by UV filters, a group of emerging contaminants, have attracted much attention. The removal of two typical UV filters benzophenone (BP) and 4,4 -dihydroxy-benzophenone (HBP) in water was investigated by the UV/H 2 O 2 process. The response surface methodology (RSM) and central composite design (CCD) were applied to investigate the effects of the process parameters on the degradation rate constants, including the initial contaminant concentration, H 2 O 2 dose, and UV light intensity. BP is more easily degraded by the UV/H 2 O 2 process. Both processes followed pseudo-first-order kinetics. The results obtained with the built RSM model are in accordance with the experimental results (adjusted coefficients R 2 (adj)= 0.9835 and 0.9778 for BP and HBP, respectively). For both processes, the initial contaminant concentration (exerting a negative effect) were the most important factors controlling the degradation, followed by H 2 O 2 dose and UV intensity (exerting positive effects). A total of 15 BP degradation products and 13 HBP degradation products during the UV/H 2 O 2 process were identified by LC/MS and GC/MS. A series of OH radical irritated reactions, including hydroxylation, carboxylation, and ring cleavage, led to the final degradation of BP and HBP. Degradation pathways of BP and HBP were also proposed. On the whole, this work is a unique contribution to the systematic elucidation of BP and HBP degradation by the UV/H 2 O 2 process.United States, Japan, and Switzerland [5,[8][9][10][11][12]. There are reports that the concentration of BP reached 250 ng/L in wastewater [13]. The potential risks resulting from the occurrence of BP and HBP must not be overlooked.Advanced oxidation processes (AOPs) are a series of processes that can generate hydroxyl radicals to efficiently degrade organic pollutants in contaminated water [4,14,15]. The UV/H 2 O 2 system is a type of AOP, in which hydrogen peroxide (H 2 O 2 ) is added in the presence of UV light to generate hydroxyl radicals [16][17][18]. It is found that the UV/H 2 O 2 process can remove a large range of organic pollutants, including cyanobacterial toxins [19], diclofenac [20], amoxicillin [21], and other emerging contaminants [22][23][24].Benzophenone-type UV filters are usually the hardly biodegradable substances [25]. There are over 20 benzophenone-type UV filters, including HBP, BP, benzophenone-2, benzophenone-3 (BP3), benzophenone-4, benzophenone-5, and benzophenone-9. Among them, BP3 is the dominant UV filter and the most-frequently detected in the aquatic environment [26,27]. Many reported works have focused on the occurrence, transformation, and fate of BP3 [28][29][30]. The removal, degradation mechanism, and ecotoxicity of BP3 by different treatment processes were assessed, such as UV/H 2 O 2 [31], ozone [32], fungal [33], chlorination [34,35], and activated persulfate [36,37]. In addition, the removal of other benzophenone-type UV filters, including BP2, BP4, and BP9, were also evaluated by different AOPs [38][39][40][4...

Occurrence, Fate, Human Exposure, and Toxicity of Commercial Photoinitiators

“…The degradation parameters of PIs in water environments have also been explored. As a dominant congener, BP in aquatic environments can be degraded by microbes or UV/H 2 O 2 . , OH free-radical-initiated degradation reactions include hydroxylation, carboxylation, and ring cleavage. Photodegradation of MK by UV/TiO 2 has also been evaluated in lab studies.…”

Stability and Removal of Benzophenone-Type UV Filters from Water Matrices by Advanced Oxidation Processes

“…Several intermediates were identified by GC-MS and the primary reaction pathway between BP-3 and •OH was proposed [ 47 ]. Similar studies were conducted on benzophenone-4 (BP-4), benzophenone-9 (BP-9) [ 48 ], benzophenone (BP), and 4,4-dihydroxy-benzophenone (HBP), with the aim to remove this type of UV filter from water by UV/H 2 O 2 process [ 49 ].…”

“…Intermediates of BP-4 and BP-9 showed greater toxicity than parent compounds. Using the ECOSAR program (EPA’s ecological structure–activity relationships), the acute toxicity of BP-4 and BP-9 and their intermediates were predicted and showed higher toxicity of intermediates to living organisms (fish, algae) than BP-4 and BP-9 [ 48 ]. This indicates that special attention should be paid to the formation of benzophenone intermediates and that a risk assessment should be done in future research.…”

Optimized Use of Ferric Chloride and Sesbania Seed Gum (SSG) as Sustainable Coagulant Aid for Turbidity Reduction in Drinking Water Treatment

“…It is a statistical approach that uses screening, characterization, and optimization analyses. This approach overcomes the limitation of the traditional one-factor-at-a-time-method, where the interaction between the factors is hard to identify [17,18]. In this experiment, the Box-Behnken design (BBD), as the standard design of RSM [19], was adopted to statistically optimize the influencing factors and evaluate the effect of the influencing factors on the turbidity reduction in drinking water treatment.…”