Photochemistry of bisphenol F in aqueous solutions: A mechanistic study

Enhanced removal of bisphenol S in ozone/peroxymonosulfate system: Kinetics, intermediates and reaction mechanism

The degradation process of bisphenol S (BPS) in ozone/peroxymonosulfate (O3/PMS) system was systematically explored. The results showed that the removal efficiency of BPS by O3 could be significantly improved with addition of PMS. Compared with ozonation alone, the pseudo-first-order constant (kobs) was increased by 2-5 times after adding 400 μM PMS. In O3/PMS system, accelerated removal of BPS was observed under neutral and alkaline conditions. The removal efficiency of BPS reached 100% after 40 s of reaction at pH 7.0, with the kobs of 0.098 s-1. Moreover, Cu2+ had a catalytic effect on the O3/PMS system, because it could catalyze the decomposition of ozone and PMS to produce •OH and SO4•-, respectively. Electron paramagnetic resonance illustrated that •OH and SO4•- were the reactive species in O3/PMS system. Twelve intermediates were identified by mass spectrometry, and the degradation reactions in O3/PMS system mainly included hydroxylation, sulfate addition, polymerization and β-scission. Finally, the toxicity of the products was evaluated by the EOCSAR program. Our results introduce an efficient method for BPS removal and would provide some guidance for the development of O3-based advanced oxidation technology.

Fulvic acid enhanced peroxymonosulfate activation over Co-Fe binary metals for efficient degradation of emerging bisphenols

Bisphenol F (BPF) and bisphenol S (BPS) are emerging bisphenols, which have become the main substitutes for bisphenol A (BPA) in industrial production and are also considered as new environmental pollution challenges. Thus, the necessity for an effective approach to remove BPF and BPS is essential. In this study, fulvic acid (FA) was used to modify Co-Fe binary metals (CFO) for peroxymonosulfate (PMS) activation. The characterization results demonstrated that CFO changed significantly in morphology after compounding with FA, with smaller particle size and 5.6 times larger specific surface area, greatly increasing the active sites of catalyst; Moreover, humic acid-like compounds increased the surface functional groups of CFO, especially phenolic hydroxyl, which could effectively prolong the PMS activation. The concentration of all reactive species, such as SO₄•^-, •OH, O₂•^-, and ¹O₂ increased in FA@CFO/PMS system. As a result, the degradation efficiency of CFO for both BPF and BPS was significantly improved after compounding FA, which also had a wide range of pH applications. The degradation pathways of both BPF and BPS were proposed based on liquid chromatography-mass spectrometry (LC-MS) analysis and the density functional theory (DFT) calculations. Our findings are expected to provide new strategies and methods for remediation of environmental pollution caused by emerging bisphenols.

Overlooked environmental risks deriving from aqueous transformation of bisphenol alternatives: Integration of chemical and toxicological insights

Owing to the widespread prevalence and ecotoxicity of bisphenol alternatives such as bisphenol S, bisphenol F, and bisphenol AF, the past decade has witnessed the publication of a remarkable number of studies related to their transformation and remediation in natural waters. However, the reactivity, removal efficiency, transformation products (TPs), and mechanisms of such emerging pollutants by different treatment processes have not been well elucidated. Particularly, the transformation-driven environmental risks have been mostly overlooked. Therefore, we present a review to address these issues from chemical and toxicological viewpoints. Four degradation systems can be largely classified as catalytic persulfate (PS) oxidation, non-catalytic oxidation, photolysis and photocatalysis, and biodegradation. It was found that bisphenol alternatives possess distinct reactivities with different oxidizing species, with the highest performance for hydroxyl radicals. All systems exhibit superior elimination efficiency for these compounds. The inadequate mineralization suggests the formation of recalcitrant TPs, from which the overall reaction pathways are proposed. The combined experimental and in silico analysis indicates that many TPs have developmental toxicity, endocrine-disrupting effects, and genotoxicity. Notably, catalytic PS systems and non-catalytic oxidation result in the formation of coupling products as well as halogenated TPs with higher acute and chronic toxicity and lower biodegradability than the parent compounds. In contrast, photolysis and photocatalysis generate hydroxylated and bond-cleavage TPs with less toxicity. Overall, this review highlights the secondary environmental risks from the transformation of bisphenol alternatives by conventional and emerging treatment processes. Finally, future perspectives are recommended to address the knowledge gaps of these contaminants in aquatic ecosystems.

UVC-assisted electrochemical degradation of novel bisphenol analogues with boron-doped diamond electrodes: kinetics, pathways and eco-toxicity removal

In the present study, the UVC-assisted electrochemical degradation ofthree novel bisphenol analogues (BPs; including bisphenol F, S, and B, i.e., BPF, BPS and BPB, respectively), along with bisphenol A (BPA), was investigated using boron-doped diamond (BDD) electrode. At first, this study demonstrated a significant influence ofcurrent density on the degradation rates of BPF by the BDD anode. The pseudo-first order rate constants for BPF were calculated as 0.012, 0.028 and 0.029 min^-1 at the applied current densities of 10, 20 and 30 mA/cm², respectively. UVC irradiation significantly enhanced the electrochemical degradation of BPF in the concentration range from 5 to 30 mg/L, with synergistic effects in the range of 32.0%-40.9%. The UVC-BDD electrolysisshowed comparable or even lower electric energy per order (E_EO) than single BDD electrolysis. The UVC-assisted degradation of the investigated BPs showed decreased pseudo-first order rate constants in the following order: BPF > BPA > BPB > BPS. Based on the identifiedtransformation products, UVC-assisted electrochemical degradation pathways of the novel BPs were proposed to be mainly hydroxylation and bond-cleavage. UVC irradiation has been proved to promote the formation of hydroxyl radicals by BDD electrode to facilitate the degradation process. For these BPs, nearly 100% mineralization can be achieved by a modified strategy using a short-time UVC-assisted BDD electrolysis (120 min) that is followed by UVC photolysis (360 min). Finally, the eco-toxicity of the BPs solutions towardsVibrio Fischeri was significantly removed after 120 min of the electrochemical degradation period. Based on these results, the UVC-assisted electrochemical treatment using a BDD electrode can be considered a promising technology for the removal of novel BPs and the reduction of their hazardous effects to aqueous environments.

Stability, biological treatment and UV photolysis of 18 bisphenols under laboratory conditions

The limited knowledge on the stability, removal, and the fate of bisphenol A analogues in the aqueous environment led us to assess the removal by hydrolysis, adsorption, biological treatment and UV photolysis of eighteen common bisphenol compounds (BPs). Hydrolysis of BPs does not occur. The main factor affecting their stability in wastewater samples is storage time, and safe storage conditions were found to be -20 °C or 4 °C for up to four weeks. The results also revealed no significant reduction in the levels of BPs standards when stored in either methanol or ultrapure water. BPE was found to be the most stable, followed by BPF isomers, BPS and BPF, while BP26DM was the least stable and BPM, BPPH, BPP, BPBP and BPFL were quickly adsorbed. For most BPs, the removal efficiency of biological treatment was >85%, and there was no difference between the suspended activated sludge and moving bed bioreactors. Different adsorption affinities of the BPs to biomass were observed and reflect the differences in their K_ow. In terms of degradability, direct UV photolysis in water produced three groups of BPs: (A) highly removable (RE > 94%), (B) moderately removable (RE 50-80%) and (C) poorly removable (RE 25-45%). In nearly all cases degradation followed pseudo-first-order kinetics.

Occurrence, fate and risk assessment of BPA and its substituents in wastewater treatment plant: A review

Several bisphenol analogues (BPs) are gradually replacing bisphenol A (BPA) in many fields, following strict restrictions on the production and use of BPA. The presence of micropollutants in wastewater treatment plants (WWTPs) may pose risks to the aquatic ecosystem and human health. In this review, we outlined the occurrence and fate of BPs in WWTPs, and estimated their potential risks to the aquatic ecosystem. BPA is still the most predominant bisphenol analogue in WWTPs with high detection rate and concentration, followed by bisphenol S (BPS) and F (BPF). Biodegradation and adsorption are the main removal pathways for removal of BPs in WWTPs. The secondary (activated sludge process, biological aerated filter, and membrane bioreactor) and advanced (membrane technique, ultraviolet disinfection, adsorption process, and ozonation) treatment processes show high removal efficiency for BPs, which are influenced by many factors such as sludge retention time and redox conditions. BPs other than BPA (assessed in this review) in effluent of WWTPs have low risks to Daphnia magna and early life stages on medaka, while BPA shows a medium or high risk under certain conditions. Knowledge gaps have been identified and future line of research on this class of chemicals in WWTPs is recommended. More data are needed to illustrate the occurrence and fate of BPs in WWTPs. Environmental risks of BPs other than BPA initiating from wastewater discharge to aquatic organisms remain largely unknown.

Photochemical degradation of BPF, BPS and BPZ in aqueous solution: Identification of transformation products and degradation kinetics

Bisphenols (BPs) are industrial chemicals that are used as monomers in the production of polycarbonate plastics and epoxy resins. These compounds can leach into the aqueous environment, where they can potentially have toxic effects. The aim of this study was to assess the photochemical degradation of three common bisphenols: BPF, BPS and BPZ in aqueous solution and determine their degradation kinetics and characterise their transformation products. Three independent experiments were performed based on: 1) direct photolysis using UV irradiation, 2) cyclodextrin-enhanced photolysis and 3) the photo-Fenton reaction. Analysis was performed using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography coupled to high-resolution quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS). This approach enabled for the first time a comparison between various conditions of photochemical degradation, revealing to be an effective way of removing (>90%) BPF, BPS and BPZ from aqueous samples. In all cases, degradation followed a pseudo-first order kinetic profile, while removal efficiency and formation of transformation products depended on the applied process. The photo-Fenton process resulted in the shortest half-lives (16.1 ̶ 21.7 min) and generated the highest number of transformation products. Overall, in this study we identified 11 novels and eight previously reported TPs.

Bisphenol Analogues Other Than BPA: Environmental Occurrence, Human Exposure, and Toxicity-A Review

Numerous studies have investigated the environmental occurrence, human exposure, and toxicity of bisphenol A (BPA). Following stringent regulations on the production and usage of BPA, several bisphenol analogues have been produced as a replacement for BPA in various applications. The present review outlines the current state of knowledge on the occurrence of bisphenol analogues (other than BPA) in the environment, consumer products and foodstuffs, human exposure and biomonitoring, and toxicity. Whereas BPA was still the major bisphenol analogue found in most environmental monitoring studies, BPF and BPS were also frequently detected. Elevated concentrations of BPAF, BPF, and BPS (i.e., similar to or greater than that of BPA) have been reported in the abiotic environment and human urine from some regions. Many analogues exhibit endocrine disrupting effects, cytotoxicity, genotoxicity, reproductive toxicity, dioxin-like effects, and neurotoxicity in laboratory studies. BPAF, BPB, BPF, and BPS have been shown to exhibit estrogenic and/or antiandrogenic activities similar to or even greater than that of BPA. Knowledge gaps and research needs have been identified, which include the elucidation of environmental occurrences, persistence, and fate of bisphenol analogues (other than BPA), sources and pathways for human exposure, effects on reproductive systems and the mammary gland, mechanisms of toxicity from coexposure to multiple analogues, metabolic pathways and products, and the impact of metabolic modification on toxicity.