Mechanism Of Bisphenol A Degradation Research Articles

Three-dimensional ordered microporous silica supported p-lanthanum ferrite and n-ceria as heterojunction photocatalyst to activate peroxymonosulfate for bisphenol a degradation

In this study, three-dimensional ordered microporous silica supported p-lanthanum ferrite and n-ceria (n-CeO2@p-LaFeO3/3DOM SiO2) was successfully synthesized as a visible light-driven photocatalyst for activating peroxymonosulfate (PMS) to degrade Bisphenol A (BPA). In a wide pH range (2–12), the BPA degradation efficiency maintained at a high level, organic matter and natural inorganic ions had no significant negative impact. When the BPA concentration was as low as 2 mg·L−1, the removal rate in 60 min still reached 95.56%, indicating that the novel photocatalyst has potential application in the treatment of trace pollutants. The pore confinement effects of catalysts and the synergistic effect between LaFeO3 and CeO2 result in the excellent photocatalytic performance. We proposed the possible mechanism of BPA degradation, specifically involving the recognition and generation mechanism of reactive oxygen species (ROSs), adsorption processes and diffusion processes. In summary, the novel n-CeO2@p-LaFeO3/3DOM SiO2 would be a promising candidate photocatalytic material for practical sewage treatment.

Bi4O5Br2 nanosheets modified by carbon quantum dots: Efficient BPA degradation induced by enhanced absorption and Z-scheme charge transfer

Constructing semiconductor photocatalysts with enhanced absorption and rapid carrier dynamics is essential for applying semiconductor photocatalysis in environmental remediation and energy conversion. In this study, we modified carbon quantum dots (CQDs) onto the surface of Bi4O5Br2 using a one-step hydrothermal method. The modification enabled the excellent degradation of bisphenol A (BPA) due to the up-conversion luminescence of CQDs and the Z-scheme charge transfer path formed by the unique energy level of the two materials. The CQDs/Bi4O5Br2 composite added with 4 mg of CQDs completely degraded BPA (20 mg/L) within 100 min when the radiation wavelength exceeded 400 nm, and Bi4O5Br2 itself only degraded BPA by 1.44%. In sharp contrast, if a xenon lamp was directly irradiated without a 400 nm filter to sift the ultraviolet components, the degradation rate of the Bi4O5Br2 monomer could reach 40% under the same conditions. This indicates that introducing CQDs plays a vital role in visible-light-driven degradation. Furthermore, on the basis of the structural characterisation, the successful introduction of CQDs was confirmed in the CQDs/Bi4O5Br2 hybrid system. On this basis, the possibility of Z-scheme charge transfer was proved by X-ray photoelectron spectroscopy and ultraviolet electron spectroscopy measurements. The degradation mechanism of BPA under Z-type charge transfer was proposed through electron paramagnetic resonance, free radical capture and total organic carbon tests. This work is expected to provide a new idea for designing an energy band that matches semiconductor heterojunction photocatalysts, enhancing the unique narrow band gap structure and up-conversion properties of CQDs. In addition, it facilitates the construction of photocatalysts with better performance.

Degradation mechanism of BPA under VUV irradiation: efficiency contribution and DFT calculations.

Bisphenol A (BPA) is regarded as a hazardous pollutant that exists widely in aquatic environments, posing a severe threat to human health. In this study, a vacuum ultraviolet (VUV) lamp emitting a hybrid of 254nm and 185nm light was used to degrade BPA. Results indicated that photolysis via 254nm wavelength accounted for 24.93% for BPA decay, while indirect oxidation was responsible for 52.27% of decay. Results confirmed that the degradation of BPA under VUV illumination mainly occurred via photo-excited degradation and ·OH electrophilic addition reactions based on average local ionization energy (ALIE) calculation and density functional theory (DFT) calculations. Therefore, only light with a wavelength of 254nm was able to induce the first three excited states of BPA, forming the electron transition type of n → π* from O atom to a single benzene ring and π → π* in the single benzene ring. Indirect oxidation by ·OH occurred as it preferentially attacked the C6 atom in BPA ring A. Moreover, the energy required for photo-excited degradation was about twofold than that of ·OH electrophilic addition reactions.

Novel S-doped BiOBr nanosheets for the enhanced photocatalytic degradation of bisphenol A under visible light irradiation

Bisphenol A (BPA), a typical endocrine disrupting chemical, is widespread in aqueous environment and cannot be efficiently treated by traditional water treatment technologies. Bismuth oxybromide (BiOBr) is a promising photocatalyst with a special layered structure. However, its band gap (2.8 eV) is not narrow enough for the efficient harvesting of visible light, severely restricting its practical use. Given that the band gap of Bi2S3 is only 1.3 eV, S-doping modification could be used to tailor the band structure of BiOBr. Here, series of S-doped BiOBr nanosheets was prepared through a facile hydrothermal procedure. The as-prepared S0.2-BiOBr nanosheets showed a narrower band gap of 2.33 eV. The intrinsic photocatalytic activity of S0.2-BiOBr sample for the degradation of BPA was 2.78 times higher than that of BiOBr under visible light degradation. Moreover, the mechanism of BPA degradation over the S-doped BiOBr under visible light irradiation was elucidated based on the experimental results and density functional theoretical calculations. Overall, a feasible and effective doping method was proposed to improve the utilization efficiency of visible light.

Novel Z-scheme Ag3PO4/Fe3O4-activated biochar photocatalyst with enhanced visible-light catalytic performance toward degradation of bisphenol A

A novel solid-state Z-scheme heterostructure, Ag3PO4/Fe3O4 co-doped bamboo-derived activated biochar (Ag–Fe@BAB), was synthesized as an efficient photocatalyst via a co-precipitation method. Ag–Fe@BAB was used as a magnetically recoverable photocatalyst to generate free radical species with peroxydisulfate (PDS) activation under visible-LED-light illumination. The successful synthesis of Ag–Fe@BAB was confirmed by various characterization techniques. Bisphenol A (BPA) was used as a model pollutant to evaluate the photocatalytic activities of the Vis/Ag–Fe@BAB/PDS system. To confirm the photocatalytic performance of the Vis/Ag–Fe@BAB/PDS system, the effects of significant operating parameters such as the contact time, concentration of oxidant, photocatalyst dosage, and solution pH on the degradation of BPA were evaluated. We confirmed that 95.6% BPA was degraded within 60 min in the Vis/Ag–Fe@BAB/PDS system under 1.0 g/L photocatalyst, pH 6.5, and 0.5 mM PDS. The degradation mechanism of BPA in the Vis/Ag–Fe@BAB/PDS system was mainly attributed to O2‾ owing to its photocatalytic performances in the presence of p-benzoquinone as a scavenger. Furthermore, the radical species produced in the Vis/Ag–Fe@BAB/PDS system were identified by electron spin resonance. Finally, we demonstrated the recyclability of the Ag–Fe@BAB photocatalyst through its excellent magnetic property.

Activation of peroxymonosulfate by novel Pt/Al2O3 membranes via a nonradical mechanism for efficient degradation of electron-rich aromatic pollutants

Novel flexible Pt/Al2O3 membranes were prepared and applied as catalysts for the degradation of organic pollutants in the presence of peroxymonosulfate (PMS). 100% of bisphenol A (BPA) could be removed within 20 min by using fresh Pt/Al2O3-membrane-activated PMS, which represents outstanding performance compared to catalysts reported in recent years. The influence of the PMS dosage, initial BPA concentration, and initial pH on BPA degradation were studied. The mechanism of BPA degradation in this system was investigated in depth. The BPA degradation process was not inhibited by the addition of radical scavengers to the system, and no free radicals were detected using ESR analysis. Additionally, the PMS molecules were only decomposed in the presence of both the catalysts and BPA. The results also demonstrated that only electron-rich aromatics could be degraded by this system. Furthermore, in contrast to typical degradation pathways involving the generation of free radicals, no intermediates formed via OH addition reaction were detected. Based on these findings, a nonradical pathway was suggested rather than a conventional OH/SO4− radical-based advanced oxidation process (AOP) mechanism. BPA is efficiently degraded by the transfer of electrons from its π-π aromatic ring to PMS via the noble metal Pt as transfer medium in this reaction. The findings in this work broaden the understanding of the use of activated PMS for the degradation of organic pollutants, and extend the application of flexible inorganic membranes in wastewater treatment.

Degradation of bisphenol A by Fe-Al layered double hydroxides: A new synergy of homo- and heterogeneous Fenton systems

Fe(II)-Al(III) layered double hydroxides (Fe-Al-LDHs) prepared by co-precipitation were used to degrade bisphenol A (BPA) in water. The LDH/H2O2 system proved to be effective in degrading BPA, even under high pH conditions. Influencing factors on the removal of BPA, such as LDH dosage, initial BPA concentration and H2O2 concentration, were studied. The adsorption results and kinetic analysis indicated that the degradation rate of BPA increased with increasing LDH and H2O2 concentration and decreasing the initial concentration of BPA. The reaction mechanism was deduced by using a number of analytical techniques, including XPS, XRD, EPR, SEM, TEM and SAED. It was found that the likely degradation mechanism of BPA by Fe-Al-LDHs is a synergy of the homo- and heterogeneous Fenton systems. In this process, when LDHs and H2O2 are present in the solution, Fe, Al and Cl− in the LDH are released into the solution due to the precipitation-solubility equilibrium. The dissolved Fe2+ reacts with H2O2 to form a homogeneous Fenton reaction system. In addition, the OH− produced during the Fenton reaction may induce ion-exchange through a dissolution-reprecipitation process. During the ion-exchange, the released Fe2+ also takes part in the homogeneous Fenton reaction and released ions reprecipitated into LDHs possibly by reaction with Al3+, Fe3+ and OH−. The undissolved and newly formed LDHs function as heterogeneous Fenton catalysts during the reaction due to the presence of Fe2+ in the structure, thus increasing the reaction efficiency. Moreover, the long term durability of the catalyst over several reaction cycles was also tested and it was found that the material only showed a slight decrease in efficiency after four cycles.

Heterogeneous degradation of bisphenol A by peroxymonosulfate activated with vanadium-titanium magnetite: Performance, transformation pathways and mechanism

The vanadium-titanium magnetite (VTM) has a high comprehensive utilization value because it is an important source of iron (Fe) and other elements such as titanium (Ti) and vanadium (V). In this study, VTM was first used as a PMS activator to evaluate the degradation of bisphenol A (BPA) in the aqueous solution. First, the characteristics of VTM were analyzed via X-ray powder diffraction (XRD), energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Then, effects of several key parameters (i.e., VTM dosage (0–15 g/L), PMS dosage (0–5 mM), initial pH (3.0–11.0) and co-existing ions) on the BPA degradation were investigated systematically. Regardless of the initial pH, 50 mg/L of BPA could be degraded effectively (≥90%) with the fixed VTM (12 g/L) and PMS (4 mM) dosage. Besides, quenching experiments confirmed that the main free radical contributed to the BPA degradation varied with the initial pH. Also, to verify the high efficiency of VTM, two control experiments (i.e., PMS alone and VTM alone systems), reusability and practical application tests were carried out. Furthermore, ten degradation intermediates of BPA were identified via ultrahigh performance liquid chromatograph-mass spectrometry/mass spectrometry (UPLC-MS/MS). Based on the detected intermediates, the degradation pathways and degradation mechanism of BPA were proposed comprehensively. In addition, toxicity tests were performed on samples during processing. Finally, a reasonable reaction mechanism of VTM/PMS system for BPA degradation was put forward thoroughly. In brief, this study provided some new insights for the use of natural ore in the wastewater treatment and all the results suggested VTM is a cheap and efficient catalyst for PMS activation.

Photo-assisted degradation of bisphenol A by a novel FeS2@SiO2 microspheres activated persulphate process: Synergistic effect, pathway and mechanism

In this study, FeS2@SiO2 microspheres were firstly employed as a heterogeneous catalyst to activate persulfate (PS) for the degradation of bisphenol A (BPA) from aqueous solutions. The most relevant findings revealed that UV irradiation induced a significant improvement in the degradation of BPA by the FeS2@SiO2 microspheres/PS system. Nearly 100% of BPA degradation by the FeS2@SiO2 microspheres/PS/UV system was achieved within 120 min at reaction conditions of 1 mM PS, 0.066 mM BPA, 1.0 g/L FeS2@SiO2 microspheres and pH 3.0. A high performance on the degradation of BPA might be attributable to a synergistic effect between the PS/UV and the FeS2@SiO2 microspheres/PS catalytic processes. It was found that the BPA degradation could be inhibited by the coexisting anions like Cl−, HCO3− and PO43− to different extents at much higher concentrations, whereas NO3− had a negligible effect. Organic acids such as ethylene diamine tetra-acetic acid (EDTA) and oxalic acid (OA) would lead to an enhancement with a lower dosage, whereas a significantly negative effect was observed at much higher dosages. Radical scavenging tests revealed that the SO4− radicals prevailed over HO. A total of seven intermediates during the degradation of BPA were identified by GC/MS, and a possible reaction pathway and mechanism of BPA degradation by the FeS2@SiO2 microspheres/PS/UV system was proposed. This study demonstrated a simple water treatment method involving the use of low cost natural iron minerals for organic pollutants removal.

Effect of nitrate, carbonate/bicarbonate, humic acid, and H2O2 on the kinetics and degradation mechanism of Bisphenol-A during UV photolysis

In this study, the effects of natural water components (nitrate, carbonate/bicarbonate, and humic acid) on the kinetics and degradation mechanisms of bisphenol A (BPA) during UV-C photolysis and UV/H2O2 reaction were examined. The presence of NO3− (0.04–0.4 mM) and CO32−/HCO3− (0.4–4 mM) ions increased BPA degradation during UV photolysis. Humic acid less than 3 mg/L promoted BPA degradation, but greater than 3 mg/L of humic acid inhibited BPA degradation. During the UV/H2O2 reaction, all water matrix components acted as radical scavengers in the order of humic acid > CO32−/HCO3− > NO3−. All of the degradation reactions agreed with the pseudo-first-order kinetics. While eight byproducts (m/z = 122, 136, 139, 164, 181, 244, 273, 289) were identified in UV-C/NO3− photolysis reaction, four (m/z = 122, 136, 164, 244) and three byproducts (m/z = 122, 136, 164) were observed during UV-C/NO3−/CO32−/HCO3− and UV-C/CO32−/HCO3− reactions. Nitrogenated and hydrogenated byproducts were first observed during the UV-C/NO3− photolysis, but only hydrogenated byproducts as adducts were detected during the UV-C/NO3−/CO32−/HCO3− photolysis. Nitrogenated and hydrogenated byproducts were formed in the early stage of degradation by OH or NO2 radicals, and these byproducts were subsequently degraded into smaller compounds with further reaction during UV-C/NO3− and UV-C/NO3−/CO32−/HCO3− reactions. In contrast, BPA was directly degraded into smaller compounds by β-scission of the isopropyl group by CO3−/HCO3 radicals during UV-C/CO32−/HCO3− reaction. Our results imply that the water components can change the degradation mechanism of BPA during UV photolysis.

The combination of Fenton process and Phanerochaete chrysosporium for the removal of bisphenol A in river sediments: Mechanism related to extracellular enzyme, organic acid and iron

In this study, Fenton process combined with bioremediation technology, as a novel treatment technology, was applied for the removal of bisphenol A (BPA) from river sediments. The removal rate of BPA reached 58.23% after 24 days of combined treatment, which was higher than those in the treatment with Phanerochaete chrysosporium (P. chrysosporium) alone (21.59%) or the Fenton treatment alone (14.48%). The degradation mechanism of BPA in treatment process was investigated. According to the analyses of pH, iron, enzyme activities and organic acids, it was found that there was a synergetic effect between Fenton process and P. chrysosporium treatment. The organic acids generated by P. chrysosporium created a better acid environment for Fenton reaction, and the ferrous iron introduced by Fenton reagents might stimulate the development of P. chrysosporium. In addition, β-cyclodextrin (β-CD) is a good chelating agent together with excellent bioavailability, so we investigated the influence of β-CD on the combination treatment. Results showed that β-CD was able to promote the combination treatment. We also obtained that the optimal dosage of FeSO4 (270 mmol/L), ratio of Fe2+ to H2O2 and dosage of β-CD (13 mmol/L) were 0.5 mL, 1:14 (mol/mol), 1 mL, respectively. The combined treatment under mild reaction conditions provides a new way for the removal of BPA from polluted river sediments.

Degradation of bisphenol A in water by the photo-Fenton reaction

The photodegradation of bisphenol A (BPA), a representative endocrine disrupting chemical, was carried out in the presence of the Fenton reagent. The degradation rate was strongly influenced by the pH, and initial concentrations of H 2O 2 and Fe(II). An initial BPA concentration of 10 mg l −1 was completely degraded after 9 min under the optimum conditions. This reaction was found to follow the first order kinetics law. The formation of CO 2 as a result of mineralization of BPA was observed during the photo-Fenton process. The degree of BPA conversion to CO 2 was more than 90% under UV irradiation for 36 h. The decomposition of BPA during the photo-Fenton treatment gave six kinds of intermediate products, such as phenol, p-hydroquinone, etc. The degradation mechanism of BPA was proposed on the base of the evidence of the identified intermediates. Based on these results, the photo-Fenton reaction could be useful technology for the treatment of wastewater containing BPA.