Photodegradation Of Bisphenol A Research Articles

Direct and indirect photodegradation of bisphenol A in the presence of natural water components.

The impacts and mechanisms of natural water constituents, such as humic acid (HA), nitrates, iron and chloride ions, to the photodegradation of bisphenol A (BPA) were investigated in aqueous media under UV light irradiation. Due to the contributions of ·OH, 1O2, O2- and BPA* to BPA photodegradation in pure water in 13.4, 7.7, 22.9 and 47.9%, respectively, BPA was attenuated through the reaction pathway of direct photodegradation more than self-sensitized photodegradation. About indirect photodegradation, BPA photolysis through inhibitory effect from HA was mainly by light screening effect and quenching effect was insignificant. NO- 3 and NO- 2 both showed inhibitory effect but due to different reactive oxidization species (ROS). The photodegradation of BPA was significantly enhanced by the addition of iron from the formation of ·OH and H2O2, due to iron-assisted indirect photolysis for the degradation process. A dual effect of chloride depending on the different concentration levels involved quenching and promotion effect on reactive photo-induced species (RPS). A simple linear model revealed that BPA photodegradation was significantly impacted by the interaction of the above factors. In natural water, the decreased photolytic rate of BPA was mainly attributed to triple-excited dissolved organic matter (3DOM*), indicating that indirect photolysis was the primary transformation pathway of BPA. The detected photolysis products, such as nitrate and chlorinated products, suggest that there might be potential ecological risk of BPA photodegradation.

Nanocomposite from tannery sludge-derived biochar and Zinc oxide nanoparticles for photocatalytic degradation of Bisphenol A toward dual environmental benefits

The growing concern over the presence of pollutants like Bisphenol A (BPA) in water sources has led to the growth of novel treatment technologies for its removal. This research work investigates the development of a novel biochar-metal oxide nanocomposite derived from tannery sludge and Zinc oxide (ZnO) nanoparticles for the photodegradation of BPA. The biochar was obtained by pyrolysis process, followed by impregnation of ZnO nanoparticles using a hydrothermal technique. The critical properties of as-prepared nanocomposite were evaluated by FT-IR, BET surface area, XRD, FE-SEM, HR-TEM, XPS, PL, EPR, and Raman Spectroscopy. In addition, the photocatalytic activity of nanocomposites was evaluated by measuring the degradation of BPA in visible light irradiation. The outcomes revealed that ZnO-loaded chemically activated biochar exhibited higher photocatalytic activity for the degradation of BPA than the pristine and non-chemically activated biochar. At pH 5, 0.2 g/L of photocatalyst dosage, 20 ppm of initial pollutant concentration, and 150 min of contact time, the maximum degradation efficiency of BPA was observed as 94.50 %. Also, nanocomposites showed good stability and reusability, with only a slight decrease in photocatalytic activity after multiple cycles of use. More importantly, the degradation mechanisms of BPA using as-prepared nanocomposites were analyzed in detail, indicating that the observed photocatalytic activity could be attributed to the synergistic effect between the biochar and ZnO, which provided a large surface area for the adsorption of BPA and promoted the generation of reactive oxygen species for its degradation. Overall, this study highlighted the potential of using nanocomposites from tannery sludge-derived biochar and ZnO nanoparticles for the degradation of BPA from polluted water sources using a photocatalytic process toward the dual environmental benefits.

MWCNTs Decorated with TiO2 as Highly Performing Filler in the Preparation of Nanocomposite Membranes for Scalable Photocatalytic Degradation of Bisphenol A in Water.

Bisphenol A (BPA), an endocrine-disrupting compound with estrogenic behavior, is of great concern within the scientific community due to its high production levels and increasing concentration in various surface aquifers. While several materials exhibit excellent capacity for the photocatalytic degradation of BPA, their powdered nature and poor chemical stability render them unsuitable for practical application in large-scale water decontamination. In this study, a new class of nanocomposite membranes based on sulfonated polyethersulfone (sPES) and multiwalled carbon nanotubes decorated with TiO2 nanoparticles (MWCNTs-TiO2) were investigated as efficient and scalable photocatalysts for the photodegradation of BPA in aqueous solutions. The MWCNTs-TiO2 hybrid material was prepared through a facile and inexpensive hydrothermal method and extensively characterized by XRD, Raman, FTIR, BET, and TGA. Meanwhile, nanocomposite membranes at different filler loadings were prepared by a simple casting procedure. Swelling tests and PFG NMR analyses provided insights into the impact of filler introduction on membrane hydrophilicity and water molecular dynamics, whereas the effectiveness of the various photocatalysts in BPA removal was monitored using HPLC. Among the different MWCNTs-TiO2 content nanocomposites, the one at 10 wt% loading (sP-MT10) showed the best photoactivity. Under UV irradiation at 254 nm and 365 nm for 240 min, photocatalytic oxidation of 5 mg/L bisphenol A by sP-MT10 resulted in 91% and 82% degradation, respectively. Both the effect of BPA concentration and the membrane regenerability were evaluated, revealing that the sP-MT10 maintained its maximum BPA removal capability over more than 10 cycles. Our findings indicate that sP-MT nanocomposite membranes are versatile, scalable, efficient, and highly reusable photocatalysts for the degradation of BPA, as well as potentially for other endocrine disruptors.

Photocatalytic degradation of bisphenol A in aqueous solution using TiO2/clinoptilolite hybrid photocatalyst.

Photocatalytic degradation of bisphenol A (BPA) was investigated using commercial TiO2 P25 nanoparticles supported on natural zeolite clinoptilolite (Cli). Employing ultrasound assisted solid-state dispersion method hybrid photocatalyst containing 20 wt% of TiO2, marked TCli-20, was prepared. The structural, morphological and surface properties, and particle size distribution of TCli-20 were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, Brunner-Emmet-Teller method and laser diffraction. The results revealed a successful loading of TiO2 P25 nanoparticles on Cli surface and the preservation of both zeolitic structure and optical properties of TiO2. The influence of catalyst dose, pH value and the addition of hydrogen peroxide (H2O2) was evaluated. The optimal reaction conditions were 2g/L of catalyst at near-neutral conditions (pH = 6.4) for complete BPA (5mg/L) photodegradation after 180min of exposure to simulated solar light. The addition of H2O2 was beneficial for the degradation process and led to the removal of BPA after 120min of irradiation. BPA removal (60% for 180min of irradiation) was reduced when TCli-20 was tested in bottled drinking water due to the presence of bicarbonate ions which acted as scavengers for hydroxyl radicals. Even though the photocatalytic activity of TCli-20 decreased after several cycles of usage, 70% of BPA was still successfully degraded during the fourth cycle. The reusability study showed easy separation, stability and good photocatalytic ability of investigated cost-effective hybrid photocatalyst.

Photodegradation of Bisphenol a in Water via Round-the-Clock Visible Light Driven Dual Layer Hollow Fiber Membrane

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) that can cause adverse effects on human health. The incorporation of materials as visible light photocatalysts and its energy storage capability allow for the photodegradation of BPA, especially in the absence of a light source. To date, there have been no significant studies regarding energy storage in membrane technology, with only a focus on the suspension form. Hence, this study was conducted to degrade the pollutant through a co-extrusion process using a mixture of copper (II) oxide and tungsten oxide as the photocatalyst and energy storage materials, respectively. Both materials were embedded into polyvinylidene (PVDF) membranes to produce a Cu2O/WO3/PVDF dual-layer hollow fiber (DLHF) membrane. The outer dope extrusion flow rate was set at 3 mL/min, 6 mL/min, and 9 mL/min with photocatalyst:polymer ratios of 0.3, 0.50, and 0.7 Cu2O/WO3/PVDF, respectively. The performance of the membranes for each ratio was evaluated using 2 ppm of BPA with visible light irradiation. The results showed that each membrane’s outer and inner layers featured finger-like void structures, while the intermediate part had a sponge-like structure. The membrane with the photocatalyst:polymer ratio of 0.5 was hydrophilic and had a high porosity of 54.97%, resulting in a high flow of 510 L/m2h. Under visible light irradiation, a 0.5 Cu2O/PVDF DLHF membrane with a 6-mL/min outer dope flow rate was able to remove 97.82% of 2-ppm BPA without copper leaching into the water sample. Under dark conditions, the DLHF sample showed the capability of energy storage performance and could drive certain degradation after lighting off up to 70.73% of 2-ppm BPA. The photocatalytic DLHF membrane with the ratio of 0.5 was the most optimal due to its potential morphology and ability to degrade a large amount of BPA. It is important to emphasize that usage of materials with the capability for energy storage can provide a significant contribution toward more practical membranes, so photodegradation can occur even in dark conditions.

Bismuth-rich oxyhalide (Bi7O9I3–Bi4O5Br2) solid-solution photocatalysts for the degradation of phenolic compounds under visible light

HypothesisThe development of solid-solution photocatalysts with tunable bandgaps and band structures, which are significant factors that influence their photocatalytic properties, is crucial. ExperimentsWe fabricated a series of novel bismuth-rich Bi7O9I3–Bi4O5Br2 solid-solution photocatalysts with controlled I:Br molar ratios (denoted as B-IxBr1-x, x = 0.2, 0.3, 0.4, or 0.6) via a rapid, facile, and energy-efficient microwave-heating route. The photodegradations under visible-light irradiation of the phenolic compounds (4-nitrophenol (4NP), 3-nitrophenol (3NP), and bisphenol A (BPA)), and the simultaneous photodegradation of BPA and rhodamine B (RhB) in a coexisting BPA − RhB system were investigated. FindingsThe B-I0.3Br0.7 solid solution provided the highest photocatalytic activity toward 4NP degradation, with degradation rates 32 and 4 times higher than those of Bi7O9I3 and Bi4O5Br2, respectively. The photodegradation efficiency of the studied phenolic compounds followed the order BPA (97.5%) > 4NP (72.8%) > 3NP (27.5%). The RhB-sensitization mechanism significantly enhanced the photodegradation efficiency of BPA. Electrochemical measurements demonstrated the efficient separation and migration of charge carriers in the B-I0.3Br0.7 solid solution, which enhanced the photocatalytic activity. The B-I0.3Br0.7 solid solution effectively activated molecular oxygen to produce •O2−, which subsequently produced other reactive species, including H2O2 and •OH, as revealed by reactive-species trapping, nitroblue tetrazolium transformation, and o-tolidine oxidation experiments.

Photocatalytic degradation of bisphenol-A (BPA) over titanium dioxide, and determination of its by-products by HF-LPME/GC-MS

In this work, analytical strategies were developed based on the technique of hollow fiber liquid-phase microextraction and chromatographic methods (LC-UV and GC/MS). These methods allowed the identification of the main Bisphenol-A by-products applying heterogeneous photocatalysis in water samples. BPA degradation in this study was in the order of 90%, and the conditions used in the HF-LPME were optimized through 23 factorial design (6 cm fiber length, stirring speed of 750 rpm, and an extraction time of 30 min). Using a HF-LPME/GC-MS analytical strategy, it was possible to identify six by-products of BPA photodegradation, two of which have not been reported in the literature so far. This knowledge was quite important since the degradation can lead to the formation of more toxic and persistent by-products than the BPA. With the Toxtree software, three degradation products were found to be persistent to the environment, in addition to BPA; however, in 360 minutes of reaction, chromatographic peaks of the precursors were not identified, suggesting that there may have been a total degradation of these compounds. The results showed a great application potential of a miniaturized extraction technique to extract and pre-concentrate the degradation products of emerging contaminants.

Facile low temperature reflux synthesis of Bi self-doped Bi2MoO6 and construction of CaFe2O4/Bi2MoO6 0D QD-2D p-n heterojunction photocatalyst for efficient bisphenol A degradation and Cr(VI) reduction

In this study, a mild reflux route was developed for facile synthesis of Bi-self doped Bi2MoO6 (BMOR) with nanoplate morphology. Microstructural study revealed substitution of Bi5+ ions in the molybdate layer which resulted in partial reduction of Mo6+ to Mo5+ ions and creation of Mo vacancy. The defect engineered BMOR material exhibited improved optical and photoelectrochemical properties compared to its undoped analogue. The BMOR material was subsequently employed as host lattice for construction of CaFe2O4/Bi2MoO6 0D-2D p-n heterojunctions by using an in situ preparative strategy. Well dispersed CaFe2O4 quantum dots over BMOR nanoplates provide a strong interfacial contact conducive for fast charge mobilization. Comprehensive characterization of the composites revealed extended UV–vis response, improved charge carrier separation, prolonged excited state life time and robust radical generation efficiency compared to pure components. The CaFe2O4/Bi2MoO6 composites displayed improved photocatalytic performance for bisphenol A (BPA) degradation (kapp = 0.0132 min−1) and Cr(VI) reduction (kapp = 0.15 min−1) with reaction rates 5–9 times higher than pure components. The involvement of •OH and •O2− radicals in the photodegradation of BPA was confirmed from radical trapping study. The formation of an interfacial p-n heterojunction and a double charge migration mechanism accounted for the improved photocatalytic efficacy of the composite.

Surface functionalization of bauxite hollow fibre membrane using copper oxide (CuO) and its reusability for photodegradation of bisphenol A from aqueous solution

This work developed and applied a CuO-impregnated bauxite hollow fibre membrane (BHFM) using hydrothermal method for bisphenol A (BPA) photodegradation. BHFM was synthesized through a phase inversion method at optimum sintering at 1300 °C. Subsequently, the physico-chemical properties of CuO-coated BHFM were characterized, while its performance for the BPA degradation was investigated at varying time of hydrothermal exposure and compared to ceramic hollow fibre membrane from alumina (AHFM) as control and commercial membranes. Oxidation by-products, resulting from BPA photodegradation, were identified and after treatment, the saturated membrane was regenerated to sustain its cost-effectiveness. As compared to the pristine BHFM membrane, we found that functionalizating BHFM surface with CuO significantly improved its mechanical strength by 130 % from 18.5 to 42.5 MPa. The removal of BPA was enhanced with the increasing hydrothermal time to 5 h due to the even distribution of CuO-impregnated BHMF on its membrane surface. 97 % of BPA removal with 10 mg/L concentration was substantially attained by the same CuO-impregnated BHFM under visible light (VIS) irradiation. Treated effluents, resulting from the BPA photocatalysis, could meet the required effluent limit of 20 mg/L set by national legislation. The possible oxidation by-products cover 4-(2-hydroxy-2-propanol)phenol, 4-isopropylphenol and dihydroxybenzene. With 25 % of efficiency, the saturated CuO-impregnated BHMF was subsequently regenerated for consecutive five cycles. This implies that functionalizing BHMF surface with CuO enabled it to possess outstanding stability and removal performance for treatment of BPA-laden wastewater.

The Roles of Different Fractions in Freshwater Biofilms in the Photodegradation of Methyl Orange and Bisphenol A in Aqueous Solutions.

Freshwater biofilms play an important role in the migration and transformation of organic pollutants, especially under illumination conditions. Nonetheless, the roles of variable fractions in freshwater biofilms, e.g., extracellular polymeric substances (EPS), microbial cells and original biofilms, in promoting the photodegradation of trace organic pollutants remain largely unclear. In this study, two contaminants, i.e., methyl orange (MO) and bisphenol A (BPA), were selected, and the roles of different fractions in freshwater biofilms in their photodegradation performances were investigated. After dosing 696 mg/L SS biofilm harvested from an effluent-receiving river, the direct photodegradation rate of MO and BPA was increased 8.7 times and 5.6 times, respectively. River biofilm EPS contained more aromatic fractions, chromogenic groups and conjugated structures than biofilm harvested from a less eutrophic pond, which might be responsible for the enhanced photodegradation process. The quenching experiments suggested that when EPS fractions derived from river biofilm were dosed, 3EPS* was the major reactive oxygen species during the photodegradation of MO and BPA. Meanwhile, for EPS derived from the pond biofilm, ·OH/1O2 was predominantly responsible for the enhanced photodegradation. Batch experimental results suggested that the cells and EPS in river biofilms could collaboratively interact with each other to enhance the preservation of reactive species and protection of microbes, thus facilitating the photoactivity of biofilms. Our results might suggest that biofilms generated from eutrophic waterbodies, such as effluent-receiving rivers, could play a more important role in the photodegradation processes of contaminants.

Photochemical behavior of constructed wetlands-derived dissolved organic matter and its effects on Bisphenol A photodegradation in secondary treated wastewater

Free water surface flow (FWS) constructed wetlands (CWs) have been broadly applied for polishing secondary treated effluents. Dissolved organic matter derived from FWS CWs (WDOM) plays key roles in contaminants transformations. Conversely, photodegradation could shape the quantity and quality of WDOM, thereby affecting its roles in the photolysis of organic micropollutants (OMPs). Nevertheless, whether and how solar irradiation-induced photodegradation modify the properties of WDOM, and the effects of WDOM on the photodegradation of OMPs remain unclear. This study elucidates the photochemical behavior of two WDOM isolated from field-scale FWS CWs for effluent polishing under simulated sunlight irradiation using spectroscopic tools and high-resolution mass spectra. Furthermore, the roles of WDOM in the photodegradation of Bisphenol A (BPA), as a representative endocrine-disrupting compound (EDC), were comprehensively investigated. Solar irradiation was demonstrated to lower the molecular weight and aromaticity of WDOM, as well as weaken its light absorption. Ultrahigh-resolution mass spectra further confirmed that aromatic and unsaturated structures were susceptible to solar irradiation-induced photodegradation reactions. Subsequently, less aromatic and more saturated structures eventually formed under sunlight irradiation, consistent with the result from spectroscopic characterization. The reactive species produced from WDOM significantly enhanced the photodegradation of BPA with the kobs noticeably increasing 4-fold compared with the kobs for direct photolysis. Additionally, 3WDOM* was identified as the dominant reactive species leading to the photolysis of BPA in the presence of WDOM. These findings improve understanding of the phototransformation behavior of WDOM under sunlight irradiation and the roles that WDOM plays in the photochemical fate of coexisting OMPs in CWs treatment systems.

Fabrication of novel Z-scheme LaCoO3/activated biochar/Ag3PO4 heterojunctions for intensifying visible-light-catalytic degradation of bisphenol A

A novel Z-scheme LaCoO3/activated biochar(AC)/Ag3PO4 heterojunctions was fabricated and characterized by XRD, SEM-EDS, TEM, XPS, FTIR, N2 adsorption–desorption isotherms, UV–Vis-DRS, PL and EIS. The catalytic activity of the photocatalyst was investigated via bisphenol A (BPA) photocatalitic degradation. The results showed that the photodegradation efficiencies of BPA catalyzed by LaCoO3/AC/Ag3PO4 (2:1:10) composite (reached 99 % after 50 min) was superior to those catalyzed by LaCoO3, Ag3PO4, and LaCoO3/Ag3PO4 (2:10). The BPA photodegradation followed the pseudo-first-order kinetic model, the photodegradation rate constants k catalyzed by LaCoO3/AC/Ag3PO4 (2:1:10) was 10.88 times of that catalyzed by Ag3PO4, 1.56 times of that catalyzed by LaCoO3/Ag3PO4 (2:10). Based on the results of characterization and the experiments of trapping active species in photocatalytic degradation process, the transfer of photo-generated carriers and Z-scheme LaCoO3/AC/Ag3PO4 heterojunctions photocatalytic mechanism were proposed. Furthermore, the possible BPA degradation pathways were involved in hydroxylation, oxidation, ketonization and cyclic cleavage. Z-scheme LaCoO3/AC/Ag3PO4 heterojunctions can be used as an efficient photocatalyst for practical applications in the removal of endocrine disrupting chemical.

Insight into the Key Role of Cr Intermediates in the Efficient and Simultaneous Degradation of Organic Contaminants and Cr(VI) Reduction via g-C3N4-Assisted Photocatalysis.

Photocatalysis provides an impetus for the synergetic removal of Cr(VI) and organic contaminants, but the generation of Cr intermediates and their potential oxidizability may be overlooked in pollutant conversion. Herein, the Cr intermediates in the Cr(VI) reduction process were emphasized in Cr(VI)/bisphenol A (BPA) by using graphitic carbon nitride as a photocatalyst. The active species for BPA photodegradation in the BPA system and Cr(VI)/BPA system suggested that the Cr(VI) reduction process indeed promotes BPA photodegradation. Electron paramagnetic resonance (EPR) of Cr complexes and in situ variable-temperature EPR analysis demonstrated Cr(V) intermediate (g = 1.978) generation in Cr(VI) reduction and its oxidization for BPA degradation in photocatalysis. By adding the electron donor Na2SO3, BPA degradation was induced in Cr(VI)/BPA solution, further confirming the positive effect of Cr(V). Moreover, the difference in BPA degradation products in the BPA/air, Cr(VI)/BPA/air, and Cr(VI)/BPA/Ar systems indirectly explained why the Cr(V) intermediate was involved in BPA degradation. Density functional theory calculations revealed that photogenerated electrons can reduce the free energy (0.98 eV) of converting Cr(VI) into Cr(V), which can facilitate the subsequent Cr(V) oxidation step for BPA degradation. This work contributes to the exploration of the Cr(VI) reduction process and the synergistic removal of organic pollutants in Cr(VI)/organics systems.

Amalgamation of g-C3N4 with KNbO3 for enhanced removal of Bisphenol A under sunlight irradiation

Bisphenol A (BPA) is a pollutant exits in an enormous amount in wastewater effluent resulted from the rapid industrialization. Advanced oxidation technology (AOP) based on solar photocatalysis can be employed to solve this issue. This study will focus on adopting photocatalyst graphitic carbon nitride (g-C3N4) with potassium niobate (KNbO3) via a simple sol-gel synthesis method. The different weight percentages 0.5, 1.0 and 1.5 wt% g-C3N4, were adopted to formed KNbO3/g-C3N4composites. The physicochemical properties of the created KNbO3/g-C3N4composites were characterized with advanced analysis methods to unveil this composite’s ability to enhance the photodegradation of BPA under sunlight irradiation. It was found that 1.0 wt% KNbO3/g-C3N4composites exhibited the highest photocatalytic degradation of 69.39% in 5 h. This superior photodegradation of BPA was achieved resulted from the presence of g-C3N4that enhances light-harvesting, especially in the visible light spectrum. The increase of light-harvesting enables the composite to excite more electrons and holes leading to the massive formation of active radicals. These massive active radicals will then enhance the redox reaction and further improve the efficacy of the photodegradation of BPA. Hence, the outcome of this study path an alternative solution for eliminating complex organic pollutants in wastewater treatment.

Enhanced photocatalytic degradation of bisphenol A over N,S-doped carbon quantum dot-modified MIL-101(Fe) heterostructure composites under visible light irradiation by persulfate

A novel nitrogen- and sulfur-doped carbon quantum dot-modified MIL-101(Fe) (N,S:CQD/MIL-101(Fe)) heterojunction for visible light-induced activation of persulfate (PS) for bisphenol A (BPA) degradation was studied. The photocatalytic performance of BPA degradation was remarkably promoted by the composite material under the simultaneous action of PS and visible light irradiation. BPA photodegradation (100%) was achieved over 60 min with 0.4 g/L of the N,S:CQD/MIL-101(Fe) composite and 3 mM PS at natural pH. The degradation kinetics rate constants (k) approached 3.6 times higher than that of MIL-101(Fe). The enhanced performance in BPA degradation can be ascribed to the interfacial transference of photoinduced electrons from N,S:CQD to MIL-101(Fe), leading to the valid separation of electron-hole pairs and greatly accelerating PS activation to generate highly reactive SO4•−. Both holes (h+), sulfate radicals (SO4•−), superoxide radicals (•O2−), and hydroxyl radicals (•OH) contributed to BPA degradation according to radical quenching experiments. N,S:CQD/MIL-101(Fe) also exhibited great reusability and excellent catalytic performance after four consecutive cycles of use. This work provides valid organic contaminant degradation under the dual action of visible light and PS with a novel perspective on the fabrication of heterojunction photocatalysts ground on Fe-based MOFs.

Photodegradation of bisphenol A from aqueous solution over reduced graphene oxide supported on tetragonal silica-zirconia nanocatalysts: Optimization using RSM

Bisphenol A (BPA) is an endocrine disruptor, and removing it from contaminated water is a major environmental concern. Herein, graphene derivatives such as graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO) supported silica-zirconia (SZ) were successfully synthesized for photodegradation of BPA. The photodegradation of BPA was ordered as follows: rGO/SZ (88%)>GO/SZ (63%)>G/SZ (58%)>SZ (55%). This is because rGO has bigger regions for π-π stacking and less negatively charged carboxyl groups, which BPA has a higher adsorption affinity than GO. In addition, the highest degradation is predominantly due to the high number of carbon-support interactions and defects sites, including oxygen vacancy. This encouraged effective mobility of charge carriers and subsequently enhanced photoactivity. In this study, the rGO/SZ catalyst was chosen to optimize further the reaction parameters including catalyst dosage, pH and initial concentration of BPA. According to the analysis of variance, the catalyst dosage was the most important variable in the degradation of BPA, followed by pH and initial concentration. The optimum BPA degradation predicted from response surface methodology is 88% at conditions of 8.09 mg L−1 using 0.469 g L−1 of rGO/SZ at pH 6.1, which is reasonably close to the predicted value (89.8%). The rGO/SZ catalyst was found to be stable even after five cycles in the reusability testing.

Photodegradation of Bisphenol A and Triclosan using ZnCl2(6OMeQ)2 complex as photosensitizer under homogeneous conditions

The complexes derived from 6-methoxyquinoline ZnCl2(6OMeQ)2 have been shown to be effective as singlet molecular oxygen photosensitizers, which can be interesting for the removal of microcontaminants such as Bisphenol A (BPA) and Triclosan (TCS). Photodegradation with eosin Y (EOY) was also carried out as standard photosensitizer. Due to the physicochemical characteristics of these synthesized photosensitizers, the analysis was carried out in a homogeneous system in simulated effluents. An experimental design was made, based on previous studies and supporting literature. It was established that, at pH 5 and at 0.00104 mM EOY concentration, 20% removals were obtained in the case of BPA. Then, using the same photosensitizer with TCS it was possible to establish photodegradation up to 56% at the same pH but at a temperature of 50 °C, associating this result with the increase in temperature generated, and an increase in speed being reflected in the results obtained. Photodegradation using the coordinated compound, at pH 5.0, and 0.00119 mM photosensitizer concentration, a 26.7% of BPA photodegradation was obtained and, at 50 °C and pH 6, a 52.3% of TCS photodegradation was obtained. This photosensitizer is comparable for the removal this kind of the micropollutant. The experiments were made with UV/VISIBLE Lamps and monitored for HPLC, and some subproducts were analyzed for GC/MS.

Novel Ti3C2/Bi@BiOI nanosheets with gradient oxygen vacancies for the enhancement of spatial charge separation and photocatalytic performance: The roles of reactive oxygen and iodine species

In this study, we reported a series of novel Ti3C2/Bi@OVs-BiOI photocatalysts using MXene to tailor the surface structure and photocatalytic activity of BiOI nanosheets. Notably, the Ti3C2 with surface terminal Ti sites can induce the formation of gradient oxygen vacancies (OVs) and in-situ generation of metallic Bi on BiOI nanosheets. Compared with pristine BiOI, 10% Ti3C2/Bi@OVs-BiOI photocatalyst exhibited a higher photodegradation efficiency and the corresponding first-order reaction rates of antipyrine (ANT) and bisphenol A (BPA) photodegradation were increased by 2.4 times and 18.6 times, respectively. The high photodegradation efficiency was mainly attributed to the enhanced light absorption ability and accelerating spatial charge carriers separation. Interestingly, there existed a significant decrease of photocatalytic performance in the ANT photodegradation cycle test, which is attributed to the break of “interlayer anion exchange” chemical equilibrium. Further radicals trapping experiments confirmed that reactive oxygen species (ROSs: h+ and •O2–) were the dominant reactive species for ANT and BPA photodegradation. In addition, free iodine analysis and LC-MS/MS results suggested that reactive iodine species (RISs: •I and •I2-) played the important roles in the photocatalysis process. According to the theoretical calculation of frontier electron densities (FEDs), the contribution and reactivity of RISs were firstly proposed in the BiOI-based photocatalysis process. These new findings not only provide a potential approach to the application of BiOI-based photocatalysis but also clarify the relationship between the stability of BiOI and interlayer anion exchange.

Graphitic carbon nitride embedded with graphene materials towards photocatalysis of bisphenol A: The role of graphene and mediation of superoxide and singlet oxygen

Composite photocatalysts comprising graphitic carbon nitride (g-C3N4) and graphene materials were synthesized and evaluated in the photocatalysis of bisphenol A (BPA) with a focus on elucidating the reaction mechanism. Embedding reduced graphene oxide (rGO) to g-C3N4 significantly accelerated the photocatalysis rate of BPA by three folds under visible light irradiation at neutral pH. We showed that rGO synthesized in intimate contact with g-C3N4 increased the surface areas and electrical conductivity of the g-C3N4 composites and promoted the electron-hole pair separation. The BPA photodegradation mechanism involved selective oxidants as superoxide (O2•−) and singlet oxygen (1O2) that were formed through one-electron reduction of O2 and the unique oxidation of O2•− by photogenerated hole (h+), respectively. The synthesized photocatalyst exhibited superior visible light photoreactivity to that of N-doped P25 TiO2, good photo-stability and reuse potential, and was operative in complex wastewater. rGO embedded g-C3N4 achieved good photomineralization of BPA at 80% in 4 h compared to 40% of bare g-C3N4. This study sheds light on the photocatalysis mechanism of BPA with a metal-free, promising rGO/g-C3N4 photocatalyst.

Bi4O5Br2 nanosheets with vertical aligned facets for efficient visible-light-driven photodegradation of BPA

Enhancing spatial charge separation efficiency through directional charge transfer is one of the vital strategies to improve the photocatalytic performances. Bi4O5Br2 nanosheets with vertical aligned (11−3), (32−2), and (112) facets were constructed to achieve the efficient directional charge transfer and separation based on the distinctive electronic and band structures of different facets. That is, the photoexcited electrons migrate to the top surface of (11−3) facet of the Bi4O5Br2 nanosheets, while the holes transfer to the lateral surface of (32−2) and (112) facets. As a result, such Bi4O5Br2 nanosheets with vertical aligned facets has highly strengthened the visible-light photodegradation efficiency of bisphenol A (BPA), which is around 6 times higher than that of BiOBr nanosheets. This work provides new sight to rational design the facets of photocatalysts for effective separation of charge carriers and promoted photocatalytic performances.