Bisphenol A Degradation Efficiency Research Articles

Carbon based cobalt titanate perovskite nanocomposite: Synthesis, characterization, and excellent visible light driven photocatalytic performance

Titanium-based perovskite oxides are the promising photocatalysts for an efficient degradation of organic pollutants. However, charge carriers recombination and wide band gap energy are still the main challenges in their visible-light-driven photocatalytic applications of Titanate perovskites, ATiO3. The immobilization of Titanium-based perovskites on a carbonaceous substrate such as nitrogen-rich carbon nitride, can be considered as an excellent option for enhancing photocatalytic performance. Here, the CoTiO3/C3N5 nanocomposite was synthesized by simple reflux method and used for photocatalytic degradation of three organic pollutants including methylene blue (MB), tetracycline hydrochloride (TC), and bisphenol A (BPA). The results indicated that the photocatalytic activity of the CoTiO3 perovskite was considerably improved by introducing C3N5 nanosheets and fabricating CoTP/C3N5 nanocomposite. The crystalline structure of CoTiO3/C3N5 (CoTP/C3N5) nanocomposites was confirmed successfully by XRD analysis. The specific surface area of the synthesized CoTP/C3N5 nanocomposite was 8.15 m2/g calculated by N2 adsorption–desorption technology. In the 60th minute of the photocatalytic process, the degradation efficiency of MB, TC, and BPA by CoTP/C3N5 were obtained as 98.70, 60.33, and 92.90 %, respectively, which were higher than pristine CoTiO3 nanorods and C3N5 nanosheets. Electrochemical impedance analysis shows that the CoTP/C3N5 nanocomposite has good electrochemical performance. The improvement photocatalytic activity CoTP/C3N5 can be attributed to the suppressing the recombination of photogenerated electrons and holes and good electrochemical performance with high electron transfer capability. The results achieved from UV–Visible Diffused Reflectance Spectroscopy (DRS), mott-schottky measurements and the photocatalytic degradation experiments in the presence of scavengers confirmed the significantly accelerating the Z-scheme charge transfer mechanism where photoexcited carriers can migrate between CoTiO3 perovskite and C3N5 nanosheets.

Peroxymonosulfate activation by CuMn-LDH for the degradation of bisphenol A: Effect, mechanism, and pathway

The remediation of water contaminated with bisphenol A (BPA) has gained significant attention. In this study, a hydrothermal composite activator of Cu3Mn-LDH containing coexisting phases of cupric nitrate (Cu(NO3)2) and manganous nitrate (Mn(NO3)2) was synthesized. Advanced oxidation processes were employed as an effective approach for BPA degradation, utilizing Cu3Mn-LDH as the catalyst to activate peroxymonosulfate (PMS). The synthesis of the Cu3Mn-LDH material was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). According to the characterization data and screening experiments, Cu3Mn-LDH was selected as the best experimental material. Cu3Mn-LDH exhibits remarkable catalytic ability with PMS, demonstrating good degradation efficiency of BPA under neutral and alkaline conditions. With a PMS dosage of 0.25 g·L−1 and Cu3Mn-LDH dosage of 0.10 g·L−1, 10 mg·L−1 BPA (approximately 17.5 μM) can be completely degraded within 40 min, of which the TOC removal reached 95%. The reactive oxygen species present in the reaction system were analyzed by quenching experiments and EPR. Results showed that sulfate free radicals (SO4•—), hydroxyl free radicals (•OH), superoxide free radicals (•O2—), and nonfree radical mono-oxygen were generated, while mono-oxygen played a key role in degrading BPA. Cu3Mn-LDH exhibits excellent reproducibility, as it can still completely degrade BPA even after four consecutive cycles. The degradation intermediates of BPA were detected by GCMS, and the possible degradation pathways were reasonably predicted. This experiment proposes a nonradical degradation mechanism for BPA and analyzes the degradation pathways. It provides a new perspective for the treatment of organic pollutants in water.

Catalytic ozonation of bisphenol A by Cu/Mn@γ-Al2O3: Performance evaluation and mechanism insight

Herein, an alumina-based bimetallic catalyst (Cu1Mn7@γ-Al2O3) was synthesized for bisphenol A (BPA) degradation in the catalytic ozonation process. The catalytic ozonation system could degrade 93.9% of BPA within 30 min under the conditions of pH = 7.0, 10 mg L−1 O3 concentration, and 24 g L−1 catalyst dosage compared to ozone alone (21.0%). The enhanced BPA degradation efficiency was attributed to the abundant catalytic sites and synergistic effects of Cu and Mn. The results revealed that the synergistic interaction between Cu and Mn effectively accelerated the electron transfer process on the catalyst surface, thus promoting the generation of reactive oxygen species (ROS). Further studies indicated that the BPA degradation in Cu1Mn7@γ-Al2O3/O3 system predominantly followed the ·OH and O2·- oxidation pathway. Based on the density functional theory (DFT) calculations and intermediates detected by LC-MS analysis, two pathways for BPA degradation in the Cu1Mn7@γ-Al2O3/O3 system were proposed. The toxicity estimation illustrated that the toxicity of BPA and its byproducts was effectively reduced in the Cu1Mn7@γ-Al2O3/O3 system. This work provides a new protocol for O3 activation and pollutant elimination through a novel bimetallic catalyst during water purification.

Immobilization of laccase on magnetic PEGDA–CS inverse opal hydrogel for enhancement of bisphenol A degradation in aqueous solution

Endocrine disruptors such as bisphenol A (BPA) adversely affect the environment and human health. Laccases are used for the efficient biodegradation of various persistent organic pollutants in an environmentally safe manner. However, the direct application of free laccases is generally hindered by short enzyme lifetimes, non-reusability, and the high cost of a single use. In this study, laccases were immobilized on a novel magnetic three-dimensional poly(ethylene glycol) diacrylate (PEGDA)–chitosan (CS) inverse opal hydrogel (LAC@MPEGDA@CS@IOH). The immobilized laccase showed significant improvement in the BPA degradation performance and superior storage stability compared with the free laccase. 91.1% of 100 mg/L BPA was removed by the LAC@MPEGDA@CS@IOH in 3 hr, whereas only 50.6% of BPA was removed by the same amount of the free laccase. Compared with the laccase, the outstanding BPA degradation efficiency of the LAC@MPEGDA@CS@IOH was maintained over a wider range of pH values and temperatures. Moreover, its relative activity of was maintained at 70.4% after 10 cycles, and the system performed well in actual water matrices. This efficient method for preparing immobilized laccases is simple and green, and it can be used to further develop ecofriendly biocatalysts to remove organic pollutants from wastewater.

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.

A novel strategy of peracetic acid activation by dielectric barrier discharge plasma for bisphenol a degradation: Feasibility, mechanism and active species dominant to degradation pathway

As a typical endocrine disruptor, bisphenol A (BPA) can not only affect the reproduction and development of aquatic organisms, but also pose a significant threat to environmental safety and human health. This work proposed a novel strategy of peracetic acid (PAA) activation by dielectric barrier discharge (DBD) plasma for BPA degradation. It can be confirmed that DBD plasma can effectively activate PAA. 93.4 % BPA was destructed in the DBD/PAA system, which was 39.8 % higher than that in the DBD system alone. The energy yield (G50) of the DBD/PAA system was 211.5 g/kWh, while the single DBD system was only 59.7 g/kWh. The degradation efficiencies of chemical oxygen demand (COD) and total organic carbon (TOC) were also improved. The active substances such as OH, CH3C(O)OO, 1O2, O2−, and e− were important for the degradation of BPA in the DBD/PAA system. The pH dropped, and the total conductivity rose in the degradation processing of BPA. Three-dimensional fluorescence spectroscopy, liquid chromatography mass spectrometry (LC-MS) and density functional theory (DFT) simulation were adopted to investigate the degradation mechanism and process. The toxicity of intermediates in three degradation pathways to aquatic organisms was reduced. The degradation efficiency of BPA was more effective as input power increased and initial concentration decreased. BPA was more easily degraded under acidic solutions than under alkaline and neutral solutions. In addition, the effects of typical inorganic ions and humic acids on BPA degradation in the DBD/PAA system were examined. Finally, the DBD/PAA system is suitable for the application of various pollutants and actual wastewater. This research proposes an innovative idea and reference for PAA activation and plasma application in wastewater treatment.

Enhanced Degradation of Bisphenol A via Ultrasound, Assisted by Chemical Treatment

Ultrasonic technology (US) can be considered a very sustainable and efficient method to remove bisphenol A (BPA) from water. Compared with other methods, the proposed method has some advantages: a simple implementation on existing water treatment and purification facilities, it does not generate residual compounds that produce sludge, a relatively fast time is required for degradation (1–2 h), and high degradation efficiencies. In this work, we present the results regarding BPA degradation efficiency using the ultrasonic technique. The influence of frequency and of some additional compounds, such as carbon tetrachloride (CCl4), FeSO4 7H2O (FS), and ethyl anthraquinone (EAC), were studied. Three different frequencies were used: 1146 kHz, 864 kHz, and 580 kHz, at 50 W. The sampling, performed every 15 min, revealed that the highest BPA degradation was achieved after 60 min. Using the liquid chromatography tandem mass spectrometry (LC-MS/MS) technique, the degradation compounds were identified. Pathways of BPA degradation were also proposed. The use of additives such as CCl4, FS, and EAC proved to have a positive effect on the BPA degradation process assisted by ultrasound. After 60 min of exposure, the degradation capacities reached values of between 50% and 75%, while the mineralization capacities were situated between 20% and 35%. CCl4 and EAC had a more pronounced stimulating action than FS, with the EAC having the highest mineralization capacity, representing around 75% of the degradation capacity.

Catalytic polymerization of bisphenol A using a horseradish peroxidase immobilized microporous membrane reactor.

Bisphenol A (BPA) is one of the most widely used chemical products, which is discharged into rivers and oceans, posing great hazards to organisms such as reproductive toxicity, hormone imbalance and cardiopathy induction. With the expansion harm of BPA, people have paid more attention to the environmental effects. In this paper, the degradation of BPA from the synthetic wastewater using the immobilization of horseradish peroxidase membrane reactor (HPR) was investigated. The immobilized HRP microporous membrane was prepared by the porous calcium alginate method. In addition, the reuse of the immobilized HPR membrane and the measurement of membrane flux showed that the membrane has good activity and stability. Finally, the experimental parameters including reaction time, pH, the concentration of BPA and the dosage of H2O2 were optimized to remove the BPA, and about 78% degradation efficiency of BPA was achieved at the optimal condition as follows: H2O2 to BPA molar ratio of 1.50 with an initial BPA concentration of 0.1 mol/L, the HPR dosage of 3.84 u/mL, the initial solution pH of 7.0, a temperature of 20 °C and a contact time of 10 min.

Synergetic effect of photocatalytic oxidation plus catalytic oxidation on the performance of coconut shell fiber biochar decorated α-MnO2 under visible light towards BPA degradation

Photocatalytic technology is regarded as a promising approach for fast degradation of refractory organic pollutant in water. However, the performance of the photocatalyst can be restricted by the variation of water matrix conditions. Herein, coconut shell fiber was pyrolyzed to biochar (CSB800) and incorporated with α-MnO2 to degrade bisphenol A (BPA) in water under visible light irradiation. The prepared α-MnO2/CSB800 composites demonstrated high efficacy in degrading BPA. Specifically, 0.01 mM of BPA could be completely degraded by 0.1 g/L of MnO2/CSB800 within 45 min. It was found that the incident light could effectively trigger the separation of electron and hole in α-MnO2. The electron and hole were afterwards converted to hydroxyl radical (●OH), superoxide radical (●O2−) and non-radical singlet oxygen (1O2), which subsequently initiated the photocatalytic degradation of BPA. Additionally, α-MnO2/CSB800 could simultaneously participate the oxidative degradation pathway of BPA with its high oxidation-reduction potential. The introduction of CSB800 led to higher BPA degradation efficiency since CSB800 could accelerate the charge carrier transferring rate during BPA degradation process via either pathway. The co-existence of both photocatalytic and oxidative degradation synergy enables α-MnO2/CSB800/visible light system with high catalytic performance stability towards various water matrices. This study proposes an effective strategy to prepare easy-available photocatalysts with high and stable performance towards for addressing organic pollution issues in water.

Hydrothermally treated peat/magnetite composites as highly efficient heterogeneous Fenton catalyst: Integrating multiple reaction mechanisms to enhance the catalytic reactivity for BPA removal

Although various strategies have been developed to boost the reactivity of heterogeneous Fenton catalysts, integrating multiple strategies in one catalyst to achieve high Fenton reactivity is still a challenge. To tackle this issue, the ball-milled peat and magnetite (Mag) composites were hydrothermally treated to synthesize novel heterogeneous Fenton catalyst (i.e., Mag-HTP) for bisphenol A (BPA) removal. The degradation efficiency of BPA (30 mg/L) by H2O2 (2 mmol/L) activated with 50 %Mag-HTP (0.2 g/L) was above 98% within 120 min at initial pH 3. The calculated degradation rate constant of Mag-HTP was 0.0873, which was 20.6 folds higher than that of Mag; moreover, it possessed high reactivity over a wide pH range (3–7) with low H2O2 dosage (0.5–2 mM), and high reaction stability (eight cycles with degradation rate over 95%). The multiple reactive mechanisms were validated: (1) NMR/XPS spectra, H2O2 decomposition, and HO production experiments proved the HTP as an electron donor could directly reduce Fe(III); (2) C-V curves proved the formed C-O-Fe bonds could lower the Fe(II)/Fe(III) redox potential; (3) Raman/EIS spectra, Tafel plot, and radical scavenging tests proved that HTP could serve as an electron shuttle for transferring electrons from H2O2 to Fe(III); (4) NMR spectra proved the formed C-O-C bonds on HTP could function as the dual-reaction-center in Fenton reaction. These multiple mechanisms collectively contributed to the high reactivity of Mag-HTP in the Fenton reaction. Therefore, Mag-HTP shows great potential for practical applications in wastewater treatment and soil remediation due to its cost-effectiveness, easy separation, and high Fenton reactivity.

Continuous degradation of plasticizer bisphenol A by catalytic Cu(FexAl2-x)O4@sediment ceramic membranes combined with peroxymonosulfate activation

The Cu(FexAl2-x)O4-embeded sediment ceramic membranes (CuFeAl@SCMs) were fabricated by the low-temperature sintering technology and further employed in a dead-end filtration device for continuous bisphenol A (BPA) degradation with peroxymonosulfate (PMS) activation. Results showed that using river sediment as precursor decreased the fabrication temperature for ceramic membranes (900 °C). The Al-doping Cu(FexAl2-x)O4 spinel solid solution was the predominant product phase, and the membrane with 42 wt% spinel content (CuFeAl@SCM-42) exhibited the highest BPA degradation efficiency (98.3%). SO4∙- and ∙OH were identified as the involved and primary reactive oxygen species (ROS). The density functional theory (DFT) calculations illustrated the forming mechanisms of SO4∙- and ∙OH. Furthermore, the DFT results confirmed that Al doping could enhance the adsorption energy and the electron transfer rate between the spinel and PMS, which encouraged PMS activation for BPA degradation. The outstanding performance of BPA degradation was observed in different pH, PMS content, transmembrane pressure, anions, natural organic matter (NOM) and water matrices, which revealed the excellent practicability, stability and recyclability of the prepared CuFeAl@SCM-42 in complex water environment. Therefore, this study demonstrated the possibility of using dredged river sediment to fabricate the superior catalytic ceramic membranes for wastewater treatment under a low-temperature sintering scheme.

Preparation of Fe-Cu bimetal from copper slag by carbothermic reduction–magnetic process for activating persulfate to degrade bisphenol A

BackgroundFe-Cu bimetal (Fe-Cu) was prepared from copper slag via a carbothermic reduction–magnetic separation process, and used as persulfate (PS) activator to degrade bisphenol A (BPA). MethodsThe characteristic of Fe-Cu was detected by XRD, SEM-EDS, and XPS. Significant findingsThe Fe-Cu is mainly composed of copper containing metallic iron, iron containing metallic copper, and copper-iron sulfide. The batch experiments results showed that the Fe-Cu offered highly effective BPA removal up to 400 mg/g in the presence of PS within 60 min, and the degradation of total organic carbon was 72.32% under optimal conditions, which proved that Fe-Cu is a highly active PS activator. Electron paramagnetic resonance and radical scavenging experiments showed that sulfate radical (SO4•−) and hydroxyl radical contributed to the degradation of BPA, and SO4•− was dominant. The reuse experiments showed that the degradation efficiency of BPA was still as high as 96.92% after the fourth use. Moreover, the possible BPA degradation pathway was proposed on the basis of intermediates analyzed by gas chromatography–mass spectrometry. This study offers a novel idea for preparing Fe-Cu and suggests that the Fe-Cu/PS system has good potential for removing refractory organic pollutants in wastewater.

Synthesis of an Environmentally Friendly Modified Mulberry Branch-Derived Biochar Composite: High Degradation Efficiency of BPA and Mitigation of Toxicity in Silkworm Larvae

In the present study, mulberry branch-derived biochar CuO (MBC/CuO) composite was successfully synthesized and used as a catalyst to activate persulfate (PS) for the degradation of bisphenol A (BPA). The MBC/CuO/PS system exhibited a high degradation efficiency (93%) of BPA, under the conditions of 0.1 g/L MBC/CuO, 1.0 mM PS, 10 mg/L BPA. Free radical quenching and electron spin-resonance spectroscopy (ESR) experiments confirmed that both free radicals •OH, SO4•- and O2•- and non-radicals 1O2 were involved in the MBC/CuO reaction system. Cl- and NOM displayed negligible influence on the degradation of BPA, while HCO3- promoted the removal of BPA. In addition, the toxicity tests of BPA, MBC/CuO and the degraded BPA solution were conducted by the 5th instar silkworm larvae. The toxicity of BPA was reduced after the treatment in the MBC/CuO/PS system, and no obvious toxicity of the synthesized MBC/CuO composite was found in the toxicity evaluation experiments. This work provides a new value-added utilization of mulberry branches as a cost-effective and environmentally friendly PS activator.

Peroxymonosulfate activation by β-cyclodextrin modified amorphous manganese oxides for a high-efficiency bisphenol A degradation

Manganese oxide activated peroxymonosulfate (PMS) has gradually become one of the research focuses in the field of advanced oxidation. In this work, β-cyclodextrin (β-CD) modified amorphous manganese oxide (CD-AM) catalyst was obtained from a mild reaction condition (80 °C oil bath), high temperature crystallization is avoided in the synthesis process, which reduces the difficulty of catalyst preparation process and energy consumption. β-CD is involved in the formation of manganese oxides. Amorphous manganese oxides have larger specific surface area and better PMS activation effect than crystalline manganese oxides, which is different from previous studies. The enrichment of cyclodextrin on BPA can improve the removal activity of amorphous manganese oxide/PMS system on BPA. The introduction of β-CD increased the bisphenol A (BPA) degradation efficiency from 33.1% to 99.4%, and brought the kinetic constant to its 14.9 times. The 94% BPA degradation efficiency was obtained under neutral conditions that is more favorable for the actual process. During the degradation process, 1O2 and ·OH were the main ROS in CD-AM/PMS system, and O·- 2 not only promoted the conversion of O·- 2 to 1O2 but also accelerated the cycle of Mn (III)/Mn (IV). In addition, a simpler material recovery process for application was achieved by transforming CD-AM into the “supported membrane” (AMSM), and better performance and lower Mn ion leaching concentration were accessible. With the utilization of AMSM, Mn ion concentration in the filtrate after first filtration was about 1.2 mg/L, which was only 37% of the Mn ion concentration firstly detected in CD-AM. And after four cycles, the BPA degradation efficiency was 96.9%. When AMSM/PMS system was used to treat BPA in river water, the final degradation efficiency reached 94.8%. CD-AM as a catalyst for activating PMS shows great application potential in actual water.

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.

Performance and Kinetics of BPA Degradation Initiated by Powdered Iron (or Ferrous Sulfate) and Persulfate in Aqueous Solutions

The widespread use of bisphenol A (BPA) in industry has resulted in BPA contamination of water bodies and even endocrine-disrupting effects on organisms and humans through water transmission. Advanced oxidation processes based on sulfate radicals have received increasing attention due to their ability to efficiently degrade endocrine disruptors (including BPA) in water. In this study, powdered iron (Fe(0)) and ferrous sulfate (Fe(II)) were used as activators to activate persulfate (PS) for the degradation of BPA. The effects of the dosage of the activator, the concentration of PS, the concentration of BPA, the initial solution pH, and the reaction temperature on the degradation efficiency of BPA in Fe(II)/PS and Fe(0)/PS systems were investigated, and the kinetics of BPA degradation under different reaction conditions were analyzed. The results showed that the optimal conditions were [Fe(II)] = 0.1 g/L, [PS] = 0.4 mM, [BPA] = 1 mg/L, T = 70 °C and pH = 5.0 for the Fe(II)/PS system and [Fe(0)] = 0.5 g/L, [PS] = 0.5 mM, [BPA] = 1 mg/L, T = 70 °C and pH = 5.0 for the Fe(0)/PS system; both systems were able to achieve equally good degradation of BPA. The degradation of BPA in the Fe(II)/PS system satisfied the pseudo-secondary kinetic equation under varying PS concentration conditions, otherwise the degradation of BPA in both systems conformed to the pseudo-first-order kinetic equation.

Synthesis of Co3O4 Nanoparticles-Decorated Bi12O17Cl2 Hierarchical Microspheres for Enhanced Photocatalytic Degradation of RhB and BPA

Three-dimensional (3D) hierarchical microspheres of Bi12O17Cl2 (BOC) were prepared via a facile solvothermal method using a binary solvent for the photocatalytic degradation of Rhodamine-B (RhB) and Bisphenol-A (BPA). Co3O4 nanoparticles (NPs)-decorated BOC (Co3O4/BOC) heterostructures were synthesized to further enhance their photocatalytic performance. The microstructural, morphological, and compositional characterization showed that the BOC microspheres are composed of thin (~20 nm thick) nanosheets with a 3D hierarchical morphology and a high surface area. Compared to the pure BOC photocatalyst, the 20-Co3O4/BOC heterostructure showed enhanced degradation efficiency of RhB (97.4%) and BPA (88.4%). The radical trapping experiments confirmed that superoxide (•O2-) radicals played a primary role in the photocatalytic degradation of RhB and BPA. The enhanced photocatalytic performances of the hierarchical Co3O4/BOC heterostructure are attributable to the synergetic effects of the highly specific surface area, the extension of light absorption to the more visible light region, and the suppression of photoexcited electron-hole recombination. Our developed nanocomposites are beneficial for the construction of other bismuth-based compounds and their heterostructure for use in high-performance photocatalytic applications.

Enhanced activation of peroxymonosulfate by abundant Co-Nx sites onto hollow N-doped carbon polyhedron for bisphenol A degradation via a nonradical mechanism

In this study, novel Co-embedded hollow N-doped carbon polyhedrons, derived from ZIF-8@ZIF-67 core–shell structure, were synthesized and used for activating peroxymonosulfate (PMS) towards efficient bisphenol A (BPA) degradation. The contents of different N species, especially Co-Nx and graphitic N sites, were tuned by different calcination temperatures (800, 900, and 1000 °C). Characterization results demonstrated that hollow polyhedron with high graphitization degree and abundant porosity anchored numerous Co nanoparticles, which could enhance the catalytic performance. Compared to other as-prepared catalysts, Co/HNCP-900 (pyrolyzed at 900 °C) showed a more outstanding performance of PMS activation towards BPA degradation, and 95.1 % of BPA (20 mg/L) could be removed within 3 min. Abundant Co-Nx sites were a critical factor to induce the reaction process. Based on trapping, radical scavenger, and electrochemical analysis experiments, a nonradical process (singlet oxygen and direct electron transfer) was proposed to play the dominant role in BPA degradation. Benefiting from the nonradical process, BPA degradation efficiency almost remained stable either in a wide pH range (2.5–8.0) or in the presence of coexisting ions and natural organic matter. The findings of this study will elucidate a new opportunity for improving environmental remediation.

Radical chemistry, degradation mechanism and toxicity evolution of BPA in the UV/chlorine and UV/H2O2

UV-assisted advanced oxidation processes (AOPs) are widely used and studied in degradation of bisphenol A (BPA). However, detailed information on their radical chemistry and degradation mechanisms is still lacking. In this study, degradation of BPA was comparatively evaluated to investigate the radical mechanisms, products and the toxicity variation in UV/chlorine and UV/H2O2 processes. In comparison with UV/H2O2, UV/chlorine had a higher BPA degradation efficiency and higher pH-dependency due to chlorination and the synergy of •OH and RCS. The •OH and Cl• played a pivotal role as the primary radicals in BPA degradation by UV/chlorine process at all pH investigated (6–8). The relative contributions of the secondary radicals ClO• gradually decreased with a variation of pH from 6 to 8 in this process. Presence of HCO3─ and HA inhibited BPA degradation to different extents in UV/chlorine process, while the effect of Cl─ could be neglected. According to the identified transformation products, chlorination (major), hydroxylation and breakage of the isopropylidene chain were BPA decomposition pathways in the UV/chlorine system. In the UV/H2O2 system, only hydroxylation (major) and breakage of the isopropylidene chain occurred. The toxicity analysis, based on the proposed degradation pathways, indicated that the generation of chlorinated products in the UV/chlorine system led to a higher toxicity of the resulting mixture than in the UV/H2O2 system. Although UV/chlorine has an excellent BPA degradation effect and it is cost-effective, the possible environmental risk should be carefully considered when UV/chlorine system is used to remove BPA in real waters.

ZIF-67(Co)-Loaded Filter Paper for In Situ Catalytic Degradation of Bisphenol A in Water

Herein, we loaded cobalt-based zeolite imidazolate frameworks, ZIF-67 (Co), onto commercial filter paper to prepare catalytic filter paper (ZFP) for the in situ degradation of bisphenol A (BPA) in water by activating peroxymonosulfate. The results showed that ZIF-67 (Co) was densely and uniformly distributed on the surface of the filter paper. The prepared ZFP could effectively degrade BPA in situ through a gravity-driven filtration process. Specifically, when the flow rate of the BPA solution passing through ZFP was lower than 10 mL/min, 0.02 mM of BPA could be completely degraded by ZFP. Furthermore, ZFP showed promising water matrix adaptability, which could provide promising BPA degradation efficiency in a wide pH range or in the existence of multiple anions. The scavenging tests demonstrated that both sulfate radical and hydroxyl radical were generated for BPA degradation, in which hydroxyl radical was the dominant active species. The ZFP also exhibited promising long-time use stability with a high mineralization rate. This study provides a novel method to prepare high-efficient catalyst paper for the in situ organic pollutant removal in water media via a prompt filtration process.