BPA Degradation Research Articles

Efficient charge separation and improved photocatalytic activity in Type-II & Type-III heterojunction based multiple interfaces in BiOCl0.5Br0.5-Q: DFT and Experimental Insight

The nanostructured, inner-coupled Bismuth oxyhalides (BiOX0.5X′0.5; X, X’ = Cl, Br, I; X≠X′) heterostructures were prepared using Quercetin (Q) as a sensitizer. The present study revealed the tuning of the band properties of as-prepared catalysts. The catalysts were characterized using various characterization techniques for evaluating the superior photocatalytic efficiency and a better understanding of elemental interactions at interfaces formed in the heterojunction. The material (BiOCl0.5Br0.5-Q) reflected higher degradation of MO (about 99.85%) and BPA (98.34%) under visible light irradiation than BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q. A total of 90.45 percent of total organic carbon in BPA was removed after visible light irradiation on BiOCl0.5Br0.5-Q. The many-fold increase in activity is attributed to the formation of multiple interfaces between halides, conjugated π-electrons and multiple –OH groups of quercetin (Q). The boost in degradation efficiency can be attributed to the higher surface area, 2-D nanostructure, inhibited electron-hole recombination, and appropriate band-gap of the heterostructure. Photo-response of BiOCl0.5Br0.5-Q is higher compared to BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q, indicating better light absorption properties and charge separation efficiency in BiOCl0.5Br0.5-Q due to band edge position. First-principles Density Functional Theory (DFT) based calculations have also provided an insightful understanding of the interface formation, physical mechanism, and superior photocatalytic performance of BiOCl0.5Br0.5-Q heterostructure over other samples.

Hollow core–shell Co9S8@ZnIn2S4/CdS nanoreactor for efficient photothermal effect and CO2 photoreduction

The hollow core–shell Co9S8 @ZnIn2S4/CdS nanoreactors are fabricated by growing ZnIn2S4 nanosheets and CdS quantum dots on hollow Co9S8 nanocages for photocatalytic CO2 reduction and H2 generation. Because of unique structural and compositional advantages, Co9S8 @ZnIn2S4/CdS exhibits a significant photocatalytic BPA degradation of 90.62%, CO production of 82.10 μmol g−1 h−1, and H2 evolution rate up to 1419.14 μmol g−1 h−1. Excellent photocatalytic performances are attributed to unique core-shell architecture, which can improve the scattering and refraction efficiency of incident light, and the separation and migration of photoinduced carriers. Furthermore, Co9S8 @ZnIn2S4/CdS possesses a broad absorption spectrum facilitating outstanding photothermal performance. The photocatalytic mechanism for the nanoreactor has been discussed in detail.

Manipulating the morphology of 3D flower-like CoMn2O4 bimetallic catalyst for enhancing the activation of peroxymonosulfate toward the degradation of selected persistent pharmaceuticals in water

A 3D flower-like CoMn2O4catalyst was synthesized via hydrothermal-calcination technique as peroxymonosulfate (PMS) activator for the remediation of pharmaceuticals, exemplified by antibiotics tetracycline (TC) in aqueous solutions. TC degradation in the CoMn2O4-PMS system took place over a broad pH range of 5 to 9. Different water matrices (tap water and lake water) did not affect the efficiency of CoMn2O4/PMS system. Multiple uses of CoMn2O4did not alter the surface properties and catalytic TC degradation efficiency. The dissolution of component metal ions was below the allowable drinking water standard. Carbon oxidation state was increased from −0.51 to 1.2, indicating high degree of mineralization. Non-radical, specifically singlet oxygen, and radical, namely, hydroxyl and sulfate radical, contributed 30.6% and 68.4% to TC degradation, respectively. The CoMn2O4-PMS system was efficient in the degradation of several pharmaceuticals, including tetracycline, SMX, Cipro CIP and BPA.

A novel snowflake dual Z-scheme Cu2S/ RGO/ Bi2WO6 photocatalyst for the degradation of bisphenol A under visible light and its effect on crop growth

In this work, a Z-scheme photocatalyst Cu2S/RGO/Bi2WO6 was synthesized to remove BPA by activation of peroxymonosulfate (PMS) to generate •SO4- with strong oxidation effect. The removal efficiency of BPA could reach 91.00% within 40 min of illumination time. Simultaneously, the effect of pH and PMS dosage on BPA degradation was also investigated, and the highest BPA removal efficiency was achieved at a pH of 9.2 and a PMS dosage of 50 mg. In addition, the degradation mechanism of BPA was proposed and the degradation pathways was analyzed based on free radical capture experiments. In particular, the effect of photocatalytic treatment of BPA solution on the growth of mung bean and soybean was investigated using mung bean and soybean as materials. The results showed that the effect on the growth of mung beans and soybeans was minimal, further demonstrating the effective degradation of BPA.

2D/3D S-scheme heterojunction of carbon nitride/iodine-deficient bismuth oxyiodide for photocatalytic hydrogen production and bisphenol A degradation

A novel 2D/3D S-scheme carbon nitride/iodine-deficient bismuth oxyiodide (g-C3N4/BiO1.2I0.6) heterojunction was constructed for the first time by calcining a mixture of g-C3N4 nanosheets and flower-like BiOI. Irradiated by visible light, this g-C3N4/BiO1.2I0.6 heterojunction exhibited excellent photocatalytic hydrogen production and BPA degradation activity with high cycle stability. In particular, the photocatalytic activity of 0.2-C3N4/BiO1.2I0.6 could reach 1402.7 μmol g-1 h−1 (hydrogen production rate) and 0.01155 min−1 (apparent rate of bisphenol A degradation), which were 3.5 and 3.2 times that of g-C3N4 respectively. The remarkable photocatalytic performance was due to the efficient charge separation of g-C3N4/BiO1.2I0.6 and the formation of S-scheme heterojunction, which maintained strong photocatalytic reduction and oxidation potentials. Noticeably, the charge density difference and band offsets of the g-C3N4/BiO1.2I0.6 were calculated. The results revealed that a built-in electric field (IEF) was created. The values of the valence band offset (ΔEVBO) and the conduction band offset (ΔECBO) were −0.84 and −1.27 eV, respectively, which further demonstrated the formation of S-scheme photocatalytic charge transfer mechanism.

Coupling morphology control and surface I grafting for boosting the photocatalytic activity of Bi2O2[BO2(OH)] nanosheets

Photocatalytic performance of semiconductors is currently limited by low solar light utilization, rapid charge recombination and limited reactive sites. Reducing the thickness of layered photocatalysts can shorten the charge transport distance to inhibit their recombination and provide more reactive sites. Surface ionic grafting can broaden the light absorption range and promote the separation efficiency of carriers. In this work, the surface iodine ion modified Bi2O2[BO2(OH)] nanosheets are synthesized by combining the surfactant-assisted hydrothermal method and room-temperature KI solution treatment route. These nanosheets show increased photoabsorption in visible region, enlarged specific surface area and promoted charge separation. Compared with the pristine Bi2O2[BO2(OH)], the surface I- modified Bi2O2[BO2(OH)] nanosheets exhibit substantially strengthened photocatalytic performance for degradation of BPA, which increases beyond 25 times. The total organic carbon content (TOC) test reveals that the mineralization process of BPA. Electron spin resonance (ESR) measurements disclose the radicals that play dominant role in the photocatalytic process and confirm their increased yield over I- modified Bi2O2[BO2(OH)] nanosheets. In addition, BiOB-S-I2 also shows universality for degradation of a variety of high-concentration pollutants, including rhodamine B, methyl orange, methylene blue, phenol, 2,4-dichlorophenol and tetracycline hydrochloride. This study may provide a combined strategy for exploring high-performance photocatalysts via microstructure control and surface ionic decoration.

Visible light-driven photocatalytic activity of wide band gap ATiO3 (A = Sr, Zn and Cd) perovskites by lanthanide doping and the formation of a mesoporous heterostructure with ZnS QDs

Charge carrier recombination and wide band gap energy are still the main challenges in the visible-light-driven photocatalytic applications of titanate perovskites, ATiO3. Herein, three strategies are rationally used to achieve a titanate-based photocatalyst with high photocatalytic performance under visible light. In the first step, SrTiO3, ZnTiO3, and CdTiO3 perovskites were synthesized and their photocatalytic activity was evaluated in the degradation of methylene blue (MB) and bisphenol A (BPA). Then, a dysprosium cation (Dy3+) was doped into an ATiO3 crystalline lattice. Systematic investigations indicate that Dy doping in SrTiO3 and CdTiO3 extends the ligand to metal charge transfer absorption edge to visible wavelengths leading to the activation of doped perovskites under visible light. Higher visible-light-driven photocatalytic performance (73.29% for MB and 52.57% for BPA) and higher total organic carbon (TOC) removal (59.20% for MB and 39.53% for BPA) have been achieved by Dy doped CdTiO3 compared to other photocatalysts. Finally, we prepared a Dy-CdTP/ZnS QD mesoporous type-II heterostructure by the in situ growth of ZnS QDs on a flower-like Dy-CdTP. This design accelerates the separation and transfer of photogenerated electron-hole pairs. The surface area of the Dy-CdTP/ZnS QD heterostructure was ∼11.6 times greater than that of Dy-CdTP, offering a large surface area for the adsorption of organics, and abundant active sites for photocatalytic degradation. Taking advantage of the large surface area and considerable suppressing of the charge carrier recombination, the optimized Dy-CdTP(0.6)/ZnS QD photocatalyst exhibits excellent and stable performance for the degradation of MB (98.25%) and BPA (89.12%) with their considerable mineralization under visible light.

Z-Scheme Heterojunction of BioI Nanosheets Grown in Situ on NH2-UiO-66 Crystals with Rapid Degradation of BPA in Real Water

Z-Scheme Heterojunction of BioI Nanosheets Grown in Situ on NH2-UiO-66 Crystals with Rapid Degradation of BPA in Real Water

Fabrication of a recyclable magnetic halloysite-based cobalt nanocatalyst for the efficient degradation of bisphenol A and malachite green

A covalently modified, surface engineered Co(II)@2-BPy@APTES@MHNTs nanocatalyst has been fabricated which showed impressive catalytic potency in accelerating degradation of BPA and MG.

Construction of Bi4o5br2 Nanosheets Modified by Carbon Quantum Dots: Visible Driven Degradation of Bpa by Broad-Spectrum Absorption and Z-Scheme Charge Transfer

Construction of Bi4o5br2 Nanosheets Modified by Carbon Quantum Dots: Visible Driven Degradation of Bpa by Broad-Spectrum Absorption and Z-Scheme Charge Transfer

CuO-TiO2/graphene ternary nanocomposite for highly efficient visible-light-driven photocatalytic degradation of bisphenol A

To prepare a visible light-responsive photocatalyst of coupled CuO-TiO2 anchored on graphene oxide (CuO-TiO2/GO) nanocomposite, CuO-TiO2 photocatalyst was initially synthesized by surfactant assisted-sol-gel method and then anchored on GO via a simple hydrothermal process. The results of XPS, TEM, SEM and Raman analyses indicated that the being of CuO-TiO2 particles are decorated on the surface of GO effectively, accordingly resulting in the effective photo-generated charge separation, which was evaluated and supported via PL spectra and time-resolved PL spectra. The photocatalytic performance of CuO-TiO2/GO could also be improved via adjusting the proportion between CuO-TiO2 and GO. The best GO percentage is 10wt%, at which CuO-TiO2/GO composite exhibited the excellent BPA removal percentage of 56.5% compared with CuO-TiO2 photocatalyst (28.8%) after 300 min. of visible light. In addition, the postulated mechanism of the photocatalytic performance of this CuO-TiO2/GO ternary nanocomposite has been evaluated. The dominant reactive oxygen species (ROS) formed during the photocatalytic reactions were determined to be O2.− and .OH. The effect of the presence of anions on BPA degradation was also discussed in dept. While Cl− and NO3− have an inhibitory effect, HCO3− and CO32− have an accelerating and great improving effect towards photocatalytic degradation of BPA. This work indicates that this CuO-TiO2/GO hybrid ternary nanocomposite can also be performed as a highly potential photocatalyst in secondary treatments to degrade other organic pollutants.

One-pot synthesis of C-doping and defects co-modified g-C3N4 for enhanced visible-light photocatalytic degradation of bisphenol A

Doping and defects were often used for g-C3N4 modification to improve its photocatalytic performance. In this work, modified g-C3N4 (CE) was successfully synthesized by a simple one-pot thermal polymerization using urea as precursor and EDTA-2Na as modifier. The results showed that the addition of EDTA-2Na increased the carbon content and formed defects in the modified g-C3N4, but excessive EDTA-2Na might lead to disorder of the g-C3N4 structure. The co-modification of C-doping and defects can narrow the energy band gap of g-C3N4 and improve the photogenerated carrier mobility, which enables it to utilize visible light more efficiently. The modified g-C3N4 (0.02CE) synthesized by adding 0.02 g EDTA-2Na exhibited the best catalytic activity and it was 8.68 times higher than that of the original g-C3N4 for the degradation of BPA (10 mg/L). In addition, it was able to completely degrade BPA (0.2 mg/L) in aqueous solution within 40 min and reach 83.1% degradation rate for BPA (0.2 mg/L) in municipal sewage. 0.02CE showed the best photocatalytic activity at pH 11. Superoxide radicals (·O2-) and photogenerated holes (h+) were proved to be the dominant active species in the reaction process of catalytic degradation of bisphenol A by free radical scavenging experiments and ESR testing.

Unveiling the role of cobalt species in the Co/N-C catalysts-induced peroxymonosulfate activation process

In this study, three Co/N-C catalysts were prepared by pyrolysis of bimetallic zeolitic imidazole frameworks with different Co/Zn ratio, and the critical active Co species in peroxymonosulfate (PMS) activation was investigated. The three catalysts had distinct cobalt species but similar N configuration and graphitization degree. The Co species were distributed as single atoms (Co SAs) at a Co/Zn molar ratio of 1:8, while Co nanoclusters (Co NCs) and Co nanoparticles (NPs) would be formed with further increase in Co content. The degradation efficiency of BPA did not show correlation with the increasing of Co content in catalyst. Based on the catalytic performance comparison and reactive species detection, Co SAs was identified as active sites, which could interact with PMS to generate 1O2 via path of PMS→HOO*→O*→1O2. However, the role of NCs and NPs in directly activating PMS was negligible. In addition, the increase of Co content in Co/N-C catalyst would result in mass cobalt leaching, which enhanced the BPA degradation via homogeneous catalytic reactions with CoIV as reactive species. It is an effective way to design the Co/N-C catalyst with high catalytic activity and stability via regulating the formation of Co SAs.

Mesoporous carbon framework supported Cu-Fe oxides as efficient peroxymonosulfate catalyst for sustained water remediation

Large-scale green synthesis of high-performance catalysts is desirable for practical application of peroxymonosulfate (PMS) based advanced oxidation process. In this study, mesoporous carbon framework supported Cu-Fe oxides (CuO/CuFe2O4) was synthesized via calcination of cost-effective metal-plant phenolic networks for PMS activation to degrade organic pollutants. The mesoporous carbon framework enables highly spatial dispersion of nanosized Cu-Fe oxides, enhanced adsorption of organic pollutant (Bisphenol A, BPA) and improved electron transfer efficiency. Benefiting from the advantageous structure, the mesoporous carbon framework supported Cu-Fe oxides manifested excellent catalytic efficiency in PMS activation, enabling fast and sustained removal of BPA in simulated and actual contaminated water at neutral pH. Chemical scavenging experiments and electron paramagnetic resonance (EPR) tests revealed that reactive oxygen species (ROS) including SO4•−, OH• and 1O2 all participated in the degradation of BPA. The kinetic study and in situ characterization with ATR-FTIR indicated that PMS was activated by surface Cu(II) through an outer-sphere interaction, and a redox cycle of Cu(II)-Cu(I)-Cu(II) was responsible for the generation of ROS. This work demonstrates a reliable method for rational design of hybrid catalyst of metal oxide and carbon material for efficient wastewater remediation.

Tailored d-Band Facilitating in Fe Gradient Doping CuO Boosts Peroxymonosulfate Activation for High Efficiency Generation and Release of Singlet Oxygen.

In the field of heterogeneous catalysis, limitations of the surface reaction process inevitably make improving the catalytic efficiency to remove pollutants in water a major challenge. Here, we report a unique structure of Fe surface-gradient-doped CuO that improves the overall catalytic processes of adsorption, electron transfer, and desorption. Interestingly, gradient doping leads to an imbalanced charge distribution in the crystal structure, thereby promoting the adsorption and electron transport efficiency of peroxymonosulfate (PMS). The orbital hybridization of Fe also improves the electronic activity. More importantly, the occupied d-orbital distribution is closer to the lower energy level, which improves the desorption of the reaction intermediate (1O2). As a result, the production and desorption of 1O2 have been improved, resulting in excellent BPA degradation ability (kinetic rate increased by 67.3 times). Two-dimensional infrared correlation spectroscopy is used to better understand the doping process and catalytic mechanism of Fe-CuO. Fe-O changes before Cu-O and is more active. The Fe-required active sites, active species intensity, and kinetic reaction rates show a good correlation. This research provides a scientific basis for expanding the purification of toxic organic pollutants in complex water environments by heterogeneous catalytic oxidation.

Degradation of bisphenol A through Ti–BiOI/ZIF-8/peroxymonosulfate (PMS): Catalyst preparation, experimental design and catalytic mechanism

In this work, zeolitic imidazolate framework-8 (ZIF-8) was loaded onto Ti-modified BiOI (Ti–BiOI) by in-situ synthesis to prepare novel binary photocatalytic materials (Ti–BiOI/ZIF-8), its physical parameters, chemical parameters, crystal structure and electrochemical properties were characterized. A novel photocatalytic oxidation system (Ti–BiOI/ZIF-8/PMS/Vis) consisting of Ti–BiOI/ZIF-8 and peroxymonosulfate (PMS) could efficiently remove BPA under visible light. In the first 2 ​min of the photocatalytic reaction, Ti–BiOI/ZIF-8 and PMS were excited to generate a large number of active groups (•O2−, •OH, •SO4− and h+), more than 90% of BPA was removed, and the degradation rate of Ti–BiOI/ZIF-8/PMS/Vis was 3.5 times higher that of monomer BiOI, and the removal rate of total-organic-carbon reached about 60%. In addition, the effects of PMS dosage and catalyst dosage on the removal of BPA were also investigated. The stability and reusability of the Ti–BiOI/ZIF-8 were verified through four cycles of degradation of BPA.

Modulating the biofunctionality of enzyme-MOF nanobiocatalyst through structure-switching aptamer for continuous degradation of BPA

Encapsulating enzyme within MOF (enzyme-MOF) gives rise to new opportunity to improve the fragility of enzyme, but practical application of enzyme-MOF composite is far from being realized. The development of a novel enzyme-MOF composite system should simultaneously guarantee the enhanced activity and controllably complete recycling, and only in this way can we efficiently and economically utilize the enzyme-MOF composite. Herein, we addressed all these fundamental limitations of current enzyme-MOF composite by establishing aptamer-functionalized enzyme-MOF composite (HRP-ZIF-8@P1). HRP-ZIF-8@P1 relied on automatic structure switch of aptamer-target binding and aptamer-cDNA (complementary DNA) hybridization, achieving effectiveness in self-enriching substrate around HRP-ZIF-8@P1 to boost enzymatic activity first, subsequently hybridizing spontaneously with magnetically controllable cDNA sequence (Fe3O4@P3) to completely recover the HRP-ZIF-8@P1, where preferentially capturing substrate could further induce the release of the hybridized HRP-ZIF-8@P1 for automatically starting the cyclic enzyme catalysis. A 5.6-fold enhancement in the catalytic efficiency for BPA degradation was endowed, and 94.7% catalytic activity was retained for 8 consecutive degradations of BPA, both of which were even more significant than HRP-ZIF-8. Additionally, remarkable stability of HRP-ZIF-8@P1 was afforded by dual-layer protection of ZIF-8 and P1 in denaturing conditions. Taking the possibility of discovering an aptamer for any target into account, the aptamer-functionalized enzyme-MOF composites provide a generic and simple guide for simultaneously boosting enzymatic activity and controllably full recycling the enzyme-MOF systems, accelerating their commercial utilizations.

Modulating Photon Harvesting Through Constructing Oxygen Vacancies‐Rich 0D/2D Plasmonic Bi/Bismuth Oxybromide Upconversion Nanosheets Toward Improved Solar Photocatalysis

To harness solar energy comprehensively, developing photocatalysts with a broad spectrum response has received enormous attention. Herein, a full‐spectrum‐responsive Bi/BiOBr:Yb3+,Er3+ (BYE/Bi) heterostructure with oxygen vacancies (OVs) is designed and fabricated using the solvothermal method with subsequent heat treatment. The surface plasmon resonance (SPR) effect of Bi metal and OVs can not only extend the light absorption spectra but also promote the charge separation efficiency. The result of upconversion (UC) luminescence shows that the SPR absorption band of Bi nanoparticles overlaps with the excitation and emission bands of BiOBr:Yb3+,Er3+ nanosheets, which can induce a near‐infrared (NIR) plasmonic energy UC process and results in an enhanced green UC luminescence. The photocatalytic BPA degradation test shows that BYE/Bi‐2 shows the best photocatalytic activity, which is about 2.13‐fold, 1.41‐fold, and 2.73‐fold higher than that of BYE under UV−visible (vis)−near infrared (NIR), vis, and NIR light irradiations, respectively. Results reveal that the enhanced photocatalytic activity is ascribed to the Bi SPR effect and UC luminescence of BiOBr:Yb3+,Er3+ nanosheets, as well as the synergistic effects of OVs. This work not only provides ideas for the development of nonmetallic plasmon‐modified UC luminescent materials but also offers a pathway to develop high‐performance full‐spectrum photocatalysts for environmental applications.

Hydrothermal carbons/ferrihydrite heterogeneous Fenton catalysts with low H2O2 consumption and the effect of graphitization degrees

As the heterogeneous Fenton reactions are always restricted by the unsatisfied reduction efficiency of Fe(III) and ineffective consumption of H2O2, many strategies have been developed. In this work, we prepared hydrothermal carbons (HTC) with different graphitization degrees using glucose under different hydrothermal times, and then they were combined with ferrihydrite (Fh). Interestingly, although 30%HTC/Fh has much better BPA degradation efficiency than Fh (26 times larger of calculated degradation rate constants), the decomposition rate of H2O2 in the former system is lower. The generated Fe(II) of HTC/Fh is much higher than that of Fh during the heterogeneous Fenton reactions, and the degradation of BPA is almost unaffected by p-benzoquinone (scavenger of superoxide radicals (O2•−)) while greatly inhibited by isopropanol (scavenger of hydroxyl radicals (HO•)). These results indicate that HTC act as electron donors due to the abundant carbon-centered persistent free radicals (PFRs) to directly reduce Fe(III) to Fe(II) and therefore decrease the H2O2 consumption by Fe(III), which subsequently inhibits the generation of less active O2•− and promote the utilization efficiency of H2O2. HTC with a low graphitization degree contain more PFRs for Fe(III) reducing, significantly enhancing the Fenton catalytic activity of Fh.

Catalyst bridging-mediated electron transfer for nonradical degradation of bisphenol A via natural manganese ore-cornstalk biochar composite activated peroxymonosulfate

Designing efficient, low-cost and eco-friendly catalysts is important for activating peroxymonosulfate (PMS) to remediate the water environment. Hence, two eco-friendly substances, natural manganese ore and agricultural waste cornstalks, were selected as raw materials to prepare biochar-based composite catalyst (MCC) for removing bisphenol A by activating PMS. Quenching studies, electron paramagnetic resonance analysis, and electrochemical measurements were used to elucidate the activation mechanism, indicating the nonradical pathway with catalyst bridging-mediated electron transfer resulted in BPA degradation. In addition, the loading of natural manganese ore in MCC greatly enhanced the electrochemical properties of biochar and improved the electron transfer capacity of the composite, thus promoting the degradation of pollutants. Peculiarly, the excellent degradation rate in actual water demonstrated that the MCC/PMS system was highly resistant to surrounding organic or inorganic compounds. Meanwhile, toxicology experiments also showed the extremely high practical application potential of the MCC/PMS system. Overall, the study developed a PMS activator with low cost, excellent performance and high practical potential, which gave a new direction for the application of natural minerals and agricultural waste.