Reactive Resonance Research Articles

Synthesis of Fe-doped sludge biochar from Fenton sludge for efficient activation of peroxymonosulfate in tetracycline hydrochloride degradation

Traditional sludge treatment methods have problems in terms of environmental safety and cost-effectiveness. In this study, we followed the principle of "waste for waste" to synthesize magnetic sludge biochar (FSBC800) from biochemical sludge and Fenton sludge to activate persulfate (PMS) to remove persistent pollutants. Tetracycline hydrochloride (TC-HCl) was degraded up to 90.9% by FSBC800 using an active PMS system in just 30 minutes. This removal rate is higher than that of Fenton sludge biochar and biochemical sludge biochar by 2.7 and 1.8 times, respectively. The self-contained Fe in Fenton sludge formed evenly distributed Fe3O4 particles, while the biochemical sludge provided a large number of oxygen-containing functional groups, which increased the reactive active sites of FSBC800 and improved the catalytic performance. The dominant role of SO₄•⁻, •OH, and ¹O₂ in the degradation of TC-HCl was demonstrated by the identification of reactive oxygen species and electron paramagnetic resonance (EPR) analysis. By examining the intermediates, a potential TC-HCl degradation pathway was postulated. The catalyst has good reusability and practical application, and the removal of TC-HCl was still 84.8% after four replicated experiments. This study establishes a cost-effective, efficient, and recyclable biochar-based catalyst for water remediation, and at the same realizes resourceful utilization of sludge.

2D/2D Bi2MoO6/CoAl LDH S-scheme heterojunction for enhanced removal of tetracycline: Performance, toxicity, and mechanism

In this paper, the two-dimensional (2D) layered CoAl LDH (CoAl) was coupled with Bi2MoO6 (BMO) nanoplate and used for tetracycline (TC) degradation. Based on the results of UV–visible diffuse reflectance spectrum (UV–vis DRS), Motty-Schottky curves, and in situ X-ray photoelectron spectroscopy (XPS), a novel 2D/2D Bi2MoO6/CoAl LDH S-scheme heterojunction photocatalyst was built. The photodegradation rate constant of TC by the optimized sample BMO/CoAl30 was 3.637 × 10−2 min−1, which was 1.26 times and 4.01 times higher than that of Bi2MoO6 and CoAl LDH, respectively. The favorable photocatalytic performance of the heterojunction was attributed to the increased interfacial contact area of the 2D/2D structure. Besides, the transfer of photogenerated electrons from Bi2MoO6 to CoAl LDH under the effect of the built-in electric field (BIEF) reduced the recombination of photogenerated carriers and further improved the photocatalytic performance. The reactive species of h+, ·O2−, and 1O2 exhibited critical roles to degrade TC molecules by reactive radicals capture experiments and electron spin resonance (ESR) tests. The intermediate products of TC degradation and toxicity of intermediates were analyzed by liquid chromatography-mass spectrometer (LC-MS) and Toxicity Estimation Software Tool (T.E.S.T). Additionally, the BMO/CoAl composite photocatalysts showed high stability and environmental tolerance during the testing of cycles and environmental impacts with various water sources, organic contaminants, initial pH, and inorganic ions. This work provides a new protocol for designing and constructing novel 2D/2D S-scheme heterojunction photocatalysts for wastewater treatment.

Synergistic interface engineering in n-p-n type heterojunction Co3O4/MIL/Mn-STO with dual S-scheme multi-charge migration to enhance visible-light photocatalytic degradation of antibiotics

Constructing an effective multi-heterojunction photocatalyst with maximum charge carrier separation remains challenging. Herein, a high-efficient Co3O4/MIL-88A/Mn–SrTiO3 (Co3O4/MIL/Mn-STO) n-p-n heterojunction photocatalyst was successfully prepared by a simple hydrothermal method for the photodegradation of sulfamethoxazole (SMX). The combination of MIL and Co3O4/Mn-STO established an internal electric field and heterojunction, accelerating the separation of carriers, and thus improved photocatalytic performance. In the Co3O4/MIL/Mn-STO photocatalytic system, 95.5 % of SMX was degraded in 90 min. The photocatalytic kinetic removal rate of Co3O4/MIL/Mn-STO reached 0.0337 min−1, 8 times of Co3O4 (0.0041 min−1), 5.2 times of Mn-STO (0.0062 min−1), 4.6 times of MIL (0.0078 min−1), and 3.6 times of MIL/Mn-STO (0.0095 min−1). Remarkably, superoxide radicals (•O2−) and holes (h+) have been recognized as the main active species in the degradation process through reactive species elimination experiments and electron spin resonance (ESR) tests. The experimental and theoretical proved the in-built interfacial contact and synergistic effect between the photocatalyst accomplished with low bandgaps, high specific surface area, more reaction sites, high electron-hole pair separation, and maximum solar-light utilization. The molecular structure and possible degradation routes with intermediate products in the photocatalytic system were investigated using a liquid chromatography-mass spectrometer (LC-MS) and DFT calculations. This work provided new insight into the guidelines of rational design/growth of new multicomponent photocatalysts to remove antibiotics and other emerging contaminants in wastewater.

Visible light activation of ferrate(VI) by oxygen doped ZnIn2S4/black phosphorus nanolayered heterostructure: Accelerated oxidation of trimethoprim

The increasing consumption of antibiotics and their subsequent release to wastewater or groundwater and ultimately to the water supply (or drinking water) has great concerns. This paper presents a visible light (VL) activated ferrate(VI) (FeVIO42-, Fe(VI)) system to degrade the selected antibiotic, trimethoprim (TMP), efficiently. An oxygen doped ZnIn2S4 nanosheet (O-ZIS) coupled with a black phosphorus (BP) heterostructure (O-ZIS/BP), is fabricated by a simple electrostatic self-assembly method. The O-ZIS/BP photocatalyst is comprehensively characterized by surface and analytical techniques, which show superior separation efficiency of the photoinduced charge carriers in the heterostructure. A VL-O-ZIS/BP-Fe(VI) system achieves more than 80% removal in 1.0 min and complete removal of TMP in 3.0 min. Comparatively, only ⁓7% and ⁓24% of TMP are degraded by O-ZIS/BP and Fe(VI) in 1.0 min, respectively. The degradation experiments using probe molecules of reactive species and electron paramagnetic resonance (EPR) measurements reveal involvement of superoxide (O2-•), hydroxyl radical (•OH), and iron(V)/iron (IV) (FeV/FeIV) species in the mechanism of TMP degradation. Oxidized products of TMP are identified and reaction pathways are given. Theoretical calculations predict the initial attack on the TMP molecule by the reactive species in the VL-O-ZIS/BP-Fe(VI) system. The activation of Fe(VI) by VL-heterostructure photocatalysts accelerates the degradation of antibiotics, demonstrating its potential for water depollution.

Novel MIL-88B(Fe)/ZnTi-LDH high-low junctions for adsorption and photodegradation of tetracycline: Characteristics, performance, and mechanisms

In this paper, a high-efficient MIL-88B(Fe)/ZnTi-LDH high-low junction photocatalyst was successfully prepared by a simple method for the photodegradation of tetracycline (TC). The combination of MIL-88B(Fe) and ZnTi-LDH created an internal electric field and high-low junction, facilitated the separation of carriers, and thus enhanced photocatalytic activity. The optimized MZ-30% sample showed the highest photocatalytic degradation of TC about 93.51%. The photocatalytic kinetic removal rate of MZ-30% reached 0.0941 min−1, 31.36 times of MIL-88B(Fe) (0.003 min−1) and 1.7 times of ZnTi-LDH (0.0550 min−1). Furthermore, MZ-30% possessed the highest adsorption capacity for TC (543.89 mg/L). The effects of co-existing ions, initial pH, water source, and humic acid (HA) on TC degradation were examined. The main active substances of MIL-88B(Fe)/ZnTi-LDH in photocatalytic reaction were 1O2, h+, and ·O2- confirming by reactive species elimination experiment and electron spin resonance (ESR) tests. The molecular structure and toxicity of intermediates were investigated by a high-performance liquid chromatography-mass spectrometer (HPLC-MS) and Toxicity Estimation Software Tool (T.E.S.T), and the possible degradation pathway of TC was revealed. The results highlight that MIL-88B(Fe)/ZnTi-LDH high-low junction composite is a desirable photocatalyst for removing antibiotics and other emerging contaminants in water.

Designing of graphene oxide-induced p-NiO/n-MoO3 heterostructures for improved photocatalytic activity through plasmon-enhanced S-scheme mechanism and its biological and electrochemical performance.

An environmentally benign, economically advantageous microwave hydrothermal approach is used in synthesis of desirably tailored graphene oxide-induced p-NiO/n-MoO3 (GNM) heterostructures. Various analytical techniques such XPS, XRD, UPS, EIS, and Mott-Schottky were conducted to comprehend complete morphology and functioning of the novel ternary heterostructure photocatalysts. Also, SEM and HR-TEM images were presented for better interpretation. The strategic plasmonic step scheme (S-scheme) charge migration approach was used to describe the effective charge recombination process. Hydroxyl and oxide active species were corollaries of the reactive radical-scavenging experiments and electron spin resonance. The work function has been confirmed using ultraviolet photoelectron spectroscopy (UPS), which assessed an electron transfer between NiO and MoO3, yielding work function values of 6.32eV and 5.26eV, respectively. The cell apoptosis of the HeLa cell line approves the material's biocompatibility. Cyclic voltammetry and electrochemical impedance spectroscopy reveal electrochemical performance of GNM heterostructures. We anticipate our results would pave the way for current and future applications. In order to ensure eco-restoration such photocatalyst which are eco and cost friendly are synthesized. Assessment of pollutant risks presents the impact of them on human and terrestrial and aquatic animals. Sustainability of material is acknowledge as they use solar light for photocatalysis and dye degradation, and hence can be green material. One such material for the treatment of wastewater, dye-infused waters, and industrial water has been tailored, which is capable of dye degradation, heavy metal, and other pollutant removal. Very importantly, the synthesized material is a biocompatible one.

Efficient degradation of norfloxacin using a novel biochar-supported CuO/Fe3O4 combined with peroxydisulfate: Insights into enhanced contribution of nonradical pathway

Nonradical persulfate oxidation techniques have evolved as a new contaminated water treatment approach due to its great tolerance to water matrixes. The catalysts of CuO-based composites have received much attention in that aside from SO4•−/•OH radicals, the nonradicals of singlet oxygen (1O2) can be also generated during persulfate activation via CuO. However, the issues regarding particles aggregation and metal leaching from the catalysts during the decontamination process remain to be addressed, which could have a remarkable impact on the catalytic degradation of organic pollutants. Accordingly in the present study, a novel biochar-supported bimetallic Fe3O4–CuO catalyst (CuFeBC) was facilely developed to activate peroxodisulfate (PDS) for the degradation of norfloxacin (NOR) in aqueous solution. The results showed CuFeBC has a superior stability against metal ions Cu/Fe leaching, and NOR (30 mg L−1) was degraded at 94.5% within 180 min in the presence of CuFeBC (0.5 g L−1) and PDS (6 mM) in pH 8.5. The scavenging of reactive oxygen species and electron spin resonance analysis revealed that 1O2 dominated the degradation of NOR. Compared with pristine CuO–Fe3O4, the interaction between biochar substrate and metal particles could significantly enhance the contribution of the nonradical pathway to NOR degradation from 49.6% to 84.7%. Biochar substrate could efficiently reduce the leaching of metal species from the catalyst, thereby maintaining excellent catalytic activity and lasting reusability of the catalyst. These findings could enlighten new insights into fine-tuning radical/nonradical processes from CuO-based catalysts for the efficient remediation of organic contaminants in polluted water.

Preparation of Z‐type heterojunction SiCf/g‐C3N4 composites with enhanced photocatalytic degradation of tetracycline under visible light

Novel visible light‐driven silicon carbide‐based composites were prepared via in situ deposition of g‐C3N4 on fibrous SiC. The X‐ray diffractometry, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectrometer characterization showed that a Z‐type heterojunction was formed. According to the UV diffuse reflectance spectroscopy and (αhv)1/2 versus hv plots, it was demonstrated that the addition of g‐C3N4 extended the light absorption of the sample in visible light, narrowing its band gap. The EIS plots and PL spectra showed an increase in the efficiency of the charge carriers' mobility of the sample and a decrease in the recombination of its photogenerated electron–hole pairs. The photocatalytic degradation experiments showed that using a 0.03‐g·L−1 suspension concentration and a pollutant concentration of 10 mg·L−1, the degradation rate under visible light irradiation was 100 and 3.6 times higher than that of bare SiCf and g‐C3N4, respectively. The possible photocatalytic mechanism was proposed based on reactive species capture experiments and electron paramagnetic resonance showing that ·O2− and e− were the active entities.

Co3O4/carbon felt three‐dimensional electrode promoted electrocatalytic oxidation – peroxymonosulfate system for p‐nitrophenol degradation: effect of radical and non‐radical mechanisms

AbstractBACKGROUNDConventional electrochemical oxidation (EO) processes do not easily activate peroxymonosulfate (PMS) and are susceptible to the effects of electrode size, material and large‐distance two‐dimensional (2D) electrode structures, resulting in low mass transfer efficiency and low electrolytic productivity, limiting their ability to degrade pollutants. It is still a challenge to design and prepare a system and materials to enhance the activation of PMS and the EO process.RESULTSCo3O4‐loaded carbon felt three‐dimensional (3D) electrode material (Co/CF) was prepared and used to construct a 3D electrocatalytic synergistic system (EO‐Co/CF‐PMS). The system combined the advantages of bipolar electrochemistry, three‐dimensional electrochemistry and advanced oxidation processes based on sulfate radical (SR‐AOPs) to facilitate the activation of PMS for degradation of p‐nitrophenol (PNP) in water. In addition, the synergistic system showed excellent pollutant degradation performance, achieving 89.51% PNP degradation in 10 min with an energy consumption of 0.4255 kWh m−3. After being used for four consecutive cycle experiments, the synergistic system still achieved 83% PNP removal. Besides, the EO process also facilitated the Co cycle, resulting in a continuous and efficient degradation of the pollutants. The effects of experimental parameters (initial pH, PMS dose, and applied voltage) on PNP elimination were determined. The results of a reactive oxygen species scavenging experiment and electron spin resonance analysis showed that ·OH, SO4·−, and 1O2 all played a major role in the PNP elimination process.CONCLUSIONSThe research demonstrated that the composite catalyst Co/CF improved the property of the EO process for catalyzing PMS and thus enlarged the practical application of AOPs in pollutant degradation in aqueous solution. © 2022 Society of Chemical Industry (SCI).

Generating a captivating S-scheme CuBi2O4/CoV2O6 heterojunction with boosted charge spatial separation for efficiently removing tetracycline antibiotic from wastewater

In this work, a captivating S-scheme CuBi2O4/CoV2O6 heterojunction was innovatively constructed by in situ growing CoV2O6 nanoparticles on the surface of CuBi2O4 microrods. Of note, the unique CuBi2O4 microrods served as an outstanding substrate to achieve the uniform loading of CoV2O6 nanoparticles. Compared with neat CoV2O6 and CuBi2O4, as expected, the resulting CuBi2O4/CoV2O6 illustrated significantly boosted photocatalytic efficiency for degrading tetracycline (TC) under visible light illumination. More impressively, the optimized CuBi2O4(30 wt%)/CoV2O6 manifested the best TC removal rate of 0.01328 min−1 after 120 min of reaction, which was roughly 33.2 and 14.4 times larger than those of neat CoV2O6 and CuBi2O4, separately. Such an exceptional photocatalytic activity was mainly ascribed to the expedited the charge spatial detachment and transport, and synchronously reserved the strong redox ability driven by the established S-scheme heterojunction between CoV2O6 and CuBi2O4. Moreover, the reactive species scavenging tests and electron spin resonance analysis substantiated that the superoxide radicals combined with photogenerated holes were unquestionably responsible for removing TC. Eventually, the possible degradation mechanism and pathways of TC over CuBi2O4/CoV2O6 were also put forward.

Visible-light-driven photocatalytic activation of peroxymonosulfate by K+-reformed polymeric carbon nitride for effective sulfamethoxazole decomposition

The SO4•– radical based advanced oxidation process (SR-AOP) is the effective remediation strategy for addressing the concern of severe pollution risk caused by recalcitrant pollutants. In this study, we report the visible-light-driven photocatalytic activation (VL-PCA) of PMS by using K+-induced structure remodeling high crystallinity of (KPCN). The degradation of sulfamethoxazole (SMX) by KPCN+PMS+VL system (the corresponding kinetic constant is 0.1452 min–1) was enhanced remarkably compared with PCN+PMS+VL system (0.0263 min–1). •O2–, 1O2, •OH and SO4•– radicals were the dominant reactive species for the enhanced decomposition of SMX, evidently demonstrated by reactive species scavenger and electron paramagnetic resonance (EPR) experiments. The KPCN crystalline semiconductors maintain the properties of long-range atomic order configuration and nonlinear optical (NLO) response of pristine PCN. The unique NLO effects of KPCN enable it to produce more photogenerated carriers and minimize the electron-hole pair recombination, which exhibit superior VL-PCA performance of PMS toward SMX degradation. This study gives a proof-in-concept demonstration of the increased activity of the C3N4-based PMS photocatalytic-activator by regulating the disordered structure and phase defects of PCN, shedding light on the development of highly efficient VL-PCA catalysts based on carbon nitride.

Effects of Lewis acid-base site and oxygen vacancy in MgAl minerals on peroxymonosulfate activation towards sulfamethoxazole degradation via radical and non-radical mechanism

Radicals of SO4•-, OH•, non-radical of 1O2 and even direct oxidation all occurred in peroxymonosulfate (PMS) activation process. Hence, to regulate the above radical or non-radical mechanism is of great significance for the treatment of organic pollutants in practical water. In this work, MgAl-minerals exhibited a satisfied performance in controlling the contribution of radicals (SO4•-, OH•) and non-radical (1O2) towards PMS activation based on results of reactive oxygen species scavenger experiments and electron spin resonance spectra. Compared with MgAl-1(61.8%) and MgAl-2 (61.4%) (Al/Mg = 1, 2), MgAl-3 (Al/Mg = 3) exhibited the highest sulfamethoxazole (SMX) removal efficiency (92.5%). Moreover, the contribution of radical and non-radical to SMX degradation were 56.7% and 30.1%, which was different from that of MgAl-1(7.8% and 39.5%) and MgAl-2 (5.2% and 41.6%). The roles of Lewis acid-base site and oxygen vacancies (OVs) in MgAl-minerals on radical and non-radical processes were detailed investigated. Lewis acid sites and OVs can enrich SMX and PMS at the solid-water interface. Simultaneously, OVs promote electron transfer from SMX to PMS acts as electron media, resulting in more SO4•- and OH• generation. While the basic sites favored the generation of 1O2 via PMS self-decomposition mechanism. Therefore, in PMS activation process over MgAl-minerals, the involved reactive oxygen species can be regulated via controlling the amounts of Lewis acid-base sites and oxygen vacancies. This finding provided new insights into PMS oxidation over non-transition metal-based catalysts and water remediation with complex water characteristics.

Impact of Peripheral Microvascular Endothelial Dysfunction on White Matter Hyperintensity

BackgroundWhite matter hyperintensity (WMH), characterized by hyperintensities on T2‐weighted fluid‐attenuated inversion recovery brain magnetic resonance imaging, has been linked to an increased risk of ischemic stroke (IS). Endothelial dysfunction is an indicator of vascular dysfunction, predicting the risk of IS. This study aimed to investigate the association between endothelial dysfunction and regional WMH, and its impact on future risk of IS.Methods and ResultsWe enrolled 219 patients (mean age, 53.1±14.1 years; 34.7% men) who underwent peripheral endothelial function assessment using reactive hyperemia peripheral arterial tonometry and brain magnetic resonance imaging without any history of IS. Volumetric WMH segmentation was automatically extrapolated using a validated automated digital tool. Total and juxtacortical WMH volume/intracranial volume (%) increased with aging and became more prominent in patients aged >50 years (n=131) than those aged ≤50 years (n=88) (total WMH: ≤50 years, Pearson r=0.24, P=0.03; >50 years, Pearson r=0.62, P<0.0001; juxtacortical WMH: ≤50 years, Pearson r=0.09, P=0.40; >50 years, Pearson r=0.55, P<0.0001). Reactive hyperemia peripheral arterial tonometry index was negatively associated with total and juxtacortical WMH volume/intracranial volume (%) in patients aged >50 years after adjustment for other covariates (reactive hyperemia peripheral arterial tonometry index, standardized β coefficient −0.17, P=0.04). Juxtacortical WMH volume/intracranial volume (%) was associated with an increased risk of IS during median follow‐up of 6.5 years (hazard ratio, 1.47; 95% CI, 1.05–1.92; P=0.03).ConclusionsPeripheral endothelial dysfunction is associated with an increased volume of juxtacortical WMH in patients aged >50 years, which is a potential marker to predict future risk of IS.

Metal-organic frameworks with different oxidation states of metal nodes and aminoterephthalic acid ligand for degradation of Rhodamine B under solar light

Metal-organic frameworks (MOFs) have been investigated recently as effective visible light photocatalysts. In this report, we synthesized nickel, iron, and titanium-based MOFs with different oxidation states of metal ions and aminoterephthalic acid ligand for photocatalytic degradation of Rhodamine B (RhB) dye under solar light irradiation. The photoluminescence analysis revealed that the Fe-MOF could suppress the recombination of photoinduced charges and effectively degrade the dye. The photocatalytic experiment demonstrated that the Fe-MOF exhibited higher degradation efficiency of dye (90 %) compared to the Ni-MOF (9 %) and Ti-MOF (50 %) at pH 7 in 90 min. In addition, the effects of catalyst amount, dye concentration, and solution pH on dye degradation were investigated. The photodegradation of dye using Fe-MOF was well-fitted to the first-order kinetics with an R2 value of 0.9987. Furthermore, reactive oxygen species test and electron paramagnetic resonance study revealed that the superoxide anion radicals were mainly responsible for the dye degradation. Cyclic test analysis indicates that there was no substantial decrease in the degradation efficiency of dye after four consecutive cycles.

Reactive resonance and the role of electron angular momentum

Understanding the reaction mechanism at the atomic and molecular level is a central task of chemistry. Within the Born-Oppenheimer approximation, a chemical reaction is envisioned as nuclear dynamics evolving from reactants to products on a potential energy surface (PES). To reveal the detailed mechanistic origin of such an old bond-breaking and new bond-forming process, a measurement of state-to-state differential cross-sections (DCSs) is essential. Its fine structure often serves as a fingerprint to identify quantum dynamics phenomena in a bimolecular reactive encounter.

SiO2 mediated templating synthesis of γ-Fe2O3/MnO2 as peroxymonosulfate activator for enhanced phenol degradation dominated by singlet oxygen

Cost-effective and low-toxicity of MnO2 is regarded as a promising alternative to Co-based catalyst for peroxymonosulfate (PMS) activation to degrade recalcitrant organic pollutants. However, the sluggish Mn(IV)/Mn(III) redox cycling and limited specific surface area greatly hampered its wide application. To solve this challenge, a mesoporous γ-Fe2O3@MnO2 magnetic catalyst with SiO2 assistance (s-γ-Fe2O3@MnO2) was synthesized. Physicochemical characterization confirmed part MnO2 was coated on γ-Fe2O3 surface while the other existed independently. Furthermore, BET surface area of s-γ-Fe2O3@MnO2 was more than two times that of the counterpart without SiO2 assistance (ws-γ-Fe2O3@MnO2). s-γ-Fe2O3@MnO2 exhibited enhanced PMS activation capacity with 97.6% phenol removal efficiency within 80 min, superior to other samples. Various influencing parameters on phenol oxidation were optimized. Reactive oxygen species (ROS) scavenging experiment and electron paramagnetic resonance (EPR) validated co-existence of hydroxyl radicals (·OH) and sulfate radicals (SO4·−) as well as singlet oxygen (1O2) during PMS activation. However, phenol degradation was a non-radical oxidation process dominated by 1O2. A rational reaction mechanism was proposed. Fe(II) promoted Mn(IV)/Mn(III) redox cycling and the enlarged surface area derived from SiO2 mediated templating synthesis were responsible for the enhanced phenol degradation. This strategy can give a guidance for synthesis of highly efficient catalyst for sewage remediation.

Engineering Z-scheme silver oxide/bismuth tungstate heterostructure incorporated reduced graphene oxide with superior visible-light photocatalytic activity

Photocatalytic degradation of multiple organic contaminants has received extensive research attention and rational design of visible-light driven photocatalyst has been considered as an efficient approach. In this study, a visible-light Ag2O/Bi2WO6 heterostructure incorporated reduced graphene oxide (ABW-RGO) composite photocatalyst was prepared through a facile hydrothermal method for the first time and exhibited synergetic degradation behavior for contaminants in aqueous solutions. Under visible light, Tetracycline antibiotics has degraded 95.3% within only 40 min, and dye pollutants including Crystal Violet (cationic dye) and Congo Red (anionic dye) reached over 98.5% decomposition. The synthesized composite is also highly efficient in a wide pH range and multi-components system, maximizing the utilization of common sunlight, which make it suitable for industrial wastewater. The reactive oxidant species (ROS) experiment and electron spin resonance (ESR) measurement revealed the critical role of hydroxyl and superoxide radicals, clarifying the degradation pathway and mechanism analysis. The superior photocatalytic activity could be attributed to the formation of effective Z-scheme heterostructure and the excellent sorption capacity and conductivity of reduced graphene oxide. This research provides the design pathway to a novel catalyst using semiconductors composite and graphene support material, which can be extended to the energy-saving treatment of various organic pollutants.

From Reactive Rainbow to Dynamic Resonance Well.

Scattering resonance is a fascinating phenomenon which manifests as a peak or a dip in an observable as a function of collisional energy (Ec). Its occurrence requires a potential well to support the resonance states. In this regard, reactive resonance is unusual in that it can exist in a reaction with unbound Born-Oppenheimer potential energy surface, on which the quasi-bound states are dynamically trapped-meaning that some energy is temporarily tied to the other degrees of freedom than the reaction coordinate. The concept of vibrational adiabaticity has been the cornerstone in understanding this phenomenon, for which the vibrationally adiabatic well depth is of primary concern. Recent studies on the F + CH3D reaction have accumulated compelling evidence for a dominant resonance-mediated pathway at low Ec as well as for a rainbow feature in pair-correlated angular distribution at higher Ec. Here, we report an in-depth study to not only substantiate both claims but also, more importantly, make the first attempt to quantify the vibrationally adiabatic well depth directly from the observed rainbow structure and then compare with the theoretical prediction.

Double photoelectron-transfer mechanism in Ag−AgCl/WO3/g-C3N4 photocatalyst with enhanced visible-light photocatalytic activity for trimethoprim degradation

Antibiotic contamination is increasing scrutinized recently. In this work, the Ag−AgCl/WO3/g-C3N4 (AWC) nanocomposites were successfully synthesized using a two-step process involving electrostatic self-assembly and in-situ deposition for trimethoprim (TMP) degradation. The as-prepared photocatalysts were investigated and characterized by XRD, FTIR, XPS, TGA, SEM, TEM, UV–vis, PL and EIS. The experimental results indicated that 99.9% of TMP (4 mg/L) was degraded within 60 min when the concentration of AWC was 0.5 g/L. Reactive species scavenging experiments and electron spin resonance (ESR) experiments illustrated that superoxide radical (•O2−) and photogenerated holes (h+) were the main active species. The functional theory calculation and identification of intermediates via HPLC-MS revealed the possible degradation pathways of TMP. A double photoelectron-transfer mechanism in AWC photocatalyst was proposed. Five cycling photocatalytic tests and reactions under different solution matrix effects further supported that the AWC was a promising photocatalyst for the removal of TMP from the aquatic environment.

Synthesis of a carbon dots modified g-C3N4/SnO2 Z-scheme photocatalyst with superior photocatalytic activity for PPCPs degradation under visible light irradiation

As an emerging carbon nanomaterial, carbon dots (CDs) have superior prospects for applications in the area of photocatalysis due to their unique optical and electronic properties. In this study, a novel CDs modified g-C3N4/SnO2 photocatalyst (CDs/g-C3N4/ SnO2) was successfully synthesized by the thermal polymerization. Under visible light irradiation, the resulting CDs/g-C3N4/SnO2 photocatalyst exhibited excellent photocatalytic activity for the degradation of indomethacin (IDM). It was demonstrated that a 0.5 % loading content of CDs led to the highest IDM degradation rate, which was 5.62 times higher than that of pristine g-C3N4. This improved photocatalytic activity might have been attributed to the unique up-conversion photoluminescence (PL) properties and efficient charge separation capacities of the CDs. Moreover, the combination of g-C3N4 with SnO2 improved the separation of photoinduced carriers and augmented the specific surface area. Reactive species (RSs) scavenging experiments and electron spin resonance (ESR) revealed that superoxide radical anions (O2·−) and photogenerated holes (h+) played critical roles during the photocatalytic process. The results of the detection of H2O2 and ESR confirmed that CDs/g-C3N4/ SnO2 was a Z-scheme heterojunction photocatalyst. Further, HRAM LC–MS/MS was employed to identify the byproducts of IDM, and the major IDM degradation pathways of the CDs/g-C3N4/SnO2 photocatalyst were proposed. This study provides new ideas for the design of novel CDs modified photocatalysts for environmental remediation.