Lasers Research Articles

Elucidation of synergism in Ce-Zr/SBA-15 mesoporous catalysts and the effects on the activity in selective glycerol to lactic acid reaction

The continued conversion of glycerol to value-added chemicals is essential in ensuring the sustainable development of the biodiesel industry. Selective catalytic oxidation of glycerol to lactic acid provides an alternative approach to valorizing glycerol. A mesoporous SBA-15 supported mixed-metallic oxide catalyst is deemed essential to selectively produce lactic acid in this mixed parallel and multi-step reaction. SBA-15-supported bimetallic Ce and Zr oxides were proved to be highly efficient catalysts for the selective glycerol oxidation into lactic acid in base-free media. The synergism between Ce and Zr in the bimetallic oxide compounds could enhance the creation of oxygen vacancies in the catalyst via the reduction of Ce4+ to Ce3+. The 2:1CeZr/SBA-15 catalyst exhibited prominent catalytic activity in selectively oxidizing glycerol to lactic acid, with a glycerol conversion of 91.8% and a lactic acid yield of 35.1%. This work achieved superior catalytic performance compared to previously conducted studies, primarily due to the significantly higher initial glycerol concentration employed in this study. To ascertain the intrinsic active sites of the catalyst, the physicochemical properties of the catalyst were thoroughly examined using BET, FTIR, XRD, FESEM, TEM, CO2-TPD, O2-TPD, and H2-TPR analysis. This work concluded that the synergistic interaction of the active sites, which led to the formation of active oxygen species, facilitated primary dehydrogenation of the terminal -OH bond in glycerol. Hence, in this work, a plausible glycerol conversion mechanism over the 2:1CeZr/SBA-15 catalyst was also proposed.

Dual activation of peroxymonosulfate with FeS2@Co3O4-C catalyst and visible light for the efficient degradation of tetracycline

Antibiotics have garnered global attention as a pressing concern due to their wide spread discharge to the environment and resulting significant threats to both human health and the environment. The Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) technique has already been verified as an effective process for pollutant degradation. Herein, FeS2@Co3O4-C composites, utilizing ZIF-67-derived Co3O4-C as the substrate material, were fabricated using a single-step solvothermal technique for the degradation of tetracycline (TC) by activated peroxymonosulfate (PMS) in combination with visible light irradiation. In the FeS2@Co3O4-C/PMS/Vis system, the FeS2@Co3O4-C showed better activation performance than the single chemical activation system or photocatalytic system, with 97.2 % TC removed in 20 min. The FeS2@Co3O4-C composite material was thoroughly investigated employing X-ray diffraction (XRD) for analyzing its crystal structure, transmission electron microscopy (TEM) for detailed structural insights, scanning electron microscopy (SEM) for morphological examination, and X-ray photoelectron spectroscopy (XPS) for the elemental valence states. The quenching experiments, along with EPR test, revealed that the primary active oxygen species consisted of 1O2, O2·-, and h+. The results presented here suggest the impressive stability and recyclability of FeS2@Co3O4-C making it a potential candidate as an efficient catalyst for initiating the activation of PMS in degrading persistent organic pollutants present in water.

Development of a γ-Al2O3-Based Heterogeneous Fenton-like Catalyst and Its Application in the Advanced Treatment of Maotai-Flavored Baijiu Wastewater

Heterogeneous Fenton technology was employed for the advanced treatment of Maotai-flavored Baijiu wastewater. Novel catalysts were prepared by loading different active ingredients (Mn, Fe, and Cu) on γ-Al2O3 using an impregnation method. The effects of active ingredient, reaction time, initial pH, H2O2 dosage, catalyst dosage, and other factors on the reaction were examined. The properties of the new catalysts were analyzed using BET analysis, XPS, and SEM. Moreover, the mechanisms of Fenton-like oxidation and its reaction kinetics were explored through experiments and analyses including GC–MS and intermediate active species scavenging by tertiary butyl alcohol (TBA) and/or para-benzoquinone. The results revealed that the most effective removal of organic matter was achieved with a Mn-Fe/Al (2:1 wt%) catalyst dosage of 30 g/100 g water, pH of 5.0, H2O2 dosage of 0.3 g/L, and reaction time of 60 min; the effluent COD value was 12 ± 1 mg/L, and the degradation rate was 65.7 ± 3%, approximately 14% higher than that of the conventional Fenton catalyst under similar conditions; moreover, the catalytic efficacy remained high after seven cycles. Kinetic analysis indicated that the heterogeneous Fenton oxidation reaction followed a third-order kinetics model, with R2 = 0.9923 and K = 0.0006 min−1.

Insights into reverse oxygen spillover effect induced via CeO2 modulation to enhance the stability of CuCoOx catalysts in hydrodeoxygenation of biomass derivatives

In hydrodeoxygenation (HDO) reactions, the evolution of the chemical states of active species in the catalyst caused by the spillover effects greatly influences their catalyst performance. Herein, the HDO of guaiacol (GUA) over CuCoOx and CuCoCeOx catalysts synthesized by co-precipitation method was systematically investigated. During the HDO reaction of GUA, acid sites (Co(II)) facilitated the C-O bond (demethylation via -OCH3) cleavage, which was the rate-determining step. A series of characterizations and experimental results revealed that introducing CeO2 into the CuCoOx catalyst could enable the catalyst to undergo reverse oxygen spillover in the hydrogenation environment, promoting the regeneration of CoO in the catalyst. Therefore, the deactivation of the CuCoOx catalyst due to hydrogen spillover leading to CoO reduction could be avoided, and the catalyst stability improved. The present study methodically investigated the spillover effects induced by Cu and CeO2 and provided the theoretical basis for the structural design of heterogeneous catalysts.

Efficient removal of tetrabromobisphenol A in the Mn1Fe0.5Al0.5-LDO@BC/peroxymonosulfate water purification system

Tetrabromobisphenol A (TBBPA) brominated flame retardants in water posed threat to the ecological system due to its persistence and biomagnification. In this work, an efficient water purification system based on sulfate radical-based advanced oxidation processes (SR-AOPs) with Mn1Fe0.5Al0.5-LDO@BC as the core was constructed by adjusting the key preparation parameters, optimizing catalyst performance and exploring operating conditions. Under the optimal conditions of Mn1Fe0.5Al0.5-LDO@BC/PMS system (calcination temperature of 600 oC, 0.1 g/L Mn1Fe0.5Al0.5-LDO@BC, 0.15 mM PMS, pH value of 7–), 15 mg/L TBBPA was almost completely degraded within 30 min. Mn1Fe0.5Al0.5-LDO@BC/PMS water purification system exhibited resistance to inorganic anions and humic acid. In addition, Mn1Fe0.5Al0.5-LDO@BC reflected better cycle stability and ecological environmental protection. Electron paramagnetic resonance (EPR) and quenching experiments verified the existence of a large number of dominant active species in the water purification system, especially the contribution of O2•– and 1O2 to the degradation of TBBPA. Finally, the catalytic mechanism and possible degradation pathway of TBBPA were elucidated, and the toxicity of the intermediates was predicted. This work provided novel insights into the efficient purification of TBBPA brominated flame retardants in wastewater.

Silver-doped Cadmium Aluminate and its MXene Based Composite for Visible-Light Driven Photocatalytic Degradation of Organic Pollutants

Visible-light-driven photocatalysis has attracted enormous prominence as a sustainable approach to address escalating environmental pollution. Consequently, it is paramount to develop photocatalysts featuring absorption in visible light with enhanced charge separation to perform well under solar light irradiation. Herein, we have fabricated pure (CdAl2O4) and silver-doped cadmium aluminate (Ag-CdAl2O4) by following the facile coprecipitation route while the MXene-based composite of doped material (Ag-CdAl2O4/MXene) by ultrasonication. The photocatalytic activity of the as-prepared photocatalysts was estimated by degrading crystal violet and phenol as sample pollutants. The composite material displayed substantially enhanced photocatalytic performance and degraded ∼95% (0.0204 min-1) and ∼84.6% (0.0130 min-1) of crystal violet and phenol, respectively. This enhanced catalytic performance corresponds to the synergism of silver doping and composite fabrication, enhancing the visible-light-response and efficient decoupling of the photo-generated charge carriers. Additionally, active species generated during the photocatalytic process and their role in the breakdown of the targeted pollutants were determined by the scavenging investigation. The kinetics study revealed the first-order kinetics model for the degradation reaction of the targeted pollutants. The present findings unveil the significant catalytic potential of the as-fabricated composite (Ag-CdAl2O4/MXene) for the degradation of organic pollutants.

Introducing attapulgite to prepare manganese-based monolithic catalyst for catalytic combustion of toluene

A series of attapulgite-loaded manganese oxides cordierite monolithic catalysts with different KMnO4/Mn(NO3)2 molar ratios (3:1, 1:1, and 1:3 for KMnO4/Mn(NO3)2, respectively) were prepared by a hydrothermal-ball mill impregnation method. According to the analysis of the characterization findings, the main active species of the catalyst was Mn4+ species. By incorporating acid-treated attapulgite (HATP) and adjusting the molar ratio of KMnO4/Mn(NO3)2, the content of Mn4+ and surface-adsorbed oxygen species on the catalyst surface increased, subsequently enhancing catalytic activity at low temperatures. Experimental results revealed that the Mn/HATP/cordierite catalyst with a KMnO4 to Mn(NO3)2 molar ratio of 3:1, Mn loading amount of 30 wt%, and active coating deposition of 250 g/L exhibited the highest catalytic activity, achieving a 90 % conversion of toluene at 298 °C (T90 = 298 °C, GHSV = 10000 h−1). These findings will provide valuable support for the design of highly efficient monolithic catalysts for toluene removal.

Effective inhibition of chloride ion interference in photocatalytic process by negatively charged molecularly imprinted photocatalyst: Behavior and mechanism

The ubiquitous chloride ions (Cl−) in water seriously interfere with pollutant oxidation and inevitably generate undesirable chlorinated byproducts. In this study, we report for the first time that a negatively charged molecularly imprinted photocatalyst (MIP) can effectively inhibit Cl− interference and suppress the production of chlorination byproducts (the yield of chloroacetic acid was only 16 % of the bare photocatalyst system) while ensuring efficient degradation of target pollutants, thereby greatly improving the safety of the pollutant degradation process. Taking antibiotics as target pollutant, we investigated the mechanism of action of MIP by comparing the antibiotic degradation pathways, fate of photogenerated active species and production of reactive chlorine species (RCS) in the MIP and bare photocatalyst system. The mechanism by which MIP inhibits Cl− interference was mainly based on a synergy between electrostatic repulsion and steric hindrance induced by the specific capture of antibiotics in imprinted cavity, which effectively suppressed the production of RCS and hindered the participation of RCS in antibiotics degradation. In addition, MIP showed good compatibility with common cations, anions and organic matter, and performed well within a broad pH range in various water environments. Thus, the negatively charged MIP provides a feasible approach for the safe and efficient removal of pollutants in Cl− containing water.

Co-doped C3N5 with enhanced RhB degradation by activating PMS

The application of advanced oxidation processes in wastewater treatment has attracted wide attention, in the past year. With excellent photoelectric properties and catalytic stability, graphitic carbon nitride and its derivatives have high catalytic performance. Compared to traditional g-C3N4 materials, g-C3N5 has a narrower band gap (g-C3N5 has a band gap of about 2.0 eV and g-C3N4 has a band gap of about 2.6 eV) and better electron excitation distribution due to it has a higher proportion of N atoms. In this study, the composites of Co atom doped g-C3N5 were synthesized and characterized. Co atoms are successfully doped into g-C3N5, which is proved by TEM, XPS and XRD experimental results. PMS can be activated by Co-C3N5, and RhB degradation efficiency is as high as 95.8 % within 40 min. The experimental results show that the doping of metal Co can effectively improve the catalytic performance of carbon nitride materials. The degradation efficiency of RHB activated by C3N5, C3N4 and Co-C3N4 was 18.2 %, 11.2 % and 41.8 %, respectively, while the degradation efficiency of Co-C3N5 was as high as 95.8 %. RhB was effectively degraded over a wide pH range (3.0–10.9) and under various anion conditions, indicating the excellent environmental suitability of Co-C3N5. The results of free radical quenching experiments and EPR tests showed that the contribution of active species to RhB degradation was as follows: SO4•− >1O2 > O2•−. This paper provides a new perspective using Co-C3N5 as a catalyst for PMS-based Fenton reaction.

Low-coordinated Mn–N2 sites in graphene oxide induce peroxydisulfate activation for tetracycline degradation: Process optimization and theoretical calculation

Atom-dispersed low-coordinated transition metal-Nx catalysts exhibit excellent efficiency in activating peroxydisulfate (PDS) for environmental remediation. However, their catalytic performance is limited due to metal-N coordination number and single-atom loading amount. In this study, low-coordinated nitrogen-doped graphene oxide (GO) confined single-atom Mn catalyst (Mn-SA/NGO) was synthesized by molten salt-assisted pyrolysis and coupled to PDS for degradation of tetracycline (TC) in water. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analysis showed the successful doping of single-atom Mn (weight percentage 1.6%) onto GO and the formation of low-coordinated Mn–N2 sites. The optimized parameters obtained by Box-Behnken Design achieved 100% TC removal in both prediction and experimental results. The Mn-SA/NGO + PDS system had strong anti-interference ability for TC removal in the presence of anions. Besides, Mn-SA/NGO possessed good reusability and stability. O2•−, •OH, and 1O2 were the main active species for TC degradation, and the TC mineralization reached 85.1%. Density functional theory (DFT) calculations confirmed that the introduction of single atoms Mn could effectively enhance adsorption and activation of PDS. The findings provide a reference for the synthesis of high-performance single-atom catalysts for effective removal of antibiotics.

GO/Bi2O2CO3/NiWO4 with Z-scheme heterojunction: efficiently enhanced degradation of organic pollutants under visible light and DFT studies

A ternary composite of GO/Bi2O2CO3/NiWO4 (GBCNWO) was prepared via an in-situ of Bi2O2CO3 onto the surface of NiWO4 and Bi2O2CO3/ NiWO4 being warped by GO, which was thereafter untilled as catalyst in photodegradation of organic pollutants. The microstructure, and optical properties of all the prepared samples were characterized using various techniques such as XRD, FT-IR, SEM, TEM, TG-DTG, XPS, UV-Vis, ESR, and N2-adsorption. Amongst the studied samples, GBNWO possessed the largest specific surface area, which would efficiently afford much more spaces for the exposing of active sites. Results of UV-vis and XPS suggested that GBNWO was more efficient for the adsorption and conversion of visible light, and photocurrent conduction through graphite carbon ring could lessen the recombination rate of photoelectrons and holes. Also, the minor arc radius of GBCNWO unveiled its lowest photoresistors among the composites, indicating that the GBNWO structured with GO, Bi2O2CO3 and NiWO4 has synergistic catalysis in the photodegradation. Importantly, 95.15% of degradation rate was observed under the optimized conditions (pH=7, catalyst weight of 30mg, 40mg/L of MB, 25oC). Additionally, the degradation rate of various substrates followed the order: MB (99.34%) > ciprofloxacin (97.28%) > RHB (97.01%) > indole (27.47%) > phenol (9.47%). The quenching experiment and ESR test suggested that three kinds of active species (•OH, •O2− and h+) can be photogenerated during visible light radiation. Among them, •O2− was confirmed as the key species during the photocatalytic process, which could be adduced that the existence of oxygen vacancies made the receiving photoelectrons to reduce O2, forming the superoxide radical. Finally, a Z-scheme mechanism about the production of active radicals was proposed, which was also validated by DFT calculations.

Electrical modeling of an electrochemical sensor operating at the redox cycling mode

In this work, the direct current vs. voltage (DC) characteristics, and the alternate current (AC) impedance of a 1D four-electrode electrochemical cell, operating under redox-cycling conditions, are presented and discussed. The analysis refers to a four-electrode electrochemical system with one positively biased working electrode, one negatively biased working electrode, one auxiliary electrode, and one reference electrode operating in a redox cycling mode. This configuration is useful, for example, for electrochemical biosensors that can benefit from the inherent redox-cycling amplification of the apparatus. An aqueous buffered electrolyte is assumed, containing electrochemically active species that can be oxidized on the anode, with a positive overpotential. Meanwhile, the product of the oxidation reaction can diffuse to the other working electrode which has a negative overpotential, where the product is reduced. The analysis in this paper assumes that oxidation is the dominant mechanism at the anode, reduction is the dominant mechanism at the cathode, and the transport between them is dominated by diffusion. Since it is a 1D model, an ideal lossless redox cycling, i.e. both working electrodes’ currents (anodic and cathodic) are of the same magnitude with opposite signs, is assumed. Next, the small signal (AC) impedance of the electrochemical cell was calculated assuming that the AC signal modifies the oxidation reaction rate at the anode while the reduction reaction rate at the cathode is fixed. The impedance under redox cycling is calculated vs. frequency for various oxidation and reduction rates and both Bodé and Nyquist plots of the impedance are presented. The last part of the paper presents measured data for both DC and AC (i.e. Bodé and Nyquist plots) experiments with interdigitated array (IDA) electrodes, 5 & 10 μm spacing, operating under redox cycling conditions. The DC measurements were conducted in a 6 mM ferricyanide [K3Fe(CN)6] in 0.1 M Phosphate Buffer Saline (PBS) solution, pH 7.4. The AC measurements were conducted in 10 mM & 100 nM ferricyanide (K3Fe(CN)6) in 100 mM KNO3 aqueous electrolyte. A critical discussion follows the results section where the highlights and problems of the models are discussed.

Ultrafast solid-state microwave fabrication of CoFe2O4@carbon black composite with coupling reinforcement effect towards actualizing effective water decontamination

Due to the synergistic redox coupling between the two metals, cobalt ferrite-based materials demonstrate stable degradation properties for organic pollutants by activating peroxomonosulfate (PMS). However, the challenge lies in developing the simplest and fastest methods to construct and modulate cobalt ferrite composites. In this study, CoFe2O4 nanoparticle-integrated carbon black composite catalysts (CoFe2O4-CB-x) were prepared using an environmentally friendly solid-state microwave method. The CoFe2O4-CB-120 catalyst showed excellent efficiency in degrading tetracycline (TC) through PMS activation, achieving a removal rate of nearly 90 % in 30 min with an apparent rate constant of 0.1232 min−1. The catalyst also effectively degraded various organic compounds and real-life wastewater by almost 80 %, promising application potential. Furthermore, CoFe2O4-CB-120 maintained its high activity after five cycles, attributed to its its magnetic properties facilitating good separation and preventing catalyst loss during cycling tests. The degradation mechanism of the CoFe2O4-CB-120/PMS system was thoroughly investigated, identifying key active species such as SO4•−, •OH, and 1O2, with proposed pathways for TC degradation. This study presents an innovative, simple, and efficient strategy for producing spinel cobalt ferrite and carbon composites for PMS activation in organic pollutant degradation.

Insights into reverse oxygen spillover effect induced via CeO2 modulation to enhance the stability of CuCoOx catalysts in hydrodeoxygenation of biomass derivatives

In hydrodeoxygenation (HDO) reactions, the evolution of the chemical states of active species in the catalyst caused by the spillover effects greatly influences their catalyst performance. Herein, the HDO of guaiacol (GUA) over CuCoOx and CuCoCeOx catalysts synthesized by co-precipitation method was systematically investigated. During the HDO reaction of GUA, acid sites (Co(II)) facilitated the C-O bond (demethylation via -OCH3) cleavage, which was the rate-determining step. A series of characterizations and experimental results revealed that introducing CeO2 into the CuCoOx catalyst could enable the catalyst to undergo reverse oxygen spillover in the hydrogenation environment, promoting the regeneration of CoO in the catalyst. Therefore, the deactivation of the CuCoOx catalyst due to hydrogen spillover and CoO reduction could be avoided, and the catalyst stability improved. The present study methodically investigated the spillover effects induced by Cu and CeO2 and provided the theoretical basis for the structural design of heterogeneous catalysts.

Oxygen vacancy-rich β-Bi2O3/Bi2O2SiO3 Z-Scheme heterojunction: A strategy to enhance visible light-driven photocatalytic removal of ARB and ARGs

Oxygen vacancy-rich β-Bi2O3/Bi2O2SiO3 (BO/BOS) Z-Scheme heterojunction was prepared by hydrothermal method-assisted calcination. Under visible light, β-Bi2O3/Bi2O2SiO3 photocatalyst demonstrated superior photocatalytic efficacy in degrading antibiotics and antibiotic-resistant Escherichia coli (AR E. coli) compared to individual β-Bi2O3 and Bi2O2SiO3. The experimental results showed that BO/BOS-450 sample possessed the best photocatalytic activity against tetracycline (2 h, 80.8%), amoxicillin (4 h, 57.9%) and AR E. coli (3 h, 107.43 CFU·mL−1). BO/BOS-450 sample showed 91.8% electrostatic capture of AR E. coli in the bacterial capture experiment. In the antibiotic-resistant genes (ARGs) degradation experiment, BO/BOS-450 sample was able to bring the log10 (Ct/C0) value of tetA to -3.49 after 2 h. Oxygen vacancies (OVs) were verified through HR-TEM, XPS and EPR analyses. ESR experiments aligned with the quenching experiment results, confirming that the crucial active species were ‧O2- and h+ during photocatalytic sterilization. A small-scale sewage treatment equipment was designed for the effective removal of ARB from real water samples.

Efficiently enhanced degradation for the organic pollutants over GO/BiOI/NiWO4 with Z-scheme heterojunction and DFT studies

In this work, a series GO/BiOI/NiWO4 (n%GBINWO, n=5, 10, 15, 20) were hydrothermally prepared and applied as photocatalysts for the degradation of organic dyes under ambient conditions. The physico-chemical and microstructure of the studied samples were characterized by XRD, SEM, TEM, TG-DTG, XPS, UV-Vis, EIS, and N2-adsorption. Compared with pure NiWO4, the photocatalytic activity of BiOI/NiWO4 and GO/BiOI/NiWO4 were obviously enhanced, and the highest photocatalytic efficiency of 10% GBINWO was observed to be 98.59% (methylene blue, MB) under the optimized conditions (catalyst weight of 30mg, pH of 3, 3h, 30 °C). The excellent catalytic performance of the 10% GBINWO was due to the existence of interfacial heterojunction, which endows the ternary composite with the large visible light capacity and high charge separation efficiency. Importantly, after the hybrid model constructed with NiWO4 (-1 1 1) and BiOI (0 0 2) was optimized via DFT calculations, a newly-formed bond of I-Bi-O-M (Ni and W), which promoted the transportation of the photogenerated electrons through newly-formed bridge was observed. Furthermore, the difference in degradation efficiency of various organic pollutants was related to the steric hindrance as well as the molecular structure. Moreover, •O2− was also confirmed as the key active species for 10% GBINWO catalyzing the degradation process. Besides, the Z-scheme heterojunction between BiOI and NiWO4 was confirmed by TD-DFT calculations.

Construction of a novel OS/BiVO4 catalyst for enhancing the photocatalytic degradation performance of sulfonamide

Exploiting of high-value-added environmental materials related to oily sludge (OS) is an important development direction for OS resource utilization. A series of OS/BiVO4 catalysts were synthesized by activation-pyrolysis and hydrothermal methods. Photocatalytic performance was estimated through sulfanilamide (SA) degradation (SA) under visible light irradiation. The OS/BiVO4–20% has the best photodegradation ability for SA. The degradation rate of SA was about 97.8% after six hours of visible light irradiation. The first-order kinetics degradation rate constants of OS/BiVO4–20% for SA is 8.3 times that of pure BiVO4. The radical quenching and ESR experiments reveal that the hole (h+) and hydroxyl radical (·OH) were the primary active species for SA photocatalytic degradation. The presence of OS and H2O2 can significantly improve the charge separation efficiency, and inhibit electron-hole complexes, thereby extending the lifetime of electron carriers and producing many active hydroxyl radicals and holes on the surface of catalyst particles. Due to the introduction of OS, OS/BiVO4 has good texture properties and high oxygen absorption content, which is also conducive to the photodegradation of SA. Fourier-transform infrared (FTIR), in combination with two-dimensional correlation spectroscopy (2D-COS), indicated that the C–N (1351 cm-1), CC (1450 cm-1), SO2–N (1116 or 1182 cm-1), and N–H (1636 cm-1) groups can change in turn during the catalytic degradation process. This work improves the surface properties of BiVO4 semiconductor materials by introducing OS, thereby increasing the photodegradation efficiency of BiVO4 catalysts against antibiotics, which provides valuable insights into the design of next-generation photocatalysts.

Photocatalytic degradation of tetracycline by g-C3N4/stilbite under visible light: Mechanistic insights and degradation pathways

In this study, the g-C3N4/stilbite composite was fabricated by the in-situ synthesis method, and the photocatalytic performance was investigated by degrading tetracycline (TC) under visible light. The results indicated that the photocatalytic degradation efficiency of g-C3N4/stilbite-6 (86.8%) was about 2.7 times higher than that of pure g-C3N4 (31.8%). The introduction of the stilbite carrier effectively resolved the issues of g-C3N4 such as easy self-agglomeration and the difficulty in separating photo-generated carriers, thereby improving the photocatalytic activity of g-C3N4. From the quenching experiment, it was found that h+ and •O2− were main active species for TC degradation. By HPLC-MS analysis, TC degradation products were identified, and three degradation pathways were proposed. In addition, the impacts of solution pH, light intensity, and catalyst dosage on TC degradation performance were also evaluated. Overall, a simple and successful strategy has been proposed to synthesize high-performing visible-light-driven photocatalysts for efficiently eliminating organic contaminants from wastewater.

Indium-doped tungsten oxide architectures anchored on 2D rGO Matrix with enhanced visible-light-response and efficient charge separation for photocatalytic degradation of organic pollutants

Visible-light-responsive photocatalysis has been recognized as a sustainable strategy to address environmental pollution, but semiconductor-based photocatalysts often suffer from many shortcomings, including low visible light absorption and rapid recombination of photo-generated charge carriers. In this regard, rationally designed composite materials have gained substantial prominence, as achieving an ideal photocatalyst's characteristics in a single component material is frequently difficult. In the present study, we have synthesized pure (WO3) and indium-doped tungsten oxide (In-WO3) by the facile solvothermal route. The doped material was anchored on a 2D rGO matrix to fabricate the In-WO3/rGO composite. The structural, morphological, electrical, and optical properties of the as-synthesized materials were investigated as a function of doping and composite fabrication by various physical and electrochemical techniques. The comparative photocatalytic performance was evaluated by degrading Congo Red (CR) dye and paracetamol (PCM) drug. The composite material shows degradation efficiencies of ~96% (K=0.0174min-1) and ~91% (K=0.0144min-1) for CR dye and PCM drug, respectively. The boosted catalytic performance corresponds to the declined band gap (2.53eV) and increased conductivity (0.1270 Sm-1), which enhances its visible light absorption and a surge in the charge carrier's population. The kinetics, relative contribution of different active species generated, and the potential mechanism of photodegradation reaction are discussed in detail. The significant increase in photocatalytic performance of the fabricated In-WO3/rGO composite discloses its promising catalytic potential for the degradation of recalcitrant organic pollutants.

MoS2 nanosheets wrapped magnetic foamed recycled glass (NMG) for efficient photo-Fenton degradation of tetracycline: Sustainable mindset of “treating waste with waste”

Every year, tens of millions of tons of waste glass are buried on-site, causing serious resource waste and challenging environmental problems. Therefore, dealing with the problem of waste glass is a technical challenge with important economic significance. We used waste glass as a precursor to obtain foam recycled glass and then used a simple impregnation method to obtain magnetic foamed recycled glass (MG) and MoS2 nanosheets wrapped magnetic foamed recycled glass (NMG). Subsequently, we established an excellent NMG/H2O2 system for the efficient degradation of tetracycline (TC) under low-power light sources. The NMG/H2O2 system has a 92.2% removal rate of TC, accompanied by the apparent reaction kinetic constant is 0.01865 min−1. Meanwhile, the degradation mechanism of ·OH and 1O2 as the main active species was determined. Finally, the theoretical reaction sites of TC in the NMG/H2O2 system were obtained through density functional theory (DFT) calculation. The theoretical reaction sites were consistent with the reaction sites in the possible degradation pathways we obtained through the degradation fragment. In our work, we approach environmental issues with a “treating waste with waste” mindset, which combines economic and environmental considerations and may become the mainstream mindset in future environmental treatment.