Advanced Oxidation Research Articles

Long-lasting BDD/Si3N4–TiN electrodes for sustainable water remediation

Boron-doped diamond (BDD) thin films have the potential to revolutionize water remediation through electrochemical oxidation, converting persistent pollutants into CO2 and water. However, a significant challenge in implementing BDDs on a large scale is the choice of substrate material. Electrode failure typically occurs due to BDD delamination from the substrate. We propose using a ceramic composite of silicon nitride (Si3N4) and titanium nitride (TiN) as a substrate to address this issue. This electroconductive composite combines Si3N4's high wear resistance, chemical stability, and high affinity for diamond film growth with the TiN's metal-like conductivity. In this work, BDD films were grown by Hot Filament Chemical Vapor Deposition (HF-CVD) over Si3N4–TiN substrates containing 30%vol. TiN. The resulting BDD/Si3N4–TiN electrodes were analyzed concerning their microstructure, diamond quality, conductivity, adhesion strength, service life, and electrochemical properties. Phenol was used as a model to test the electrode's ability to oxidize pollutants. We found that the BDD/Si3N4–TiN electrode could eliminate phenol entirely and up to 98.8 % of the model solution's Chemical Oxygen Demand (COD) after 5 h of direct anodic oxidation, with an Average Current Efficiency (ACE) of 14 % and an energy consumption of 138 kW h kgCOD−1. Furthermore, the BDD/Si3N4–TiN electrode could withstand more than 2016 h of accelerated life test without film delamination. Overall, the results demonstrate that BDD/Si3N4–TiN electrodes are a potential long-lasting solution for large-scale water treatment by electrochemical advanced oxidation processes (EAOPs) in a sustainable manner, especially if combined with renewable energy sources.

Strategies for the quantification and characterization of nanoplastics in AOPs research

There is a growing interest in developing new targeted degradation technologies for the removal of micro- and nanoplastics (NPs) in water, corresponding to increased public concerns regarding their potential negative impacts on urban water systems, and consequently on human life quality. Recently, Advanced Oxidation Processes (AOPs) have been proposed as promising treatment alternatives for effective degradation of NPs in water. However, the selection of appropriate analytical methods for monitoring these oxidation tests remains a challenge. Herein, the feasibility of different characterization strategies for monitoring the evolution of NPs in water upon oxidation tests was systematically studied using polystyrene (PS) NPs of different particle sizes (D0 = 140, 252, 460, and 909 nm) as model plastic pollutants. To quantify NPs in water, Total Organic Carbon (TOC), Chemical Oxygen Demand (COD) and turbidity measurements were assessed. Moreover, turbidity was correlated to the particle size and PS NPs concentration by developing a response surface. Among the analytical techniques employed to characterize the solid particles, transmission electronic microscopy (TEM) was used to evaluate morphology and particle size. Alternatively, the viability of Dynamic Light Scattering (DLS), Nanoparticle Tracking Analysis (NTA) and Atomic Force Microscopy (AFM) to determine particle size is discussed. Chemical surface modifications were explored by Fourier-Transform Infrared Spectroscopy (FTIR). As a proof of concept, the degradation of PS NPs in water upon photo-Fenton oxidation was investigated at ambient conditions and fully characterized using the mentioned techniques.

Recent developments in moving bed biofilm reactor (MBBR) for the treatment of phenolic wastewater -A review

BackgroundPhenol, a toxic and carcinogenic compound found in industrial effluent, poses a severe threat to the environment and aquatic life. Conventional methods such as physio-chemical techniques have limitations in efficiency, cost, and sustainability, leading to the development of advanced hybrid approaches like the Moving Bed Biofilm Reactor (MBBR) to treat phenols. Review methodIn this study, we aimed at an in-depth review of MBBR for the remediation of phenolic wastewater at an industrial scale. The review uses a methodology that involves a comparative analysis of various conventional methods, including activated sludge process (ASP), sequencing batch biofilm reactor (SBBR), Fluidized Bed Biofilm Rector (FBBR), and trickling filter (TF) with MBBR, to determine their efficacy in phenol degradation. In this context, a thorough bibliometric assay of MBBR is carried out to understand the recent publication trends. The study also examines the impact of different types and shapes of bio-carriers and their filling ratios on phenol biodegradation. Significant findingThe present work demonstrates the feasibility of using an aerobic MBBR along with a Fenton-like system (advanced oxidation processes) to treat phenolic effluent LCCA is discussed for selected treatment methods for assessing the sustainability aspects. In light of recent advancements, future research endeavors should prioritize the refinement and optimization of MBBR systems to strengthen their efficiency and sustainability, thus paving the way for a greener and cleaner future.

Unraveling the intrinsic activity origin of sludge-derived biochar for boosted chlorination of diclofenac: Key role of persistent free radicals

Economical and eco-friendly chlorine-based advanced oxidation processes (AOPs) have been urgently demanded to enhance the green abatement of emerging micropollutants. Herein, sludge-derived biochar (SBC) was innovatively introduced to activate free available chlorine (FAC) to enhance the elimination of diclofenac (DCF) among pH 5.0–11.0. Pyrolysis of municipal sludge endowed biochar with superior structure, various chemical compositions, and electronic properties, among which carbon-centered persistent free radicals (PFRs) were verified as the dominant active sites for enhanced chlorination based on correlation analysis. Electron spin resonance and electrochemical tests firstly verified that PFRs could mediate electron transfer toward FAC and dissolved oxygen to generate multiple reactive species of •OH, ClO•, 1O2, and O2•−. Further investigation revealed that enhanced DCF chlorination relied on both radical attack by •OH, ClO•, and O2•− and direct electron transfer. Meanwhile, the regeneration of PFRs mediated by FAC and electron-rich DCF greatly promoted the reusability of SBC800. SBC800/FAC system was much superior to sole chlorination in terms of toxicity reduction and anti-interference capacity. This study innovatively introduced SBC as a green and sustainable catalyst to enhance chlorination efficiency, and provided new insights into the activation potential and mechanism of PFRs for chlorination.

Removal and risk assessment of emerging contaminants and heavy metals in a wastewater reuse process producing drinkable water for human consumption

This study focuses on the removal and risk assessment of twenty emerging contaminants (ECs) and heavy metals in a REMIX water treatment plant (RWTP) that produces drinking water from combination of wastewater reuse and desalination. The membrane biological reactor (MBR) exhibit removal rates exceeding 95% of pharmaceuticals like acetaminophen, trimethoprim, diclofenac, naproxen, and emtricitabine. The efficiency of brackish reverse osmosis (BWRO) in removing ECs is highlighted, showing substantial efficacy with reduction rates of 99.5%, 75.5%, and 51.2% for sulfamethoxazole, venlafaxine, and benzotriazole, respectively. The advanced oxidation process based on Fenton process reveals removal (>95%) of emtricitabine, efavirenz, and carbamazepine. The study confirms that the combination of treatment units within the RWTP effectively removes heavy metals (>90%), complying with acceptable limits. Risk quotient (RQ) calculations indicate the efficiency of the RWTP in EC removal, serving as benchmarks for public acceptance of reclaimed water. In the context of heavy metals, the study concludes negligible cancer risks associated with reclaimed water consumption over a lifetime. Quantitative structure-activity relationship and occurrence, persistence, bioaccumulation and toxicity (OPBT) models were used to assess EC risk. The study screened and identified potential persistant, bio accumulating and toxic PBT ECs. Critical control points (CCPs) in the RWTP are identified, with brackish and seawater reverse osmosis (BWRO and SWRO) and advanced oxidation process (AOP) recognized as pivotal in hazard management. The study provides valuable insights on the removal of ECs and heavy metals in a wastewater reuse process and demonstrates potential of adopted process configuration in supplying safe drinking water from wastewater recycling.

Simultaneous incorporation of Co and Fe into sulfur-vacancy-enriched MoS2 enhances the activation of peroxymonosulfate

Developing efficient and low-cost catalysts in peroxymonosulfate (PMS)-based advanced oxidation processes is vital but challenging. Here, a series of Co,Fe co-doped MoS2 with abundant S vacancies were prepared and utilized as PMS activators. The OTC removal efficiency (92.0%) in 1-Co,Fe-MoS2/PMS system was significantly higher than that (53.5%) in MoS2/PMS system. SO4•–/•OH, O2•−, and 1O2 played dominant roles, while high-valent metal and electron transfer mechanism played limited roles for OTC removal in both systems. The contributions of reactive species in 1-Co,Fe-MoS2/PMS system ranked as follows: 1O2 > SO4•–/•OH > O2•−, while that was O2•− > SO4•–/•OH >1O2 in MoS2/PMS system. Co and Fe doping promoted the generation of S vacancy in MoS2. Co(II)/Co(III), Fe(II)/Fe(III) and Mo(IV)/Mo(VI) all contributed to the activation of PMS, but Co and Fe sites were the major active sites of 1-Co,Fe-MoS2. Moreover, 1-Co,Fe-MoS2 was deposited on a polytetrafluoroethylene membrane, and exhibited excellent catalytic effect for OTC removal via a flow-through setup. Thus, this study provided a promising Co,Fe-MoS2/PMS process for organic pollutant removal.

Degradation of diethyl phthalate by photolysis of hydrogen peroxide electrogenerated using a Printex L6 carbon modified with Benzophenone cathode in an improved tangential flow cell

In this work, a gas diffusion electrode (GDE) made of Printex L6 carbon modified with 2.0% w/w of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (PL6C/BTDA 2%) was employed as cathode in a new 3D printed electrochemical cell with tangential flow. With this configuration, the performance of the technology was evaluated for hydrogen peroxide (H2O2) electrogeneration and remediation of aqueous wastes contaminated with diethyl phthalate (DEP) using different H2O2-based advanced oxidation processes (AOPs). The electrogeneration study was carried out varying the current density applied to the system, and it was found that 50mAcm-2 was the best performing value, resulting in remarkable faradaic efficiencies of nearly 100%. This led to the production of higher amounts of H2O2 (442.5mgL-1) in 90minutes at an acceptable energy consumption (8.5 kWh kg-1) compared to values reported in the literature. Based on these findings, H2O2-based AOPs were employed to investigate the removal of DEP in cathodic compartment, including mediated electrochemical degradation with electrogenerated H2O2 (e-H2O2) and the integration of this technology with ultraviolet-C (UVC) photolysis (e-H2O2/UVC). The integrated e-H2O2/UVC obtained the best performance compared to single photolysis and e-H2O2, leading to the total elimination of DEP (90 μmol L-1) within only 30min of treatment, reaching the highest kinetic rate constant (0.3min-1). Fifteen by-products, generated through oxidation processes studied, were successfully identified by LC-MS/MS, enabling the proposal of the degradation mechanism of DEP.

Electrocatalytic activation of permanganate as a highly efficient advanced oxidation strategy for water purification

Electrocatalytic activation of permanganate as a highly efficient advanced oxidation strategy for water purification

Edge state engineering of nitrogen/phosphorus co-doped graphene nanoribbons towards electron-transfer-based peroxydisulfate activation

The electron transfer-based nonradical advanced oxidation processes (AOPs) exhibit great potential for degrading organic pollutants. However, achieving efficient electron transfer-based nonradical AOPs remains challenging. In this study, we developed the edge-rich and nitrogen/phosphorus (N/P) co-doped graphene nanoribbons by unfolding the multi-walled carbon nanotubes (MWCNTs). The catalysts with the edge-rich structure are capable of efficiently activating the peroxydisulfate (PDS) towards the degradation of carbamazepine (CBZ), a representative pharmaceutical and personal care products (PPCPs). Through adjusting the N/P ratio, the N/P co-doped graphene nanoribbons presented the optimal degradation kinetic constant of 0.452 min−1, compared with 0.0611 min−1 for the intact MWCNTs. Electrochemical characterizations, in situ Raman, galvanic oxidation tests, and quenching experiments confirmed that the N/P co-doped graphene nanoribbons followed an electron transfer-dominated nonradical pathway for pollutant degradation. Density functional theory (DFT) demonstrated that the exposed N/P co-doped edges at the boundary of graphene nanoribbons could elongated OO bond of PDS in facilitating PDS activation. This study provides a new approach to develop the nonradical AOPs-based techniques.

A hydrodynamic cavitation prototype reactor evaluation for decreasing cephalexin concentration in aqueous solution

A prototype of a hydrodynamic cavitation reactor was evaluated to determine the effectiveness of this system on the percentage decrease of cephalexin concentration present in an aqueous solution prepared with ultrapure water. The process variables or factors were pH (5 and 9), number of holes in the cavitation plate (5 and 7) and reaction time (30 min and 60 min). The results indicate that the percentage removal of Cephalexin (CFX) and total organic carbon (TOC) depends on the variables studied and the interaction between them. The highest yields were achieved at pH 5, 5 holes in the cavitation plate and 60 min of reaction reaching values of 24.16 % for CFX and 16.8 % for TOC. It was determined that, for the lowest number of holes in the cavitation plate and acid pH, the phenomenon that guides the process is the hydrodynamic cavitation, when increasing the number of holes and therefore decreasing the intensity of cavitation, the pH becomes more relevant and has incidence on the performance of the analyzed process. On the other hand, it was determined that, also in reaction times of 30 min, removal values very close to the maximum values obtained are achieved. The process can be intensified by the simultaneous application of other advanced oxidation processes to increase the effectiveness.

Photocatalytic activation of sodium percarbonate by C3N5/C2N3 homojunction for rapid water purification: Efficient electron transfer of built-in electric field

The sodium percarbonate (SPC) activation by photogenerated electron from metal-free semiconductors is a potential advanced oxidation process in water treatment. C2N3, a novel CxNy material, was used to construct a nonmetallic homojunction catalyst via loading C3N5. The C3N5/C2N3 homojunction catalyst was used to photocatalytic activate SPC to degrade acetaminophen (AP), sulfamethoxazole, tetracycline, oxytetracycline and acyclovir. The CN-2/SPC/Vis system can completely remove AP within 20 min at 15 °C, and achieve excellent removal rate in a wide pH range. Its reaction rate constant was 24 times higher than that of C3N5/C3N4/SPC/Vis system. The CN-2/SPC/Vis system showed outstanding removal efficiency in tap and lake water. Notably, CN-2 was prepared as a photocatalytic suspension sponge and exhibited superior practicability in secondary effluent simulation experiment. CN-2 sponge can completely degrade AP within 50 min. The dominant active species for AP removal were h+, •O2− and 1O2. DFT calculations and electrochemical experiments demonstrated that the built-in electric field of nonmetallic homojunction accelerated the carrier separation, and more photogenerated electrons activated SPC to generate ROS. This work provides new insights into the construction of heterojunction in photocatalytic system and reveals the application potential of homojunction in wastewater purification.

(1 1 1) Facet-dominant peracetic acid activation by octahedral CoO anchored hollow carbon microspheres for tetracycline degradation

Peracetic acid (PAA), an environmental friendly disinfectant, has attracted increasing interest in applications on advanced oxidation processes for treating emerging pollutants. Herein, octahedral cobalt oxide anchored on cation exchange resin (CER)-derived hollow carbon microspheres were fabricated via a facile strategy and employed as the heterogeneous catalyst for PAA activation to degrade tetracycline (TC) antibiotic. Calcination temperature was demonstrated to play a significant role in resulted structure and composition, physicochemical properties and catalytic activities of the cobalt-based compounds/carbon composites. With the optimal catalyst which was calcined at 600 °C, namely the Co@CER-600, complete elimination of TC was achieved within 10 min in Co@CER-600/PAA system. The determination of reactive oxygen species (ROS) indicated that both non-radical (singlet oxygen) and radical (superoxide radical) mechanisms were evidenced in Co@CER-600/PAA system. Particularly, it is notable that the extensively exposed (111) facet in octahedral CoO was confirmed to show remarkable PAA activation activity, therefore promoted the ROS generation process. Considering that facet engineering is a novel whilst important strategy for catalyst regulation, the proposed (111) facet-dominant octahedral CoO anchored hollow carbon microspheres might suggest new inspirations for catalyst design in PAA-based AOPs toward antibiotic contamination remediation.

Accelerated removal of organic pollutants by biochar-based iron carbon granule-activated periodate in chloride-containing water: The role of active chlorine

Ubiquitous in water environments, the chloride ion (Cl−) can impact the decontamination capacity of an oxidation system. However, minimal studies are available on its effects in periodate (PI)-based advanced oxidation processes. In this study, a novel biochar-based iron-carbon (FeBC) granule was synthesized to activate PI and remove organic pollutants from water containing Cl−. The FeBC/PI/Cl− system (FeBC: 0.5 g/L; PI: 0.5 mM; AO7: 20 mg/L; NaCl: 50 mM) exhibited excellent performance on various organic pollutants, with ˃ 85 % of Acid Orange (AO7) removal over a pH range of 3–10. Within 20 min after the tenth run, approximately 80 % of AO7 was removed. Inorganic ions and natural organic matter had a negligible effect on AO7 removal. Characterization results confirmed that the presence of Cl− enhanced Fe corrosion, thereby improving PI activation efficiency for removing AO7. Electron paramagnetic resonance spectroscopy and active species trapping experiments verified that radicals (•OH and O2•−) and nonradical (1O2, Fe(IV), and electron transfer) oxidation processes participated in the FeBC/PI system. Moreover, the presence of Cl− accelerated •OH, O2•−, 1O2, and Fe(IV) formation and generated active chlorine, such as HOCl. The main pathways involved in the generation of multiple reactive species were evaluated. AO7 degradation pathways were proposed, and numerous intermediates exhibited decreased toxicity. These findings provide new insights for the decontamination of organic contaminants in water containing Cl−.

Efficiently activate peracetic acid by FeS2-anchored molybdenum species for the rapid degradation of sulfamethazine

Peracetic acid (PAA) based advanced oxidation processes are increasingly used as alternative strategies for sulfonamide antibiotics (SAs) degradation. In this study, molybdenum (Mo) species were successfully anchored on the FeS2 surface. This catalyst (Mo-FeS2) could be used as an excellent PAA activator for the removal of sulfamethazine (SMT). Electrochemical measurements revealed that anchored Mo species lowered the electron transfer resistance on the FeS2 surface, and density functional theory (DFT) calculation suggested more electrons can be shifted from FeS2 to Mo, which is prone to transfer electrons for PAA activation. After 30 min reaction, 87.6 % of SMT could be removed by Mo-FeS2/PAA at pH 4, and reactive species (RSs) including HO•, CH3COO• and Fe(IV) were responsible for the SMT degradation. Increasing the dosages of PAA (0.02 – 0.5 mM) or Mo-FeS2 (0.1 – 0.4 g/L) facilitated the SMT degradation. DFT calculation results suggest that the aniline ring of SMT is vulnerable to attack induced by RSs. The degradation pathways of SMT, including Smiles rearrangements, hydroxylation of aniline ring, oxidation of the –NH2 group and coupling reaction, were proposed according to the identified oxidation products. Sulfamethoxazole, sulfadiazine, sulfanilamide and sulfathiazole could also be degraded by Mo-FeS2/PAA (>50 %), suggesting that the Mo-FeS2/PAA would be a competitive strategy for the remediation of SAs-contaminated water.

New Insights into the pH-Dependent Removal of Sulfamethoxazole in Peracetic Acid Activation Systems: from Mechanistic Exploration to Practical Application Potentials

Peracetic acid (PAA) as emerging oxidant in advanced oxidation processes (AOPs) has attracted widespread attention in purifying water pollution. In this research, the removal of target contaminant (sulfamethoxazole, SMX) was investigated through PAA activation by a facile catalyst (Co@C), and the active sites of catalyst were identified as sp3-C, Oads, and Co0 by correlation analysis. Especially, different pH adjustment strategies were designed, including System A (adjusting pH after adding PAA) and System B (adjusting pH before adding PAA), to investigate the impact of oxidant acidity and alkalinity on solution microenvironment as well as effect and mechanism of pollutant removal. The results showed that HO· and CH3C(O)OO· dominated in System A, while Co(IV)O2+ was also observed in System B. Both systems showed optimal SMX degradation (98%). However, System A exhibited excellent water quality tolerance (efficiency > 78%), superior sustained catalyst activation (efficiency > 80% in 40h), less ion leaching (41μgL-1), and lower products toxicity. Moreover, the pH of solution after reaction in System B was intensely acidic, requiring costly pH adjustments for discharge. This study unveils the strategy of adjusting pH after adding PAA is preferable for water purification, enriching the emerging research of PAA-based AOPs for the remediation of environments. Environmental ImplicationsAs emerging contaminants, the consumption of antibiotics is increasing. Due to their difficult biodegradability, antibiotics have become hazardous substances of great concern as they trigger bacterial resistance and threaten the ecosystem. In this research, two pH adjustment strategies, including System A and System B (adjusting pH after and before adding PAA), were designed to investigate the effective removal of sulfamethoxazole through peracetic acid activation by a facile catalyst (Co@C). In comparison, System A was more suitable for remediation of water pollution owing to its excellent water quality tolerance, superior catalyst sustained activation, less ion leaching, and lower products toxicity.

Boosting organics degradation via sulfite activation by Fe/Mn@CF composite electrode: Performance and mechanism

Sulfite has been proven to promote advanced oxidation processes (AOPs) to achieve low-cost and efficient degradation of contaminants, serving as an alternative to persulfate. In this study, a novel composite Fe/Mn@carbon felt (CF) electrode was successfully constructed to remove carbamazepine (CBZ). The capacity of the Fe/Mn@CF anode to activate sulfite was evaluated under various electrode preparation conditions and operating parameters. Results clearly indicated that the complete removal of CBZ was achieved in Fe/Mn@CF anode activated sulfite system under the specific conditions including Na2SO4 electrolyte concentration of 50 mM, sulfite dosage of 1 mM, initial pH of 7, and current density of 1 mA/cm2. The capacity of Fe/Mn@CF anode for sulfite activation was further presented by its excellent reusability and stability in terms of CBZ removal and metal ion release. Both radical and non-radical pathways were significantly contributed to the CBZ removal, including OH, SO4·-, O2·-, 1O2, and other reasons. Density functional theory (DFT) calculations demonstrated that Fe-Mn bimetals effectively promoted sulfite activation, with the electric field further boosting the process of Fe-Mn valence cycle and oxidation. Overall, the novel Fe/Mn@CF activated sulfite system exhibited outstanding performance and had great potential for sustainable use in removing organics.

Energy-efficient Treatment of Refractory Industrial Effluent Using Flow-through Electrochemical Processes: Oxidation Mechanisms and Reduction of Chlorinated Byproducts

While flow-through anodic oxidation (FTAO) technique has demonstrated high efficiency to treat various refractory waste streams, there is an increasing concern on the secondary hazard generation thereby. In this study, we developed an integrated system that couples FTAO and cathodic reduction processes (termed FTAO-CR) for sustainable treatment of chlorine-laden industrial wastewater. Among four common electrode materials (i.e., Ti4O7, β-PbO2, RuO2, and SnO2-Sb), RuO2 flow-through anode exhibited the best pollutant removal performance and relatively low ClO3 and ClO4 yields. Because of the significant scavenging effect of Cl− in real wastewater treatment, the direct electron transfer process played a dominant role in contaminant degradation for both active and nonactive anodes though active species (i.e., active chlorine) were involved in the subsequent transformation of the organic matter. A continuous FTAO-CR system was then constructed for simultaneous COD removal and organic and inorganic chlorinated byproduct control. The quality of the treated effluent could meet the national discharge permit limit at low energy cost (~4.52 kWh m3 or ~0.035 kWh g1-COD). Results from our study pave the way for developing novel electrochemical platforms for the purification of refractory waste streams whilst minimizing the secondary pollution. Environmental ImplicationsIndustrial wastewater usually features high organic matter content and complex composition, posing a significant environmental risk. While anodic oxidation has demonstrated high efficiency, there is increasing concern on the secondary hazard generation thereby. An energy-efficient system coupling flow-through anodic oxidation and cathodic reduction processes is therefore proposed, achieving simultaneous organic contaminant removal and chlorinated byproduct control. The direct electron transfer process imparts an advantage in treating chlorine-laden wastewater compared to the •OH-based advanced oxidation counterparts. The results of this study pave the way for developing novel electrochemical platforms for the purification of refractory waste streams whilst minimizing the secondary pollution.

Constructing S-scheme Au/g-C3N4/BiVO4 heterojunction with peroxymonosulfate-enhanced photocatalytic activity and mechanism insight

Dissolved organic matter (DOM) in black-odorous water can cause excessive growth of plants and algae, leading to deterioration of water quality. Herein, an S-scheme Au/g-C3N4/BiVO4 heterojunction was constructed using a three-step method for DOM degradation in real black-odorous water in the presence of peroxymonosulfate (PMS). 4Au/g-C3N4/BiVO4/PMS exhibited highly efficient photocatalytic performance, and the DOM removal rate could reach 92.9%, which was 19.1 and 9.9 times higher than that of g-C3N4/PMS and BiVO4/PMS, respectively. The changes of fluorescence components in DOM were detected using synchronous fluorescence spectra and two-dimensional correlated spectroscopy analysis, and the toxicity of catalytically treated black-odorous water was evaluated by growth inhibition of Escherichia coli. A reasonable S-scheme mechanism was suggested by theoretical calculations and photoelectrochemical tests. The S-scheme mechanism and the synergistic effect of photocatalysis and hybrid advanced oxidation process (HAOP) increased the catalytic activity of Au/g-C3N4/BiVO4/PMS.

Bi-ZFO/BMO-Vo Z-scheme heterojunction photocatalysis-PMS bidirectionally enhanced coupling system for environmental remediation

Given the urgency of organic pollutant removal and the low efficiency of advanced oxidation processes (AOPs), a novel Bi-ZFO/BMO-Vo photocatalyst was fabricated via the solvothermal method. A coupling system was constructed to combine photocatalysis with peroxymonosulfate (PMS) oxidation processes, which synergistically degrade organic pollutants. Bi-ZFO/BMO-Vo exhibited excellent photocatalytic performance, which could remove 100% RhB in 110 min and degrade 100% MG in 70 min, and 88% H-TC in 50 min. The excellent catalytic performance of Bi-ZFO/BMO-Vo was not only attributed to the synergistic effect of PMS activation and photocatalysis, but also attributed to the SPR effect of Bi nanoparticles, electron capture of oxygen vacancies, and intense contact of Bi-ZFO/BMO-Vo heterojunctions. The active species capture experiments and EPR tests indicated that 1O2, SO4–·, ·OH, and O2–· worked together for the RhB removal. The degradation intermediates of RhB were identified by LC-MS. Based on the experimental results, the band structure and Z-scheme charge transfer mechanism were proposed. Toxicity evaluation indicated that Bi-ZFO/BMO-Vo-Vis/PMS could significantly reduce RhB toxicity. This efficient and stable catalyst is expected to be used in organic wastewater degradation and practical applications.

Controllable introduction of edged nitrogen sites in CVD-derived carbon materials for enhanced fenton-like reactions

Nitrogen doped carbon materials have great potential in the peroxymonosulfate based advanced oxidation processes due to their high efficiency. However, because of the limitation of prepared method, the doped N species are usually uncontrollable. In this work, a series of metal-free N-doped carbon materials are synthesized by chemical vapor deposition (CVD) with a CaO template and through regulating the deposition temperature we achieve the gradient control of the edged-N species. Taken phenol as the pollutant probe, the catalytic performances of N-doped carbon material are investigated, and 700 °C is determined to be the optimal deposition temperature for carbon material with a reaction rate constant of 0.335 min−1. After the analysis of kinetics and the N species, we demonstrate that the content of pyrrolic N has an exponential relationship with the activity. Radicals quenching experiments, electron paramagnetic resonance and electrochemical test are also employed to verify that O2•–, 1O2, and direct electron transfer are the dominated reactive oxidation species rather than typic hydroxyl and sulfate radicals. Overall，this doped strategy through CVD give a new insight of controlling doped species in carbon materials preparation.