Degradation Pathway Research Articles

Enhanced Removal Performance and Economical Efficiency of Volatile Organic Sulfur Compounds by Silver-Modified ZSM-5 Zeolites under a High-Humidity Environment: A Mechanistic Study of the Adsorption-Plasma Catalytic Process.

Dimethyl sulfide (DMS) is a harmful volatile organic sulfur compound (VOSC), which must be effectively controlled. The adsorption-plasma catalytic (APC) process is an efficient and economical route for the elimination of low-concentration VOSCs; however, there are still many challenges in humid environment. In this study, a series of zeolites with different Si/Al ratios and Ag loadings were designed, and were performed for DMS removal by APC process. At 80% relative humidity, the DMS adsorption capacity of Ag5-ZSM25 reached 33.9 mg/g, which was 7.9 times that of ZSM25 and nearly 2 times that of Ag5-ZSM200. Analyses via UV-vis, X-ray photoelectron spectroscopy (XPS), and CO-FTIR confirmed that Ag+ was the predominant species for DMS adsorption and degradation in Ag5-ZSM25. DMS-temperature-programmed desorption (TPD) and density functional theory (DFT) calculations indicated that Ag+ significantly enhanced the binding energy with DMS and weakened the competitive adsorption impact of H2O. In the plasma regeneration stage, Ag5-ZSM25 demonstrated an 89% mineralization, with Ag+ being crucial for DMS mineralization. Based on the in situ plasma DRIFT spectra, a possible degradation pathway for DMS was proposed. The APC process achieved an energy efficiency of 1.66 g/kWh, tripling that of the continuous plasma catalytic process and providing guidance for low-concentration DMS elimination.

Warming and UV Radiation Alleviate the Effect of Virus Infection on the Microalga Emiliania huxleyi.

The marine microalga Emiliania huxleyi is widely distributed in the surface oceans and is prone to infection by coccolithoviruses that can terminate its blooms. However, little is known about how global change factors like solar UV radiation (UVR) and ocean warming affect the host-virus interaction. We grew the microalga at 2 temperature levels with or without the virus in the presence or absence of UVR and investigated the physiological and transcriptional responses. We showed that viral infection noticeably reduced photosynthesis and growth of the alga but was less harmful to its physiology under conditions where UVR influenced viral DNA expression. In the virus-infected cells, the combination of UVR and warming (+4°C) led to a 13-fold increase in photosynthetic carbon fixation rate, with warming alone contributing a change of about 5-7-fold. This was attributed to upregulated expression of genes related to carboxylation and light-harvesting proteins under the influence of UVR, and to warming-reduced infectivity. In the absence of UVR, viral infection downregulated the metabolic pathways of photosynthesis and fatty acid degradation. Our results suggest that solar UV exposure in a warming ocean can reduce the severity of viral attack on this ecologically important microalga, potentially prolonging its blooms.

Bacterial Degradation of Petroleum Hydrocarbons in Saudi Arabia.

The Kingdom of Saudi Arabia (KSA) is the leading oil-exploring and -exploiting country in the world. As a result, contamination of the environment by petroleum products (mainly hydrocarbons) is common, necessitating strategies for their removal from the environment. Much work has been conducted on bacterial degradation of hydrocarbons in the KSA. This review comprehensively analyzed 43 research investigation articles on bacterial hydrocarbon degradation, mainly polyaromatic hydrocarbons (PAHs) within the KSA. More than 30 different bacterial genera were identified that were capable of degrading simple and complex PAHs, including benzo[a]pyrene and coronene. Different strategies for selecting and isolating these bacterial strains and their advantages and disadvantages were highlighted. The review also discussed the origins of sample inocula and the contributions of various research groups to this field. PAH metabolites produced by these bacteria were presented, and biochemical pathways of PAH degradation were proposed. More importantly, research gaps that could enrich our understanding of petroleum product biodegradation mechanisms were highlighted. Overall, the information presented in this paper will serve as a baseline for further research on optimizing bioremediation strategies in all petroleum-contaminated environments.

Increasing coil temperature of a third-generation e-cigarette device modulates C57BL/6 mouse lung immune cell composition and cytokine milieu independently of aerosol dose

ABSTRACT Higher coil temperature in e-cigarette devices increases the formation of aerosols and toxicants, such as carbonyls. At present, the health implications of vaping at higher temperatures, including exacerbation of pulmonary inflammation, are largely unknown when aerosol dose is considered. To isolate the pulmonary effects of coil temperature, C57BL/6 mice were exposed to e-cigarette aerosols generated at lower (190°C) or higher (250°C) temperature for 3 days, while maintaining a similar chamber aerosol concentration. Increasing coil temperature did not markedly alter aerosol mass-normalized emissions of select carbonyls formed from thermal degradation pathways including formaldehyde, acetaldehyde, propionaldehyde, and acetone under the tested environment. Total bronchoalveolar cells, primarily macrophages, were significantly decreased in mice exposed to aerosols generated with higher coil temperatures compared to lower temperature exposures. The gene expression of IFNβ, IL-1β, TNFα, and IL-10 in mouse lung tissue was significantly reduced following e-cigarette exposure under both conditions, compared to filtered air exposure. Higher temperature exposures further exacerbated downregulation of IFNβ and IL-1β. Data suggest that higher temperature vaping might modulate acute pulmonary immune responses, potentially inducing immune suppression, even when normalized for aerosol dose exposure. Coil temperature thus appears to be an important parameter that needs to be regulated to ensure harm reduction for e-cigarette users.

Activation of Persulfate by NiFe-Layered Double Hydroxides Toward Efficient Degradation of Doxycycline in Water

In recent years, the excessive use and improper disposal of antibiotics have led to their pervasive presence in the environment, resulting in significant antibiotic pollution. To address this pressing issue, the present study synthesized nickel–iron-layered double hydroxides (NiFe-LDHs) with varying molar ratios using a hydrothermal method, employing these LDHs as catalysts for the oxidative degradation of doxycycline, with peroxymonosulfate (PMS) serving as the oxidant. X-ray diffraction analysis confirmed that the synthesized NiFe-LDHs exhibited a hexagonal crystal structure characteristic of layered double hydroxides. Experimental results demonstrated that the catalytic efficiency of NiFe-LDHs increased with both the dosage of the catalyst and the concentration of PMS, achieving a high degradation efficiency for doxycycline at a catalyst concentration of 0.5 g/L. Furthermore, the catalytic performance was notably effective across a range of pH conditions, with the highest degradation efficiency being observed at a Ni–Fe molar ratio of 3:1. The activation of PMS by NiFe-LDHs for the catalytic degradation of pollutants primarily occurs through singlet oxygen (1O2), superoxide radicals (O2−·), and sulfate radicals (SO4−·). The study also proposed three potential degradation pathways for doxycycline, indicating that the final degradation products have lower environmental toxicity. This research offers novel approaches and methodologies for the treatment of antibiotic-contaminated wastewater.

Recent Advances in Silica-Based Nanomaterials for Enhanced Tumor Imaging and Therapy.

Cancer remains a formidable challenge, inflicting profound physical, psychological, and financial burdens on patients. In this context, silica-based nanomaterials have garnered significant attention for their potential in tumor imaging and therapy owing to their exceptional properties, such as biocompatibility, customizable porosity, and versatile functionalization capabilities. This review meticulously examines the latest advancements in the application of silica-based nanomaterials for tumor imaging and therapy. It underscores their potential in enhancing various cancer imaging modalities, including fluorescence imaging, magnetic resonance imaging, computed tomography, positron emission tomography, ultrasound imaging, and multimodal imaging approaches. Moreover, the review delves into their therapeutic efficacy in chemotherapy, radiotherapy, phototherapy, immunotherapy, gas therapy, sonodynamic therapy, chemodynamic therapy, starvation therapy, and gene therapy. Critical evaluations of the biosafety profiles and degradation pathways of these nanomaterials within biological environments are also presented. By discussing the current challenges and prospects, this review aims to provide a nuanced perspective on the clinical translation of silica-based nanomaterials, thereby highlighting their promise in revolutionizing cancer diagnostics, enabling real-time monitoring of therapeutic responses, and advancing personalized medicine.

Autophagy is essential for somatic embryogenesis in citrus through regulating amyloplast degradation and lipid homeostasis.

Autophagy is a conserved degradation pathway that regulates the clearance of paternal substrate at the early embryogenesis stage of animals. However, its mode of action is likely different in plants, which can regenerate through apomixis without fertilisation. Somatic embryogenesis (SE) is a unique plant process widely used for plant propagation and germplasm utilisation. Here, we studied citrus as an example and found a higher autophagic activity after SE initiation. Interestingly, amyloplasts were frequently found inside autophagosomes, whereas the inhibition of autophagy blocks amyloplasts/starch degradation and hinders somatic embryo formation. Furthermore, the consumption of storage lipids was faster in autophagy mutants, suggesting lipid metabolism is activated when starch utilisation is blocked. Exogenous application of autophagy-inducing chemicals (e.g. spermidine) significantly promoted the formation of autophagosomes and increased SE efficiency, indicating a positive correlation between autophagy, energy metabolism, and somatic embryo formation in citrus. Taken together, our study unveils a pathway for the degradation of plant-specific organelles and provides an effective approach for plant propagation.

Preparation of high performance CoCuAl@SiC catalytic ceramic membrane for nonradical degradation of sulfamethoxazole

Catalytic ceramic membranes (CCM) featuring catalytic and separating functions, show huge potential in water treatment. Nevertheless, the inability of catalytic ceramic membrane with high catalytic performance to be produced by current fabrication method are the bottleneck preventing their applications. Herein, the high performance CoCuAl@SiC CCM were successfully prepared by coating Al gel interlayer, hydrothermal reaction and annealing in reductive atmosphere. Annealing in reductive atmosphere play key role in enhancing the catalytic property of CoCuAl@SiC CCM. 99.3 % sulfamethoxazole (10 mg·L−1) degraded by CoCuAl@SiC CCM annealing at 300 °C and 0.5 mM PMS in 1 min under a wide pH range of 3.5–11.0 and in the presence of anions. Quenching tests confirmed the dominant role of singlet oxygen (1O2) in SMX degradation. The abundant oxygen vacancies and redox cycles of Co3+/Co2+ and Co2+/Co0 on CoCuAl@SiC CCM are crucial for PMS activation. In addition, the SMX degradation pathways were found to comprise deamination, hydroxylation, and ring open according to the degradation intermediates of SMX. This study not only provides an approach for the preparation of catalytic membranes with excellent catalytic activity, but also sheds a novel insight into the indispensable role of oxygen vacancy.

A highly-efficient peroxymonosulfate activator using a sewage sludge derived biochar supported cobalt oxide: Mechanism and characteristics

The application of biochar derived from sewage sludge (BS) in Fenton-like reactions for contaminant removal has attracted considerable attention. Herein, a BS-supported Co3O4 (BS-Co3O4) catalyst was synthesized using a simple two-step hydrothermal-calcination process to achieve highly efficient activation of peroxymonosulfate (PMS). The introduction of biochar effectively inhibited the aggregation of Co3O4 and reduced cobalt leaching. Compared to Co3O4, the mesoporous BS-Co3O4 exhibited an 8-fold increase in specific surface area (SSA) to 111.92 m2∙g−1, and a 46 %-66.4 % reduction in crystal plane size. The interaction between biochar and cobalt oxide resulted in several notable enhancements in the BS-Co3O4 composite. Specifically, there was an increase in sp2 carbon content, a 42.69 % rise in capacitance, and a 79.99 % reduction in charge transfer resistance. These improvements contributed to enhanced PMS activation performance. The BS-Co3O4 also contained a higher content of Co(II), sp2 carbon, and oxygen vacancies (OV). Co(II) played a crucial role in the redox reaction, accelerating the formation of SO4•− and 1O2 during the PMS activation process. Additionally, OV acted as electron capture centers, further promoting the generation of 1O2. Evidence from reactive species investigations and electron paramagnetic resonance (EPR) tests indicated that SO4•− and 1O2 were the main reactive radicals for eliminating tetracycline (TC). Based on the identification of TC intermediates, two potential degradation pathways were proposed, and a reduction in intermediate toxicity was observed. Experiments involving interference and repetition demonstrated that the BS-Co3O4 catalyst was stable and reusable. This work provides a solution with low metal leaching, high recycling performance, and safety for antibiotic wastewater treatment.

A novel Cu/Fe cathode prepared by a facile redox pathway for phenol degradation electrocatalytically via the electro-fenton assisted electro-chlorination process

Electrochemical methods for treating phenolic wastewater have been widely studied, with most research focusing primarily on the anode, while the cathode has generally served as a counter electrode. This study aims to enhance the electrocatalytic process by developing a new Fe/Cu-based cathode using a simple redox method. We created a CuOCu@Fe-Fe2O3-x (0 < x < 1, combining Fe2O3 and FeO) electrode, referred to as CCFFO, to facilitate the electro-Fenton process without requiring additional H2O2 or Fe2+. In our electrolysis system with NaCl as the electrolyte for electro-chlorination process, phenol concentration was reduced from 100 mg/L to below 0.5 mg/L within 10 min. Optimal experimental conditions were determined by evaluating various parameters such as chloride electrolyte concentration, current density, electrode plate spacing, aeration, pH, and cathode types. Additionally, the role of chloride ions in phenol degradation was investigated through free radical quenching experiments. A 500-hour continuous flow experiment demonstrated the durability of the CCFFO cathode. GC/MS analysis identified intermediates formed during phenol degradation and the underlying catalytic mechanism was explored. The results indicate that the electro-chlorination process at the anode is the primary driver of phenol degradation, assisted by the electro-Fenton process on the CCFFO cathode. The CCFFO cathode effectively prevents the production of harmful by-products like perchlorate. The degradation efficiencies of chemical oxygen demand (COD) and total organic carbon (TOC) were 63.5 % and 80.25 %, respectively. Achieving a phenol degradation efficiency of 99.5 % within 10 min, the CCFFO cathode and electrolytic system show significant potential for wastewater treatment applications.

Insights into the enhancement of trace level NO2− on 2,4,6-tribromophenol degradation in UV/PS process: Experimental study and theoretical calculation

Sulfate radical (SO4−)-based UV/persulfate (PS) process is extensively studied to remove organic pollutants in water, while the wide presence of nitrite (NO2−) in natural water can quickly react with SO4− and hydroxyl radicals (OH) to form reactive nitrogen species (RNS). In this study, the degradation of 2,4,6-tribromophenol (TBP) in UV/PS process in the presence of low concentration of NO2− was systematically investigated through experimental studies and theoretical calculations. The introduction of trace NO2− enhanced the TBP degradation by UV/PS process due to the formation of RNS (such as NO2 and BrNO2) and both RNS and SO4− played the important role in the pH range of 6.0–8.0. TBP was more easily photolyzed under alkaline conditions due to higher photodegradation coefficient at pH 8.0. When TBP underwent deprotonation, the reaction energy barrier of TBP with SO4−, OH and NO2 significantly decreased and subsequent debromination may be more likely to occur. Additionally, NO2 attacked ionized TBP at relatively high rate mainly through electron transfer. The degradation pathways of TBP mainly involved in the debromination, hydroxylation and nitrosylation and the generated products all presented lower toxicity than TBP. Moreover, the effects of PS dosage, NO2− concentration, humic acid, bicarbonate and chloride on TBP elimination also were thoroughly assessed. The presence of low concentration of NO2− reduced the toxicity risk caused by the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) during the chlorination process after UV/PS pre-oxidation. This study broadens the knowledge of trace NO2− enhancing organic pollutants degradation by UV/PS process.

One-step synthesis of iron and carbon-quantum-dot co-decorated graphitic carbon nitride photocatalysts for carbamazepine degradation

In this study, a one-step hydrothermal preparation strategy was employed to synthesize a graphitic carbon nitride (g-C3N4) composite photocatalyst co-decorated with Fe sites and carbon quantum dots (Fe–CQDs/g-C3N4). Through a series of characterisation techniques, the successful integration of Fe atoms and carbon quantum dots (CQDs) onto g-C3N4 was achieved. Moreover, the presence of Fe, specifically Fe–N bonds, enhanced the charge-carrier transfer. With carbamazepine (CBZ) as the model pollutant, Fe–CQDs/g-C3N4 increased the photocatalytic activity with efficient peroxymonosulfate (PMS) activation under solar light irradiation, achieving 100 % CBZ degradation in 15 min over a wide pH range (3–9). Doping of the catalyst with Fe and CQDs resulted in a narrowing of the catalyst bandgap (2.25 eV) compared to that of g-C3N4 (2.79 eV), confirming the promotion of photo-induced charge separation. The CBZ degradation pathways were elucidated by ultrahigh-performance liquid chromatography and high-definition mass spectrometry. The Fe–CQDs/g-C3N4 composite was found to possess substantial potential for the efficient degradation of pollutants.

Transcriptome analysis to identify genes related to programmed cell death resulted from manipulating of BnaFAH ortholog by CRISPR/Cas9 in Brassica napus

Fumarylacetoacetate hydrolase (FAH) catalyzes the final step of the tyrosine degradation pathway. In this study, we isolated and characterized two homologous BnaFAH genes in Brassica napus L. variant Westar, and then used CRISPR/Cas9-mediated targeted mutagenesis to generate a series of transgene-free mutant lines either with single or double-null bnafah alleles. Among these mutant lines, the aacc (bnafah) double-null mutant line, rather than the aaCC (bnaa06fah) mutant line, exhibited programmed cell death (PCD) under short days (SD). Histochemical staining and content measurement confirmed that the accumulation of reactive oxygen species (ROS) in bnafah was significantly higher than that in bnaa06fah. To further elucidate the mechanism of PCD, we performed transcriptomic analyses of bnaa06fah and bnafah at different SD stages. A heatmap cluster of differentially expressed genes (DEGs) revealed that PCD may be related to various redox regulatory genes involved in antioxidant activity, ROS-responsive regulation and calcium signaling. Combined with the results of previous studies, our work revealed that the expression levels of BnaC04CAT2, BnaA09/C09SAL1, BnaA08/C08ACO2, BnaA07/C06ERO1, BnaA08ACA1, BnaC04BIK1, BnaA09CRK36 and BnaA03CPK4 were significantly different and that these genes might be candidate hub genes for PCD. Together, our results underscore the ability of different PCD phenotypes to alter BnaFAH orthologs through gene editing and further elucidated the molecular mechanisms of oxidative stress-induced PCD in plants.

4D-label free based comparative proteomics revealed the responsive mechanisms of quality deterioration driven by spore release in shiitake mushrooms

Label-free quantitative proteomics profiles combined with biochemical analysis were applied in three spore release stages to investigate the proteome responses related to spore release inducing the quality loss of mushrooms. During the spore release, the mushrooms softened, and malondialdehyde (MDA) and total free amino acids accumulated, especially bitter amino acids. Among the 2720 identified proteins, aminoacyl-tRNA biosynthesis, oxidative phosphorylation, and other glycan degradation pathways were primarily implicated. ATP-binding cassette (ABC) transporters and purine metabolism stimulated energy consumption in the second stage, which could be responsible for the spore release. Moreover, aminoacyl-tRNA ligase and ribosomal proteins were identified as hub proteins, actively expressed, and significantly associated with quality traits. The hub proteins might play a dominant role in mediating the quality deterioration triggered by the spore release in shiitake mushrooms. The results expand the understanding of the molecular mechanisms underlying the response to spore release in shiitake mushrooms.

Degradation of dioxins in chelated municipal solid waste incineration fly ash by low-temperature pyrolysis

In this study, low-temperature pyrolysis is applied to raw and chelated municipal solid waste incinerator fly ash to degrade and remove PCDD/F (polychlorinated dibenzo-p-dioxins, and dibenzofurans) and corresponding I-TEQs (international toxic equivalents), respectively. Additionally, PCDD/F degradation pathways are identified based on PCDD/F signatures. From the analysis of the average signal intensity of dioxin isomers in thermally treated fly ashes, the PCDD/F degradation rate was between 89.97 and 99.80 %, and the I-TEQs removal rate was 98.96 and 99.90% across all samples compared to untreated raw fly ash. The chelating agent EDTA enhanced the thermal degradation of PCDD/F, but the addition of Na2HPO4 in chelated fly ash as an inhibitor promoted PCDD/F regeneration. Further, there is a variable output of dioxins and corresponding I-TEQs under different temperatures and reaction times; however, longer reaction duration and higher temperatures proved highly effective. The overall toxicity of all thermally tested fly ashes was lesser than the permissible value of 50 ng I-TEQ/kg for resource utilization and observed in the range of 1.84 ± 0.15 to 19.45 ± 0.89 ng I-TEQ/kg. The investigation of the PCDD and PCDF signatures suggests that thermal destruction was a major pathway of degradation by breakage of the C-O bond, compared to dechlorination as observed by a high percentage contribution of HpCDD/F and OCDD/F congeners in thermally treated fly ashes. Low-temperature pyrolysis is an auspicious disposal technology that requires additional studies for large-scale applications.

Insights into sulfamethazine degradation by peroxymonosulfate activation using H2 reduced hematite in high-salinity wastewater: Performances and mechanisms

Sulfamethazine (SMT) is recognized as a persistent, bioaccumulate, and toxic antibiotic pollutant that is difficult to be completely eliminated through traditional wastewater treatment methods. Although advanced oxidation processes (AOPs) utilizing peroxymonosulfate (PMS) have demonstrated potential in degrading SMT, the lack of inexpensive and efficient PMS activators remains a significant obstacle for its practical application. In this study, we present the synthesis of a highly effective PMS activator, the naturally-occurring minerals-based material − H2– reduced hematite (HRH), on an industrial scale using a fluidized bed reactor. Impressively, within the PMS AOPs system, the synthesized HRH catalyst not only achieves 99.3 % degradation of SMT within 20 min, demonstrating a remarkable 10-fold increase in the degradation rate compared to pristine hematite, but also showcases excellent recyclability and durability. Additionally, this HRH/PMS system were proved to effectively remove SMT under high-salinity conditions. More importantly, through systematic characterization and theoretical calculations, an in-depth investigation into the primary activation mechanism and degradation pathway in this reaction process is provided. This work provided a highly feasible strategy for the application of natural mineral-based catalyst for the degradation of pollutants via PMS activation in high-salinity wastewater.

Methionine restriction reduced growth performance and exacerbated lipid deposition in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) under high-lipid diets by suppressing the lipid degradation pathways with the single-cell RNA-seq analysis

The experiment mainly focused on the liver of the hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) with low methionine levels by single-cell RNA-seq under high-lipid diets. Both weight gain rate (WGR) and specific growth rate (SGR) in the MR group were obviously lower than the C group, and the intraperitoneal fat (IPF) in the MR group was obviously enhanced than HL and C groups, which led to more visible growth inhibition and lipid deposition. By using the scRNA-seq analysis, nine cell types were classified as: liver parenchymal cells, erythrocytes, hepatic stellate cells, cholangiocytes, macrophages, T cells, epidermal cells, eosinophil and fibroblasts. Lipid and carbohydrate metabolisms were mainly enriched in liver parenchymal cells. The lipid degradation pathways were obviously inhibited in the MR group, such as cholesterol degradation pathway. The lipid degradation genes were obviously decreased in the MR group. In conclusion, methionine restriction might suppress the lipid degradation pathways in liver parenchymal cells, led to obvious lipid deposition.

Degradation of a novel herbicide fluchloraminopyr in soil: Dissipation kinetics, degradation pathways, transformation products identification and ecotoxicity assessment

With the continuous application of new agricultural chemicals in agricultural systems, it is imperative to study the environmental fate and potential transformation products (TPs) of these chemicals to better assess their ecological and health risks, as well as guide scientific application. The dissipation of fluchloraminopyr was firstly evaluated under aerobic/anaerobic condition in four representative soils, with Dissipation Time 50 (DT50) values ranging from 0.107 to 4.76 days. Eight TPs generated by soil degradation were identified via Ultra-High Performance Liquid Chromatography coupled with Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-QTOF/MS) and Density Functional Theory (DFT) calculations. The predominant transformation reactions of fluchloraminopyr in soil include oxidation, dechlorination, hydroxylation, and acetylation. The predictions from toxicological software indicated that the acute and chronic toxicity of TPs to aquatic organisms was significantly lower than that of fluchloraminopyr. Moreover, both M267 and M221 exhibited higher acute oral toxicity to terrestrial organisms compared to the parent compound. Consequently, these findings offer essential ecological risk evaluation data for the judicious application of fluchloraminopyr.

Perylene diimide configuration to construct g-C3N4 and iron phthalocyanine composite catalyst as PMS activator for contaminant degradation

The photocatalysis-assisted peroxymonosulfate (PMS) activation process has shown great potential for organic wastewater treatment. Herein, the composite photocatalyst (FeTAPc/PDI/CN) was obtained by grafting graphitic carbon nitride (CN) and amino iron phthalocyanine (FeTAPc) onto both ends of perylene tetracarboxylic anhydride (PTCDA) through an imidization process. Under simulated solar irradiation, the catalyst exhibited a remarkable degradation performance toward the target pollutant by activated PMS over a wide pH range from 3 to 11. The degradation efficiency of SMX reached 100 % in 7 min with the reaction kinetic constant of 0.845 min−1, which was 13 times higher than that of pure CN. In addition, the removal rate of FeTAPc/PDI/CN-4 for SMX was more than 80 % after 9 cycles. The introduction of phthalocyanine and PDI improved the separation efficiency of photogenerated electron-hole pairs. Furthermore, the active species involved in the SMX degradation were identified as •OH, SO4•-, •O2– and 1O2. The possible degradation pathways were proposed based on the identified intermediates, in which the oxidation of the amino group on the benzene ring was the main degradation pathway. This study is anticipated to result in a favorable method for designing CN-based photocatalysts with high stability and excellent catalytic activity for environmental remediation.

Alkali-decorated carbon nitride enhances the removal of enrofloxacin by ferrihydrite-H2O2 system: Mechanistic insights and degradation pathways

Antibiotic pollution affects water quality. Based on the ferrihydrite-H2O2 (Fh-H2O2) photo-Fenton system, alkali-decorated carbon nitride was introduced, and KC3N4/Fh, with ·OH and ·O2− as the primary reactive oxygen species, was synthesized for the degradation of veterinary antibiotic enrofloxacin in water. The modification with KOH induced the formation of cyano groups and nitrogen vacancies in KC3N4/Fh. The presence of cyano groups altered the original charge distribution and energy band structure of the material, thereby establishing an internal electric field. Directed driving of nitrogen vacancies accelerated the transfer of photogenerated charges from the conduction band of KC3N4 to the surface of Fh, facilitating the cycle process of Fe(III) and Fe(II). Meanwhile, the nitrogen vacancies significantly enhanced the adsorption capacity of KC3N4/Fh for H2O2 and accelerated the reaction between the generated Fe(II) and H2O2 to produce ·OH, which subsequently led to the efficient degradation and mineralization of enrofloxacin. The results demonstrated that the degradation rate of enrofloxacin by KC3N4/Fh reached 95.96 % within 30 min, highlighting its high efficiency and stability. Furthermore, KC3N4/Fh exhibited effective degradation of actual effluent under sunlight. This work proposes a novel approach to creating a Fh-H2O2-based photo-Fenton system for the efficient antibiotic degradation.