Typical Organic Pollutants Research Articles

Accumulation of typical persistent organic pollutants and heavy metals in bioretention facilities: Distribution, risk assessment, and microbial community impact

Bioretention facilities have proven highly effective in removing pollutants from runoff. However, there is a concerning paucity of research on the contamination characteristics and associated risks posed by refractory pollutants in these facilities following long-term operation. This research focuses on the distribution, sources, microbial community impact, and human health risks of pollutants in eight bioretention facilities that have been operational for 5–11 years. The results showed that the distribution of Cu, Zn, and Cd was closely related to anti-seepage measures. PAHs, PCBs, and OCPs primarily accumulated in the surface, with concentrations ranging from 7.42 to 20.34 mg/kg, 31.8–77.3 μg/kg, and 60.5–163.6 μg/kg, respectively. Their concentrations inversely correlate with the depth of the media. Although the majority of contaminants remained below their respective risk thresholds, their concentrations typically exceeded those of background soil values, indicating an enrichment phenomenon. Source analysis revealed that PAHs primarily originate from oil combustion, PCBs were linked to their related industrial products, DDTs had their main sources in technical DDx and residues from the use of dicofol, while HCHs were traced back to historical residues from agricultural activities. Microbial α-diversity (Chao 1 and Shannon) decreased by 8.3–23.4% and 0.8–4.4%, respectively, in different facilities after long-term operation. The most dominant microbial phylum in the facilities was Proteobacteria (all relative abundances >48%). The total relative abundance of dominant genera was 6.7–34.3% higher than the control site, and Pseudomonas, a typical POPs-heavy metal degrading bacterium, had the highest relative abundance (>1.2%). Cu, Zn, and Cd present no non-carcinogenic risks and have low potential ecological risks. However, the lifetime cancer risk for PAHs is 10−6 ∼10−4 in most facilities and is of concern. The cancer risk for PCBs is acceptable, while OCPs pose a low cancer risk only for children.

Gradual effects of gradient concentrations of perfluorooctane sulfonate on the antioxidant ability and gut microbiota of red claw crayfish (Cherax quadricarinatus)

Perfluorooctane sulfonate (PFOS) is a typical persistent organic pollutant that is characterized by environmental persistence, bioaccumulation, and toxicity. In this study, we investigated the gut microbial response of the red claw crayfish Cherax quadricarinatus after 28 days of exposure to 0 ng/L, 1 ng/L, 10 μg/L, or 10 mg/L of PFOS as a stressor. We measured oxidative stress-related enzyme activities and expression of molecules related to detoxification mechanisms to evaluate the toxic effects of PFOS. We found that PFOS disturbed microbial homeostasis in the gut of C. quadricarinatus, resulting in increased abundance of the pathogen Shewanella and decreased abundance of the beneficial bacterium Lactobacillus. The latter especially disturbed amino acid transport and carbohydrate transport. We also found that the activities of glutathione S-transferase and glutathione peroxidase were positively correlated with the expression levels of cytochrome P450 genes (GST1-1, GSTP, GSTK1, HPGDS, UGT5), which are products of PFOS-induced oxidative stress and play an antioxidant role in the body. The results of this study provided valuable ecotoxicological data to better understand the biological fate and effects of PFOS in C. quadricarinatus.

Leaching Characteristics of Glutaraldehyde and Organic Dyes Utilized in Tannery Industry in Soil

ABSTRACT The discharge of effluents and sludge from the leather industry is raising a growing concern. However, the mobility and hazards of tannery organic pollutants in soils are easily ignored. Herein, soil column leaching experiments were conducted using typical tannery organic pollutants glutaraldehyde (GA) and two azo dyes [Acid Red 73 (AR 73) and Direct Blue 6 (DB 6)]. Under simulated rain conditions, the leaching behavior of GA and organic dyes showed significant differences even though they were both water-soluble organic pollutants. AR 73 and DB 6 could be detected in the leachates throughout 7 leaching events for 28 days and in soil columns after leaching, while GA failed to be detected in both leachates and soil columns, indicating that AR 73 and DB 6 with more complex molecular structures had poorer degradability than GA under the condition of similar initial concentrations. The results demonstrated that the azo dyes AR 73 and DB 6 used in the experiment were more likely to cause adverse effects on soil and underground water under the condition of the covering thickness of dyes ≥ 0.5 mm on soil, and thus possessed higher environmental risk than GA. This study is also conducive to further evaluating the risk of tannery contamination sites.

Removal of Organic Dyes, Polymers and Surfactants Using Carbonaceous Materials Derived from Walnut Shells.

A series of new granular carbonaceous adsorbents was prepared via single-stage physical and chemical activation of walnut shells. Their suitability for removing various types of organic pollutants (represented by dyes, surfactants and water-soluble polymers) from the liquid phase was assessed. The activation of the precursor was carried out with CO2 and H3PO4 using conventional heating. Activated biocarbons were characterized in terms of chemical composition, acidic-basic nature of the surface, textural and electrokinetic properties as well as thermal stability. Depending on the type of activating agent used during the activation procedure, the obtained biocarbons differed in terms of specific surface area (from 401 to 1361 m2/g) and the type of porous structure produced (microporosity contribution in the range of 45-75%). Adsorption tests proved that the effectiveness of removing organic pollutants from the liquid phase depended to a large extent on the type of prepared adsorbent as well as the chemical nature and the molecular size of the adsorbate used. The chemically activated sample showed greater removal efficiency in relation to all tested pollutants. Its maximum adsorption capacity for methylene blue, poly(acrylic acid), poly(ethylene glycol) and Triton X-100 reached the levels of 247.1, 680.9, 38.5 and 61.8 mg/g, respectively.

Fabrication of N-doped graphitic carbon encapsulated Fe3C/Fe nanoparticles with dual-reaction centers for highly effective Fenton-like degradation of organic pollutants

The highly active and durable design of heterogeneous catalysts holds vital importance in the popularization of Fenton-like process for wastewater remediation. In this study, we successfully fabricated magnetic N-doped graphitic carbon (NC) encapsulated Fe3C/Fe nanoparticles, designated as Fe3C/Fe@NC-2.8, with a two-step pyrolysis method. We employed chitosan as a green precursor of NC, which is used as a heterogeneous Fenton-like catalyst to degrade refractory organic pollutants. Density functional theory (DFT) calculations revealed that the built-in electric field from the shell to core promoted electron transfer from NC to Fe3C/Fe, and thereby improved regeneration of Fe(II) and H2O2 activation. Because of the strong synergistic effects of the dual-reaction regions of Fe and Fe3C, as well as the core-shell structure advantages, the optimized Fe3C/Fe@NC rapidly degraded the typical refractory organic pollutants, and showed a much higher activity than the reference Fe2O3 and Fe3O4 samples. The total organic carbon removal efficiency of bisphenol A reached 70 % after reaction for 60 min. In addition, Fe3C/Fe@NC-2.8 possessed trace Fe leaching and satisfactory magnetically separable ability. This work provides mechanistic and practical perspectives for the development of advanced catalysts for recalcitrant pollutant treatment.

Nitrogen-Doped Biochar for Enhanced Peroxymonosulfate Activation to Degrade Phenol through Both Free Radical and Direct Oxidation Based on Electron Transfer Pathways.

Nowadays, super nitrogen-doped biochar (SNBC) material has become one of the most promising metal-free catalysts for activating peroxymonosulfate (PMS) to degrade organic pollutants. To understand the evolution of SNBC properties with fabrication conditions, a variety of SNBC materials were prepared and characterized by elemental analysis, N2 adsorption-desorption, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. We systematically investigated the activation potential of these SNBC materials for PMS to degrade phenol. SN1BC-800 with the best catalytic performance was obtained by changing the activation temperatures and the ratio of biochar to melamine. The effects of catalyst dosage, the PMS concentration, pH, and reaction temperature on phenol degradation were studied in detail. In the presence of 0.3 g/L SN1BC-800 and 1 g/L PMS, the removal rate of 20 mg/L phenol could reach 100% within 5 min. According to electron paramagnetic resonance spectra and free radical quenching experiments, a nonfree radical pathway of phenol degradation dominated by 1O2 and electron transfer was proposed. More interestingly, the excellent catalytic performance of the SN1BC-800/PMS system is universally applicable in the degradation of other typical organic pollutants. In addition, the degradation rate of phenol is still over 80% after five reuses, which shows that the SN1BC-800 catalyst has high stability and good application prospects in environmental remediation.

Differentiated cognition of the effects of human activities on typical persistent organic pollutants and bacterioplankton community in drinking water source

Accelerated urbanization in developing countries led to a typical gradient of human activities (low, moderate and high human activities), which affected the pollution characteristics and ecological functions of aquatic environment. However, the occurrence characteristics of typical persistent organic pollutants, including organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), and bacterioplankton associated with the gradient of human activities in drinking water sources is still lacking. Our study focused on a representative case – the upper reaches of the Dongjiang River (Pearl River Basin, China), a drinking water source characterized by a gradient of human activities. A comprehensive analysis of PAHs, OCPs and bacterioplankton in the water phase was performed using gas chromatography-mass spectrometry (GC-MS) and the Illumina platform. Moderate human activity could increase the pollution of OCPs and PAHs due to local agricultural activities. The gradient of human activities obviously influenced the bacterioplankton community composition and interaction dynamics, and low human activity resulted in low bacterioplankton diversity. Co-occurrence network analysis indicated that moderate human activity could promote a more modular organization of the bacterioplankton community. Structural equation models showed that nutrients could exert a negative influence on the composition of bacterioplankton, and this phenomenon did not change with the gradient of human activities. OCPs played a negative role in shaping bacterioplankton composition under the low and high human activities, but had a positive effect under the moderate human activity. In contrast, PAHs showed a strong positive effect on bacterioplankton composition under low and high human activities and a weak negative effect under moderate human activity. Overall, these results shed light on the occurrence characteristics of OCPs, PAHs and their ecological effects on bacterioplankton in drinking water sources along the gradient of human activities.

Efficient piezocatalytic properties of Na0.5Bi0.5TiO3 nanoparticles for dye degradation and hydrogen peroxide production

Piezocatalysis has emerged as a promising environmental remediation technique, and the exploration of environmentally friendly and high-performance piezocatalysts is crucial for their practical applications. In this work, the bismuth sodium titanate (Na[Formula: see text]Bi[Formula: see text]TiO3 (NBT)) exhibited efficient piezocatalytic activity toward typical organic pollutants degradation, including acid orange 7, methylene blue, rhodamine B and methyl orange. Notably, rhodamine B was degraded by 98.1% within 30[Formula: see text]min with a reaction rate constant of 0.130[Formula: see text]min[Formula: see text]. Furthermore, the NBT achieved a hydrogen peroxide production efficiency of 538[Formula: see text][Formula: see text]mol/g⋅h without the sacrificial agent, indicating that the NBT is a superior piezocatalyst for dye degradation and hydrogen peroxide generation. This work demonstrated that by using mechanical energy, the NBT can be used for degrading organic pollutants in wastewater and hydrogen peroxide generation.

Migration and distribution characteristics of typical organic pollutants in condensable particulate matter of coal-fired flue gas and by-products of wet flue gas desulfurization system.

The wet flue gas desulfurization (WFGD) system of coal-fired power plants shows a good removal effect on condensable particulate matter (CPM), reducing the dust removal pressure for the downstream flue gas purification devices. In this work, the removal effect of a WFGD system on CPM and its organic pollutants from a coal-fired power plant was studied. By analyzing the organic components of the by-products emitted from the desulfurization tower, the migration characteristics of organic pollutants in gas, liquid, and solid phases, as well as the impact of desulfurization towers on organic pollutants in CPM, were discussed. Results show that more CPM in the flue gas was generated by coal-fired units at ultra-low load, and the WFGD system had a removal efficiency nearly 8% higher than that at full load. The WFGD system had significant removal effect on two typical esters, especially phthalate esters (PAEs), with the highest removal efficiency of 49.56%. In addition, the WFGD system was better at removing these two esters when the unit was operating at full load. However, it had a negative effect on n-alkanes, which increased the concentration of n-alkanes by 8.91 to 19.72%. Furthermore, it is concluded that the concentration distribution of the same type of organic pollutants in desulfurization wastewater was similar to that in desulfurization slurry, but quite different from that in coal-fired flue gas. The exchange of three organic pollutants between flue gas and desulfurization slurry was not significant, while the concentration distribution of organic matters in gypsum was affected by coal-fired flue gas.

Triphenyltin induced darker body coloration by disrupting melanocortin system and pteridine metabolic pathway in a reef fish, Amphiprion ocellaris

Triphenyltin (TPT) is a typical persistent organic pollutant whose occurrence in coral reef ecosystems may threaten the survival of reef fishes. In this study, a brightly colored representative reef fish, Amphiprion ocellaris was used to explore the effects of TPT at environmental levels (1, 10, and 100 ng/L) on skin pigment synthesis. After the fish were exposed to TPT for 60 days, the skin became darker, owing to an increase in the relative area of black stripes, a decrease in orange color values while an increase in brown color values, and an increase in the number of melanocytes in the orange part of the skin tissues. To explore the mechanisms by which TPT induces darker body coloration, the enzymatic activity and gene expression levels of the members of melanocortin system that affect melanin synthesis were evaluated. Leptin levels and lepr expression were found to be increased after TPT exposure, which likely contributed to the increase found in pomc expression and α-melanocyte-stimulating hormone (α-MSH) levels. Then Tyr activity and mc1r, tyr, tyrp1, mitf, and dct were upregulated, ultimately increasing melanin levels. Importantly, RT-qPCR results were consistent with the transcriptome analysis of trends in lepr and pomc expression. Because the orange color values decreased, pterin levels and the pteridine metabolic pathway were also evaluated. The results showed that TPT induced BH4 levels and spr, xdh, and gch1 expression associated with pteridine synthesis decreased, ultimately decreasing the colored pterin content (sepiapterin). We conclude that TPT exposure interferes with the melanocortin system and pteridine metabolic pathway to increase melanin and decrease colored pterin levels, leading to darker body coloration in A. ocellaris. Given the importance of body coloration for the survival and reproduction of reef fishes, studies on the effects of pollutants (others alongside TPT) on body coloration are of high priority.

Comprehensive Characterization of Organic Light-Emitting Materials in Breast Milk by Target and Suspect Screening.

Organic light-emitting materials (OLEMs) are emerging contaminants in the environment and have been detected in various environment samples. However, limited information is available regarding their contamination within the human body. Here, we developed a novel QuEChERS (quick, easy, cheap, effective, rugged, and safe) method coupled with triple quadrupole/high-resolution mass spectrometry to determine OLEMs in breast milk samples, employing both target and suspect screening strategies. Our analysis uncovered the presence of seven out of the 39 targeted OLEMs in breast milk samples, comprising five liquid crystal monomers and two OLEMs commonly used in organic light-emitting diode displays. The cumulative concentrations of the seven OLEMs in each breast milk sample ranged from ND to 1.67 × 103 ng/g lipid weight, with a mean and median concentration of 78.76 and 0.71 ng/g lipid weight, respectively, which were higher compared to that of typical organic pollutants such as polychlorinated biphenyls and polybrominated diphenyl ethers. We calculated the estimated daily intake (EDI) rates of OLEMs for infants aged 0-12 months, and the mean EDI rates during lactation were estimated to range from 30.37 to 54.89 ng/kg bw/day. Employing a suspect screening approach, we additionally identified 66 potential OLEMs, and two of them, cholesteryl hydrogen phthalate and cholesteryl benzoate, were further confirmed using pure reference standards. These two substances belong to cholesteric liquid crystal materials and raise concerns about potential endocrine-disrupting effects, as indicated by in silico predictive models. Overall, our present study established a robust method for the identification of OLEMs in breast milk samples, shedding light on their presence in the human body. These findings indicate human exposure to OLEMs that should be further investigated, including their health risks.

Biomass C-doped three-dimensional Bi2WO6 for enhanced visible-light-driven photodegradation of diclofenac and rhodamine B

Photocatalysis as a green and efficient pollutant degradation technology, displaying great potential in environmental purification. By one step hydrothermal method in this study, flower-like Bi2WO6 with a large specific surface area was obtained, and the preparation of biomass carbon modified Bi2WO6 with sorghum stalks was also proposed to construct a series (BWO/x%C). The composites were effectively characterized in terms of several aspects of structure and properties. With the dyes rhodamine B and diclofenac as typical organic pollutants, the photocatalytic activity of the proposed photocatalysts was evaluated. Under visible light irradiation, the removal of rhodamine B by BWO/4%C reached 97.27% within 50 min and that of diclofenac reached 96.19% within 120 min, which were significantly favorable to single-phase Bi2WO6. The superiority of this system BWO/4%C is mainly due to its large specific surface area (33.51 m2/g), which provides additional reaction sites for contaminants. The UV–Vis DRS findings indicated that the modified biomass C reduced the band gap of Bi2WO6 and improved the availability of Bi2WO6 to visible light, and the separation efficiency of the electron and hole pairs of Bi2WO6 was improved due to the strong electron transfer ability of biomass C. The analyzing results of free radical trapping experiments confirmed that h+ and •O2- are the main active substances involved in the photodegradation reaction. The results of five cycle experiments exhibited that the degradation rate of rhodamine B still reached higher than 90%, confirming the good stability of the prepared material. Finally, a feasible degradation mechanism was proposed for the degradation of rhodamine B and diclofenac. It offers new ideas for the development of composite nano-photocatalytic materials targeting difficult-to-degrade organic pollutants.

A H2O2 Oxidation Approach to Ti3C2/TiO2 for Efficient Photocatalytic Removal of Distinct Organic Pollutants in Water.

To develop versatile photocatalysts for efficient degradation of distinct organic pollutants in water is a continuous pursuit in environment remediation. Herein, we directly oxidize Ti3C2 MXene with hydrogen peroxide to produce C-doped anatase TiO2 nanowires with aggregates maintaining a layered architecture of the MXene. The Ti3C2 MXene provides a titanium source for TiO2, a carbon source for in situ C-doping, and templates for nanowire aggregates. Under UV light illumination, the optimized Ti3C2/TiO2 exhibits a reaction rate constant 1.5 times that of the benchmark P25 TiO2 nanoparticles, toward photocatalytic degradations of trace phenol in water. The mechanism study suggests that photogenerated holes play key roles on the phenol degradation, either directly oxidizing phenol molecules or in an indirect way through oxidizing first the surface hydroxyl groups. The unreacted Ti3C2 MXene, although with trace amounts, is supposed to facilitate electron transfer, which inhibits charge recombination. The unique nanostructure of layered aggregates of nanowires, abundant surface oxygen vacancies arising from the carbon doping, and probably the Ti3C2/TiO2 heterojunction guarantee the high photocatalytic efficiency toward removals of organic pollutants in water. The photocatalyst also exhibits an activity superior to, or at least comparable to, the benchmark P25 TiO2 toward photodegradations for typical persistent organic pollutants of phenol, dye molecule of rhodamine B, antibiotic of tetracycline, pharmaceutical wastewater of ofloxacin, and pesticide of N,N-dimethylformamide, when evaluated in total organic carbon removal.

Health risk assessment and development of human health ambient water quality criteria for PCBs in Taihu Basin, China

Polychlorinated biphenyls (PCBs) are a class of typical persistent organic pollutants (POPs) with carcinogenicity and extensively found in diverse environmental mediums. The Taihu Basin is one of the most economically developed regions in China, and it has also caused a lot of historical legacy and unconscious emissions of PCBs, posing a threat to the health of people in the region. This study counted the concentrations of PCBs in five environmental media (water, soil, air, dust, and food) in the Taihu Basin from 2000 to 2020 and used Monte Carlo simulation to simulate the multi-channel exposure of PCBs in people of different ages (children, teenagers, and adults), and evaluated their noncarcinogenic and carcinogenic health risks. Finally, the human health ambient water quality standards (AWQC) for PCBs were obtained using regional exposure parameters and bioaccumulation factors. The results showed that the pollution of PCBs in the Taihu Basin was relatively serious in China. The concentration of PCBs in dust is higher than other environmental media. And exposure to water and food is the main exposure pathway for PCBs in the population of the region. Besides, PCBs pose no noncarcinogenic risk to people in this region, but their carcinogenic risk to residents exceeds the safety threshold. Among the three population groups, adults have the highest risk of cancer, and prevention measures need to be taken by controlling the intake of related foods and the concentration of PCBs in water. The following human health AWQC values of the PCBs in Taihu Basin is 3.2 × 10−9 mg/L.

Polychlorinated biphenyls exposure and type 2 diabetes: Molecular mechanism that causes insulin resistance and islet damage.

Polychlorinated biphenyls (PCBs) are typical persistent organic pollutants that have been associated with type 2 diabetes (T2DM) in cohort studies. This review aims to comprehensively assess the molecular mechanisms of PCBs-induced T2DM. Recent progress has been made in the research of PCBs in liver tissue, adipose tissue, and other tissues. By influencing the function of nuclear receptors, such as the aryl hydrocarbon receptor (AhR), pregnancy X receptor (PXR), and peroxisome proliferator activated receptor γ (PPARγ), as well as the inflammatory response, PCBs disrupt the balance of hepatic glucose and lipid metabolism. This is associated with insulin resistance (IR) in the target organ of insulin. Through androgen receptor (AR), estrogen receptor α/β (ERα/β), and pancreato-duodenal-homeobox gene-1 (PDX-1), PCBs affect the secretion of insulin and increase blood glucose. Thus, this review is a discussion on the relationship between PCBs exposure and the pathogenesis of T2DM. It is hoped to provide basic concepts for diabetes research and disease treatment.

Covalent organic framework modified magnetic MXene for high enrichment and sensitive detection of polycyclic and sulfur-containing heterocyclic aromatic hydrocarbons in Chinese tea samples

Polycyclic aromatic hydrocarbons (PAHs) and sulfur-containing heterocyclic aromatic hydrocarbons (PASHs) are typical organic pollutants that are commonly present in the environment. Due to the continuous accumulation and transfer in the food chain, they will pose a significant threat to human life and health. In the present work, a new method was constructed with a ternary magnetic nanocomposite (Fe0@MXene@COF-LZU1) based magnetic solid phase extraction in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS) for sensitive determination of them at trace level in Chinese tea samples. The magnetic nanomaterial Fe0@MXene@COF-LZU1 was synthesized via reduction and Schiff base reactions. The experimental results demonstrated that Fe0@MXene@COF-LZU1 had high adsorption ability and satisfactory chemical stability. Under the optimal experimental conditions, the method possessed good linearity in the concentration ranges of 0.0005 μgL−1 - 50 μg L−1 for dibenzothiophene (DBT), phenanthrene (PHE), fluoranthene (FLT) and pyrene (PYR), and 0.001 μg L−1 - 50 μg L−1 for 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The detection limits of this method were in the range of 0.014 ng L−1-0.83 ng L−1. The results of real samples demonstrated that the designed magnetic nanocomposite had a promising application prospect for measuring PAHs and PASHs.

Efficient photodegradation of perfluoroalkyl substances under visible light by hexagonal ZnIn2S4 nanosheets

Perfluoroalkyl substances (PFASs) are typical persistent organic pollutants, and their removal is urgently required but challenging. Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of photoinduced charge carriers in photocatalysts. Herein, hexagonal ZnIn2S4 (ZIS) nanosheets were synthesized by a one-pot oil bath method and were well characterized by a series of techniques. In the degradation of sodium p-perfluorous nonenoxybenzenesulfonate (OBS), one kind of representative PFASs, the as-synthesized ZIS showed activity superior to P25 TiO2 under both simulated sunlight and visible-light irradiation. The good photocatalytic performance was attributed to the enhanced light absorption and facilitated charge separation. The pH conditions were found crucial in the photocatalytic process by influencing the OBS adsorption on the ZIS surface. Photogenerated e− and h+ were the main active species involved in OBS degradation in the ZIS system. This work confirmed the feasibility and could provide mechanistic insights into the degradation and defluorination of PFASs by visible-light photocatalysis.

Enhanced photocatalytic performance of the N-rGO/g-C3N4 nanocomposite for efficient solar-driven water remediation.

This paper describes the synthesis and analysis of a photocatalyst made from a combination of reduced graphene oxide (rGO) and graphitic carbon nitride (g-C3N4) through a simple hydrothermal process. The effectiveness of the N-rGO/g-C3N4 heterostructure in photocatalysis was examined by studying the breakdown of different types of organic pollutants, such as cationic and anionic dyes, as well as antibiotics, under simulated solar light irradiation. Due to the presence of Schottky junctions formed between rGO and g-C3N4, the electron transfer process is significantly enhanced, leading to a reduction in the recombination of photogenerated electrons and holes. As a result, the photocatalytic activity of the rGO/g-C3N4 photocatalyst is significantly higher compared to that of g-C3N4 alone. The photocatalytic performance was further augmented through the nitrogen doping of rGO, which led to an increase in conductivity due to electron doping and an enhancement in the charge separation process. The heterojunction of rGO/g-C3N4 with an optimum concentration of 60% rGO attained a degradation efficiency of 98.7% for rhodamine B (RhB) dye after 50 minutes of light irradiation. In comparison, the nitrogen-doped photocatalyst (N-rGO/g-C3N4) achieved a photodegradation efficiency of 99.99% within 30 minutes. The reaction rate constant of the N-rGO/g-C3N4 nanocomposite was found to be 0.11 min-1 using pseudo first-order rate kinetics. This value is about 16 times more than that of pure g-C3N4 (0.007 min-1) for the degradation of rhodamine B. Additionally, N-rGO/g-C3N4 effectively degraded various contaminants, such as methylene blue, methyl orange, and tetracycline hydrochloride. The paper also addresses the photocatalytic mechanism, which entails the facilitated movement of electrons and holes produced by light, owing to the alignment of energy bands at the interface of the N-rGO/g-C3N4 heterojunction. These findings contribute to the advancement of a metal-free and porous photocatalyst that is highly interconnected and can be used for waste water treatment and environmental remediation.

Microplastics are effective carriers of bisphenol A and facilitate its escape from wastewater treatment systems.

Microplastics (MPs) pollution is a major issue in aquatic environments. Wastewater treatment plants are significant point sources of MPs, which may also be carriers of organic pollutants. We analyzed MP number, shape, color, and polymer type distribution in sewage wastewater treatment plants. The potential of MPs to act as carriers for typical organic pollutants in sewage, such as bisphenol A (BPA), was also assessed. The predominant MPs in the influent were fibers, primarily transparent and black in color, and composed of polyethylene, polypropylene, and polystyrene. During wastewater treatment, the concentration of MPs decreased from 10.89 items per L in the influent to 0.89 items per L in the treated effluent, with significant differences in treatment efficiency at different stages. In the simulated wastewater, the three predominant MPs exhibited certain adsorption capacities for bisphenol A. Changing the temperature and pH within the range expected for wastewater could interfere with the interactions between MPs and bisphenol A, with a limited impact on adsorption. The results show that although wastewater treatment plants intercept a significant amount of MP, a considerable number of them enter the aquatic environment daily because of the high volume of wastewater discharge. These MPs, which carry pollutants such as bisphenol A, may threaten the health of fish and other aquatic organisms. However, by scientifically adjusting operational parameters, wastewater treatment plants could become "controllable sources" of MP compound pollutants.

Effects of electron acceptors and donors on anaerobic biodegradation of PAHs in marine sediments

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants accumulated in the environment. PAHs' bioremediation in sediments can be promoted by adding electron acceptor (EA) and electron donor (ED). Bicarbonate and sulfate were chosen as two EAs, and acetate and lactate were selected as two EDs. Six groups of amendments were added into the sediments to access their role in the anaerobic biodegradation of five PAHs, containing phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene. The concentrations of PAHs, EAs and EDs, electron transport system activity, and microbial diversity were analyzed during 126-day biodegradation in serum bottles. The HA group (bicarbonate and acetate) achieved the maximum PAH degradation efficiency of 89.67 %, followed by the SL group (sulfate and lactate) with 87.10 %. As the main PAHs degrading bacteria, the abundance of Marinobacter in H group was 8.62 %, and the addition of acetate significantly increased the abundance of Marinobacter in the HA group by 75.65 %.