High mobility and toxicity of arsenic As (III) limit its removal from an aquatic environment and pose a threat to human health. In this work, batch adsorption experiments were conducted to ...investigate the adsorption capacity of bismuth-impregnated aluminum oxide (BiAl). Continuous application of As (III) removal was achieved via a lab-scale column reactor. Bismuth impregnation decreased the specific surface area of aluminum oxide and affected its pore size distribution. However, because of its abundant and well-proportioned mesoporous character, it also enhanced its adsorption capacity through the surface complexation of As (III). Batch adsorption experiments demonstrated a suitable Freundlich model and a fitted pseudo-second-kinetic model for As (III) adsorption. The main mechanism was chemisorption with both bismuth and aluminum atoms; however, physisorption also contributed to arsenic adsorption at the initial stage of the reaction. The Adams-Bohart model better described the breakthrough curves than the Thomas model. BiAl exhibited efficient As (III) adsorption over a wide pH range and could be applied to As (III) removal from wastewater. A high As (III) removal efficiency (91.6%) was obtained at an initial As (III) concentration of 5 mg L−1 at a flow rate of 1 mL min-1. This study indicates the potential for the practical application of BiAl in As (III) removal.
•Bismuth impregnated aluminum oxide showed a strong ability for arsenic (III) removal.•Bismuth inclusion optimized the pore size distribution of aluminum oxide.•The chemisorption made the main contribution to arsenic (III) adsorption.•BiO bond played an important role in arsenic (III) adsorption.
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•CdS NPs photocatalysis was integrated with periphyton for nitrate removal.•Nitrate removal loadings was enhanced 1.5 times without nitrous oxide emission.•CdS NPs promoted ...productivity of EPS and amounts of electroactive bacteria.•EPS facilitated separation of electron-hole of CdS NPs under light irradiation.•EPS worked as electron transfer mediators between CdS NPs and periphyton.
The concept of improving in-situ nitrate removal was demonstrated in a CdS nanoparticles (NPs)-assisted periphyton bioelectrochemical system (PCdS-BES). Compared to the control (periphyton bioelectrochemical system, P-BES), nitrate reduction to nitrogen gas by the PCdS-BES was enhanced by 1.5 times on day 7 under stimulated sunlight irradiation (20 W m−2), avoiding nitrous oxide emission. The presence of CdS NPs optimized the community structure of periphyton, enhanced its activities (represented by ATPase), stimulated more extracellular polymeric substance (EPS) production and increased the relative abundance of electroactive bacteria strains (e.g. Family Xanthomonadaceae, Hyphomonadaceae and Sphingobacteriales). The enhancement of nitrate reduction under irradiation was primarily attributed to the synergistic effect of EPS, electroactive bacteria strains and CdS NPs. Specifically, CdS NPs provided photoexcited electrons under light irradiation. The EPS facilitated the stability of CdS NPs in the periphyton matrix and separation of photo-induced electron-hole on the surface of CdS NPs. EPS served as extracellular electron transfer mediators for electron transfer from CdS NPs to microorganisms. The electroactive bacteria were beneficial to the acquisition of electrons produced by CdS NPs under irradiation, promoting catalytic nitrate reduction. This study gives an insight into the mechanism of nitrate reduction via the synergistic action of photoexcited electrons, EPS and electroactive bacteria. The successful combination of photocatalyst (i.e. CdS NP) and microbial community in BES also provides a promising approach for nitrate removal.
The presence of nitrite (NO2−) is inevitable with concentrations of several mg L−1 in some typical water bodies. In this study, UV at wavelength of 365 nm was investigated to degrade contaminants of ...emerging concern (CECs) in the presence of NO2− at environmentally relevant concentrations (0.1–5.0 mg L−1). Six selected CECs with different structures were efficiently removed because of the generation of reactive nitrogen species (RNS) and hydroxyl radical (HO•) from photolysis of NO2−. Contributions of UV365 photolysis, RNS, and HO• to CEC degradation in UV365/NO2− system were calculated, and RNS were found to be the predominant species that are responsible for CEC degradation. The second major contributor is HO• for the degradation of selected CECs except for the case of sulfadiazine. Impacts of water matrix components (including dissolved oxygen, solution pH, and natural organic matter) on CEC degradation in UV365/NO2− system were evaluated. Furthermore, evolution profiles of CECs and NO2− in UV365/NO2− system were tracked when actual water samples were used as background, and a simultaneous removal of CECs and NO2− was observed. Transformation products of bisphenol A and carbamazepine were proposed according to the results of HPLC/MS and quantum chemistry calculations. Nitration induced by RNS and hydroxylation induced by HO• are main reactions occurred during CEC degradation in UV365/NO2− system. Overall, UV365 is a potential technology to remove CECs and NO2− in aquatic environment when residual NO2− is present. Our present study also provides possibility for the application of sunlight to remediate water co-polluted by CECs and NO2−.
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•Photolysis of residual NO2− by UV365 can also lead to CEC degradation.•RNS is the predominant contributor to CECs degradation at NO2− of 0.1–5.0 mg L−1.•CECs and NO2− can be simultaneous removed in UV365/NO2− system in actual water.•Nitration induced by RNS and hydroxylation induced by HO.• are main reactions.
Inspired by the features of both transition metal oxide and natural clinoptilolite (flaky structure with suitable pore diameter and open skeleton structure), we adopted a robust strategy by ...immobilization of nickel ferrite nanoparticles (NiFe2O4) on the clinoptilolite surface via typical citric acid combustion method. The hybrid catalyst exhibited enhanced peroxymonosulfate (PMS) activation efficiency and bisphenol A (BPA) degradation performance. Calculated by effective equivalent of NiFe2O4, it is found that the reaction rate constant (k) of NiFe2O4/clinoptilolite/PMS system (0.1859 min−1) was 11.9 times higher than that of bare NiFe2O4/PMS system (0.0156 min−1), which demonstrated that catalyst would be conjugated to PMS or contaminant efficiently and renders the rapid degradation and mineralization in the presence of clinoptilolite. After comprehensive characterization analysis and DFT simulations, natural mineral carrier effect (i.e. decreased crystalline size, increased oxygen vacancy content, etc.), abundant surface-bonded and structural hydroxyl groups as well as effective bonding with iron or nickel ions charged for the potential activation mechanism of PMS by NiFe2O4/clinoptilolite composite. And it is indicated that not only •OH and SO4•−, but also 1O2 was involved into series reactions. Overall, this study put forward a green and promising technology for high-toxic wastewater treatment.
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•NiFe2O4/clinoptilolite was structural assembled through spontaneous combustion.•Carrier effect and hydroxyl groups bonding with metal ions charged for the activation mechanism.•The reaction rate constant of NiFe2O4/clinoptilolite was 11.9 times higher than that of bare NiFe2O4.•This study put forward a green and promising technology for high-toxic wastewater treatment.
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•Bismuth-containing biochar (BiPB) was synthesized through an impregnation method.•Persistent free radical (PFRs) increased with bismuth impregnation in BiPB matrix.•The synergistic ...effect between biochar and Bi/Bi2O3 made the contribution to estrone degradation.•BiPB showed high catalytic performance for estrone removal.
An innovative advanced oxidation process was successfully developed to photocatalytic-degradation of estrone through the synergistic effect of biochar and Bi/Bi2O3 in bismuth-containing photocatalytic biochar (BiPB). The highest reaction rate constant (kobs) of estrone degradation by BiPB was 0.045 min−1 under the conditions of initial concentration of estrone =10.4 μmol L−1, BiPB =1 g L−1, pH = 7.0. The kobs was almost tenfold and more than 20 times than that of biochar without bismuth impregnation and pristine Bi/Bi2O3, respectively. The best photocatalytic performance of BiPB composites for the degradation of estrone was primarily attributed to generation of OH radicals. Impregnation of bismuth helped control the concentration of persistent free radicals (PFRs) and develop a hierarchical porous structure of biochar. The presence of biochar facilitated pre-concentration estrone on BiPB and improved the separation and transfer efficiency of charge carriers. The synergistic effect between biochar and Bi/Bi2O3 contributed to the generation of OH radicals for estrone degradation under neutral pH conditions. The transformation pathway of estrone was also proposed based on the measured transformation products in the presence of BiPB. The high efficiency of BiPB composites indicated that this easily-obtained material was promising for estrone-wastewater treatment applications as a low-cost composite photocatalyst.
The abundance of microplastics (MPs) in soil environments has attracted significant attentions, due to their impact on soil physico-chemical properties. However, limited information is available on ...the influences of MPs on soil carbon composition and microbial utilization characteristics. Therefore, a two-month incubation experiment was conducted to add polyethylene microplastics (PE-MPs) with different levels (1%, 10%) and sizes (150–300 μm and 75–150 μm) into different soils. After that, soil chemical properties including the dissolved organic carbon (DOC), spectral characteristics of dissolved organic matter (DOM) and soil microbial characteristics were analyzed. Results revealed that PE-MPs addition caused significant differences in soil chemical properties between farmland and woodland soils, particularly in soil pH, DOM composition, and soil phosphatase activity. Woodland soil always exhibited higher levels of DOC content, microbial diversity, and soil carbon source utilization compared to farmland soil, leading to increased humification in the DOM of woodland soil. PE-MPs with a larger particle size significantly increased both the soil DOC content and enzyme activity. Addition of PE-MPs altered the soil DOM composition, and the fluorescence parameters like the biological index (BIX) and humification degree. Moreover, the carbon source utilization intensity of microorganisms on PE MPs-contaminated soils is higher in woodland soils. Various analyses confirmed that compared to other soil properties, characteristics of soil DOM had a more significant impact on soil microbial community composition. Thus, PE-MPs in conjunction with soil DOM spectral characteristics regulated soil microbial diversity, which is crucial for understanding soil carbon sequestration.
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•Significant differences in DOM composition between woodland and farmland soils.•PE addition increased the carbon utilization intensity of soil microorganisms.•PE size coupled with DOM spectral characteristic regulated the soil microbial diversity.
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•Carbon doped TiO2/kaolinite composite was rationally designed and assembled.•The composite’s reaction rate constant is about 25 times higher than that of pure TiO2.•TiIII defects and ...localized occupied states are responsible for performance enhancement.•Kaolinite induced carrier effect plays important role in catalytic activity enhancement.•The composite material might be a promising candidate for degrading trace amounts of pollutants.
In this work, kaolinite supported monodispersed TiO2 with carbon regulation was prepared through rational design and different dimensions’ assembly, leading to generation of TiIII species in carbon doped TiO2/kaolinite (C-TiO2/kaolinite) composite. The C-TiO2/kaolinite composite exhibited improved degradation performance towards ciprofloxacin under visible light, with a reaction rate constant of 0.00597 min−1, which is about 3.24 and 24.88 times higher than that of 2.0C-T (2.0% carbon-doped TiO2) and pure TiO2, respectively. Based on various materials characterization methods and DFT calculations, it was indicated that the electronic structure was correlated with the changes in light absorption, charge carrier lifetime, and reactive oxygen species (ROS). The enhanced visible light responding ability could be attributed to the synergistic effect between natural kaolinite and nanosized TiO2, the formation of localized occupied states in the gap, and the formation of TiIII defects consisted of surface oxygen vacancies. All of them effectively increase the separation efficiency, migration velocity, and lifetime of the photoinduced charge carriers under visible-light irradiation. Overall, our study provides a promising candidate for effective degradation of trace amounts of pharmaceutical and personal care products and other highly toxic contaminants with the assistance of solar light.
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•The influence of UV light wavelengths on degradation of ATZ was investigated.•UV285/nitrate showed better performance than UV255/nitrate.•RNS are major contributor to degradation of ...ATZ in UV285/nitrate.•RNS are helpful to accelerate the photo-transformation of ATZ.
The role of reactive nitrogen species (RNS) formed from nitrate photolysis has aroused interests in transformation of contaminants of emerging concern. This study investigated the influence of UV wavelengths (255, 285 and 365 nm) on photolysis of nitrate for degradation of atrazine (ATZ). The UV285/nitrate system showed the fastest rate constant for degradation of ATZ with kobs of 0.0022 cm2 mJ−1. UV photolysis, RNS, and hydroxyl radical (HO) were identified as main contributors to ATZ degradation in UV/nitrate system. Among the contributors, RNS made the major contribution to degradation of ATZ in UV285/nitrate system, while HO is the predominant specie in UV255/nitrate system. Variance decomposition analysis showed that degradation of ATZ was slightly impacted by natural organic matter and carbonate/bicarbonate in UV285/nitrate system but was dramatically affected in UV255/nitrate system. Main transformation products of ATZ in UV285/nitrate system were identified and possible pathways were proposed. RNS were confirmed to be favorable for acceleration of ATZ photolysis through further reaction of RNS with hydroxyatrazine (with electron-rich moieties). Our study provides deep insights on the influence of UV wavelength on nitrate photolysis and ATZ degradation, and provides a novel method for remediation of water co-contaminated by nitrate and organic contaminants.
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•CeO2 nanoparticles (NPs) distribution was detected by scanning transmission X-ray microscopy.•Uneven distribution of CeO2 NPs induced microbial community shifts.•Community ...composition of periphytic biofilm was investigated at phylum, class and genus level.•Pollutants removal was sustained via self-regulation of community composition.
The responses of periphytic biofilm to CeO2 nanoparticle (CNP) exposure were explored by investigating community shifts and pollutant removal. Results showed that CNPs entered the sensitive microbial cells in the periphytic biofilm, leading to cytomembrane damage and intracellular reactive oxygen species (ROS) generation. The periphytic biofilm communities were, however, able to adapt to the prolonged exposure and maintain their pollutant removal (i.e., phosphorus, nitrogen and copper, organic matter) performance. Observations under synchrotron radiation scanning transmission X-ray microscopy revealed that fewer CNPs were distributed in algal cells compared to bacterial cells, wherein the transformation between Ce(IV) and Ce(III) occurred. High-throughput sequencing further showed that the proportion of algae, such as Leptolyngbya and Nostoc, significantly increased in the periphytic biofilm exposed to CNPs while the proportion of bacteria, such as Bacilli and Gemmatimonadetes, decreased. This change in community composition might be the primary reason for the sustained pollutant removal performance of the periphytic biofilm.
Researchers are devoting great effort to combine photocatalytic nanoparticles (PNPs) with biological processes to create efficient environmental purification technologies (i.e., intimately coupled ...photobiocatalysis). However, little information is available to illuminate the responses of multispecies microbial aggregates against PNP exposure. Periphytic biofilm, as a model multispecies microbial aggregate, was exposed to three different PNPs (CdS, TiO2, and Fe2O3) under xenon lamp irradiation. There were no obvious toxic effects of PNP exposure on periphytic biofilm as biomass, chlorophyll content, and ATPase activity were not negatively impacted. Enhanced production of extracellular polymetric substances (EPS) is the most important protection mechanism of periphytic biofilm against PNPs exposure. Although PNP exposure produced extracellular superoxide radicals and caused intracellular reactive oxygen species (ROS) accumulation in periphytic biofilm, the interaction between EPS and PNPs could mitigate production of ROS while superoxide dismutase could alleviate biotic ROS accumulation in periphytic biofilm. The periphytic biofilms changed their community composition in the presence of PNPs by increasing the relative abundance of phototrophic and high nutrient metabolic microorganisms (families Chlamydomonadaceae, Cyanobacteriacea, Sphingobacteriales, and Xanthomonadaceae). This study provides insight into the protection mechanisms of microbial aggregates against simultaneous photogenerated and nanoparticle toxicity from PNPs.
