Showing papers in "Environmental Science & Technology in 2020"
TL;DR: This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfates and the formation pathways of oxidizing species and the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry.
Abstract: Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.
1,412 citations
TL;DR: There is a need to assess alternatives that allow reductions of PPE and reinforce awareness on the proper public use and disposal, and assessment of contamination and impacts of plastics driven by the pandemic will be required once the outbreak ends.
Abstract: Plastics are essential in society as a widely available and inexpensive material. Mismanagement of personal protective equipment (PPE) during the COVID-19 pandemic, with a monthly estimated use of 129 billion face masks and 65 billion gloves globally, is resulting in widespread environmental contamination. This poses a risk to public health as waste is a vector for SARS-CoV-2 virus, which survives up to 3 days on plastics, and there are also broad impacts to ecosystems and organisms. Concerns over the role of reusable plastics as vectors for SARS-CoV-2 virus contributed to the reversal of bans on single-use plastics, highly supported by the plastic industry. While not underestimating the importance of plastics in the prevention of COVID-19 transmission, it is imperative not to undermine recent progress made in the sustainable use of plastics. There is a need to assess alternatives that allow reductions of PPE and reinforce awareness on the proper public use and disposal. Finally, assessment of contamination and impacts of plastics driven by the pandemic will be required once the outbreak ends.
582 citations
TL;DR: Given the life-time inevitable exposure to microplastics, it is urgently called for a better understanding of the potential hazards of microplastic to human health.
Abstract: The ubiquity of microplastics in aquatic and terrestrial environments and related ecological impacts have gained global attention. Microplastics have been detected in table salt, drinking water, and air, posing inevitable human exposure risk. However, rigorous analytical methods for detection and characterization of microplastics remain scarce. Knowledge about the potential adverse effects on human health via dietary and respiratory exposures is also limited. To address these issues, we reviewed 46 publications concerning abundances, potential sources, and analytical methods of microplastics in table salt, drinking water, and air. We also summarized probable translocation and accumulation pathways of microplastics within human body. Human body burdens of microplastics through table salt, drinking water, and inhalation were estimated to be (0-7.3)×104, (0-4.7)×103, and (0-3.0)×107 items per person per year, respectively. The intake of microplastics via inhalation, especially via indoor air, was much higher than those via other exposure routes. Moreover, microplastics in the air impose threats to both respiratory and digestive systems through breathing and ingestion. Given the lifetime inevitable exposure to microplastics, we urgently call for a better understanding of the potential hazards of microplastics to human health.
447 citations
TL;DR: It is illustrated that the roles of nitrogen species in CNT-based persulfate systems are intrinsically different, which provides new insights into the intrinsic roles of heteroatom doping in nanocarbons for persulfates activation and unveils the principles for rational design of reaction-oriented carbocatalysts for pers fulfilment in advanced oxidation processes.
Abstract: Persulfates activation by carbon nanotubes (CNT) has been evidenced as nonradical systems for oxidation of organic pollutants. Peroxymonosulfate (PMS) and peroxydisulfate (PDS) possess discrepant atomic structures and redox potentials, while the nature of their distinct behaviors in carbocatalytic activation has not been investigated. Herein, we illustrated that the roles of nitrogen species in CNT-based persulfate systems are intrinsically different. In PMS activation mediated by nitrogen-doped CNT (N-CNT), surface chemical modification (N-doping) can profoundly promote the adsorption quantity of PMS, consequently elevate potential of derived nonradical N-CNT-PMS* complexes, and boost organic oxidation efficiency via an electron-transfer regime. In contrast, PDS adsorption was not enhanced upon incorporating N into CNT due to the limited equilibrium adsorption quantity of PDS, leading to a relatively lower oxidative potential of PDS/N-CNT system and a mediocre degradation rate. However, with equivalent persulfate adsorption on N-CNT at a low quantity, PDS/N-CNT exhibited a stronger oxidizing capacity than PMS/N-CNT because of the intrinsic higher redox potential of PDS than PMS. The oxidation rates of the two systems were in great linearity with the potentials of carbon-persulfate* complexes, suggesting N-CNT activation of PMS and PDS shared the similar electron-transfer oxidation mechanism. Therefore, this study provides new insights into the intrinsic roles of heteroatom doping in nanocarbons for persulfates activation and unveils the principles for a rational design of reaction-oriented carbocatalysts for persulfate-based advanced oxidation processes.
420 citations
TL;DR: The quantitative structure-activity relationships (QSARs) were established and correlated to the Tafel equation, suggesting that the nonradical oxidation by the CNT-PDS* undergoes a mechanism analogous to anodic oxidation.
Abstract: Carbon-driven advanced oxidation processes are appealing in wastewater purification because of the metal-free feature of the carbocatalysts. However, the regime of the emerging nonradical pathway i...
371 citations
Washington University in St. Louis1, Dalhousie University2, University of California, Berkeley3, Goddard Space Flight Center4, Universities Space Research Association5, California Institute of Technology6, Institute for Health Metrics and Evaluation7, University of British Columbia8, University of Texas at Austin9, University of Colorado Boulder10, Earth System Research Laboratory11, Tsinghua University12, Colorado State University13, Harvard University14
TL;DR: Global estimates of annual PM2.5 concentrations and trends for 1998-2018 are developed using advances in satellite observations, chemical transport modeling, and ground-based monitoring, identifying significant trends for eastern North America, Europe, and globally.
Abstract: Exposure to outdoor fine particulate matter (PM2.5) is a leading risk factor for mortality. We develop global estimates of annual PM2.5 concentrations and trends for 1998-2018 using advances in satellite observations, chemical transport modeling, and ground-based monitoring. Aerosol optical depths (AODs) from advanced satellite products including finer resolution, increased global coverage, and improved long-term stability are combined and related to surface PM2.5 concentrations using geophysical relationships between surface PM2.5 and AOD simulated by the GEOS-Chem chemical transport model with updated algorithms. The resultant annual mean geophysical PM2.5 estimates are highly consistent with globally distributed ground monitors (R2 = 0.81; slope = 0.90). Geographically weighted regression is applied to the geophysical PM2.5 estimates to predict and account for the residual bias with PM2.5 monitors, yielding even higher cross validated agreement (R2 = 0.90-0.92; slope = 0.90-0.97) with ground monitors and improved agreement compared to all earlier global estimates. The consistent long-term satellite AOD and simulation enable trend assessment over a 21 year period, identifying significant trends for eastern North America (-0.28 ± 0.03 μg/m3/yr), Europe (-0.15 ± 0.03 μg/m3/yr), India (1.13 ± 0.15 μg/m3/yr), and globally (0.04 ± 0.02 μg/m3/yr). The positive trend (2.44 ± 0.44 μg/m3/yr) for India over 2005-2013 and the negative trend (-3.37 ± 0.38 μg/m3/yr) for China over 2011-2018 are remarkable, with implications for the health of billions of people.
359 citations
TL;DR: The most fundamental aspects of selective phosphate removal processes are discussed and gains from the latest developments of phosphate-selective sorbents are highlighted, along with a discussion of some overlooked facts regarding the development of high-performance sor bents for selective phosphate Removal from water and wastewater.
Abstract: Eutrophication of water bodies is a serious and widespread environmental problem. Achieving low levels of phosphate concentration to prevent eutrophication is one of the important goals of the wastewater engineering and surface water management. Meeting the increasingly stringent standards is feasible in using a phosphate-selective sorption system. This critical review discusses the most fundamental aspects of selective phosphate removal processes and highlights gains from the latest developments of phosphate-selective sorbents. Selective sorption of phosphate over other competing anions can be achieved based on their differences in acid-base properties, geometric shapes, and metal complexing abilities. Correspondingly, interaction mechanisms between the phosphate and sorbent are categorized as hydrogen bonding, shape complementarity, and inner-sphere complexation, and their representative sorbents are organic-functionalized materials, molecularly imprinted polymers, and metal-based materials, respectively. Dominating factors affecting the phosphate sorption performance of these sorbents are critically examined, along with a discussion of some overlooked facts regarding the development of high-performance sorbents for selective phosphate removal from water and wastewater.
339 citations
TL;DR: A first comprehensive overview of chemicals on the market as an essential first step toward a global understanding of chemical pollution is achieved.
Abstract: Chemicals, while bringing benefits to society, may be released during their lifecycles and possibly cause harm to humans and ecosystems. Chemical pollution has been mentioned as one of the planetar...
331 citations
University of Notre Dame1, Royal Institute of Technology2, Commonwealth Scientific and Industrial Research Organisation3, Massachusetts Institute of Technology4, Stanford University5, Georgia Institute of Technology6, Catalan Institute for Water Research7, University of Calabria8, University of Pisa9, Mario Negri Institute for Pharmacological Research10, Federal University of Bahia11, North Carolina State University12, Howard University13, Bangor University14, École Polytechnique Fédérale de Lausanne15, University of Arizona16, Southern Nevada Water Authority17, University of Barcelona18, University of Yamanashi19, University of California, Santa Barbara20, Hokkaido University21, Indian Institute of Technology Gandhinagar22, Toyama Prefectural University23, Istituto Superiore di Sanità24, University of Naples Federico II25, University of Wisconsin–Milwaukee26, University of Washington27, University of Queensland28, University of North Carolina at Chapel Hill29, University of Antwerp30, Yale University31, Tufts University32, Michigan State University33, Spanish National Research Council34, University of Southern California35, Rice University36, Georgia State University37, University of Osnabrück38, University of Michigan39
TL;DR: Author(s): Bivins, Aaron; North, Devin; Ahmad, Arslan; Ahmed, Warish; Alm, Eric; Been, Frederic; Bhattacharya, Prosun; Bijlsma, Lubertus; Boehm, Alexandria B; Brown, Joe; Buttiglieri, Gianluigi; Calabro, Vincenza; Carducci, Annalaura; Castiglioni, Sara; Cetecioglu Guro
Abstract: Author(s): Bivins, Aaron; North, Devin; Ahmad, Arslan; Ahmed, Warish; Alm, Eric; Been, Frederic; Bhattacharya, Prosun; Bijlsma, Lubertus; Boehm, Alexandria B; Brown, Joe; Buttiglieri, Gianluigi; Calabro, Vincenza; Carducci, Annalaura; Castiglioni, Sara; Cetecioglu Gurol, Zeynep; Chakraborty, Sudip; Costa, Federico; Curcio, Stefano; de Los Reyes, Francis L; Delgado Vela, Jeseth; Farkas, Kata; Fernandez-Casi, Xavier; Gerba, Charles; Gerrity, Daniel; Girones, Rosina; Gonzalez, Raul; Haramoto, Eiji; Harris, Angela; Holden, Patricia A; Islam, Md Tahmidul; Jones, Davey L; Kasprzyk-Hordern, Barbara; Kitajima, Masaaki; Kotlarz, Nadine; Kumar, Manish; Kuroda, Keisuke; La Rosa, Giuseppina; Malpei, Francesca; Mautus, Mariana; McLellan, Sandra L; Medema, Gertjan; Meschke, John Scott; Mueller, Jochen; Newton, Ryan J; Nilsson, David; Noble, Rachel T; van Nuijs, Alexander; Peccia, Jordan; Perkins, T Alex; Pickering, Amy J; Rose, Joan; Sanchez, Gloria; Smith, Adam; Stadler, Lauren; Stauber, Christine; Thomas, Kevin; van der Voorn, Tom; Wigginton, Krista; Zhu, Kevin; Bibby, Kyle
325 citations
TL;DR: Nitrogen-doped carbon nanosheets derived from graphitic carbon nitride was developed for activation of PMS and elucidation of 1O2 production, highlighting the important role of electron-deficient carbon atoms in 1O1 generation from PMS oxidation and furnishes theoretical support for further relevant studies.
Abstract: A nonradical oxidation process via metal-free peroxymonosulfate (PMS) activation has recently attracted considerable attention for organic pollutant degradation; however, the origin of singlet oxygen (1O2) generation still remains controversial. In this study, nitrogen-doped carbon nanosheets (NCN-900) derived from graphitic carbon nitride were developed for activation of PMS and elucidation of 1O2 production. With a large specific surface area (1218.7 m2 g-1) and high nitrogen content (14.5 at %), NCN-900 exhibits superior catalytic activity in PMS activation, as evidenced by complete degradation of bisphenol A within 2 min using 0.1 g L-1 NCN-900 and 2 mM PMS. Moreover, the reaction rate constant fitted by pseudo-first-order kinetics for NCN-900 reaches an impressive value of 3.1 min-1. Electron paramagnetic resonance measurements and quenching tests verified 1O2 as the primary reactive oxygen species in the NCN-900/PMS system. Based on X-ray photoelectron spectroscopy analysis and theoretical calculations, an unexpected generation pathway of 1O2 involving PMS oxidation over the electron-deficient carbon atoms neighboring graphitic N in NCN-900 was unraveled. Besides, the NCN-900/PMS system is also applicable for remediation of actual industrial wastewater. This work highlights the important role of electron-deficient carbon atoms in 1O2 generation from PMS oxidation and furnishes theoretical support for further relevant studies.
315 citations
TL;DR: In this paper, the authors reported that magnesium oxides (MgO) in CuOMgO/Fe3O4 not only enhanced the catalytic properties but also switched the free radical peroxymonosulfate (PMS)-activated process into the 1O2 based nonradical process.
Abstract: Nonradical-based advanced oxidation processes for pollutant removal have attracted much attention due to their inherent advantages. Herein we report that magnesium oxides (MgO) in CuOMgO/Fe3O4 not only enhanced the catalytic properties but also switched the free radical peroxymonosulfate (PMS)-activated process into the 1O2 based nonradical process. CuOMgO/Fe3O4 catalyst exhibited consistent performance in a wide pH range from 5.0 to 10.0, and the degradation kinetics were not inhibited by the common free radical scavengers, anions, or natural organic matter. Quantitative structure-activity relationships (QSARs) revealed the relationship between the degradation rate constant of 14 substituted phenols and their conventional descriptor variables (i.e., Hammett constants σ, σ-, σ+), half-wave oxidation potential (E1/2), and pKa values. QSARs together with the kinetic isotopic effect (KIE) recognized the electron transfer as the dominant oxidation process. Characterizations and DFT calculation indicated that the incorporated MgO alters the copper sites to highly oxidized metal centers, offering a more suitable platform for PMS to generate metastable copper intermediates. These highly oxidized metals centers of copper played the key role in producing O2•- after accepting an electron from another PMS molecule, and finally 1O2 as sole reactive species was generated from the direct oxidation of O2•- through thermodynamically feasible reactions.
TL;DR: Human-to-human transmission of COVID-19 occurs when individuals are in the incubation stage or showing symptoms, while some individuals remain contagious while remaining asymptomatic (superspreaders).
Abstract: I the last two decades, the emergence of viral epidemics poses great threats to human health and society. These infectious viruses have been identified as hemorrhagic fever viruses (Lassa, Ebola), novel coronaviruses including severe acute respiratory syndrome CoV (SARS-CoV), Middle East respiratory syndrome MERS-CoV), and highly pathogenic influenza. Coronaviruses (CoVs), as a class of enveloped, positive-sense single-stranded RNA virus, cause various diseases in humans. CoVs are subdivided into four groups: Alphacoronavirus, Betacoronavirus (βCoV), Gammacoronavirus, and Deltacoronavirus. Two novel βCoVs, severe acute respiratory syndrome CoV (SARSCoV) and Middle East respiratory syndrome CoV (MERS-CoV), have recently emerged and can induce a high mortality. The current outbreak of novel coronavirus COVID-19 (HCoV-19 or SARS-CoV-2), has resulted in the World Health Organization (WHO) declaring this outbreak a global pandemic. By March 15, 2020, infected cases had reached 81 048 in China and a total of 72 600 cases outside China have been reported to the WHO from 146 countries and territories (https://experience. a r c g i s . c o m / e x p e r i e n c e / 685d0ace521648f8a5beeeee1b9125cd). Similar to the SARS-CoV, symptoms of COVID-19 infection at onset of the illness include fever, myalgia, fatigue, and cough, and more than half of patients developed dyspnoea. Some patients had radiographic ground-glass lung alterations, and lower than average circulating lymphocyte and platelet populations. To date, the global deaths reached 5746, and the fatality rate was estimated as 3.7% for COVID-19 virus ( h t t p s : / / e x p e r i e n c e . a r c g i s . c o m / e x p e r i e n c e / 685d0ace521648f8a5beeeee1b9125cd), which is lower than that of SARS-CoV (10%) or MERS-CoV (37%). The major challenge of the coronavirus family and similar infectious agents is that no effective drugs or vaccine are available, and it may take many months for research and development. Human-to-human transmission of COVID-19 occurs when individuals are in the incubation stage or showing symptoms, while some individuals remain contagious while remaining asymptomatic (superspreaders). Transmission is thought to occur via touching infected surfaces (skin-to-skin, touching infected inanimate objects) then mediating the COVID-19 infection through the mouth, nose, or eyes. Transmission can also be through inhalation of exhaled virus in respiratory droplets. It has been reported that infectious viruses, including coronavirus, can survive for long periods outside of its host organism. COVID-19 virus is thought to survive for several hours on surfaces such as aluminum, sterile sponges, or latex surgical gloves, increasing the opportunity for transmission via touch. Transmission via the inhalation of small, exhaled respiratory droplets may occur as the aerosol droplets remain airborne for prolonged periods, mediating long-range humanto-human transmission via air movement. The relative contributions of large respiratory droplets, smaller airborne aerosol, or direct surface contacts to the transmissibility of COVID-19 still need to be evaluated to enable a fully effective control of transmission and infection. Faecal transmission routes should also be considered, as the COVID-19 virus has been positively detected in stool samples of infected patients. Studies have shown that SARS-CoV can
TL;DR: A "coating-pyrolysis" method to synthesize porous 2D N-rich nanocarbon materials (PCN-x) derived from dopamine and g-C3N4 in different weight proportions is reported, and mechanistic understanding of the critical role of N species during non-radical PMS activation is advanced.
Abstract: Nitrogen-doped carbon materials attract broad interest as catalysts for peroxymonosulfate (PMS) activation toward an efficient, nonradical advanced oxidation process. However, synthesis of N-rich carbocatalysts is challenging because of the thermal instability of desirable nitrogenous species (pyrrolic, pyridinic, and graphitic N). Furthermore, the relative importance of different nitrogenous configurations (and associated activation mechanisms) are unclear. Herein, we report a "coating-pyrolysis" method to synthesize porous 2D N-rich nanocarbon materials (PCN-x) derived from dopamine and g-C3N4 in different weight proportions. PCN-0.5 calcined at 800 °C had the highest surface area (759 m2/g) and unprecedentedly high N content (18.5 at%), and displayed the highest efficiency for 4-chlorophenol (4-CP) degradation via PMS activation. A positive correlation was observed between 4-CP oxidation rates and the total pyridinic and pyrrolic N content. These N dopants serve as Lewis basic sites to facilitate 4-CP adsorption on the PCN surface and subsequent electron-transfer from 4-CP to PMS, mediated by surface-bound complexes (PMS-PCN-0.5). The main degradation products were chlorinated oligomers (mostly dimeric biphenolic compounds), which adsorbed to and deteriorated the carbocatalyst. Overall, this study offers new insights for rational design of nitrogen-enriched carbocatalysts, and advances mechanistic understanding of the critical role of N species during nonradical PMS activation.
TL;DR: The use of nanostructured interlayers not only improves the formation of polyamide rejection layers but also provides an optimized water transport path, which enables TFNi membranes to potentially overcome the longstanding trade-off between membrane permeability and selectivity.
Abstract: The separation properties of polyamide reverse osmosis and nanofiltration membranes, widely applied for desalination and water reuse, are constrained by the permeability-selectivity upper bound. Although thin-film nanocomposite (TFN) membranes incorporating nanomaterials exhibit enhanced water permeance, their rejection is only moderately improved or even impaired due to agglomeration of nanomaterials and formation of defects. A novel type of TFN membranes featuring an interlayer of nanomaterials (TFNi) has emerged in recent years. These novel TFNi membranes show extraordinary improvement in water flux (e.g., up to an order of magnitude enhancement) along with better selectivity. Such enhancements can be achieved by a wide selection of nanomaterials, ranging from nanoparticles, one-/two-dimensional materials, to interfacial coatings. The use of nanostructured interlayers not only improves the formation of polyamide rejection layers but also provides an optimized water transport path, which enables TFNi membranes to potentially overcome the longstanding trade-off between membrane permeability and selectivity. Furthermore, TFNi membranes can potentially enhance the removal of heavy metals and micropollutants, which is critical for many environmental applications. This review critically examines the recent developments of TFNi membranes and discusses the underlying mechanisms and design criteria. Their potential environmental applications are also highlighted.
TL;DR: The preparation of bimetallic oxides and oxygen co-doped g-C3N4 was successfully prepared, which was an effective PMS activator for degradation of toxic organic pollutants and cycling experiments demonstrated the good stability of Fe-Co-O-g-C 3N4.
Abstract: Graphite carbon nitride (g-C3N4) has a stable structure but poor catalytic capability for activating peroxymonosulfate (PMS). In this study, the codoping of g-C3N4 with bimetallic oxides (iron and cobalt) and oxygen was investigated to enhance its catalytic capability. The results showed that iron, cobalt, and oxygen codoped g-C3N4 (Fe-Co-O-g-C3N4) was successfully prepared, which was capable of completely degrading sulfamethoxazole (SMX) (0.04 mM) within 30 min, with a reaction rate of 0.085 min-1, indicating the superior catalytic activity of Fe-Co-O-g-C3N4. The mineralization efficiency of SMX was 22.1%. Sulfate radicals and singlet oxygen were detected during the process of PMS activation. However, the role that singlet oxygen played in degrading SMX was not obvious. Surface-bound reactive species and sulfate radicals were responsible for SMX degradation, in which sulfate radicals contributed to 46.6% of SMX degradation. The superior catalytic activity was due to the synergistic effect of metal oxides and O-g-C3N4, in which O-g-C3N4 could act as a carrier and an activator as well as an electron mediator to promote the conversion of Fe(III) to Fe(II) and Co(III) to Co(II). Four main steps of SMX degradation were proposed, including direct oxidation of SMX, bond fission of N-C, bond fission of N-S, and bond fission of S-C. The effect of the pH, temperature, PMS concentration, chloridion, bicarbonate, and humic acids on SMX degradation was investigated. Cycling experiments demonstrated the good stability of Fe-Co-O-g-C3N4. This study first reported the preparation of bimetallic oxide and oxygen codoped g-C3N4, which was an effective PMS activator for degradation of toxic organic pollutants.
TL;DR: Attention should be given to the emerging routes for dye decolorization via the enzymatic action of oxidoreductases, which have already a strong presence in various other bioremediation applications.
Abstract: Up to 84 000 tons of dye can be lost in water, and 90 million tons of water are attributed annually to dye production and their application, mainly in the textile and leather industry, making the d...
TL;DR: It is reported that defect-rich carbon nanotubes (CNTs) exhibit a superior activity in activation of peroxymonosulfate (PMS) for O MPs oxidation, and the established CNTs@PMS oxidative system achieves outstanding selectivity and realizes the target-oriented elimination of specific OMPs in complicated aquatic environment.
Abstract: Nanocarbon-based persulfate oxidation emerges as a promising technology for the elimination of organic micropollutants (OMPs). However, the nature of the active site and its working mechanism remain elusive, impeding developments of high-performance oxidative technology for water treatment practice. Here, we report that defect-rich carbon nanotubes (CNTs) exhibit a superior activity in the activation of peroxymonosulfate (PMS) for OMP oxidation. Quantitative structure-activity relationship studies combined with theoretical calculations unveil that the double-vacancy defect on CNTs may be the intrinsic active site, which works as a conductive bridge to facilitate the potential difference-dominated electron transfer from the highest occupied molecular orbital of OMPs to the lowest unoccupied molecular orbital of PMS. Based on this unique mechanism, the established CNTs@PMS oxidative system achieves outstanding selectivity and realizes the target-oriented elimination of specific OMPs in a complicated aquatic environment. This work sheds new light on the mechanism of carbocatalysis for selective oxidation and develops an innovative technology toward remediation of practical wastewater.
TL;DR: It is reported in this research that trace cupric species (Cu(II) in several μM) can efficiently trigger peroxymonosulfate (PMS) oxidation of various organic pollutants under slightly alkaline conditions.
Abstract: Activation of persulfates to degrade refractory organic pollutants is currently a hot topic of advanced oxidation. Developing simple and effective activation approaches is crucial for the practical application of persulfates. We report in this research that trace cupric species (Cu(II) in several μM) can efficiently trigger peroxymonosulfate (PMS) oxidation of various organic pollutants under slightly alkaline conditions. The intermediate oxidant dominating this process was investigated with electron paramagnetic resonance (EPR), chemical probing, and in situ Raman spectroscopy. Unlike conventional PMS activation, which generates sulfate radical, hydroxyl radical, or singlet oxygen as major oxidants, Cu(III) was confirmed to be the primary and selective intermediate oxidant during the Cu(II)/PMS oxidation. Hydroxyl radical is the secondary intermediate oxidant formed from the reaction of Cu(III) with OH-. Hybrid oxidation by the two oxidants imparts Cu(II)/PMS with high efficiency in the degradation of a series of pollutants. The results of this work suggest that, with no need of introducing complex catalysts, trace Cu(II) inherent in or artificially introduced to some water or wastewater can effectively trigger PMS oxidation of organic pollutants.
TL;DR: It is suggested that for improved simulation and prediction, artificial aging methods must shift from qualitative to quantitative approaches and artificial preaging may serve to synthesize engineered biochars for green and sustainable environmental applications.
Abstract: Biochar has triggered a black gold rush in environmental studies as a carbon-rich material with well-developed porous structure and tunable functionality. While much attention has been placed on its apparent ability to store carbon in the ground, immobilize soil pollutants, and improve soil fertility, its temporally evolving in situ performance in these roles must not be overlooked. After field application, various environmental factors, such as temperature variations, precipitation events and microbial activities, can lead to its fragmentation, dissolution, and oxidation, thus causing drastic changes to the physicochemical properties. Direct monitoring of biochar-amended soils can provide good evidence of its temporal evolution, but this requires long-term field trials. Various artificial aging methods, such as chemical oxidation, wet-dry cycling and mineral modification, have therefore been designed to mimic natural aging mechanisms. Here we evaluate the science of biochar aging, critically summarize aging-induced changes to biochar properties, and offer a state-of-the-art for artificial aging simulation approaches. In addition, the implications of biochar aging are also considered regarding its potential development and deployment as a soil amendment. We suggest that for improved simulation and prediction, artificial aging methods must shift from qualitative to quantitative approaches. Furthermore, artificial preaging may serve to synthesize engineered biochars for green and sustainable environmental applications.
TL;DR: A critical review on the different published methods for sampling, extraction, purification and identification/quantification of microplastics in complex environmental matrices, with the main focus on their applicability for soil samples.
Abstract: Research on microplastics in soils is still uncommon, and the existing publications are often incomparable due to the use of different sampling, processing, and analytical methods. Given the comple...
TL;DR: The developed kinetic model successfully simulated PMSO loss, PMSO2 production, SMX degradation, and/or PMS decomposition under varying conditions, which further supported the proposed mechanism.
Abstract: Sulfate radical (SO4•–) is widely recognized as the predominant species generated from the cobalt(II)-activated peroxymonosulfate (PMS) process. However, in this study, it was surprisingly found th...
TL;DR: The catalytic active sites and adsorption behaviors of O3 molecules on the catalyst surface are regarded as the key clues for further elucidating the O3 activation processes, evolution of reactive oxygen species (ROS), organic oxidation pathways.
Abstract: Heterogeneous catalytic ozonation (HCO) processes have been widely studied for water purification. The reaction mechanisms of these processes are very complicated because of the simultaneous involvement of gas, solid, and liquid phases. Although typical reaction mechanisms have been established for HCO, some of them are only appropriate for specific systems. The divergence and deficiency in mechanisms hinders the development of novel active catalysts. This critical review compares the various existing mechanisms and categorizes the catalytic oxidation of HCO into radical-based oxidation and nonradical oxidation processes with an in-depth discussion. The catalytic active sites and adsorption behaviors of O3 molecules on the catalyst surface are regarded as the key clues for further elucidating the O3 activation processes, evolution of reactive oxygen species (ROS) or organic oxidation pathways. Moreover, the detection methods of the ROS produced in both types of oxidations and their roles in the destruction of organics are reviewed with discussion of some specific problems among them, including the scavengers selection, experiment results analysis as well as some questionable conclusions. Finally, alternative strategies for the systematic investigation of the HCO mechanism and the prospects for future studies are envisaged.
TL;DR: It is concluded that research so far has not shown Plastisphere communities to starkly differ from microbial communities on other inert surfaces, which is particularly true for mature biofilm assemblages.
Abstract: Plastics become rapidly colonized by microbes when released into marine environments. This microbial community-the Plastisphere-has recently sparked a multitude of scientific inquiries and generated a breadth of knowledge, which we bring together in this review. Besides providing a better understanding of community composition and biofilm development in marine ecosystems, we critically discuss current research on plastic biodegradation and the identification of potentially pathogenic "hitchhikers" in the Plastisphere. The Plastisphere is at the interface between the plastic and its surrounding milieu, and thus drives every interaction that this synthetic material has with its environment, from ecotoxicity and new links in marine food webs to the fate of the plastics in the water column. We conclude that research so far has not shown Plastisphere communities to starkly differ from microbial communities on other inert surfaces, which is particularly true for mature biofilm assemblages. Furthermore, despite progress that has been made in this field, we recognize that it is time to take research on plastic-Plastisphere-environment interactions a step further by identifying present gaps in our knowledge and offering our perspective on key aspects to be addressed by future studies: (I) better physical characterization of marine biofilms, (II) inclusion of relevant controls, (III) study of different successional stages, (IV) use of environmentally relevant concentrations of biofouled microplastics, and (V) prioritization of gaining a mechanistic and functional understanding of Plastisphere communities.
TL;DR: After reaction in Co/PAA process, numerous carbon source that could be provided for bacteria and algae growth can be produced, suggesting that the proposed Co/ PAA process contains good potential in the combination with bio-treatment processes.
Abstract: An advanced oxidation process of combining cobalt and peracetic acid (Co/PAA) was developed to degrade sulfamethoxazole (SMX) in this study. The formed acetylperoxy radical (CH3CO3•) through the ac...
TL;DR: Investigation of the effect of microplastics and drought on plant productivity and community structure in a plant community consisting of seven plant species that co-occur in temperate grassland ecosystems showed that at the community level, shoot and root mass decreased with drought but increased with microfibers, an effect likely linked to reduced soil bulk density, improved aeration, and better penetration of roots in the soil.
Abstract: Microplastics in soils can affect plant performance, as shown in studies using individual plants. However, we currently have no information about potential effects on plant community productivity a...
TL;DR: It is demonstrated that phosphorus reduction can mitigate eutrophication in most large lakes but a dual N and P reduction may be needed in eutrophic lakes, especially in shallow ones (or bays).
Abstract: Eutrophication mitigation is an ongoing priority for aquatic ecosystems. However, the current eutrophication control strategies (phosphorus (P) and/or nitrogen (N)) are guided mainly by nutrient addition experiments in small waters without encompassing all in-lake biogeochemical processes that are associated largely with lake morphological characteristics. Here, we use a global lake data set (573 lakes) to show that the relative roles of N vs P in affecting eutrophication are underpinned by water depth. Mean depth and maximum depth relative to mixing depth were used to distinguish shallow (mixing depth > maximum depth), deep (mixing depth < mean depth), and transitional (mean depth ≤ mixing depth ≤ maximum depth) lakes in this study. TN/TP ratio (by mass) was used as an indicator of potential lake nutrient limitation, i.e., N only limitation if N/P < 9, N + P colimitation if 9 ≤ N/P < 22.6, and P only limitation if N/P ≥ 22.6. The results show that eutrophication is favored in shallow lakes, frequently (66.2%) with N limitation while P limitation predominated (94.4%) in most lakes but especially in deep ones. The importance of N limitation increases but P limitation decreases with lake trophic status while N and P colimitation occurs primarily (59.4%) in eutrophic lakes. These results demonstrate that phosphorus reduction can mitigate eutrophication in most large lakes but a dual N and P reduction may be needed in eutrophic lakes, especially in shallow ones (or bays). Our analysis helps clarify the long debate over whether N, P, or both control primary production. While these results imply that more resources be invested in nitrogen management, given the high costs of nitrogen pollution reduction, more comprehensive results from carefully designed experiments at different scales are needed to further verify this modification of the existing eutrophication mitigation paradigm.
TL;DR: It is speculated that sludge composts may act as a vehicle of MPs into soils, and then enter soil biota and in turn influence the spread of MPs in the environment.
Abstract: The widespread application of sewage sludge produced from wastewater treatment plants for agricultural use has been regarded as a primary source of microplastics (MPs) into soils. However, little is known regarding MPs in sludge-based fertilizers and their relevant fate in soils as being applied in agriculture. We comprehensively investigated the abundance, polymer size, type, and morphology of MPs in dewatered sludge, sewage sludge composts, sludge-based fertilizer-amended soils, and earthworms by stereoscopy and micro Fourier transform infrared (μ-FTIR) spectrometry methods. The results clearly showed that the quantity of MPs in soils exhibited a close correlation with the application rate of sludge-based fertilizers. The total abundances of MPs were 545.9 and 87.6 items/kg in soils after annual amendment with 30 (field A) and 15 t/ha (field B) of sludge composts, which is significantly higher than that without compost application (field C, 5.0 items/kg). Correspondingly, MPs were found in earthworms with low quantities of 1.8 and 0.4 items/individual in fields A and B, respectively, while no MP was detected in field C. We speculate that sludge composts may act as a vehicle of MPs into soils and then enter soil biota and in turn influence the spread of MPs in the environment.
TL;DR: It is proposed that the inactivation of viruses is governed by the cumulative dose of solutes, or the product of concentration and time, as in disinfection kinetics, which is influenced by osmotic pressure resulting from elevated concentration of salts as droplets evaporate.
Abstract: The transmission of some infectious diseases requires that pathogens can survive (i.e., remain infectious) in the environment, outside the host. Relative humidity (RH) is known to affect the survival of some microorganisms in the environment; however, the mechanism underlying the relationship has not been explained, particularly for viruses. We investigated the effects of RH on the viability of bacteria and viruses in both suspended aerosols and stationary droplets using traditional culture-based approaches. Results showed that viability of bacteria generally decreased with decreasing RH. Viruses survived well at RHs lower than 33% and at 100%, whereas their viability was reduced at intermediate RHs. We then explored the evaporation rate of droplets consisting of culture media and the resulting changes in solute concentrations over time; as water evaporates from the droplets, solutes such as sodium chloride in the media become more concentrated. Based on the results, we suggest that inactivation of bacteria is influenced by osmotic pressure resulting from elevated concentrations of salts as droplets evaporate. We propose that the inactivation of viruses is governed by the cumulative dose of solutes or the product of concentration and time, as in disinfection kinetics. These findings emphasize that evaporation kinetics play a role in modulating the survival of microorganisms in droplets.
TL;DR: The results indicate that textile quantity is one of the main factors affecting microplastic abundance in indoor air, while air conditioner-induced airflow turbulence can cause microplastics migration in indoor environments.
Abstract: Microplastics in the air have gradually attracted our attention in recent years; however, temporal and spatial trends of microplastics in indoor air are rarely discussed. In the present study, we tracked microplastic fallout in a dormitory, an office, and a corridor on both workdays and weekends for three months. In addition, an air conditioner was used to understand airflow influence on microplastic resuspension in the dorm. Among the three sampling sites, the highest average microplastic abundance appeared in the dormitory (9.9 × 103 MPs/m2/d), followed by the office (1.8 × 103 MPs/m2/d) and the corridor (1.5 × 103 MPs/m2/d). In the dormitory, the average MP abundance on weekends (1.4 × 104 MPs/m2/d) was approximately three times of that on weekdays (5.8 × 103 MPs/m2/d). In the office; however, the abundance on weekends (1.2 × 103 MPs/m2/d) was 50% of that on weekdays (2.4 × 103 MPs/m2/d). Microplastic fallout existed mostly in the form of fibers and showed similar polymer compositions to the textile products used in indoor environments. The airflow tests using an air conditioner suggested that airflow turbulence increased resuspension of microplastics. Taken together, we conclude that indoor environments are prone to serious microplastic pollution, but microplastic level varies greatly due to different characteristics of indoor setting. Our results also indicate that textile quantity is one of the main factors affecting microplastic abundance in indoor air, whereas air conditioner-induced airflow turbulence can cause microplastic migration in indoor environments.
TL;DR: With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improve the oxidation of toluene to CO2.
Abstract: Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is usually the rate-determining step of toluene oxidation into CO2. Series of CeO2 probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2 in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2 to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.