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1.
J Environ Sci (China) ; 110: 119-128, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34593182

RESUMO

Odor problems in source water caused by 2-methylisoborneol (MIB) have been a common issue in China recently, posing a high risk to drinking water safety. The earthy-musty odorant MIB has an extremely low odor threshold (4-16 ng/L) and is hard to remove via conventional processes in drinking water plants (DWP), and therefore could easily provoke complaints from consumers. This compound is produced by a group of filamentous cyanobacteria, mainly belonging to Oscillatoriales. Different from the well-studied surface-blooming Microcystis, filamentous cyanobacteria have specific niche characteristics that allow them to stay at a subsurface or deep layer in the water column. The underwater bloom of these MIB producers is therefore passively determined by the underwater light availability, which is governed by the cell density of surface scum. This suggests that drinking water reservoirs with relatively low nutrient contents are not able to support surface blooms, but are a fairly good fit to the specialized ecological niche of filamentous cyanobacteria; this could explain the widespread odor problems in source water. At present, MIB is mainly treated in DWP using advanced treatment processes and/or activated carbon, but these post-treatment methods have high cost, and not able to deal with water containing high MIB concentrations. Thus, in situ control of MIB producers in source water is an effective complement and is desirable. Lowering the underwater light availability is a possible measure to control MIB producers according to their niche characteristics, which can be obtained by either changing the water level or other measures.


Assuntos
Cianobactérias , Água Potável , Microcystis , Purificação da Água , Ecossistema , Odorantes/análise
2.
Water Res ; 202: 117443, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34333298

RESUMO

Low molecular weight (LMW) dissolved organic matter (DOM) is the predominant competitor for adsorption sites against organic micropollutants (OMPs) in activated carbon adsorption. However, top-down approaches using highly complex mixtures of real water DOM do not allow to concisely examine the impacts of specific LMW DOM molecular properties on competitive adsorption. Therefore, we followed a bottom-up approach using fifteen model compounds (mDOM) to elucidate how important DOM characteristics, including hydrophobicity and unsaturated structures (ring, double/triple bond), impact competitiveness. Large concentration asymmetry (~500 µg DOC/µg OMP) made mDOM compounds, which were overall less preferentially adsorbed than OMPs, become competitive against OMPs and inhibit OMP adsorption kinetics by pre-occupation of adsorption sites. Our results revealed that both hydrophobicity interactions and π-interactions increased mDOM competitiveness, while π-interactions outweighed hydrophobic interactions. However, π-interactions could not be satisfactorily evaluated with a parameter such as specific ultraviolet absorbance (SUVA) due to interferences of carboxyl groups in aromatic mDOMs. Instead, mDOM adsorbability, described by mDOM adsorption capacity, proved to be a comprehensive indicator for mDOM competitiveness. To our knowledge, this is the first study that systematically clarifies the impacts of intricately interacting molecular properties on DOM adsorption and the related competition against OMP adsorption. DOM adsorbability may inspire a new fractionation, and assist the further isolation, identification and detailed characterization of LMW DOM competitors in real DOM-containing waters.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Carvão Vegetal , Cinética , Peso Molecular , Poluentes Químicos da Água/análise
3.
Chemosphere ; 286(Pt 1): 131551, 2021 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-34303909

RESUMO

The frequent detection of phenols and indoles in source water gives rise to concern about the taste and odor problems mainly caused by some chemicals. Exploration for the efficient removal of trace amounts of phenols and indoles in source water is imperative. This study investigated the removals and oxidation kinetics of 3-methylphenol (3-MP), 2,6-dichlorophenol (2,6-DCP), indole and 3-methylindole (3-MI) by NaClO and KMnO4. The results showed that the selected chemical odorants could be removed by NaClO and KMnO4. Meanwhile, the oxidation processes could be well described by the second-order kinetics model, in which kinetics constants of chemical odorants were from 1.44 × 104 to 1.45 × 106 L·mol-1·min-1 and followed the order 3-MI > indole> 3-MP> 2,6-DCP by NaClO. However, the kinetics constants for the selected chemical odorants were also determined from 1.10 × 103 to 2.25 × 104 L·mol-1·min-1 and in the order 2,6-DCP> 3-MI> 3-MP > indole by KMnO4. The phenols degradation mechanisms by NaClO are chlorine substitution, and the products generated are 3,4,6-trichloro-2-methylphenol, 2,4,6-trichlorophenol, etc. And that of indoles are chlorine substitution and hydroxylation by NaClO, which generated 6-chloroindole, 2,6-dichloroaniline, etc. The phenols degradation pathways are oxidative coupling reactions by KMnO4, and that of indoles are hydroxylation reactions by KMnO4. This study provides a further basis for NaClO and KMnO4 oxidation to remove trace phenols and indoles in drinking water pre-treatments.

4.
Chemosphere ; 285: 131352, 2021 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-34246937

RESUMO

Ozone is widely applied for disinfection in drinking water treatment and the disinfection by-product bromate would be produced during the ozonation of bromide-bearing water. Hydrogen peroxide (H2O2) addition could effectively control the formation of bromate. However, the bromate depression performance would be impacted by water qualities. In this study, typical source water containing bromide in eastern China was selected to investigate bromate depression effect under different organic matter, ammonia and bromide concentrations during the H2O2-O3 process. The results display that organic matter, ammonia and bromide concentration could influence the formation of bromate significantly. As tyrosine was applied to increase the dissolved organic carbon (DOC) concentration of source water by 2.0 and 3.0 mg/L, the total concentration of bromate produced decreased gradually as the H2O2/O3 (g/g) doses increased from 0 to 1.0 and bromate concentration could be controlled below 10 µg/L as H2O2/O3 (g/g) was 0.5 and 1.0. As ammonia concentration increased by 0.1 and 0.5 mg/L, lower H2O2/O3 (g/g) doses would lead to an increase in bromate generation. As more H2O2 was added in water, the bromate formation would be suppressed. The increase of bromide concentration induced higher bromate formation. When the bromide concentration increased by 50 and 200 µg/L, bromate concentration was 10.7 µg/L and 41.2 µg/L respectively at the H2O2/O3 (g/g) of 1.0, higher than the standard level. As 200 µg/L of bromide was added to the water, bromate concentration increased significantly and then decreased as H2O2/O3 (g/g) increased and more H2O2 would be needed for bromate control.

5.
Int J Biol Macromol ; 185: 287-296, 2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34153359

RESUMO

Cellulose microcrystalline (MCC) was widely used in pharmaceutical and chemical industries because of its low degree of polymerization and large specific surface area. As its modified form, dialdehyde cellulose (DAC) was used for cross-linking and immobilizing Rhizopus lipase together with magnetic nanoparticles (MNPs) due to its active aldehyde groups. In this study, in order to maintain the original enzyme activity as much as possible and improve the stability of lipase, the Rhizopus lipase was successfully immobilized on the magnetic dialdehyde cellulose nanoparticles (MDC). Specifically, the immobilization conditions including dosage of DAC, concentration of enzyme, immobilization time and temperature together with pH value of the reaction medium were optimized. Maximum immobilization yield (60.03 ± 0.49%) and recovery activity (88.88 ± 0.61%) can be obtained under the optimal process conditions. The changes in secondary structures of immobilized enzyme revealed the increment in conformational rigidity, which can be reflected in temperature and pH stability as well as tolerance of organic reagents. Additionally, the recovery activity of immobilized enzyme still reached 50.60 ± 0.59% after 30 d of storage and 52.10 ± 0.57% retained after 6 cycles. These results indicated the ideal application prospect of MDC in immobilized enzymes.


Assuntos
Celulose/análogos & derivados , Lipase/química , Nanopartículas de Magnetita/química , Rhizopus/enzimologia , Celulose/química , Estabilidade Enzimática , Enzimas Imobilizadas/química , Proteínas Fúngicas/química , Concentração de Íons de Hidrogênio , Estrutura Secundária de Proteína , Temperatura , Tempo
6.
J Hazard Mater ; 418: 126298, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34119980

RESUMO

This work investigated the removal efficiency of disinfection by-product (DBP) precursors by different drinking water treatment processes and evaluated the feasibility of using fluorescence components removal as an indicator. A four-component (including tryptophan-like, protein-bound, tyrosine-like, and humic-like components) parallel factor analysis model was developed basing on 288 fluorescence excitation-emission matrices. Among all treatment processes, coagulation-sedimentation process showed the best performance, with mean removal ratios of 30% in total fluorescence intensity and 31% in total formation potential (FP) of DBPs, respectively. It preferentially removed humic-like component C4 (43%). Advanced treatment processes were less effective in comparison. Ozone and biological activated carbon (BAC) combined process reduced 20% of total fluorescence intensity, while ultrafiltration process reduced < 3%. Ozonation and BAC filtration preferentially removed free amino acids (i.e., C1 and C3) and protein-bound (i.e., C2) components, with mean removal ratios of 12% and 17%, respectively. Significant correlations (p < 0.01, double-tailed) were observed between four fluorescence components removal and FPs reduction of three trihalomethanes, dichloroacetonitrile (DCAN), and 1,1-dichloropropanone (1,1-DCP). Specifically, the correlation coefficients for three trihalomethanes and 1,1-DCP followed the order of C4 > C1 > C2 > C3, while the order for DCAN was C2 > C4 > C1 > C3.


Assuntos
Água Potável , Poluentes Químicos da Água , Purificação da Água , Desinfecção , Água Potável/análise , Análise Fatorial , Poluentes Químicos da Água/análise
7.
Artigo em Inglês | MEDLINE | ID: mdl-34060196

RESUMO

Side-chain engineering is an effective strategy to regulate the solubility and packing behavior of organic materials. Recently, a unique strategy, so-called terminal side-chain (T-SC) engineering, has attracted much attention in the field of organic solar cells (OSCs), but there is a lack of deep understanding of the mechanism. Herein, a new noncovalently fused-ring electron acceptor (NFREA) containing two T-SCs (NoCA-5) was designed and synthesized. Introduction of T-SCs can enhance molecular rigidity and intermolecular π-π stacking, which is confirmed by the smaller Stokes shift value, lower reorganization free energy, and shorter π-π stacking distance in comparison to NoCA-1. Hence, the NoCA-5-based device exhibits a record power conversion efficiency (PCE) of 14.82 % in labs and a certified PCE of 14.5 %, resulting from a high electron mobility, a short charge-extraction time, a small Urbach energy (Eu ), and a favorable phase separation.

8.
Biomed Chromatogr ; 35(10): e5183, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34058018

RESUMO

Dyslipidemia is a common, chronic metabolic disease associated with cardiovascular complications. Due to the multiplicity of etiological factors, the pathogenesis of dyslipidemia is still unclear. In this study, we combined proteomics and metabolomics methods to analyze the plasma of patients with dyslipidemia and healthy subjects. isobaric tags for relative and absolute quantification (iTRAQ) markers, combined with LC-MS/MS proteomics technology and the UHPLC/Orbitfast-X Tribrid system, were used to establish the metabolite profile in clinical dyslipidemia. A total of 137 differentially expressed proteins, mainly related to biological processes such as protein activation cascades, adaptive immune responses, complement activation, acute inflammatory responses, and regulation of acute inflammatory responses, were identified. These proteins are involved in the regulation of important metabolic pathways, such as immunity and inflammation, coagulation and hemostasis, lipid metabolism, and oxidation and antioxidant defenses. The analysis of clinical metabolites showed there were 69 different metabolites in plasma, mainly related to glycerolipid, sphingolipid, porphyrin, α-linolenic acid, linoleic acid, and arachidonic acid metabolism, suggesting that the regulation of inflammation and lipid metabolism may be disturbed in patients with dyslipidemia. Among these, significant changes were observed in indole-3-propionic acid (IPA), which is considered as a potential biomarker of dyslipidemia. The combined analysis of proteins and metabolites showed that arachidonic acid, linoleic acid, and lipid metabolic pathways were closely related to dyslipidemia. IPA may be a potential biomarker. The information provided in this study may provide new insights into the pathogenesis of animal models of dyslipidemia and related disease models, as well as potential intervention targets.


Assuntos
Dislipidemias , Metaboloma/fisiologia , Metabolômica/métodos , Proteoma/análise , Proteômica/métodos , Adulto , Biomarcadores/sangue , Biomarcadores/metabolismo , Proteínas Sanguíneas/análise , Cromatografia Líquida , Dislipidemias/sangue , Dislipidemias/metabolismo , Humanos , Redes e Vias Metabólicas , Espectrometria de Massas em Tandem , Adulto Jovem
9.
Artigo em Inglês | MEDLINE | ID: mdl-33955726

RESUMO

A combination of high open-circuit voltage (Voc) and short-circuit current density (Jsc) typically creates effective organic solar cells (OSCs). Y5, a member of the Y-series acceptors, can achieve high Voc of 0.94 V with PM6 but low Jsc of 12.8 mA cm-2. To maintain the high Voc while increasing the Jsc of devices, we developed a new nonfullerene acceptor, namely, BTP-C2C4-N, by extending the conjugation of a Y5 molecule with a naphthalene-based end acceptor. In comparison with Y5-based devices, PM6:BTP-C2C4-N-based devices exhibited significantly higher Jsc of 18.2 mA cm-2 followed by a high Voc. To further increase the photovoltaic properties of BTP-C2C4-N analogues, BTP-C4C6-N and BTP-C6C8-N molecules with better processability and film morphology are obtained by adjusting the alkyl branched chain length. The optimized OSCs based on BTP-C4C6-N with a moderate alkyl branched chain length exhibited the best PCE of 12.4% with a high Voc of 0.94 V and Jsc of 20.7 mA cm-2. Notably, the devices achieved a low energy loss of 0.49 eV (0.51 eV for Y5 system) accompanied by a small nonradiative energy loss. The results indicate that nonfullerene acceptors with extended terminal motifs and optimized branched chain lengths can effectively enhance the performance of OSCs and reduce energy loss.

10.
Artigo em Inglês | MEDLINE | ID: mdl-33749088

RESUMO

Noncovalently fused-ring electron acceptors (NFREAs) have attracted much attention in recent years owing to their advantages of simple synthetic routes, high yields and low costs. However, the efficiencies of NFREAs based organic solar cells (OSCs) are still far behind those of fused-ring electron acceptors (FREAs). Herein, a series of NFREAs with S⋅⋅⋅O noncovalent intramolecular interactions were designed and synthesized with a two-step synthetic route. Upon introducing π-extended end-groups into the backbones, the electronic properties, charge transport, film morphology, and energy loss were precisely tuned by fine-tuning the degree of multi-fluorination. As a result, a record PCE of 14.53 % in labs and a certified PCE of 13.8 % for NFREAs based devices were obtained. This contribution demonstrated that combining the strategies of noncovalent conformational locks and π-extended end-group engineering is a simple and effective way to explore high-performance NFREAs.

11.
Water Res ; 192: 116848, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33524635

RESUMO

Identification of MIB(2-methylisoborneol)-producing cyanobacteria in source water has been a big challenge for reservoir authorities because it normally requires isolation of cyanobacteria strains. Here, a protocol based on Pearson's product moment correlation analysis combined with standardized data treatment and expert judgement was developed to sort out the MIB producer(s), mainly based on routine monitoring data from an estuary drinking water reservoir in the Yangtze River, China, and a risk model using quantile regressions was established to evaluate the risk of MIB occurrences. This reservoir has suffered from MIB problems in summer since 2011. Among 323 phytoplankton species, Planktothrix was judged to be the MIB producer in this reservoir because it exhibited the highest correlation coefficient (R = 0.60) as well as the lowest false positive-ratio (FP% = 0) and false-negative rate (FN% = 14). The low false-positive rate is particularly important, since MIB should not detected without detection of the producer. A high light extinction coefficient (k=5.57±2.48 m-1) attributed to high turbidity loading in the river water lowered the subsurface water light intensity, which could protect the low irradiance Planktothrix from excessive solar radiation, and allow them to grow throughout the summer. The risk model shows that the probability of suffering unacceptable MIB concentrations (>15 ng L-1) in water is as high as 90% if the cell density of Planktothrix is >609.0 cell mL-1, while the risk will be significantly reduced to 50% and 10% at cell densities of 37.5 cell mL-1 and 9.6 cell mL-1, respectively. The approach developed in this study, including the protocol for identification of potential producers and the risk model, could provide a reference case for the management of source water suffering from MIB problems using routine monitoring data.


Assuntos
Água Potável , China , Estuários , Odorantes/análise , Medição de Risco
12.
J Am Chem Soc ; 2021 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-33566603

RESUMO

Despite the significant progresses made in all-polymer solar cells (all-PSCs) recently, the relatively low short-circuit current density (Jsc) and large energy loss are still quite difficult to overcome for further development. To address these challenges, we developed a new class of narrow-bandgap polymer acceptors incorporating a benzotriazole (BTz)-core fused-ring segment, named the PZT series. Compared to the commonly used benzothiadiazole (BT)-containing polymer PYT, the less electron-deficient BTz renders PZT derivatives with significantly red-shifted optical absorption and up-shifted energy levels, leading to simultaneously improved Jsc and open-circuit voltage in the resultant all-PSCs. More importantly, a regioregular PZT (PZT-γ) has been developed to achieve higher regiospecificity for avoiding the formation of isomers during polymerization. Benefiting from the more extended absorption, better backbone ordering, and more optimal blend morphology with donor component, PZT-γ-based all-PSCs exhibit a record-high power conversion efficiency of 15.8% with a greatly enhanced Jsc of 24.7 mA/cm2 and a low energy loss of 0.51 eV.

13.
Environ Pollut ; 271: 116373, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33418288

RESUMO

The odor problems in river-type micro-polluted water matrixes are complicated compared to those in lakes and reservoirs. For example, the TY River in Jiangsu Province has been associated with complex odors, whereas the specific odor compounds were not clear. In this paper, a comprehensive study on characterizing the odors and odorants in source water from the TY River was conducted. Six odor types, including earthy, marshy, fishy, woody, medicinal, and chemical odors, were detected for the first time; correspondingly, thirty-three odor-causing compounds were identified. By means of evaluating odor activity values and reconstituting the identified odorants, 95, 93, 92, 90, 89 and 88% of the earthy, marshy, fishy, woody, medicinal and chemical odors in the source waters could be clarified. Geosmin and 2-methylisoborneol were associated with earthy odor, while amyl sulfide, dibutyl sulfide, propyl sulfide, dimethyl disulfide, dimethyl trisulfide and indole were related to marshy odor. The major woody and fishy odor compounds were vanillin, geraniol, ß-cyclocitral and 2,4-decadienal, 2-octenal, respectively. Medicinal and chemical odors were mainly caused by 2-chlorophenol, 4-bromophenol, 2,6-dichlorophenol and naphthalene, and 1,4-dichlorobenzene, respectively. This is the first study in which six odor types and thirty-three odorants were identified simultaneously in a river-type micro-polluted water source, which can offer a reference for odor management in drinking water treatment plants.


Assuntos
Odorantes , Purificação da Água , Animais , Rios , Água , Poluição da Água
14.
Chemosphere ; 269: 128691, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33162163

RESUMO

Ozone and biological activated carbon (BAC) are known to be effective at removing odors in drinking water. However, the specific variations in complex odors and odorants along the course of advanced treatments in full-scale drinking water treatment plants (DWTP) have remained unclear. In this paper, the migration of odors and odorants through pre-ozonation, sedimentation, post-ozonation, and BAC treatment processes were studied from January to December 2019 in a DWTP. The results indicated that septic, musty, and chemical odors with intensities of 6-6.7, 6-7.5, 4-5 could be removed by both ozonation and BAC, while grassy, fishy odors with intensities of 3.3-4.8, 2.3-5.8 could not be removed until the BAC step. Twenty-four odorants identified in raw water were classified as musty (2-methylisoborneol, geosmin), chemical (e.g. indane, eucalyptol), septic (e.g. dimethyl disulfide, pentanethiol), fishy (2,4-decadienal) and grassy (nonanal, decanal) odor compounds. It is noteworthy that eleven additional odorants were produced after ozonation; in addition, the concentrations of fishy and grassy odorants were increased after ozonation, and the concentrations of musty, septic, fishy, and grassy odorants were increased after sedimentation, suggesting that sedimentation and ozonation should be carefully managed. BAC was the most effective at removing the above odorants simultaneously. This study would be helpful for providing more insights into the migration of odorants along treatment processes and understanding the mitigation of odors in DWTPs using raw waters with complex odors.


Assuntos
Água Potável , Ozônio , Poluentes Químicos da Água , Purificação da Água , Água Potável/análise , Odorantes/análise , Poaceae , Poluentes Químicos da Água/análise
15.
Water Res ; 189: 116643, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33246216

RESUMO

Swampy/septic odor caused by various sulfides is one of the most frequently encountered odor problems in drinking water. However, even though it is much more offensive, few studies have specifically focused on swampy/septic odor compared to the extensively studied musty/earthy problems. In this work, four sulfide odorants, diamyl sulfide (DAS), dipropyl sulfide (DPS), dimethyl disulfide (DMDS) and diethyl disulfide (DEDS), were selected to evaluate the treatment performance of different oxidation processes in drinking water. The results demonstrated that DMDS, DEDS, DPS and DAS could be oxidized effectively by KMnO4, NaClO and ClO2. The oxidation processes could be well described by the second-order kinetic model, in which k values of selected sulfides followed the order DMDS≈DEDS ≪ DPS≈DAS. As for the three oxidants, the order of reactivity was KMnO4 ≪ ClO2 < NaClO, which was also verified in raw water. The results of oxidation treatability, reaction kinetics and mechanisms confirmed that the characteristics of the central sulfur atom rather than the side chain is the decisive factor in controlling the oxidation rate and transformation pathway of sulfides. The transformation products and pathways were significantly different for the three oxidants. Sulfones (DPSO, DASO) were always formed by cycloaddition reactions during KMnO4 oxidation, yet recombination reactions proceeded during ClO2 oxidation and formed more products, such as MADS, DADS and EADS. Density functional theory (DFT) calculations confirmed that the differences in transformation pathways were caused by the variations in the activity of the oxidants and sulfides. Finally, NaClO was certified as the most effective oxidant for controlling sulfide odorants in drinking water treatment.


Assuntos
Água Potável , Purificação da Água , Água Potável/análise , Cinética , Odorantes/análise , Oxirredução , Sulfetos
16.
J Hazard Mater ; 403: 123986, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33265025

RESUMO

This study investigated the occurrence and removal of 29 pesticides in 4 drinking water treatment plants (DWTPs) with conventional and advanced treatment processes (i.e., ozonation + biological activated carbon, and ultrafiltration) in Shanghai, China from 2018 to 2019. The concentration levels of target pesticides in raw waters ranged from below the limit of quantification (

Assuntos
Água Potável , Praguicidas , Poluentes Químicos da Água , Purificação da Água , China , Humanos , Praguicidas/análise , Praguicidas/toxicidade , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
17.
Adv Mater ; 32(43): e2004183, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32954584

RESUMO

Narrow-bandgap polymer semiconductors are essential for advancing the development of organic solar cells. Here, a new narrow-bandgap polymer acceptor L14, featuring an acceptor-acceptor (A-A) type backbone, is synthesized by copolymerizing a dibrominated fused-ring electron acceptor (FREA) with distannylated bithiophene imide. Combining the advantages of both the FREA and the A-A polymer, L14 not only shows a narrow bandgap and high absorption coefficient, but also low-lying frontier molecular orbital (FMO) levels. Such FMO levels yield improved electron transfer character, but unexpectedly, without sacrificing open-circuit voltage (Voc ), which is attributed to a small nonradiative recombination loss (Eloss,nr ) of 0.22 eV. Benefiting from the improved photocurrent along with the high fill factor and Voc , an excellent efficiency of 14.3% is achieved, which is among the highest values for all-polymer solar cells (all-PSCs). The results demonstrate the superiority of narrow-bandgap A-A type polymers for improving all-PSC performance and pave a way toward developing high-performance polymer acceptors for all-PSCs.

18.
Water Res ; 182: 115971, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32554269

RESUMO

The presence of earthy-musty odors in drinking water is a major concern for water suppliers and consumers worldwide. While geosmin and 2-methylisoborneol are the most studied earthy-musty odor-causing compounds, pyrazine and its alkyl and methoxy compounds possess similar odors and are widely distributed in nature, foods, and beverages. In this study, odor characteristics of pyrazines and their presence in natural and treated waters were determined. Pyrazine, 2,6-dimethyl-pyrazine (DMP), 2,3,5-trimethyl-pyrazine (TrMP), 2-ethyl-5(6)-methyl-pyrazine (EMP), 2,3,5,6-tetramethyl-pyrazine (TeMP), 2-isobutyl-3-methoxy-pyrazine (IBMP) and 2-isopropyl-3-methoxy-pyrazine (IPMP) were measured in source and finished drinking water across China. 2-Methoxy-3,5-dimethyl-pyrazine (MDMP), IBMP, and IPMP were investigated in rivers in Virginia, USA. The results showed that "musty" and "sweet" were the most common descriptors for pyrazine, DMP, MDMP, TrMP, and TeMP. While IBMP and IPMP were never detected in 140 source or drinking water samples from across China, pyrazine, DMP, MDMP, TrMP, and TeMP occurred throughout with concentrations of n.d.-62.2 ng/L-aq in source water and n.d.-39.6 ng/L-aq in finished water. IBMP, IPMP, and MDMP were present in two Virginia rivers; MDMP occurred in 18% of the samples with concentrations of n.d.-4.4 ng/L, many of which were above the aqueous odor threshold of 0.043 ng/L MDMP. The removal efficiencies through conventional water treatment were poor, ranging from negative removals to ∼10%. Advanced oxidation water treatment could only remove EMP and TrMP. The widespread presence of earthy-musty-sweet pyrazines in source and drinking waters on two continents, their poor removal during water treatment, and ng/L odor threshold concentrations confirm their potential to be T&O issues for consumers.


Assuntos
Água Potável , Poluentes Químicos da Água/análise , China , Comportamento do Consumidor , Odorantes/análise , Pirazinas/análise , Virginia
19.
Water Res ; 178: 115797, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32375110

RESUMO

In this study, the adsorption capacities of two common odor compounds, 2-methylisoborneol (2-MIB) and dimethyl disulfide (DMDS), onto nine common types of powdered activated carbon (PAC) were comprehensively compared to screen the critical surface chemical properties affecting the adsorption performance. The results showed that the adsorption capacities of all the PACs for DMDS were generally lower than those for 2-MIB. The Spearman's rank correlation analysis indicated that the adsorption capacity for 2-MIB did not have any correlation with the PAC surface sites, while the DMDS adsorption capacity was positively related to the number of basic sites. The effect of the PAC basic sites on the DMDS adsorption was further verified by density functional theory (DFT) calculation in two adsorption modes (facial mode and edge mode). The graphene structure in the edge mode was the most favorable for DMDS adsorption with the lowest adsorption enthalpy, followed by the ketone-doped structure under the facial mode. An independent gradient model indicated that van der Waals forces were dominant in the DMDS adsorption. Moreover, thermal modification was conducted to further prove the relationship between the basic sites and the DMDS adsorption. After thermal modification, the PAC with more basic sites and graphene structures was found to be more effective for DMDS adsorption. Overall, this study could offer guidance for water treatment plants with respect to the selection of PAC to solve the odor problems caused by various compounds (e.g., DMDS or 2-MIB), and the modification of PAC, aiming at more efficient odor removal.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Carvão Vegetal , Odorantes , Propriedades de Superfície
20.
Angew Chem Int Ed Engl ; 59(35): 15043-15049, 2020 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-32385920

RESUMO

Triplet acceptors have been developed to construct high-performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T1 ) are close to those of charge-transfer states (3 CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π-conjugated core and D-A structure, were confirmed to be triplet materials, leading to high-performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin-orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T1 is close to 3 CT, facilitating the split of triplet exciton to free charges.

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