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1.
Environ Res ; 204(Pt A): 112032, 2021 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-34516980

RESUMO

A novel FeVO4/BiVO4 heterojunction photocatalyst was synthesized by hydrothermal method. The FeVO4/BiVO4 nanostructures were characterized by XRD, SEM, XPS, UV-vis, and photoluminescence spectroscopy. The effects of catalyst dosage, contaminant concentration, initial hydrogen peroxide (H2O2) concentration, and pH value on the degradation of levofloxacin were investigated and several repeated experiments were conducted to evaluate the stability and reproducibility. The optimized process parameters were used for mineralization experiments. Reactive oxygen species, degradation intermediates, and possible catalytic mechanisms were also investigated. The results showed that the sonophotocatalytic performance of the FeVO4/BiVO4 heterojunction catalyst was better than that of sonocatalysis and photocatalysis. In addition, the Type II heterojunction formed by the material still had good stability in the degradation of levofloxacin after 5 cycles. The possible degradation pathway and mechanism of levofloxacin by sonophotocatalysis were put forward. This work develops new sono-photo hybrid process for potential application in the field of wastewater treatment.

2.
Bioresour Technol ; 341: 125916, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34523585

RESUMO

In this study, thiosulfate-driven denitratation (TDD) system was successfully established under optimal S/N molar ratio of 1.00, with nitrite accumulation efficiency (NAE) of 82.24 ± 17.09%. This work highlighted that thiosulfate significantly preferred the reduction of nitrate than nitrite. However, after the depletion of thiosulfate, the in-situ formed intermediate product element sulfur (S0) served as the main electron donor, and significantly favored the reduction of nitrite than nitrate, which constrained nitrite accumulation and nitrate removal. In addition, metagenomic sequencing revealed that the functional denitratation species might be Thiobacillus_sp._65-29, but the occurrence of Nir-annotated species would decrease nitrite accumulation. Under S/N ratio of 1.00, the decreased abundant Nir-annotated species (e.g., Thiobacillus_sp.), as well as the down-regulated quorum sensing interactions between Nar- and Nir-annotated species were key microbial metabolisms of high NAE in the TDD system. Overall, this work provides new sight into the metagenome-base functional species and metabolic potential of thiosulfate-driven denitratation.


Assuntos
Desnitrificação , Tiossulfatos , Reatores Biológicos , Metagenômica , Nitrogênio
3.
Sci Total Environ ; 801: 149611, 2021 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-34428657

RESUMO

Ultrafiltration is an environmentally friendly water treatment technology, but membrane fouling significantly impacts membrane performance and service life. Photocatalytic modification of membrane is regarded as an effective way for membrane fouling control. In this study, graphite oxide (GO), Ag3PO4 and Ag3PO4-GO nanomaterials were applied in polyvinylidene fluoride (PVDF) ultrafiltration membranes modification, and the membranes was denoted as P-GO, P-AgP and P-AgP@GO, respectively. Filtration of humic acid (HA) at different operating conditions was adopted in evaluation of membrane performance. Among them, P-AgP@GO had the best permeation, rejection and antifouling performances, and could maintain excellent properties when operation conditions (HA concentration, operation pressure, pH and ionic strength) were changed. Furthermore, the effect of photocatalysis on the self-cleaning performance and its mechanism were revealed. The overall performance of P-AgP@GO could be enhanced by visible light irradiation, and extending the visible illumination time during the filtration was conducive to the reusability.

4.
J Hazard Mater ; 421: 126703, 2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34315026

RESUMO

Water eutrophication leads to increasingly serious harmful algal blooms (HABs), which poses tremendous threats on aquatic environment and human health. In this work, a novel magnetically separable ZnFe2O4/Ag3PO4/g-C3N4 (ZFO/AP/CN) photocatalyst with double Z-scheme was constructed for Microcystis aeruginosa (M. aeruginosa) inactivation and Microcystin-LR (MC-LR) degradation under visible light. The photocatalyst was characterized by XRD, SEM, EDS, TEM, XPS, FTIR, UV-vis, PL, and VSM. Approximately 96.33% of chlorophyll a was degraded by ZFO/AP/CN (100 mg/L) after 3 h of visible light irradiation. During the photocatalytic process, the malondialdehyde (MDA) of M. aeruginosa increased, the activities of superoxide dismutase (SOD) and catalase (CAT) increased initially and decreased afterwards. Furthermore, the photocatalytic removal efficiency of M. aeruginosa (OD680 ≈0.732) and MC-LR (0.2 mg/L) reached 94.31% and 76.92%, respectively, in the simultaneous removal of algae and algal toxin experiment. Reactive species scavenging experiments demonstrated that·O2- and·OH played key roles in inactivating M. aeruginosa and degrading MC-LR. The excellent recoverability and stability of ZFO/AP/CN were proved by cycling photocatalytic experiment which using magnetic recovery method. In summary, the synthesized magnetically separable ZFO/AP/CN photocatalyst has remarkable photocatalytic activity under visible light and shows promising potential for practical application of alleviating HABs.

5.
Chemosphere ; 284: 131283, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34323790

RESUMO

Cyanobacterial harmful algal blooms (CyanoHABs) and the release of cyanotoxins have posed adverse impacts to aquatic system and human health. In this study, a novel self-floating Ag/AgCl@LaFeO3 (ALFO) photocatalytic hydrogel was prepared via freeze-thaw method for removal of Microcystis aeruginosa (M. aeruginosa). The ALFO hydrogel performed an excellent photocatalytic activity with a 99.4% removal efficiency of chlorophyll a within 4 h. It can still remove above 95% chlorophyll a after six consecutive recycles. Besides it has also shown excellent mechanical strength and elasticity, which can ensure its use in practical applications. The mechanisms of M. aeruginosa inactivation are attributed to •O2- and •OH generated by the ALFO hydrogel under visible light radiation. In addition, •O2- and •OH can further oxidative degrade and even mineralize the leaked algae organic matter, avoiding the recurrence of CyanoHABs. What's more, the ALFO hydrogel owns good photocatalytic degradation performance for microcystins-LR (MC-LR) with a 97% removal efficiency within 90 min. A possible photocatalytic degradation pathway of MC-LR was proposed through the identification of the intermediate products during the photocatalytic reaction, which confirmed the reduction of MC-LR toxicity. This work develops recyclable a self-floating ALFO hydrogel to simultaneously inactivate M. aeruginosa and degrade MC-LR, providing a prospective method for governing and controlling CyanoHABs in practical application.


Assuntos
Microcystis , Clorofila A , Proliferação Nociva de Algas , Humanos , Hidrogéis , Microcistinas
6.
ACS Appl Mater Interfaces ; 13(26): 31066-31076, 2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-34137247

RESUMO

The serious problem of pharmaceutical and personal care product pollution places great pressure on aquatic environments and human health. Herein, a novel coating photocatalyst was synthesized by adhering Ag-AgCl/WO3/g-C3N4 (AWC) nanoparticles on a polydopamine (PDA)-modified melamine sponge (MS) through a facile layer-by-layer assembly method to degrade trimethoprim (TMP). The formed PDA coating was used for the anchoring of nanoparticles, photothermal conversion, and hydrophilic modification. TMP (99.9%; 4 mg/L) was removed in 90 min by the photocatalyst coating (AWC/PDA/MS) under visible light via a synergistic photocatalytic-photothermal performance route. The stability and reusability of the AWC/PDA/MS have been proved by cyclic experiments, in which the removal efficiency of TMP was still more than 90% after five consecutive cycles with a very little mass loss. Quantitative structure-activity relationship analysis revealed that the ecotoxicities of the generated intermediates were lower than those of TMP. Furthermore, the solution matrix effects on the photocatalytic removal efficiency were investigated, and the results revealed that the AWC/PDA/MS still maintained excellent photocatalytic degradation efficiency in several actual water and simulated water matrices. This work develops recyclable photocatalysts for the potential application in the field of water remediation.


Assuntos
Nanopartículas/química , Trimetoprima/química , Catálise/efeitos dos fármacos , Grafite/química , Grafite/efeitos da radiação , Indóis/química , Indóis/efeitos da radiação , Luz , Nanopartículas/efeitos da radiação , Compostos de Nitrogênio/química , Compostos de Nitrogênio/efeitos da radiação , Óxidos/química , Óxidos/efeitos da radiação , Polímeros/química , Polímeros/efeitos da radiação , Prata/química , Prata/efeitos da radiação , Compostos de Prata/química , Compostos de Prata/efeitos da radiação , Temperatura , Triazinas/química , Triazinas/efeitos da radiação , Tungstênio/química , Tungstênio/efeitos da radiação , Purificação da Água/métodos
7.
J Hazard Mater ; 419: 126407, 2021 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-34175707

RESUMO

In this work, a recyclable self-floating A-GUN-coated (Ag/AgCl@g-C3N4@UIO-66(NH2)-coated) foam was fabricated for effective inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The floating photocatalyst was able to inactivate 98% of M. aeruginosa within 180 min under the visible-light irrigation, and the floating photocatalyst exhibited a stable performance in various conditions. Moreover, the inactivation efficiency can still maintain nearly 92% after five times recycle experiments, showing excellent photocatalytic stability. Furthermore, effects of A-GUN/SMF floating catalyst on the physiological properties, cellular organics, and algal functional groups of M. aeruginosa were studied. The floating photocatalyst can not only make full use of excellent photocatalytic activities of A-GUN nanocomposite, but also promote contact between catalyst and algae, and realize the effective recovery of the photocatalyst. Finally, possible photocatalytic inactivation mechanisms of algae were obtained, which provides references for removing cyanobacteria blooms in real water bodies.


Assuntos
Cianobactérias , Microcystis , Nanocompostos , Catálise , Luz
8.
Artigo em Inglês | MEDLINE | ID: mdl-34117975

RESUMO

Steroid estrogens have received worldwide attention and given rise to great challenges of aquatic ecosystems security, posing potential adverse effects on aquatic organisms and human health even at low levels (ng/L). The present study focused on understanding the mobility and abiotic transformation of estrone (E1) and estrone-3-sulfate (E1-3S) over spatial and time scales during soil transport. Column transport experiments showed that the migration capacity of E1-3S was far stronger than E1 in soil. The calculated groundwater ubiquity score and leachability index values also indicated the high leaching mobility of E1-3S. The hydrolysis of E1-3S and abiotic transformation into estradiol and estriol was observed in the sterilized soil. Furthermore, possible transformation products (e.g., SE239, E2378, E1 dimer538, E1-E2 dimer541) of E1 and E1-3S in soil were analyzed and identified after the column transport experiments. The estrogenic activity was estimated by 17ß-estradiol equivalency values during the transport process in aqueous and soil phases. Additionally, the potential leaching transport to groundwater of E1-3S requires further critical concern.

9.
J Hazard Mater ; 409: 125018, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33422753

RESUMO

A novel plasmonic Ag/AgCl@LaFeO3 (ALFO) photocatalyst was successfully synthesized by a simple in-situ synthesis method with enhanced photocatalytic activity under visible light for harmful algal blooms (HABs) control. The structure, morphology, chemical states, optical and electrochemical properties of the photocatalyst were systematically investigated using a series of characterization methods. Compared with pure LaFeO3 and Ag/AgCl, ALFO-20% owned a higher light absorption capacity and lower electron-hole recombined rate. Therefore, ALFO-20% had higher photocatalytic activity with a near 100% removal rate of chlorophyll a within 150 min, whose kinetic constant was 15.36 and 9.61 times faster than those of LaFeO3 and Ag/AgCl. In addition, the changes of zeta potential, cell membrane permeability, cell morphology, organic matter, total soluble protein, photosynthetic system and antioxidant enzyme system in Microcystis aeruginosa (M. aeruginosa) were studied to explore the mechanism of M. aeruginosa photocatalytic inactivation. The results showed that ALFO-20% could change the permeability and morphology of the algae cell membrane, as well as destroy the photosynthesis system and antioxidant system of M. aeruginosa. What's more, ALFO could further degrade the organic matters flowed out after algae rupture and die, reducing the secondary pollution and avoiding the recurrence of HABs. Finally, the species of reactive oxygen species (ROS) (mainly •O2- and •OH) produced by ALFO were determined through quenching experiments, and a possible photocatalytic mechanism was proposed. Overall, ALFO can efficiently remove the harmful algae under the visible light, providing a promising method for controlling HABs.


Assuntos
Luz , Prata , Compostos de Cálcio , Clorofila A , Óxidos , Titânio
10.
J Environ Manage ; 281: 111884, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33385902

RESUMO

A new method for algal community restructuring is proposed, where harmful algae growth is inhibited through the addition of remedial nano-agent, while probiotic algae growth is promoted or only affected indistinctively. In this paper, the inhibiting effects of five different nanomaterials on Microcystis aeruginosa (M. aeruginosa) and Cyclotella sp. were studied, and the optimal nanomaterial was served as algae-inhibition ingredient of the remedial agent. The effects of the remedial agent on algal growth and their physiological characteristics were investigated, and the restructuring of algal community in actual water samples was explored. The results indicated that the inhibition ratio of 10 mg/L nm-Cu2O/SiO2 on M. aeruginosa and Cyclotella sp. could reach 293.1% and 82.8% respectively, acting as the best candidate for algae-inhibiting ingredient. After adding the remedial nano-agent made with nm-Cu2O/SiO2, the content of chlorophyll a, protein, and polysaccharides of M. aeruginosa decreased sharply, while the physiological characteristics of Cyclotella sp. were not significantly affected. Besides, the total biomass and proportion of cyanobacteria dropped (P < 0.05), but the Bacillariophyta biomass increased significantly (P < 0.05). The uniformity index, Shannon-Wiener index, and richness index all increased significantly (P < 0.05). Meanwhile, the quality of actual water samples has been improved evidently (P < 0.001). Therefore, the prepared remedial nano-agent in this study can control the harmful algae bloom to a certain extent by restructuring the algal community in eutrophic water bodies.


Assuntos
Diatomáceas , Microcystis , Clorofila A , Proliferação Nociva de Algas , Dióxido de Silício , Água
11.
J Hazard Mater ; 404(Pt B): 124062, 2021 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-33068992

RESUMO

In this work, a novel Ag/AgCl@g-C3N4@UIO-66(NH2) heterojunction was constructed for photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The photocatalyst was synthesized by a facile method and characterized by XRD, SEM, TEM, BET, XPS, FT-IR, UV-vis DRS, PL and EIS. The nanocomposite can not only provide lots of active sites, but also improve capacities to utilize visible-light energy and effectively transfer charge carriers, thus enhancing removal efficiencies of cyanobacteria (99.9% chlorophyll a was degraded within 180 min). Various factors in photodegradation of chlorophyll a were studied. Besides, changes on cellular morphologies, membrane permeability, physiological activities of M. aeruginosa during photocatalysis were investigated. Moreover, the cycle test indicated that Ag/AgCl@g-C3N4@UIO-66(NH2) exhibits excellent reusability and photocatalytic stability. Finally, a possible mechanism of M. aeruginosa inactivation was proposed. In a word, Ag/AgCl@g-C3N4@UIO-66(NH2) can efficiently inactivate cyanobacteria under visible light, thus providing useful references for further removal of harmful algae in real water bodies.


Assuntos
Microcystis , Nanocompostos , Clorofila A , Luz , Prata , Espectroscopia de Infravermelho com Transformada de Fourier
12.
J Hazard Mater ; 403: 123964, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33265006

RESUMO

Antibiotic contamination is increasing scrutinized recently. In this work, the Ag-AgCl/WO3/g-C3N4 (AWC) nanocomposites were successfully synthesized using a two-step process involving electrostatic self-assembly and in-situ deposition for trimethoprim (TMP) degradation. The as-prepared photocatalysts were investigated and characterized by XRD, FTIR, XPS, TGA, SEM, TEM, UV-vis, PL and EIS. The experimental results indicated that 99.9% of TMP (4 mg/L) was degraded within 60 min when the concentration of AWC was 0.5 g/L. Reactive species scavenging experiments and electron spin resonance (ESR) experiments illustrated that superoxide radical (•O2-) and photogenerated holes (h+) were the main active species. The functional theory calculation and identification of intermediates via HPLC-MS revealed the possible degradation pathways of TMP. A double photoelectron-transfer mechanism in AWC photocatalyst was proposed. Five cycling photocatalytic tests and reactions under different solution matrix effects further supported that the AWC was a promising photocatalyst for the removal of TMP from the aquatic environment.


Assuntos
Nanocompostos , Prata , Catálise , Luz , Trimetoprima
13.
Environ Pollut ; 267: 115405, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32866865

RESUMO

The ubiquitous occurrence of steroid estrogens (SEs) in the aquatic environment has raised global concern for their potential environmental impacts. This paper extensively compiled and reviewed the available occurrence data of SEs, namely estrone (E1), 17α-estradiol (17α-E2), 17ß-estradiol (17ß-E2), estriol (E3), and 17α-ethinyl estradiol (EE2), based on 145 published articles in different regions all over the world including 51 countries and regions during January 2015-March 2020. The data regarding SEs concentrations and estimated 17ß-estradiol equivalency (EEQ) values are then compared and analyzed in different environmental matrices, including natural water body, drinking and tap water, and wastewater treatment plants (WWTPs) effluent. The detection frequencies of E1, 17ß-E2, and E3 between the ranges of 53%-83% in natural water and WWTPs effluent, and the concentration of SEs varied considerably in different countries and regions. The applicability for EEQ estimation via multiplying relative effect potency (REPi) by chemical analytical data, as well as correlation between EEQbio and EEQcal was also discussed. The risk quotient (RQ) values were on the descending order of EE2 > 17ß-E2 > E1 > 17α-E2 > E3 in the great majority of investigations. Furthermore, E1, 17ß-E2, and EE2 exhibited high or medium risks in water environmental samples via optimized risk quotient (RQf) approach at the continental-scale. This overview provides the latest insights on the global occurrence and ecological impacts of SEs and may act as a supportive tool for future SEs investigation and monitoring.


Assuntos
Poluentes Químicos da Água , Água , Monitoramento Ambiental , Estradiol/análise , Estrogênios/análise , Estrona/análise , Etinilestradiol/análise , Medição de Risco , Poluentes Químicos da Água/análise
14.
J Environ Manage ; 275: 111288, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32866925

RESUMO

The spatial distribution of water quality status, especially in water bodies near intensively urbanized areas, is tightly associated with patterns of human activities. For establishing a robust assessment of the sediment quality in an urban aquatic environment, the source apportionment and risk assessment of Cr, Mn, Ni, Cu, Zn, As, Cd, Hg, and Pb in sediments from an anthropogenic-influenced lake were carried out with considering uncertainties from the analysis methods, random errors in the sample population and the spatial sediment heterogeneity. The distribution analysis of the trace metals with inverse distance weighting-determined method showed that the pollutants were concentrated in the middle and southern areas of the lake. According to the self-organizing map and constrained positive matrix factorization receptor model, agricultural sources (24.8%), industrial and vehicular sources (42.5%), and geogenic natural sources (32.7%) were the primary contributors to the given metals. The geogenic natural had the largest random errors, but the overall result was reliable according to the uncertainty analysis. Furthermore, the stochastic contamination and ecological risk models identified a moderate/considerable contamination level and a moderate ecological risk to the urban aquatic ecosystem. With consideration of uncertainties from the spatial heterogeneity, the contamination level of Hg, and the ecological risk of Cd in had a 20-30% probability of the increase.


Assuntos
Metais Pesados , Oligoelementos , Poluentes Químicos da Água , China , Ecossistema , Monitoramento Ambiental , Sedimentos Geológicos , Humanos , Metais Pesados/análise , Medição de Risco , Incerteza , Poluentes Químicos da Água/análise
15.
Sci Total Environ ; 741: 140341, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32615428

RESUMO

The frequent harmful algae blooms (HABs) in eutrophic waters pose serious threats to the water environment and health of human beings and animals. In this study, a new type of photocatalytic coating was prepared by loading Ag2CO3-N:GO (AGON) on the polyurethane sponge modified by silica sol via a dip coating method for the photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) and degradation of Microcystin-LR (MC-LR). The factors including photocatalyst loading dosage, natural organic matter (NOM), and alkalinity were studied. The effects on the physiological characteristics of M. aeruginosa and reactive oxygen species (ROS) were also investigated to reveal the photocatalytic inactivation mechanisms. The results showed that the AGON coating-4 (the initial concentration of AGON suspension used for loading is 4 g/L) exhibited the optimum photocatalytic performance under visible light, which can completely remove chlorophyll a after 5 h of irradiation. And the NOM and alkalinity in water have relatively negative effects on the photocatalytic inactivation of algae. The prepared AGON coating also exhibited excellent photocatalytic performance in the degradation of MC-LR under visible light. It only needed 20, 60 and 120 min to completely degrade 0.1, 0.3 and 0.5 mg/L MC-LR, respectively. However, the mixed systems of algae and MC-LR required a longer time to achieve photocatalytic degradation. The O2- were the predominant reactive oxygen species, causing the damage of cell membranes and walls and the leakage of cellular content, which eventually led to the irreversible damage to algal cells. What's more, the coating can be reused several times due to its good cyclability and stability. Therefore, the AGON coating has promising prospects for the treatment of algal blooms in eutrophic waters.


Assuntos
Microcystis , Prata , Animais , Clorofila A , Proliferação Nociva de Algas , Luz , Microcistinas
16.
J Hazard Mater ; 389: 122092, 2020 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-31972526

RESUMO

The environmental behaviors of steroid estrogens (SEs) associated with land irrigation and application are of critical concern worldwide. Understanding the spatio-temporal distribution and transformation process of these estrogenic compounds in soil is greatly significant. In this study, laboratory soil column experiments were conducted to investigate and explore the migration and abiotic transformation of 17α-estradiol (17α-E2) and 17ß-estradiol (17ß-E2) over spatial and time scales. Results indicated that the migration tendency of 17α-E2 and 17ß-E2 was similar. Discrepancies in transport for different SEs groups might be due to the competitive sorption and isomeric transformation in the binary-solute system. 17α-E2 and 17ß-E2 can also undergo the abiotic transformation during soil column transport. The soil with naturally abundant mineral substances (e.g., iron and manganese oxides) indicated that E2 isomers tended to mineral-promoted racemization, oxidation, reduction, and radical coupling reactions. Some possible transformation products (e.g., SE239, E2378, and SE dimer476) were identified and proposed in soil samples. Compared to the single compound tests, the estimated 17ß-estradiol equivalency (EEQ) values of E2 mixture were higher during SEs migration process.


Assuntos
Estradiol/química , Poluentes do Solo/química , Solo/química , Poluentes Químicos da Água/química , Oxirredução , Estereoisomerismo
17.
Chemosphere ; 239: 124721, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31493752

RESUMO

In this work, Metal-organic Frameworks (MOFs) were applied to inactivate algae under visible light with low doses. Five MOFs with different compositions (Zn and Fe; carboxylates or imidazolates) were successfully synthesized and characterized by XRD, SEM and UV-vis. The effects of MOFs on Microcystis aeruginosa were evaluated with regard to morphology characteristics, physiological activity, cell integrity and pigment degradation. The results indicated that Ag/AgCl@ZIF-8 outperformed MOF-235, ZIF-8, Bi2WO6/MIL-100(Fe) and BiOBr/MOF-5 in the degradation of chlorophyll a at the dose of 10 mg L-1. After 6 h of irradiation, 93.1% of Microcystis aeruginosa died and was unable to regrow and reproduce, which was demonstrated by changes in cell morphology, damage of cell membrane integrity and antioxidant enzyme system. Besides, the intracellular organic matter (IOM) and extracellular organic matter (EOM) were proven to be efficiently removed by MOF-assisted photocatalytic inactivation. Superoxide radical (O2·-) was demonstrated to be the major reactive oxygen species. A probable mechanism was proposed that the electrons in the valence band of Ag/AgCl@ZIF-8 transfer into the conduction band under irradiation to produce O2·- which inactivated the algae cells. Furthermore, Ag/AgCl@ZIF-8 can effectively remove Microcystis aeruginosa under sunlight and is of great application prospects for algae removal in real water bodies.


Assuntos
Estruturas Metalorgânicas/química , Microcystis/química , Purificação da Água/métodos , Clorofila A/química , Luz , Microcystis/metabolismo , Microscopia Eletrônica de Varredura , Processos Fotoquímicos , Compostos de Prata/química , Espectrofotometria Ultravioleta , Luz Solar , Difração de Raios X
18.
Nanomaterials (Basel) ; 9(12)2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31766783

RESUMO

In this study, a novel nanomaterial Cu2O/SiO2 was synthesized based on nano-SiO2, and the inhibitory effects of different concentrations of Cu2O/SiO2 on the growth of Microcystis aeruginosa (M. aeruginosa) were studied. At the same time, the mechanism of Cu2O/SiO2 inhibiting the growth of M. aeruginosa was discussed from the aspects of Cu2+ release, chlorophyll a destruction, oxidative damage, total protein, and the phycobiliprotein of algae cells. The results showed that low doses of Cu2O/SiO2 could promote the growth of M. aeruginosa. When the concentration of Cu2O/SiO2 reached 10 mg/L, it exhibited the best inhibitory effect on M. aeruginosa, and the relative inhibition rate reached 294% at 120 h. In terms of the algae inhibition mechanism, Cu2O/SiO2 will release Cu2+ in the solution and induce metal toxicity to algae cells. At the same time, M. aeruginosa might suffer oxidative damage by the free radicals, such as hydroxyl radicals released from Cu2O/SiO2, affecting the physiological characteristics of algae cells. Moreover, after the addition of Cu2O/SiO2, a decrease in the content of chlorophyll a, total soluble protein, and phycobiliprotein was found, which eventually led to the death of M. aeruginosa. Therefore, Cu2O/SiO2 can be used as an algaecide inhibitor for controlling harmful cyanobacteria blooms.

19.
Chemosphere ; 232: 54-62, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31152903

RESUMO

Bioretention systems have been extensively studied as a highly efficient technical measure to tackle the global threat of nitrogen pollution during global rainfall runoff. However, the migration and transformation of various forms nitrogen in bioretention system is unclear. So, in this paper, the bioretention systems with different flow regimes and planted configurations were designed to study the nitrogen removal performance and migration and transformation mechanism. The dynamic changes of NH4+-N and NO3--N were continuously monitored within 60 h after rainfall, and the abundance of 15N isotopes in soil layer NH4+-N was simultaneously measured. The results indicated that NH4+-N was mainly intercepted in soil layer in four constructed bioretention systems with similar removal efficiencies (95.42-97.69%). However, NO3--N was retained in submerged layer with significant different removal efficiencies (43.03-83.00%). After fitting calculation, the nitrification rate of NH4+-N (0.0626 mg kg-1 h-1) in soil was 5.31 times higher than that of the accumulation rate of NO3--N (0.0118 mg kg-1 h-1). During the elimination process of residual NH4+-N in soil, 41.46% removed by denitrification and plant absorption assimilation, another 57.28% stored in the form of organic nitrogen or inorganic nitrogen, only 1.26% leaked out. Based on this, the content variation of TN, NH4+-N and NO3--N could be analyzed by a system-wide and established the nitrogen balance model, which provides a new insight into the enhancement of nitrogen removal in the bioretention system.


Assuntos
Nitrogênio/análise , Eliminação de Resíduos Líquidos , Desnitrificação , Nitrificação , Chuva , Solo
20.
Ecotoxicol Environ Saf ; 176: 270-278, 2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-30947030

RESUMO

This study examines the adsorption and desorption characteristics of heavy metals in road dust (RD) for the aspect of integrated stormwater management. The chemical fractionations of Cu, Zn, Ni, and Cd were determined by a three-step sequential extraction protocol. Pseudo-first-order and Pseudo-second-order kinetic models, along with Langmuir, Freundlich, and Temkin isotherms were adopted to simulate the batch experimental data. The proportional shift of metals' chemical fractionations in original RD, adsorption equilibrium, and desorption equilibrium were determined. Results show that RD has a remarkable affinity to adsorb heavy metal within a short time. The adsorption processes were well described by the Pseudo-second-order kinetic model (R2 = 0.98-0.99) and Freundlich isotherm (R2 = 0.89-0.98) for most of the given metals indicating that the chemical adsorption was probably the rate-controlling step and the binding energy for each site was not identical. The maximum adsorption capacities for Cu, Cd, Zn, and Ni were 6300 mg kg-1, 5800 mg kg-1, 4000 mg kg-1, and 3200 mg kg-1, respectively. A linear fit to the equilibrium pH and the total amounts of the adsorbed metals indicates a strong pH-dependent adsorption. According to the proportional shift of metals' chemical fractionations during the adsorption and desorption processes, the exchangeable fractions of heavy metals in RD were irreversible. It suggests that a portion of the surface sites of RD would be not exchangeable once it was occupied.


Assuntos
Poeira/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise , Adsorção , Cinética
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