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1.
Bioresour Technol ; 312: 123564, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32506041

RESUMO

Biochar was prepared by rapid pyrolysis using pine nut shell as raw materials. Then cetyl trimethyl ammonium bromide modified magnetic biochar material (CTAB-MC) was obtained after modifying biochar by FeCl3 and cetyl trimethyl ammonium bromide. The CTAB-MC was characterized by SEM, FTIR, XRD and Magnetic analyses. Adsorptive property of the CTAB-MC for acid chrome blue K (AK) was studied. It was found that adsorption capacity was affected by solution pH, temperature, adsorption time, initial concentration and ionic strength. The CTAB-MC showed higher adsorption ability toward acid chrome blue K, which was up to 40% higher than that of MC. The experimental results showed that adsorption data of AK on the CTAB-MC well conformed to the Langmuir isotherm adsorption model and the pseudo-second order kinetic model. The CTAB-MC can be recycled three times. This work reveals that CTAB-MC is a promising adsorbent with broad application prospects.


Assuntos
Cetrimônio , Poluentes Químicos da Água , Adsorção , Compostos Azo , Brometos , Carvão Vegetal , Cinética , Fenômenos Magnéticos , Naftalenossulfonatos , Nozes , Compostos de Amônio Quaternário
2.
Chemosphere ; 255: 126864, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402869

RESUMO

This work demonstrates the ability of aqueous phase corona discharge to chemically reduce bromate and chlorate ions, common disinfection byproducts, to bromide and chloride ions, respectively. A high voltage pulse was applied to a needle electrode, submerged in the target solution, to generate highly reactive oxidative and reductive species in a temperature-controlled reactor. Optimal water matrix conditions were sought through changing the solution pH, temperature, and dissolved oxygen concentration. Additionally, several oxidative species scavengers were investigated, including methanol, ethanol, sucrose, and D-sorbitol. Chemical reduction rates were improved at low pH (3.5). The presence of dissolved oxygen significantly reduced the chemical reduction rate, and thus high solution temperature (50 °C) also achieved better chemical reduction. All oxidative species scavengers improved the chemical reduction rate; however, methanol and ethanol were superior as these compounds generate hydrogen bubbles in the presence of plasma, which deoxygenates the solution further improving the chemical reduction rate. The application of this technology to 30 µM bromate and chlorate solutions, under optimal water matrix conditions and with the addition of 72 g/L-COD methanol, achieved greater than 95% removal of the target compounds within 60 min. Increasing the initial concentration of the target compounds to 300 µM required 90 and 150 min to achieve similar chemical reductions for bromate and chlorate, respectively.


Assuntos
Bromatos/química , Cloratos/química , Poluentes Químicos da Água/química , Brometos/química , Cloretos , Cloro , Desinfecção , Hidrogênio , Concentração de Íons de Hidrogênio , Metanol , Oxirredução , Temperatura , Água/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
3.
Chemosphere ; 251: 126452, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443227

RESUMO

Microplastics (MPs) are prevalent global pollutants that are being detected in aquatic ecosystems and drinking water sources around the world. In addition to plastic polymers, MPs contain various chemical substances (known as "additives") that can leach and risk water quality. In this paper, we investigated for the first time the potential release of disinfection byproducts (DBPs) precursors when MPs are exposed to hydrolysis and/or degradation by simulated sunlight. Seventeen MPs with seven different polymer types were collected either as commercial products (e.g. drinking water bottles, shopping bags, recycled plastics, etc.) or pure/virgin polymers. Results showed high release of dissolved organic carbon (DOC) from five MP samples and a significant increase in bromide concentrations from four MPs. DBPs formation potential (DBPFP) experiments with MPs' leachates showed higher concentrations of chlorinated trihalomethanes (THMs), haloacetonitriles (HANs), and total organic halogens (TOX) in three samples, while a significant shift to brominated DBPs was observed in samples containing bromide. Extending the leaching experiments to four consecutive cycles showed that the leaching of DOC and DBPs' precursor significantly decreased after the second leaching cycle. Further analysis revealed that the reactivity of the leached DOC - indicated by THMFP yields - was comparable to those of several raw waters that supply drinking water treatment plants. The leached THMs and TOX from MPs that were exposed to UVA irradiation were in general higher than MPs that were run under dark conditions.


Assuntos
Monitoramento Ambiental , Microplásticos/análise , Poluentes Químicos da Água/análise , Brometos/análise , Desinfetantes/química , Desinfecção , Água Potável/análise , Ecossistema , Halogenação , Halogênios/análise , Plásticos , Trialometanos/análise , Qualidade da Água
4.
Chemosphere ; 252: 126596, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32240859

RESUMO

Minimizing bromate formation by adding H2O2 is one major option for bromide-containing source water when applying ozone in drinking water. However, difference in background water quality can have a significant influence on bromate depression. In this study, three bromide-bearing source waters (YZ, HR and HP) were selected to investigate bromate depression during the H2O2-ozonation process. The results showed that there was strong correlation between bromate formation and molecular ozone consumption during ozonation process for the three waters. Compared to YZ and HR, ozone was consumed quickly within about 10 min for HP water, inducing lower bromate formation during ozonation process. In the initial step of bromide oxidation, molecular ozone oxidation was responsible for more than 80% of oxidation, much higher than that by hydroxyl radicals. Specifically, 94% of the oxidation of bromide occurred with ozone for YZ water, which might be attributed to the low concentration of organic matter in the water. The residual molecular ozone would be a restrictive factor and affect the bromate formation significantly. For YZ and HP water, as H2O2/O3 (g/g) increased to 0.5, the ozone decomposition rate increased 61 times and 7.2 times respectively, which resulted in difference in bromate depression performance when applying H2O2. Humic acid and tyrosine in water were confirmed to have effects on bromate formation and depression after H2O2 addition. This study could elucidate the different bromate depression effects occurring in different source waters when adding H2O2, which will provide an informative guide for bromate control in drinking water treatment.


Assuntos
Bromatos/química , Peróxido de Hidrogênio/química , Ozônio/química , Poluentes Químicos da Água/química , Animais , Brometos , Transtorno Depressivo , Substâncias Húmicas , Radical Hidroxila , Oxirredução , Tardígrados , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Qualidade da Água
5.
Water Res ; 176: 115725, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32222545

RESUMO

Sulfate radical-based advanced oxidation processes (SR-AOPs) show a good prospect for effective elimination of organic contaminants in water due to the powerful oxidation capability and good adaptability of sulfate radical (SO4•-). However, great concerns have been raised on occurrence of the carcinogenic byproduct bromate (BrO3-) in SR-AOPs. The present article aims to provide a critical review on BrO3- formation during bromine (Br)-containing water oxidation by various SR-AOPs. Potential reaction mechanisms are elaborated, mainly involving the sequential oxidation of bromide (Br-) by SO4•- to Br-containing radicals (e.g., bromine atom (Br•)) and then to hypobromous acid/hypobromite (HOBr/OBr-), which acts as the requisite intermediate for BrO3- formation. Some key influencing factors on BrO3- formation are discussed. Particularly, dissolved organic matter (DOM) as a component ubiquitously present in aquatic environments shows a significant suppression effect on BrO3- formation, primarily attributed to the reduction of Br• by DOM to Br-. The reaction of Br• with DOM can hardly produce organic brominated byproducts, while their formation is mainly due to the bromination of HOBr/OBr- generated through nonradical pathways such as the direct reaction of Br- with oxidants (e.g., peroxymonosulfate (PMS)) or other reactive species derived from catalytic activators (e.g., Co(III) in the Co(II)/PMS process). The debromination of brominated pollutants during their oxidation by SO4•- results in the release of Br-, which, however, is not further transformed to BrO3- until coexisting organic matters are mineralized nearly completely. Furthermore, possible strategies for control of BrO3- formation in SR-AOPs as well as the future research needs are proposed.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Bromatos , Brometos , Oxirredução , Sulfatos
6.
PLoS One ; 15(3): e0230540, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32182285

RESUMO

Halide vacancies and associated metallic lead (Pb°) observed at the surface and deep inside macroscopic organolead trihalide perovskite crystals is removed through a facile and noninvasive treatment. Indeed, Br2 vapor is shown to passivate Br-vacancies and associated Pb° in the bulk of macroscopic crystals. Controlling the exposure time can markedly improve the overall stoichiometry for moderate exposures or introduce excessive bromide for long exposures, resulting in p-doping of the crystals. In the low dose passivation regime, Hall effect measurements reveal a ca. 3-fold increase in carrier mobility to ca. 15 cm2V-1s-1, while the p-doping increases the electrical conductivity ca. 10000-fold, including a 50-fold increase in carrier mobility to ca. 150 cm2V-1s-1. The ease of diffusion of Br2 vapor into macroscopic crystals is ascribed to the porosity allowed in rapidly grown crystals through aggregative processes of the colloidal sol during growth of films and macroscopic crystals. This process is believed to form significant growth defects, including open voids, which may be remnants of the escaping solvent at the solidification front. These results suggest that due to the sol-gel-like nature of the growth process, macroscopic perovskite crystals reported in this study are far from perfect and point to possible pathways to improving the optoelectronic properties of these materials. Nevertheless, the ability of the vapor-phase approach to access and tune the bulk chemistry and properties of nominally macroscopic perovskite crystals provides interesting new opportunities to precisely manipulate and functionalize the bulk properties of hybrid perovskite crystals in a noninvasive manner.


Assuntos
Compostos de Cálcio/química , Óxidos/química , Titânio/química , Brometos/química , Doping nos Esportes , Compostos Heterocíclicos/química , Humanos
7.
Chemosphere ; 248: 125940, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006828

RESUMO

This study examined the potential of six aliphatic and aromatic amides, commonly found in natural waters or used as chemical aids in water treatment, to act as organic precursors for nine haloacetamides (HAcAms), five haloacetonitriles (HANs), regulated trihalomethanes (THMs) and haloacetic acids (HAAs) upon chlorination and chloramination. The impact of key experimental conditions, representative of drinking water, including pH (7 & 8), retention time (4 & 24 h) and bromide levels (0 & 100 µg/L), on the generation of the target DBPs was investigated. The highest aggregate DBP yields upon chlor(am)ination were reported for the aromatic and hydrophobic hydroxybenzamide; 2.7% ± 0.1% M/M (chlorination) and 1.7% M/M (chloramination). Increased reactivity was observed in aliphatic and hydrophilic compounds, acrylamide (2.5 ± 0.2% M/M) and acetamide (1.3 ± 0.2% M/M), in chlorination and chloramination, respectively. The addition of bromide increased average DBP yields by 50-70%. Relative to chlorination, the application of chloramines reduced DBP formation by 66.5% (without Br-) and by 46.4% (with Br-). However, bromine incorporation in HAAs and HAcAms was enhanced following chloramination, of concern due to the higher toxicological potency of brominated compounds.


Assuntos
Desinfetantes/análise , Poluentes Químicos da Água/análise , Acetamidas , Amidas , Brometos/química , Bromo , Cloraminas/química , Cloro/química , Desinfetantes/química , Desinfecção , Halogenação , Trialometanos/química , Purificação da Água
8.
Ecotoxicol Environ Saf ; 190: 110137, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31901815

RESUMO

Ionic liquids (ILs) are acknowledged as green chemicals and favorable substitutes for volatile organic solvents, which are currently used. However, previous studies have shown that these compounds had toxicological impacts on aquatic organisms. To investigate the effects of 1-hexyl-3- methylimidazolium bromide ionic liquid ([C6mim]Br) on embryonic development and reproduction in water flea (Daphnia magna), a series of exposure experiments were conducted, including acute toxicity, maternal exposure, and chronic exposure tests. In acute toxicity experiment, D. magna neonates exhibited developmental abnormalities in the shell spine and the second antennae in a concentration-dependent manner after exposure to [C6mim]Br. The results in maternal exposure test also revealed a certain embryo-toxicity in response to [C6mim]Br in D. magna. However, the toxicity was lower than that conveyed by direct acute exposure, this indicated that the IL could act directly on organism. During the 21 days chronic exposure, the 1.6 mg/L exposure caused marked drop in the survival, molts and the number of the first brood of D. magna. Meanwhile, the total number of offspring was significantly declined in 1.6 mg/L concentration treatment groups, whereas increased in 0.2 mg/L groups. Generally, abnormalities in the offspring were significantly increased across all of the treatment groups in contrast to the control. No effect on sex differentiation was found during the experiments. These findings suggested that [C6mim]Br could affect embryonic development and reproduction in D. magna, and provided references for further study on the mechanisms underlying toxicological effects of ILs and the assessment of their potential environmental risks.


Assuntos
Boratos/toxicidade , Daphnia/fisiologia , Imidazóis/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Organismos Aquáticos , Brometos/farmacologia , Daphnia/efeitos dos fármacos , Daphnia/embriologia , Embrião não Mamífero/efeitos dos fármacos , Desenvolvimento Embrionário , Feminino , Humanos , Líquidos Iônicos/toxicidade , Muda , Reprodução/efeitos dos fármacos , Solventes
9.
Environ Sci Technol ; 54(3): 1668-1676, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31935071

RESUMO

The freezing-induced acceleration of bromate reduction by humic substances (HS) contributes to HS bromination and the formation of organobromine compounds (OBCs). Herein, we report the enhanced reduction of bromate by dissolved organic matter and the formation of large amounts of OBCs in freezing solutions. After 48 h of freezing process, 78.1-100% of bromate was reduced by DOM at different initial concentrations of bromate and DOM in acidic solutions (pH 3 and 4). Bromide was one of the main reduction products, and it accounted for 30.9-47.8% of the total bromine content. Except for bromide, a large amount of OBCs formed by brominating DOM with reactive bromine species, like hypobromite, were detected. The conversion of bromate to OBCs, calculated as the total organobromine content to the initial bromate content, ranged from 28.2 to 52.5% and was mainly dependent on the bromate/DOM content. About 110-603 species of OBCs were detected by Fourier transform ion cyclotron resonance mass spectrometry, and they were primarily highly unsaturated and phenolic compounds. By analyzing the spectral variation before and after the freezing process, we found the disappearance of 900 compounds containing only C, H, and O with a low carbon oxidation state that was regarded as the main reductant of bromate. Our findings call for further investigation of the processes and the effects of bromate formation in aqueous environments.


Assuntos
Bromatos , Substâncias Húmicas , Brometos , Congelamento , Halogenação
10.
J Environ Sci (China) ; 89: 90-101, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31892405

RESUMO

This study investigated the speciation of halogen-specific total organic halogen and disinfection byproducts (DBPs) upon chlorination of natural organic matter (NOM) in the presence of iopamidol and bromide (Br-). Experiments were conducted with low bromide source waters with different NOM characteristics from Northeast Ohio, USA and varied spiked levels of bromide (2-30 µmol/L) and iopamidol (1-5 µmol/L). Iopamidol was found to be a direct precursor to trihalomethane (THM) and haloacetic acid formation, and in the presence of Br- favored brominated analogs. The concentration and speciation of DBPs formed were impacted by iopamidol and bromide concentrations, as well as the presence of NOM. As iopamidol increased the concentration of iodinated DBPs (iodo-DBPs) and THMs increased. However, as Br- concentrations increased, the concentrations of non-brominated iodo- and chloro-DBPs decreased while brominated-DBPs increased. Regardless of the concentration of either iopamidol or bromide, bromochloroiodomethane (CHBrClI) was the most predominant iodo-DBP formed except at the lowest bromide concentration studied. At relevant concentrations of iopamidol (1 µmol/L) and bromide (2 µmol/L), significant quantities of highly toxic iodinated and brominated DBPs were formed. However, the rapid oxidation and incorporation of bromide appear to inhibit iodo-DBP formation under conditions relevant to drinking water treatment.


Assuntos
Brometos/análise , Desinfetantes , Iopamidol/análise , Poluentes Químicos da Água , Purificação da Água , Desinfecção , Halogenação , Halogênios , Trialometanos
11.
J Biochem Mol Toxicol ; 34(1): e22419, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31702098

RESUMO

Ionic liquids (ILs) as green alternatives for volatile organic solvents are increasingly used in commercial applications. It is necessary to explore the cytotoxic mechanism of ILs to reduce the risk to human health. For this purpose, cell viability, apoptosis, cytochrome P450 3A4 (CYP3A4), glucose transporter type 2 (GLUT2), and microRNA-122 (miR-122) gene expression in HepG2 cells was evaluated after IL exposure. The results showed that ILs reduced the viability of HepG2 cells through apoptotic cell death. Moreover, ILs markedly upregulated the transcription and protein levels of CYP3A4, but did not affect the expression of GLUT2 in either messenger RNA level or protein level. Finally, ILs increased the expression of miR-122 and inhibition of miR-122 with miR-122 inhibitor blocked ILs-induced apoptosis in HepG2 cells. This finding may contribute to an increased understanding of the in vitro molecular toxicity mechanism of ILs to further understand IL-related human health risks.


Assuntos
Apoptose/efeitos dos fármacos , Brometos/farmacologia , Citocromo P-450 CYP3A/metabolismo , Imidazóis/farmacologia , MicroRNAs/metabolismo , Transportador de Glucose Tipo 2/metabolismo , Células Hep G2 , Humanos
12.
Chemistry ; 26(5): 1042-1051, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31614042

RESUMO

Following the recent discovery that traditional silver(I) oxide-promoted glycosidations of glycosyl bromides (Koenigs-Knorr reaction) can be greatly accelerated in the presence of catalytic TMSOTf, reported herein is a dedicated study of all major aspects of this reaction. A thorough investigation of numerous silver salts and careful refinement of the reaction conditions led to an improved mechanistic understanding. This, in turn, led to a significant reduction in the amount of silver salt required for these glycosylations. The progress of this reaction can be monitored by naked eye, and the completion of the reaction can be judged by the disappearance of characteristic dark color of Ag2 O. Further evidence on higher reactivity of benzoylated α-bromides in comparison to that of their benzylated counterparts has been acquired.


Assuntos
Ácidos/química , Glicosídeos/química , Brometos/química , Catálise , Glicosilação , Óxidos/química , Compostos de Prata/química
13.
Water Res ; 170: 115323, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31790888

RESUMO

In this work, we investigated the effect of bromide ion (Br-) on NDMA formation using model precursor compounds, wastewater effluents and surface waters. Previous studies showed that Br- reacts with chloramines and forms bromochloramine, a reactive compound responsible for NDMA formation enhancement. Some limitations of those studies were the highest Br- concentrations used, and the limited number of precursors considered. Here, we observed enhancement of NDMA formation from most of the model precursor compounds within the Br- range (0-1000 µg/L) but this effect was suppressed in the presence of NOM. Also, NDMA formation was favored at pH 8 in the presence of Br- compared to pH 6. Nevertheless, Br- suppressed NDMA formation in wastewater effluent samples at low monochloramine doses while no effects were observed in surface waters.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Brometos , Cloraminas , Dimetilnitrosamina , Águas Residuárias
14.
Lett Appl Microbiol ; 70(3): 159-164, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31755565

RESUMO

Conventionally, animal hide and skin necessitates 95% saturated brine solution (SBS) for its preservation. This salt is primarily derived from different sources including solar-saltern, evaporation ponds, etc., which are laden with different types of halophilic micro-organisms. Previous studies confirmed that the presence of moderately halophilic bacteria caused red heat on cured hide, which adversely affects the leather quality and causes substantial economic losses for leather industries. Thus, this investigation was carried out to examine the effects of different concentrations of alkyltrimethylammonium bromide (ATMB) on selected halophilic-bacteria attributed to the deterioration of hide quality. In nutrient broth solution (NBS), ATMB at 250 and 500 ppm reduced individual halo-bacteria, that is, Halomonas halodenitrificans, Halomonas eurihalina, Alkalibacillus haloalkaliphilus and Salimicrobium album, by averages of 0·64 and 1·90, 1·5 and 2·61, 0·90 and 2·27, 1·65 and 3·36 log CFU per ml respectively in 5 min. ATMB treatment in SBS at 500 ppm for 18 h resulted in a reduction of H. halodenitrificans, H. eurihalina, A. haloalkaliphilus and S. album by averages of 1·9, 1·25, 0·96 and 1·34 log CFU per ml respectively, when compared with the controls. Likewise, 5000 ppm ATMB reduced the cocktail population nearly to zero from that cultivated in SBS for 18 h. SIGNIFICANCE AND IMPACT OF THE STUDY: In this investigation, the inhibition of different halophilic bacteria that causes red heat in salt-preserved hides is described for the first time. The antimicrobial susceptibility test executed via solution procedures for selected halophilic bacterial strains (i.e. resistant to the salt environment) revealed significant efficacy of alkyltrimethylammonium bromide (ATMB). The current study suggests that, chemical compound like ATMB could be utilized to prevent red heat-related damage on salt-cured hides caused by halophilic bacteria, which is a persisting concern of the leather industry.


Assuntos
Bacillaceae/efeitos dos fármacos , Halomonas/efeitos dos fármacos , Soluções para Preservação de Órgãos/farmacologia , Preservação de Órgãos/métodos , Compostos de Amônio Quaternário/farmacologia , Pele/microbiologia , Animais , Brometos/farmacologia , Descontaminação/métodos , Testes de Sensibilidade Microbiana , Sais/farmacologia , Cloreto de Sódio/farmacologia
15.
Sci Total Environ ; 705: 135639, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-31841919

RESUMO

Control of antibiotic-resistant bacteria (ARB) and their related genes in secondary effluents has become a serious issue because of increased awareness of their health risks. A considerable number of techniques have been developed in recent years, particularly in relation to advanced oxidation. However, limited information is known about cellular behavior and resistance characteristic change during photocatalytic treatment. In this study, the inactivation of tetracycline (TC)-resistant Escherichia coli (TC-E. coli), removal of TC-resistant genes (TC-RGs), and antibiotic susceptibility were evaluated by employing photocatalytic treatment using Ag/AgBr/g-C3N4 with visible light irradiation. The effects of light intensity, photocatalyst dosage, and reaction ambient temperature on photocatalysis were modelled and investigated. The rate of TC-E. coli removal was also optimized. Results demonstrated that the optimal conditions for TC-E. coli removal included light intensity of 96.0 mW/cm2, photocatalyst dosage of 211.0 mg/L, and reaction ambient temperature of 23.7 °C. Under such conditions, the ARB removal rate was 6.1 log after 90 min and the related TC-RG removal rates were 49%, 86%, 69%, and 86% for tetA, tetM, tetQ, and intl1, respectively. The minimum inhibitory concentration test after photocatalysis shows that the antibiotic resistance of TC-E. coli was enhanced, which may be mainly due to the changes in the membrane potential and resulted in difficulty in destroying the bacteria through antibiotic contact. Hence, photocatalytic treatment could be an ideal method for ARB and antibiotic-resistant gene (ARG) control in wastewater, but the health risks of the remaining ARB and ARG should be investigated further.


Assuntos
Escherichia coli , Antibacterianos , Brometos , Catálise , Prata , Compostos de Prata , Tetraciclina
16.
Environ Sci Technol ; 54(2): 726-734, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31846301

RESUMO

Increases in source water bromide concentrations are challenging for drinking water utilities since bromide contributes to the formation of disinfection byproducts (DBPs) that have negative human-health effects. The present work evaluates the role of coal-fired power plant wet flue gas desulfurization (FGD)-associated bromide loads on in-stream bromide concentrations in the Monongahela River Basin in the water year (WY) 1998 (during a nationwide study) and over a five-year period from WYs 2013 through 2017. Under mean flow conditions in the lower Monongahela River for the WYs of interest, the median-estimated wet FGD bromide discharges are modeled to represent a significant fraction (27-57%) of observed bromide concentrations with the range representing the change in load conditions across WYs. Seasonal effects are predicted due to changes in the dilution capacity of the river with elevated concentrations under lower flows in the third and fourth quarters (July through December). The effect of these bromide concentration contributions, which range from 6.8 to 23 µg/L under median load estimates and median flow conditions, on trihalomethane (THM) formation and associated risk were assessed. A simple model was applied to demonstrate an analytical approach for evaluating the power plant total THM (TTHM) and risk contributions. Utilizing this model, the power plant TTHM contribution was estimated to range from 7.6 to 27 µg/L with a median risk contribution of 0.0014.


Assuntos
Rios , Trialometanos , Brometos , Carvão Mineral , Humanos , Centrais Elétricas
17.
Chemosphere ; 239: 124800, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526993

RESUMO

Biological degradation of high strength phenol and its derivatives in groundwater is problematic because these compounds are toxic to human and microbes. To evaluate the feasibility of in situ bioremediation using sequential aerobic respiration and heterotrophic denitrification, a field single-well-drift test (SWDT) was conducted in groundwater contaminated with coal tar distillates. To stimulate indigenous phenol degrading microorganisms, a 1400 L of oxygen-saturated test solution containing bromide (3.96 ±â€¯0.179 mmol-Br/L) and nitrate (5.34 ±â€¯0.187 mmol NO3--N/L) was injected into an aquifer. After injection of the test solution, significant consumption of dissolved oxygen (DO) was immediately observed; then, degradation of the methyl derivatives o-cresol and m,p-cresol was observed with average zero-order rate coefficients of 0.047 mmol/L/d and 0.23 mmol/L/d, respectively. After 73% of the injected DO was consumed, significant NO3- consumption was observed along with degradation of phenol and the dimethyl derivatives 2,4-xylenol and 3,5-xylenol, which had average zero-order rate coefficients of 0.17 mmol/L/d, 0.060 mmol/L/d, and 0.018 mmol/L/d, respectively. The production of CO2, NO2-, and N2O along with significant consumption of DO and NO3- suggest that phenolic compounds were biologically degraded by sequential aerobic respiration and heterotrophic denitrification. The results of 16s RNA analysis revealed that, after injection of the test solution, a bacterium that shared a 99% 16s rRNA sequence similarity with an uncultured bacterium revealed to be Pseudomonas stutzeri, a facultative heterotrophic denitrifier, was found in the aquifer. Thus, these results suggest that simultaneous injection of DO and NO3- is an appropriate in situ bioremediation strategy for degrading mixtures of high-strength phenolic compounds in an aquifer.


Assuntos
Água Subterrânea/microbiologia , Fenóis/metabolismo , Poluentes Químicos da Água/metabolismo , Aerobiose , Biodegradação Ambiental , Brometos/metabolismo , Cresóis/química , Cresóis/metabolismo , Desnitrificação , Estudos de Viabilidade , Água Subterrânea/química , Processos Heterotróficos , Humanos , Nitratos/metabolismo , Nitrogênio/metabolismo , Fenóis/química , Pseudomonas stutzeri/genética , Pseudomonas stutzeri/metabolismo , RNA Ribossômico 16S/metabolismo , República da Coreia , Poluentes Químicos da Água/química , Xilenos/química , Xilenos/metabolismo
18.
Chemosphere ; 240: 124919, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726585

RESUMO

Ionic liquids (ILs) are regarded as green solvents and are frequently used in the chemical industry. However, ILs may impact plant growth if they are present in the soil environment. To compare toxicity of ILs with different anions in soil, three imidazolium-based ionic liquids (1-hexyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium nitrate, 1-hexyl-3-methylimidazolium tetrafluoroborate) were used to assess impact on Vicia faba. Following 10 d of exposure to these three ILs from 0 to 2500 mg kg-1, shoot length, root length and dry weight of Vicia faba were determined. Pot trials revealed that ILs inhibited Vicia faba growth and according to EC50 values, [C6mim]BF4 was the most toxic one. In addition, physiological indicators of Vicia faba were determined following 10 d of exposure at selected IL concentrations (0, 1, 10, 100 and 500 mg kg-1). ILs led to the generation of reactive oxygen species and then caused oxidative damage, including lipid peroxidation, protein damage and DNA damage, which triggered an increase in antioxidant content and enzyme activity. The experimental results indicated that oxidative stress may be the primary underlying toxic mechanism for Vicia faba. Furthermore, based on the data of physiological experiment, integrated biomarker response (IBR) was calculated to compare the toxicity of the three ILs and toxic order was: [C6mim]NO3<[C6mim]Br<[C6mim]BF4.


Assuntos
Líquidos Iônicos/toxicidade , Vicia faba/efeitos dos fármacos , Ânions/química , Antioxidantes/metabolismo , Biomarcadores/metabolismo , Boratos/toxicidade , Brometos , Dano ao DNA , Imidazóis/toxicidade , Peroxidação de Lipídeos , Nitratos/metabolismo , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Plântula/metabolismo , Solo/química , Poluentes do Solo/metabolismo , Solventes/metabolismo , Testes de Toxicidade , Vicia faba/crescimento & desenvolvimento
19.
J Environ Manage ; 253: 109731, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31665690

RESUMO

This study proposes the use of new materials based on core-shell structure magnetic microparticles with Ag0 (Ag(0)-MPs) on their surface to remove bromides and chlorides from waters intended for human consumption. Hydrogen peroxide was used as oxidizing agent, Ag(0)-MPs is thereby oxidized to Ag (I)-MPs, which, when in contact with Cl- and Br- ions, form the corresponding silver halide (AgCl and AgBr) on the surface of Ag-MPs. The concentration of Cl- and Br- ions was followed by using ion selective electrodes (ISEs). Silver microparticles were characterized by high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy, while the presence of AgCl and AgBr on Ag-MPs was determined by microanalysis. We analyzed the influence of operational variables, including: hydrogen peroxide concentration in Ag-MP system, medium pH, influence of Cl- ions on Br- ion removal, and influence of tannic acid as surrogate of organic matter in the medium. Regarding the influence of pH, Br-and Cl- removal was constant within the pH range studied (3.5-7), being more effective for Br- than for Cl- ions. Accordingly, this research states that the system Ag-MPs/H2O2 can remove up to 67.01% of Br- ions and 56.92% of Cl- ions from water (pH = 7, [Ag-MPs]0 = 100 mg L-1, [H2O2]0 = 0.2 mM); it is reusable, regenerated by radiation and can be easily removed by applying a magnetically assisted chemical separation process.


Assuntos
Iodetos , Prata , Brometos , Cloretos , Peróxido de Hidrogênio
20.
Chemosphere ; 240: 124804, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31541900

RESUMO

Chemical oxygen demand (COD) is one of the most important water quality parameters that quantifies the amount of oxygen needed to oxidize oxidizable pollutants (mainly organics) in water samples. However, erroneous COD results were commonly observed for bromide-rich industrial wastewater samples using standard COD test. Bromide in water sample is known to seriously interfere with COD test. However, there is no satisfactory approach to effectively eliminate bromide interference thus far. In this study, two strategies, namely masking and correction, were investigated for their effectiveness to suppress bromide interference. For the masking strategy, silver ion was assessed for its effectiveness to neutralize bromide in water samples through precipitation and complex formation reactions. Silver ion offered only partial masking effect on bromide, while the residue bromide can still cause significant interference on COD determination. For the correction strategy, an equivalent redox reaction reflecting bromide interference mechanism was proposed, and a theoretical correction factor of 0.1 g COD/g Br- was found based on stoichiometry. The effectiveness of the proposed correction factor for bromide interference under different wastewater pollutant matrix was evaluated using different types of wastewater samples (synthetic wastewater, domestic wastewater and bromide-rich industrial wastewater) with varying amounts of bromide (from 0 to 2000 mg L-1) added to the samples. The findings showed that with bromide concentration up to 600 mg L-1, the correction factor of 0.1 g COD/g Br- was applicable to all the tested wastewater samples, suggesting that this correction strategy could be practically used to eliminate bromide interference in standard COD test.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Análise da Demanda Biológica de Oxigênio , Brometos , Monitoramento Ambiental , Resíduos Industriais , Indústrias , Oxigênio/química , Águas Residuárias/análise , Qualidade da Água
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