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1.
Sci Total Environ ; 803: 149783, 2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-34482132

RESUMO

Understanding the hydro-biogeochemical conditions that impact the mobility of uranium (U) in natural or artificial wetlands is essential for the management of contaminated environments. Field-based research indicates that high organic matter content and saturation of the soil from the water table create favorable conditions for U accumulation. Despite the installation of artificial wetlands for U remediation, the processes that can release U from wetland soils to underlying aquifers are poorly understood. Here we used a large soil core from a montane wetland in a 6 year lysimeter experiment to study the stability of U accumulated to levels of up to 6000 ppm. Amendments with electron acceptors showed that the wetland soil can reduce sulfate and Fe(III) in large amounts without significant release of U into the soil pore water. However, amendment with carbonate (5 mM, pH 7.5) resulted in a large discharge of U. After a six-month period of imposed drought, the re-flooding of the core led to the release of negligible amounts of U into the pore water. This long-term experiment demonstrates that U is strongly bound to organic matter and that its stability is only challenged by carbonate complexation.


Assuntos
Urânio , Carbonatos , Elétrons , Compostos Férricos , Solo , Urânio/análise , Áreas Alagadas
2.
J Colloid Interface Sci ; 607(Pt 1): 125-133, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34500413

RESUMO

HYPOTHESIS: A large number of papers discuss merits and mechanisms of low salinity waterflooding. For each mechanism proposed, there are counter examples to invalidate the stated mechanism. The effect of wettability from low salinity water, which is predominantly stated in literature as the dominant mechanism, may not be valid. We introduce a direct correlation between oil-brine interfacial viscoelasticity and oil recovery from waterflooding. EXPERIMENTS: The oil recovery is investigated in carbonate rocks for three light crude oils, by injection of a wide range of aqueous phases, ranging from deionized water to very high salinity brine of 28 wt%, and low concentration of a non-ionic surfactant at 100 ppm. The oil-brine interfacial viscoelasticity is quantified and supplementary measurements of interfacial tension and wettability are performed. FINDINGS: In our experiments, oil recovery is higher from high salinity water injection than from low salinity water injection. A strong relationship is observed between interface elasticity and oil recovery for different concentrations of salt in the injected brine as well as for ultra-low concentration surfactant. An elastic oil-brine interface results in high oil recovery. The surfactant molecule we have selected prefers the oil-water interface despite high solubility in the oil phase and makes ultra-low concentration of 100 ppm in injection water very effective. Contrary to widespread assertions in the literature, we find no definitive correlation between oil recovery and wettability.


Assuntos
Salinidade , Tensoativos , Carbonatos , Tensão Superficial , Viscosidade
3.
Sci Total Environ ; 803: 150135, 2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-34525728

RESUMO

Carbonation treatment (CT) by alkaline fly ash (FA) affects the stability of potentially toxic elements (PTEs). This study investigated the leachability and environmental risk of six PTEs contained in FA during natural and accelerated carbonation (NC, AC) using two typical leaching scenarios with distilled water (DW) and acetic acid (AA). The leaching of Pb/Cu/Cr/Ni in solidified/stabilized FA decreased due to CT in DW leaching, but the leaching of Pb/Zn/Cu/Cd increased due to CT in AA leaching. The leaching of the six PTEs (especially Pb/Cd) in AA leaching was significantly higher than that in DW leaching. CT was a promoting factor to increase the environmental risk level of PTEs in FA leachate, especially in AA leaching with H+ input. In the early stage of NC, under DW leaching tests, the environmental risk level of PTEs in FA leachate can be weakened due to the formation of carbonate minerals in the FA matrix. However, excessive NC increases the environmental risk of leached PTEs due to the decalcification of carbonate minerals. Both NC and AC increased the potential environmental risk of PTEs contained in the carbonated FA matrix. The nucleation and dissolution of carbonate minerals were interdependent with the immobilization and leaching of PTEs, which played a dominant role in the CT and leaching tests respectively. They jointly affected the occurrence behavior of PTEs in the FA matrix in CT tests and the leachability of PTEs in leaching tests. This study demonstrates that it is more scientific to evaluate the leachability of PTEs in carbonated FA according to the actual disposal scenarios.


Assuntos
Metais Pesados , Eliminação de Resíduos , Carbono , Carbonatos , Cinza de Carvão , Incineração , Metais Pesados/análise , Material Particulado , Resíduos Sólidos/análise
4.
Sci Total Environ ; 806(Pt 1): 150435, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34583070

RESUMO

Human activities have led to an increase in land use change, with effects on the structure and functioning of ecosystems. The impact of contrasting land uses along river basins on the concentration of colored dissolved organic matter (CDOM) reaching the coastal zone, and its relationship with the carbonate system of the adjacent coastal ocean, is poorly known. To understand the relationship between land use change, CDOM and its influence on the carbonate system, two watersheds with contrasting land uses in southern Chile were studied. The samples were collected at eight stations between river and adjacent coastal areas, during three sampling campaigns in the austral summer and spring. Chemical and biological samples were analyzed in the laboratory according to standard protocols. Landsat 8 satellite images of the study area were used for identification and supervised classification using remote sensing tools. The Yaldad River basin showed 82% of native forest and the Colu River basin around 38% of grassland (agriculture). Low total alkalinity (AT) and Dissolved Inorganic Carbon (DIC), but high CDOM proportions were typically observed in freshwater. A higher CDOM and humic-like compounds concentration was observed along the river-coastal ocean continuum in the Yaldad basin, characterized by a predominance of native forests. In contrast, nutrient concentrations, AT and DIC, were higher in the Colu area. Low CaCO3 saturation state (ΩAr < 2) and even undersaturation conditions were observed at the coastal ocean at Yaldad. A strong negative correlation between AT, DIC and ΩAr with CDOM/fDOM, suggested the influence of terrestrial material on the seawater carbon chemistry. Our results provide robust evidence that land uses in river basins can influence CDOM/fDOM proportion and its influence on the carbonate chemistry of the adjacent coastal, with potential implications for the shellfish farming activity in this region.


Assuntos
Ecossistema , Rios , Carbonatos , Água Doce , Humanos , Oceanos e Mares
5.
Chemosphere ; 287(Pt 2): 132235, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34826926

RESUMO

Lead (Pb) pollution has become one of the most serious environmental problems in recent decades. However, there are few remediation technologies for insoluble cerussite (PbCO3), which are common in the environment and have high bioavailability. In this study, the immobilisation of Pb(II) released from PbCO3 by Pseudomonas rhodesiae HP-7 isolated from Pb-contaminated soil was studied. The results showed that hydroxyapatite and PbCO3 were dissolved by the organic acids secreted by the HP-7 strain, and then the dissolved Pb2+ and H2PO4- reacted to form low bioavailable Pb5(PO4)3Cl precipitate. XRD and mass conservation calculations showed that 85.7% of PbCO3 was transformed to Pb5(PO4)3Cl when P:Pb was 9:5. Our research showed that the HP-7 strain and hydroxyapatite could reduce the bioavailability of Pb(II) in PbCO3, which could be used for the remediation of Pb-polluted environments.


Assuntos
Chumbo , Poluentes do Solo , Carbonatos , Durapatita , Minerais , Fosfatos , Pseudomonas , Poluentes do Solo/análise
6.
Chemosphere ; 287(Pt 3): 132318, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34826949

RESUMO

Acebutolol (ACE) has been widely used for the treatment of cardiovascular disorders, and its photochemical fate in natural waters is a matter of concern due to its ubiquitous occurrence and its toxicity to aquatic organisms. In this study, the photodegradation of ACE in river water and synthetic waters were investigated under simulated sunlight irradiation. The results demonstrated that ACE photodegradation rate in river water was 3.2 times higher than that in pure water. Then the influences of HCO3-, NO3- and DOM on ACE photolysis were investigated under their concentrations similar with the ones in river water. ACE photodegradation was significantly enhanced in the presence of HCO3- alone, and the scavenging experiments and the electron paramagnetic resonance experiments together proved that HCO3- could be oxidized by triplet-excited state of ACE to generate CO3•-, which subsequently played a key role in ACE degradation. The presence of both NO3- and DOM also increased the ACE photodegradation rates, and •OH and 3DOM* were found to be involved in the degradation. In addition, when DOM was added to a solution with HCO3-, the enhancement effect of HCO3- on ACE photodegradation was weakened due to the scavenging of CO3•- by DOM combined with the light screening effect of DOM.


Assuntos
Radical Hidroxila , Poluentes Químicos da Água , Acebutolol , Carbonatos , Fotólise
7.
Chemosphere ; 287(Pt 1): 132049, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34474390

RESUMO

Novel pre-coagulation-sedimentation integrated with ultraviolet activated sodium percarbonate (SPC) (Fe(III)-UV/SPC) processes are promising methods for ultrafiltration (UF) pretreatment to ensure the safety of rural drinking water and mitigate UF membrane fouling. The process of surface water purification using the integrated coagulation-advanced oxidation processes (AOPs)-UF system relies on the idea that pre-coagulation can remove hydrophobic macromolecular organic compounds, thus facilitating the oxidation of hydrophilic molecules or medium-sized macromolecules to improve the utilization efficiency of free radicals in AOPs. Compared with the UV/SPC process, the removal rates of UV254 and DOC in the Fe(III)-UV/SPC process (Fe(III) = 0.1 mM, SPC = 0.5 mM) were increased from 87.39 % to 41.45 %-93.56 % and 52.51 %, respectively. Furthermore, the dosage of SPC was reduced from 0.75 mM in UV/SPC process to 0.5 mM due to effects of pre-coagulation. The free radical quenching experiment showed that a significant radical sink of reactions with organic contaminants was formed by •OH and CO3•- in the UV/SPC process, rather than a single specific radical. The destruction of the cake layer structure, reduction in contaminant concentration, and appearance of many permeable holes on the membrane surface were the main reasons for the alleviation of UF membrane fouling. Finally, the trans-membrane pressure and reversible membrane resistance decreased from 22.33 kPa to 3.68 × 1011 m-1 to 18.28 kPa and 0.93 × 1011 m-1, respectively. These results provide new insights into the behavior of membrane fouling control and offer technical references for the long-term stable operation of the UF process.


Assuntos
Ultrafiltração , Purificação da Água , Carbonatos , Compostos Férricos , Radicais Livres , Membranas Artificiais
8.
Chemosphere ; 287(Pt 3): 132274, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34562709

RESUMO

Ladle furnace slag (LFS) is a by-product of the steel industry and is difficult to be reused due to its weak cementitious property, low strength, and potential leaching of heavy metals. The emission of carbon dioxide (CO2) is also a concern for the steel industry. Therefore, the aim of this study was to use CO2 to immobilize heavy metals in LFS and enhance its strength. The LFS specimens were carbonated with different initial water contents, CO2 pressures, and carbonation periods. The carbonated LFS were then studied by leaching test, unconfined compressive strength (UCS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX). The results showed that LFS had carbonation reactivity and could sequester CO2 up to 9.6% of its own mass. The carbonation also effectively reduced the leaching of heavy metals from LFS, especially Pb and Zn. The concentrations of leached Pb and Zn of carbonated LFS were significantly reduced from 2760 and 1460 µg/L to 0.11 and 0.56 µg/L, respectively, being one order of magnitude (Pb) or three orders of magnitude (Zn) lower than limits of inert waste and three drinking water regulations. The strength of the carbonated LFS also remarkably increased and was two orders of magnitude higher than that of the uncarbonated LFS. Following the carbonation, calcium carbonate, nesquehonite, and hydromagnesite were produced; these carbonates filled pores and bound LFS particles, which enhanced the strength of LFS.


Assuntos
Dióxido de Carbono , Metais Pesados , Sequestro de Carbono , Carbonatos , Resíduos Industriais/análise , Aço
9.
Sci Total Environ ; 802: 149221, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34464812

RESUMO

Selenium (Se) is an important trace element in the environment, but the interaction of Se with calcite that may control the fate and geochemical behavior of Se is not fully understood. In this study, the molecular-scale mechanism for the uptake of selenite in calcite was investigated by a combination of laboratory experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy, and quantum chemical calculations. Results showed that selenite can be largely distributed to calcite at circumneutral pH. The local structure of Se in calcite obtained from EXAFS analyses, in combination with quantum chemical calculations, demonstrated that selenite can be incorporated into calcite by substituting for the carbonate, and that the geometric incompatibility of selenite could be accommodated by a slight expansion of crystal volume. The findings from this study suggest that calcite could be a potential Se sink, providing an important insight into the understanding of the mobility and geochemical behavior of Se in the subsurface environments particularly in the groundwater system.


Assuntos
Ácido Selenioso , Selênio , Carbonato de Cálcio , Carbonatos , Selenito de Sódio , Espectroscopia por Absorção de Raios X
10.
J Hazard Mater ; 421: 126725, 2022 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-34332478

RESUMO

Pollution emitted from power plants, including a considerable amount of fly ash (FA) and carbon dioxide (CO2), annually increases and is challenging from an environmentally friendly and sustainable point of view. To date, laboratory-scaled approaches cannot efficiently replace the FA-landfilling and mitigate the stress from CO2 emission. Here, a practically operatable fundamental work by combining carbonated FA (C-FA)-immobilizing CO2 in FA-and polypropylene (PP) matrix is reported and reveals abnormal mechanical and thermal features clarified by calculating van der Waals (vdW) interaction from an atomic scale. This is the first study wherein the interaction between instantaneous dipole moment-induced PP and fillers is simulated and examined. The vdW interactions at the (hetero)interfaces are -59.66, -82.30, and -224.39 kJ mol-1 Å-2 for PP, calcium oxide (CaO; before carbonation), and calcium carbonate (CaCO3; after carbonation), respectively, which provides concrete theoretical support for interesting findings such as the independence of tensile strength on filler loadings and "well-grown" interface-induced higher conductivity characteristics of the composites. Therefore, this work can offer practical solutions to mitigate pollution, provide a new perspective on fundamental physical interactions, and guide the development of practical next-generation composite materials.


Assuntos
Cinza de Carvão , Polipropilenos , Carbonato de Cálcio , Dióxido de Carbono , Carbonatos
11.
J Colloid Interface Sci ; 607(Pt 2): 1226-1238, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34571309

RESUMO

Despite the broad range of interest and applications, controls on the electric surface charge and the zeta potential of silica in contact with aqueous solutions saturated with dissolved CO2 at conditions relevant to natural systems, remains unreported. There have been no published zeta potential measurements conducted in such systems at equilibrium, hence the effect of composition, pH, temperature and pressure remains unknown. We describe a novel methodology developed for the streaming potential measurements under these conditions, and report zeta potential values for the first time obtained with Fontainebleau sandstone core sample saturated with carbonated NaCl, Na2SO4, CaCl2 and MgCl2 solutions under equilibrium conditions at pressures up to 10 MPa and temperatures up to 40 °C. The results demonstrate that pH of solutions is the only control on the zeta potential, while temperature, CO2 pressure and salt type affect pH values. We report three empirical relationships that describe the pH dependence of the zeta potential for: i) dead (partial CO2 pressure of 10-3.44 atm) NaCl/Na2SO4, ii) dead CaCl2/MgCl2 solutions, and iii) for all live (fully saturated with dissolved CO2) solutions. The proposed new relationships provide essential insights into interfacial electrochemical properties of silica-water systems at conditions relevant to CO2 geological storage.


Assuntos
Dióxido de Carbono , Água , Carbonatos , Cloreto de Sódio , Temperatura
12.
Anal Chim Acta ; 1186: 339087, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34756248

RESUMO

Lead contamination of drinking water is a concern to all inhabitants of old cities where lead pipes and soldering are still present. Simple on-site electrochemical detection methods are promising technologies that have gained attention recently. However, conventional electrochemical techniques only quantify soluble forms of lead in water without accounting for insoluble particulates. Herein, a simple voltammetric technique for quantification of insoluble lead species is reported. Lead carbonate (PbCO3) was used as a model compound to show the possibility of detecting particulate lead species directly in solution without chemical treatment. Specifically, electrochemical generation of protons was used as an alternative method to dissolve PbCO3 and thus obtain a more realistic assessment of lead contamination. Lead was detected using cathodic stripping square wave voltammetry (CSSWV). After applying a high oxidizing potential to the electrode immersed in a PbCO3 solution with solid PbCO3 particulates, a significant increase in current was observed as compared to that of a saturated PbCO3 solution. The signal was proportional to the amount of added PbCO3, even when the solubility limit was exceeded. Thus, the combination of a local pH change with CSSWV provides a simple, rapid, and reagentless method for an in-situ detection of insoluble lead species.


Assuntos
Técnicas Eletroquímicas , Chumbo , Carbonatos , Eletrodos , Concentração de Íons de Hidrogênio
13.
Artigo em Inglês | MEDLINE | ID: mdl-34682316

RESUMO

Dental fluorosis is an irreversible condition caused by excessive fluoride consumption during tooth formation and is considered a public health problem in several world regions. The objective of this study was to evaluate the capability of micro-Raman spectroscopy to classify teeth of different fluorosis severities, applying principal component analysis and linear discriminant analysis (PCA-LDA), and estimate the model cross-validation accuracy. Forty teeth of different fluorosis severities and a control group were analyzed. Ten spectra were captured from each tooth and a total of 400 micro-Raman spectra were acquired in the wavenumber range of 250 to 1200 cm-1, including the bands corresponding to stretching and bending internal vibrational modes ν1, ν2, ν3, and ν4 (PO43-). From the analysis of the micro-Raman spectra an increase in B-type carbonate ion substitution into the phosphate site of the hydroxyapatite as fluorosis severity increases was identified. The PCA-LDA model showed a sensitivity and specificity higher than 94% and 93% for the different fluorosis severity groups, respectively. The cross-validation accuracy was higher than 90%. Micro-Raman spectroscopy combined with PCA-LDA provides an adequate tool for the diagnosis of fluorosis severity. This is a non-invasive and non-destructive technique with promising applications in clinical and epidemiological fields.


Assuntos
Fluorose Dentária , Análise Espectral Raman , Carbonatos , Análise Discriminante , Fluorose Dentária/diagnóstico , Fluorose Dentária/epidemiologia , Humanos , Fosfatos , Análise de Componente Principal
14.
Huan Jing Ke Xue ; 42(11): 5364-5374, 2021 Nov 08.
Artigo em Chinês | MEDLINE | ID: mdl-34708975

RESUMO

To investigate the impact of megacities on the chemistry of surface waters, monthly sampling and monitoring were conducted in the Chengdu section of the Minjiang and Tuojiang River basin, corresponding to the upper reaches of the Yangtze River since the spring of 2019, including the influent and effluent water samples from 57 sewage treatment plants in Chengdu. All the samples were analyzed for major ions and other water chemistry parameters, and compared with the historical data of the Minjiang and Tuojiang River. The results showed that the Chengdu surface water still presented a natural chemistry with medium-low total dissolved solids(TDS), and calcium bicarbonate chemistry type, which is the natural consequence of the weathering of carbonate rocks in the basin effected by the weathering of silicates and evaporites. The natural water chemistry of the surface waters in Chengdu presented monthly variation, i.e.,the concentration of major ions and TDS was higher in the dry season compared to the wet season, reflecting the variations of point source. Spatially, the concentration of major ions and TDS downstream of the city was higher than those in the upper reaches, and the concentration in the tributary was higher than that in the mainstream, which may reflect urban influence. Further analyses, such as simulation calculations, indicated that urban activities were the major driving factor for the chemistry change in the surface waters in Chengdu, which is evidenced by the significant contribution of the sewage discharge to the elevated Cl- and Na+ and the ratio of hardness/alkalinity>1 from anthropogenic acid gas emissions. A comparison with the water chemistry of the Minjiang and Tuojiang River in the 1960s indicated that, the current Cl-/Na+ ratio has significantly increased, which has been evidenced by a salinization trend. As a megacity nearest to the source of the Yangtze River, the impact of Chengdu on the natural water chemistry of the Yangtze River system and its environmental effects deserves more attention.


Assuntos
Monitoramento Ambiental , Poluentes Químicos da Água , Carbonatos/análise , Rios , Água , Poluentes Químicos da Água/análise
15.
Appl Microbiol Biotechnol ; 105(23): 8663-8674, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34716789

RESUMO

The stacking of steel slag has detrimental effects mainly for the waste of resources and the pollution of environment. In this study, a novel method based on microbially induced calcium precipitation (MICP) was proposed by utilizing a type of microorganism named Bacillus mucilaginosus, which could secrete carbonic anhydrase (CA) through the metabolism process, accelerating the hydration of carbon dioxide (CO2) and thus facilitating the formation of carbonate ions (CO32-). First, comparing the biologically deposited calcium carbonate with the chemically deposited one, it was found that the crystallinity and crystal size of the biological deposition was lower, leading to its cementitious properties. Under the condition of 1 wt. (weight) % dosage, the carbonation degree increased from 66.34 to 86.25% and the compressive strength improved greatly from 7.4 to 11.2 MPa as well. The weight gain rate of biologically carbonated specimens was also twice as much as the directly carbonated ones. This work strongly demonstrated that biological carbonation technology could not only improve the CO2 sequestration potential of steel slag but also enhance the mechanical properties and durability of steel slag products. KEY POINTS: • Bacillus mucilaginosus could resuscitate and proliferate in the steel slag environment. • B. mucilaginosus secreted carbon anhydrase, which could accelerate the hydration of CO2 and facilitate the precipitation of calcium carbonate. • Biologically carbonated steel slag had greater mechanical performance than directly carbonated one.


Assuntos
Resíduos Industriais , Aço , Carbonato de Cálcio , Dióxido de Carbono , Carbonatos , Resíduos Industriais/análise , Paenibacillus
16.
Astrobiology ; 21(11): 1421-1437, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34551267

RESUMO

Detecting evidence of life on other planetary bodies requires a certain understanding of known biomarkers and their chemical nature, preservation potential, or biological specificity. In a planetary search for life, carbonates are of special interest due to their known association with life as we know it. On Earth, carbonates serve as an invaluable paleogeochemical archive of fossils of up to billions of years old. Here, we investigated biomarker profiles on three Chilean Triassic-Jurassic sedimentary records regarding our search for signs of past and present life over ∼200 Ma. A multianalytical platform that combines lipid-derived biomarkers, metaproteomics, and a life detector chip (LDChip) is considered in the detection of biomolecules with different perdurability and source-diagnosis potential. The combined identification of proteins with positive LDChip inmunodetections provides metabolic information and taxonomic affiliation of modern/subrecent biosignatures. Molecular and isotopic analysis of more perdurable hydrocarbon cores allows for the identification of general biosources and dominant autotrophic pathways over time, as well as recreation of prevailing redox conditions over ∼200 Ma. We demonstrate how extraterrestrial life detection can benefit from the use of different biomarkers to overcome diagnosis limitations due to a lack of specificity and/or alteration over time. Our findings have implications for future astrobiological missions to Mars.


Assuntos
Exobiologia , Marte , Carbonatos , Planeta Terra , Meio Ambiente Extraterreno , Fósseis , Planetas
17.
Anal Chem ; 93(37): 12594-12601, 2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34491717

RESUMO

Organic carbonate electrolytes are widely used materials for lithium-ion batteries. However, detailed solvation structures and solvent coordination numbers (CNs) of lithium cations in such solutions have not been accurately described nor determined yet. Because transmission-type IR spectroscopy is not of use for measuring the carbonyl stretch modes of electrolytes due to their absorption saturation problem, we here show that simple spacer-free thin cell IR spectroscopy can provide quantitative information on the number of solvating carbonate molecules around each lithium ion. We could estimate the solvent (carbonate) CNs of lithium ions in dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propylene carbonate, and butylene carbonate over a wide range of lithium salt concentrations accurately, and they are compared with the previous results obtained with attenuated total reflection IR spectroscopy technique. We anticipate that our spacer-free thin cell approach will potentially be used to investigate the solvation dynamics, chemical exchange process, and vibrational energy transfers between solvating carbonate molecules in lithium salt electrolytes when combined with time-resolved IR spectroscopy.


Assuntos
Eletrólitos , Lítio , Carbonatos , Solventes , Espectroscopia de Infravermelho com Transformada de Fourier
18.
Huan Jing Ke Xue ; 42(10): 4687-4697, 2021 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-34581111

RESUMO

To explore the influence of human activities on the Yangtze River water chemistry, water samples were obtained from a representative section the main river stem/branch in wet and normal seasons in 2016. Ion ratio analysis, principal component analysis(PCA), and chemical ion balance calculations were performed, and carbonate rock dissolution rates were determined based on carbonate and exogenous acids. The result show that HCO3-Ca is the dominant hydrochemistry type, indicating that the dissolution of carbonate rocks in the basin is the main process affecting hydrochemistry, and carbonate acid is significant in the weathering of carbonate rocks. In addition, the proportion of carbonate acid dissolution in the wet and normal seasons accounted for 60.33% and 59.14% of the total dissolution, respectively. The dissolution ratio among the different sampling points was notable, which indicates that the carbon sink effect of exogenous acid cannot be ignored. In addition, cation exchange some influence on hydrochemistry but was not the main reaction process. Compared with hydrological monitoring data for the last few years, the weathering of rocks by sulfuric and nitrate acids has strengthened, and the negative effects of anthropogenic pollution in the Yangtze River have increased.


Assuntos
Rios , Poluentes Químicos da Água , Carbonatos/análise , Monitoramento Ambiental , Humanos , Hidrologia , Água , Poluentes Químicos da Água/análise , Tempo (Meteorologia)
19.
J Environ Manage ; 299: 113648, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34479148

RESUMO

Biodegradation is the most economical and efficient process for remediating polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap). Soil composition is pivotal in controlling PAH migration and transformation. Iron minerals such as siderite and magnetite are the primary components of soil and sediment and play key roles in organic pollutant biodegradation. However, it is unclear whether siderite and magnetite promote or inhibit Nap biodegradation. The effects of siderite and magnetite on Nap biodegradation were investigated through batch experiments in this study. The results indicated that siderite increased Nap biodegradation efficiency by 7.87%, whereas magnetite inhibited Nap biodegradation efficiency by 3.54%. In the presence of siderite, Nap-degrading bacteria with acid-producing effects promoted siderite dissolution via metabolic activity, resulting in an increased Fe (II) concentration in solution which accelerated the iron reduction process and promoted Nap biodegradation. In addition, the presence of iron minerals altered the genus-level community structure. Anaerobic sulfate-reducing bacteria such as Desulfosporosinus occurred in the presence of siderite, indicating that sulfate reduction occurred in advance under the influence of siderite. In the presence of magnetite, Fe (III) in iron minerals were converted to Fe (II), and under the mediation of microorganisms, Fe (II) combined with carbonate to form secondary minerals (e.g., siderite). Secondary minerals were attached to the surface of magnetite, which inhibited magnetite dissolution and reduced the efficiency of Fe (III) utilization by microorganisms. Furthermore, as the reaction proceeds, acid-producing microorganisms promoted magnetite further dissolution, resulting in a longer duration of the Fe (III) reduction process. Bacteria utilizing sulfuric acid as the terminal electron acceptor consumed organic matter more rapidly than those using iron as the terminal electron acceptor. Therefore, magnetite inhibited Nap degradation. These observations enhance our understanding of the interaction mechanisms of iron minerals, organic pollutants, and degrading bacteria during the biodegradation process.


Assuntos
Carbonatos , Óxido Ferroso-Férrico , Biodegradação Ambiental , Compostos Férricos , Minerais , Naftalenos , Oxirredução
20.
Water Res ; 204: 117622, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34507023

RESUMO

To alleviate algal fouling in membrane water treatment processes, conventional technologies such as coagulation with poly aluminum chloride (PACl) has been widely adopted by many drinking water treatment plants. However, coagulation alone exhibited relatively weak removal effect for algal pollutants, and the coagulant residues due to the excess dosage also raised concerns. Thus, a novel process of coupling sodium percarbonate (SPC) oxidation and PACl coagulation was proposed, integrated with membrane filtration for algae-laden water treatment. The dosages of PACl and SPC were optimized, and the SPC dosing strategies were systematically compared. The changes in the characteristics of algal pollutants were investigated, and the results revealed that the resistance of algal foulants to aggregation was decreased, and the particle size of algal foulants became larger. With the synergism of coagulation and oxidation, the degradation of fluorescent organics was strengthened, and macromolecular biopolymers were decomposed into low molecular weight organics. The fouling control efficiency was further explored, and the results indicated that both irreversible and reversible fouling were effectively controlled, among which PACl/SPC (simultaneous treatment) performed best with the irreversible fouling reduced by 90.5%, while the efficiency of SPC-PACl (SPC followed by PACl) was relatively lower (57.3%). The fouling mechanism was altered by slowing the formation of cake filtration, and the reduction of algal cells played a more important role for the fouling alleviation. The interface properties of contaminated membranes (i.e., functional groups, images, and micromorphology) were characterized, and the efficiency of the proposed strategy was further verified. The proposed strategy exhibits great application values for improving membrane performance during algae-laden water treatment.


Assuntos
Filtração , Purificação da Água , Carbonatos , Membranas , Oxirredução
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