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1.
J Environ Manage ; 300: 113773, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34560467

RESUMO

Various rare earth element (REE) deposits hosted by carbonatite complexes have been identified in southern (Montviel, Niobec) and northern Quebec (Eldor deposit). During the winter in Quebec, the use of road salts to facilitate transportation on the mine site and/or avoid water freezing during mine operation may be necessary. The sources of salinity can be diverse on a mine site: process water, precipitation, alteration of minerals in the soil. Thus, tailings may come in contact with these salts and react. The purpose of the present study was to evaluate the impact of salinity on the behaviour of flotation tailings (Eldor deposit), i.e. the mobility of the elements contained in the tailings under these conditions and the environmental risks involved. For this purpose, leaching column tests were developed. The solutions were deionized water (CW column), NaCl (25 g/L; CS1 column) and CaCl2 (25 g/L; CS2 column). The leachate analysis revealed that the divalent cations (Ba, Cd, Mg, Mn, Sr, and Zn) are more mobile in the presence of CaCl2 (CaCl2 > NaCl > deionized water). The mobility of these elements appears to be governed by the competition with Ca2+ for tailings sorption sites. U and Sc are most mobile in the presence of salts regardless of the applied salt solution, i.e. CaCl2 = NaCl > deionized water. The formation of soluble chloride complexes with these elements could therefore be the cause of this phenomenon. For S, the leaching solution has no impact on its mobility. In conclusion, the presence of salts would tend to increase the mobility of divalent cations present in these residues and enhance their contamination potential. Modeling using PHREEQC software allowed comparison of these results with post-dismantling mineralogical characterization. Both methods showed: (i) total dissolution of fluorite [CaF2], galena [PbS], richterite [Na(CaNa(Mg,Fe2+)5[Si8O22](OH)] and Ba silicate; (ii) precipitation of iron oxides/hydroxides and silicate minerals. However, the modeling was unable to predict the behaviour of carbonate minerals. Further modeling tests involving kinetics should be considered in a future study.


Assuntos
Metais Terras Raras , Salinidade , Carbonatos , Quebeque , Solo
2.
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)
3.
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
4.
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
5.
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
6.
Artigo em Inglês | MEDLINE | ID: mdl-34348536

RESUMO

Objective: To investigate the role of arterial blood gas (ABG) analysis parameters (blood carbon dioxide, pCO2; oxygen, pO2; carbonate, HCO3-; standard base excess, SBE) in monitoring respiratory function and ventilation compliance after noninvasive mechanical ventilation (NIV) adaptation, predicting survival in ALS patients. Methods: We selected the first ABG performed after NIV start in ALS patients followed from 2000 to 2015 in Turin ALS Center. Correlations between ABG parameters and survival were calculated. Risk for death/tracheostomy was computed at modifying ABG parameters by using Cox regression models, adjusted for the main prognostic factors. Kaplan-Meier curves were then performed and compared. Results: A total of 186 post-NIV ABGs were included. HCO3- and SBE showed a significant correlation with survival after NIV (respectively, R = -0.183, p = 0.018 and R = -0.200, p = 0.010). Risk for death/tracheostomy after NIV was significantly higher at increasing HCO3- and SBE blood levels, especially when HCO3- was >29 mmol/L and SBE >4 mmol/L (respectively, HR 1.466, 95% CI 1.068-2.011, p = 0.018 and HR = 1.411, 95% CI 1.030-1.32, p = 0.032). Survival in NIV was higher in patients with HCO3- < 29.0 mmol/L and SBE < 4.0 mmol/L. Conclusions: HCO3- and SBE blood levels are markers of ventilation compliance, tolerance and efficacy, being able to predict survival after NIV start in ALS.


Assuntos
Esclerose Amiotrófica Lateral , Ventilação não Invasiva , Insuficiência Respiratória , Esclerose Amiotrófica Lateral/terapia , Gasometria , Carbonatos , Humanos , Insuficiência Respiratória/etiologia , Insuficiência Respiratória/terapia
7.
An Acad Bras Cienc ; 93(4): e20200002, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34378758

RESUMO

In the current study, twenty-eight bacterial strains were isolated from home-made yogurt samples from Agri Province, Turkey. The bacterial strains were identified by conventional and molecular techniques. Among the twenty- eight isolates, seventeen isolates were identified according to the 16 S rDNA region and determined to belong to five different genus including Sphingomonas (8 isolates), Burkholderia (5 isolates), Lactobacillus (2 isolates), Lactococcus (1 isolate), Staphylococcus (1 isolate). In this study, the presence of Burkholderia in home-made yogurt samples were reported for the first time, whereas Sphingomonas was detected for the second time. We also investigated the carbonate (CaCO3 and MgCO3) and silicate ( CaSiO3 and MgSiO3) dissolving potential of seventeen bacterial isolates. Among these seventeen bacterial isolates, fifteen bacterial isolates have CaCO3-dissolving and 10 bacterial isolates have MgCO3-dissolving potential. The silicates dissolution ability was relatively less than that of carbonates dissolving. We observed that six bacterial isolates have CaSiO3 and only two bacterial isolates have MgSiO3 dissolution abilities. In conclusion, this work clearly shows the diversity of bacteria existing in fermented cow milk samples in Agri Province, Turkey, which could be considered as valuable sources for lactic acid bacteria (LAB) isolation and further probiotic potential.


Assuntos
Probióticos , Iogurte , Animais , Carbonatos , Bovinos , Feminino , Lactobacillus , Silicatos
8.
Water Res ; 204: 117564, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34455157

RESUMO

CO2 exchanges across the water-air interface in rivers and lakes are currently believed to be responsible for the dominant share of global aquatic CO2 emissions. The gas transfer velocity (k600) is the key factor that constrains the CO2 fluxes. It is also the most problematic to establish because of its high spatial and temporal variability. Here, we have evaluated the seasonal and spatial dynamics in k600 values and their physical and chemical controlling processes by gas tracer and floating chamber (FC) methods in three reaches of a low-gradient stream channel (Guancun surface stream, 'GSS') in a karst terrain in subtropical southwestern China in December 2016 and March, July and September 2017. The k600 values were highly variable in space and time in this small stream. Physical processes, including the velocity of the stream and its slope, were found to control the variations of k600. The k600 values recorded in the dry season (March and December) were at minimal levels due to very slow flow and gentle slope, and were also affected by complexation in the solute-enriched waters. The characteristics high pH and low turbulence of gentle streams in carbonate karst areas are conducive to such complexation, which is of great significance in the limiting CO2 degassing in such regions. We have obtained the first k600 prediction model for small streams in subtropical karst regions. In conclusion, we present a comprehensive approach for predicting the k600 values in small channels by comparison of independent SF6 gas tracer and floating chamber methods.


Assuntos
Dióxido de Carbono , Rios , Dióxido de Carbono/análise , Carbonatos , Monitoramento Ambiental , Lagos , Estações do Ano
9.
J Environ Manage ; 298: 113433, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34352483

RESUMO

Currently, it is essential to consider the rapidly increasing emission of CO2 into the atmosphere, causing major environmental issues such as climate change and global warming. In this work, we have developed the binary catalyst system (ZnCo2O4/inorganic salt) for chemical fixation of CO2 with epoxides into cyclic carbonates without solvent, and all reactions were performed on a large scale using a 100 ml batch reactor. Two mesoporous catalysts of ZnCo2O4 with different architecture, such as flakes (ZnCo-F) and spheres (ZnCo-S) were synthesized and utilized as a heterogeneous catalyst for cycloaddition reaction. The bifunctional property of catalysts is mainly attributed to strong acidic and basic properties confirmed by TPD (NH3 & CO2) analysis. The ZnCo-F catalyst exhibited excellent conversion of propylene oxide (99.9%) with good corresponding selectivity of propylene carbonate (≥99%) in the presence of inorganic salt (KI) at 120 °C, 2 MPa, 3 h. In addition, ZnCo-F catalyst demonstrated good catalytic applicability towards the various substrates scope of the epoxide. Furthermore, the catalytic properties were examined by evaluating the reaction parameter such as catalyst loading, pressure, temperature and time. The proposed catalyst exhibited good reusability for cycloaddition reaction without significant change in its catalytic activity and proposed a possible reaction mechanism for chemical fixation of CO2 with epoxide into cyclic carbonate over ZnCo-F/KI.


Assuntos
Dióxido de Carbono , Carbonatos , Catálise , Solventes , Temperatura
10.
Environ Sci Technol ; 55(17): 11906-11915, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34415763

RESUMO

The world adds about 51 Gt of greenhouse gases to the atmosphere each year, which will yield dire global consequences without aggressive action in the form of carbon dioxide removal (CDR) and other technologies. A suggested guideline requires that proposed CDR technologies be capable of removing at least 1% of current annual emissions, about half a gigaton, from the atmosphere each year once fully implemented for them to be worthy of pursuit. Basalt carbonation coupled to direct air capture (DAC) can exceed this baseline, but it is likely that implementation at the gigaton-per-year scale will require increasing per-well CO2 injection rates to a point where CO2 forms a persistent, free-phase CO2 plume in the basaltic subsurface. Here, we use a series of thermodynamic calculations and basalt dissolution simulations to show that the development of a persistent plume will reduce carbonation efficiency (i.e., the amount of CO2 mineralized per kilogram of basalt dissolved) relative to existing field projects and experimental studies. We show that variations in carbonation efficiency are directly related to carbonate mineral solubility, which is a function of solution alkalinity and pH/CO2 fugacity. The simulations demonstrate the sensitivity of carbonation efficiency to solution alkalinity and caution against directly extrapolating carbonation efficiencies inferred from laboratory studies and small-injection-rate field studies conducted under elevated alkalinity and/or pH conditions to gigaton-per-year scale basalt carbonation. Nevertheless, all simulations demonstrate significant carbonate mineralization and thus imply that significant mineral carbonation can be expected even at the gigaton-per-year scale if basalts are given time to react.


Assuntos
Dióxido de Carbono , Silicatos , Carbonatos , Minerais
11.
Sci Total Environ ; 798: 149214, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34333434

RESUMO

Seven cruises were carried out in a bay scallop (Argopecten irradians) farming area and its surrounding waters, North Yellow Sea, from March to November 2017 to study the dynamics of the carbonate system and its controlling factors. Results indicated that the studied parameters were highly variability over a range of spatiotemporal scales, comprehensively forced by various physical and biological processes. Mixing effect and scallop calcification played the most important role in the seasonal variation of total alkalinity (TAlk). For dissolved inorganic carbon (DIC), in addition to mixing, air-sea exchange and microbial activity, e.g. photosynthesis and microbial respiration processes, had more important effects on its dynamics. Different from the former, the changes of water pHT, partial pressure of CO2 (pCO2) and aragonite saturation state (ΩA) were mainly controlled by the combining of the temperature, air-sea exchange, microbial activity and scallop metabolic activities. In addition, the results indicated that massive scallop farming can significantly increase the DIC/TAlk ratio by reducing the TAlk concentration in seawater, thereby reducing the buffering capacity of the carbonate system in seawater especially for ΩA. Preliminary calculated, ~75.7 and ~45.5 µmol kg-1 of TAlk were removed from the surface and bottom waters respectively in one scallop cultivating cycle. If these carbonates cannot be replenished in time, it is likely to accelerate the acidification process of coastal waters. This study highlighted the control mechanism of the carbonate system under the influence of bay scallop farming, and provided useful information for revealing the potential link between human activities (shelled-mollusc mariculture) and coastal acidification.


Assuntos
Carbonatos , Pectinidae , Agricultura , Animais , Carbonatos/análise , China , Humanos , Concentração de Íons de Hidrogênio , Água do Mar , Frutos do Mar
12.
Huan Jing Ke Xue ; 42(8): 3913-3923, 2021 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-34309278

RESUMO

In China, high heavy metal concentrations in cultivated soil are mainly distributed in carbonate-covered areas. The migration and transformation of heavy metals in such soils are influenced by interactions between natural processes and human activities. This study examined the profiles of nine paddy soils, derived from carbonate rocks in Guangxi. The Cd, As, Zn, Cr, Cu, Hg, Ni, and Pb contents we determined, and soil properties such as pH, Corg content, and fractions of Cd, As, Zn, and Cr were tested. Based on the above data, we assessed the vertical distribution of heavy metal fractions, as well as the ecological risks and factors affecting the migration ability of heavy metals, under the influence of human activities and natural soil formation. The results show that compared with the carbonate rocks in Guangxi, the soil profile of the study area is significantly enriched with all eight heavy metals. Among them, Cd, As, Zn, and Cr exceeded China's agricultural land (paddy field) pollution risk screening values, and Cd and As partially exceed the risk intervention values. All fractions of Cd in the soil profiles are widely distributed. The proportion of water-soluble and ion-exchange Cd fractions with high ecological risk decreased significantly from the surface to greater depths in the soil profile. As, Zn, and Cr in the soil profile were mainly in residual states, and the proportion of water-soluble and ion-exchange fractions did not change considerably with increasing depth. The evaluation results of RAC and RSP show that Cd pollution risk in the study area is relatively high, whereas As, Zn, and Cr are generally pollution-free or risk-free. In naturally developed soil in the study area, the clay mineral content and degree of soil development have significant effects on Cd migration, whereas in the cultivated layer affected by human activities, the soil pH and organic matter content are the main controlling factors. The migration ability of soil As is mainly related to soil organic matter, Fe2O3 content, and soil development degree, but organic matter has an obviously enhanced effect in the tillage layer. The main controlling factor of Zn and Cr migration in soil is pH, and the effects are more intense under the disturbance of human activities.


Assuntos
Metais Pesados , Poluentes do Solo , Carbonatos , China , Monitoramento Ambiental , Humanos , Metais Pesados/análise , Medição de Risco , Solo , Poluentes do Solo/análise
13.
Molecules ; 26(12)2021 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-34207051

RESUMO

An ultra-high performance liquid chromatography coupled to tandem mass spectrometry method is proposed for the determination of the major ergot alkaloids (ergometrine, ergosine, ergotamine, ergocornine, ergokryptine, ergocristine) and their epimers (ergometrinine, ergosinine, ergotaminine, ergocorninine, ergokryptinine, and ergocristinine) in oat-based foods and food supplements. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure was applied as sample treatment, reducing the consumption of organic solvent and increasing sensitivity. This method involved an extraction with acetonitrile and ammonium carbonate (85:15, v/v) and a clean-up step based on dispersive solid-phase extraction, employing a mixture of C18/Z-Sep+ as sorbents. Procedural calibration curves were established and limits of quantification were below 3.2 µg/kg for the studied compounds. Repeatability and intermediate precision (expressed as RSD%) were lower than 6.3% and 15%, respectively, with recoveries ranging between 89.7% and 109%. The method was applied to oat-based products (bran, flakes, flour, grass, hydroalcoholic extracts, juices, and tablets), finding a positive sample of oat bran contaminated with ergometrine, ergosine, ergometrinine, and ergosinine (total content of 10.7 µg/kg).


Assuntos
Avena/química , Alcaloides de Claviceps/química , Alimento Funcional/análise , Carbonatos/química , Cromatografia Líquida de Alta Pressão/métodos , Ergolinas/química , Ergonovina/química , Ergotaminas/química , Contaminação de Alimentos/análise , Extração em Fase Sólida/métodos , Espectrometria de Massas em Tandem/métodos
14.
Biomaterials ; 275: 120953, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34218051

RESUMO

Designing grafted biodegradable polymers with tailored multi-functional properties is one of the most researched fields with extensive biomedical applications. Among many biodegradable polymers, polycarbonates have gained much attention due to their ease of synthesis, high drug loading, and excellent biocompatibility profiles. Among various monomers, 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) derived cyclic carbonate monomers have been extensively explored in terms of their synthesis as well as their polymerization. Since the late 90s, significant advancements have been made in the design of bis-MPA derived cyclic carbonate monomers as well as in their reaction schemes. Currently, bis-MPA derived polycarbonates have taken a form of an entire platform with a multitude of applications, the latest being in the field of nanotechnology, targeted drug, and nucleic acid delivery. The present review outlines an up to date developments that have taken place in the last two decades in the design, synthesis, and biomedical applications of bis-MPA derived cyclic carbonates and their (co)polymers.


Assuntos
Preparações Farmacêuticas , Polímeros , Carbonatos , Cimento de Policarboxilato , Propionatos
15.
Chemistry ; 27(50): 12742-12746, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34197006

RESUMO

Unlike the comprehensive development of tandem multi-metallic catalysis, bimetallic synergistic catalysis has been challenging to achieve high stereoselectivity with the generation of multi-stereogenic centers. Herein, an efficient synergistic catalysis for the diastereo- and enantioselective synthesis of multi-substituted tetrahydrofuran derivatives has been developed. Under mild reaction conditions, a series of target molecules with three consecutive stereocenters were synthesized by a palladium(0)/rhodium(III) bimetal-catalyzed asymmetric decarboxylative [3+2]-cycloaddition of vinylethylene carbonates with α,ß-unsaturated carbonyl compounds. The corresponding adducts were obtained with moderate to high yields (67 %∼98 %) and excellent stereoselectivities (>20 : 1 d.r., up to 99 % ee).


Assuntos
Ródio , Carbonatos , Catálise , Reação de Cicloadição , Furanos , Paládio , Estereoisomerismo
16.
Int J Mol Sci ; 22(12)2021 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-34201173

RESUMO

Biofilms are the reason for a vast majority of chronic inflammation cases and most acute inflammation. The treatment of biofilms still is a complicated task due to the low efficiency of drug delivery and high resistivity of the involved bacteria to harmful factors. Here we describe a magnetically controlled nanocomposite with a stimuli-responsive release profile based on calcium carbonate and magnetite with an encapsulated antibiotic (ciprofloxacin) that can be used to solve this problem. The material magnetic properties allowed targeted delivery, accumulation, and penetration of the composite in the biofilm, as well as the rapid triggered release of the entrapped antibiotic. Under the influence of an RF magnetic field with a frequency of 210 kHz, the composite underwent a phase transition from vaterite into calcite and promoted the release of ciprofloxacin. The effectiveness of the composite was tested against formed biofilms of E. coli and S. aureus and showed a 71% reduction in E. coli biofilm biomass and an 85% reduction in S. aureus biofilms. The efficiency of the composite with entrapped ciprofloxacin was higher than for the free antibiotic in the same concentration, up to 72%. The developed composite is a promising material for the treatment of biofilm-associated inflammations.


Assuntos
Biofilmes/crescimento & desenvolvimento , Carbonatos/química , Ciprofloxacina/farmacologia , Escherichia coli/crescimento & desenvolvimento , Magnetismo , Nanocompostos/administração & dosagem , Staphylococcus aureus/crescimento & desenvolvimento , Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Portadores de Fármacos/química , Sistemas de Liberação de Medicamentos , Escherichia coli/efeitos dos fármacos , Nanocompostos/química , Staphylococcus aureus/efeitos dos fármacos
17.
Water Res ; 202: 117451, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34330026

RESUMO

In this work, the novel application of chalcopyrite (CuFeS2) for sodium percarbonate (SPC) activation towards sulfamethazine (SMT) degradation was explored. Several key influencing factors like SPC concentration, CuFeS2 dosage, reaction temperature, pH value, anions, and humic acid (HA) were investigated. Experimental results indicated that SMT could be effectively degraded in the neutral reaction media by CuFeS2/SPC process (86.4%, 0.054 min-1 at pH = 7.1). The mechanism of SPC activation by CuFeS2 was elucidated, which was discovered to be a multiple reactive oxygen species (multi-ROS) process with the coexistence of hydroxyl radical (•OH), carbonate radical (CO3•-), superoxide radical (O2•-), and singlet oxygen (1O2), as evidenced by quenching experiments and electron spin resonance (ESR) tests. The generated •OH via the traditional heterogeneous Fenton-like process would not only react with carbonate ions to yield other ROS but also involve in SMT degradation. The abundant surface-bound Fe(II) was deemed to be the dominant catalytic active sites for SPC activation. Meanwhile, it was verified that the reductive sulfur species, the interaction between Cu(I) and Fe(III) as well as the available O2•- derived from the activation of molecular oxygen and the conversion of •OH favored the regeneration of Fe(II) on CuFeS2 surface. Furthermore, the degradation intermediates of SMT and their toxicities were evaluated. This study presents a novel strategy by integrating transition metal sulfides with percarbonate for antibiotic-contaminated water treatment.


Assuntos
Sulfametazina , Poluentes Químicos da Água , Carbonatos , Cobre , Compostos Férricos , Peróxido de Hidrogênio , Oxirredução , Poluentes Químicos da Água/análise
18.
Spectrochim Acta A Mol Biomol Spectrosc ; 263: 120205, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34332244

RESUMO

Raman spectroscopy and laser induced breakdown spectroscopy (LIBS) are complementary techniques that together can provide a comprehensive characterization of geologic environments. For landed missions with constrained access to target materials on other planetary bodies, discerning signatures of life and habitability can be daunting, particularly where the preservation of organic compounds that contain the building blocks of life is limited. The main challenge facing any spectroscopy measurements of natural samples is the complicated spectra that often contain signatures for multiple components, particularly in rocks that are composed of several minerals with surfaces colonized by microbes. The goal of this study was to use the combination of Raman spectroscopy and LIBS to discern different environmental regimes based on the identification of minerals and biomolecules in rocks and sediments. Iceland is a terrestrial volcano-glacial location that offers a range of planetary analog environments, including volcanically active regions, extensive lava fields, geothermal springs, and large swaths of ice-covered terrain that are relevant to both rocky and icy planetary bodies. We combined portable VIS (532 nm) and NIR (785 nm) Raman spectroscopy, VIS micro-Raman spectroscopic mapping, and UV/VIS/NIR (200 - 1000 nm) and Mid-IR (5.6 - 10 µm, 1785 - 1000 cm-1) laser induced breakdown spectroscopy (LIBS) to characterize the mineral assemblages, hydrated components, and biomolecules in rock and sediment samples collected from three main sites in the volcanically active Kverkfjöll-Vatnajökull region of Iceland: basalt and basalt-hosted carbonate rind from Hveragil geothermal stream, volcanic sediments from the base of Vatnajökull glacier at Kverkfjöll, and lava from the nearby Holuhraun lava field. With our combination of techniques, we were able to identify major mineral polytypes typical for each sample set, as well as a large diversity of biomolecules typical for lichen communities across all samples. The anatase we observed using micro-Raman spectroscopic mapping of the lava compared with the volcanic sediment suggested different formation pathways: lava anatase formed authigenically, sediment anatase could have formed in association with microbial weathering. Mn-oxide, only detected in the carbonate samples, seems to have two possible formation pathways, either by fluvial or microbial weathering or both. Even with our ability to detect a wide diversity of biomolecules and minerals in all of the samples, there was not enough variation between each set to distinguish different environments based on the limited measurements done for this study.


Assuntos
Minerais , Análise Espectral Raman , Carbonatos , Islândia , Minerais/análise
19.
Chemistry ; 27(49): 12521-12525, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34236738

RESUMO

Photochemical activation is proposed as a general method for controlling the crystallization of sparingly soluble carbonates in space and time. The photogeneration of carbonate in an alkaline environment is achieved upon photo-decarboxylation of an organic precursor by using a conventional 365 nm UV LED. Local irradiation was conducted focusing the LED light on a 300 µm radius spot on a closed glass crystallization cell. The precursor solution was optimized to avoid the precipitation of the photoreaction organic byproducts and prevent photo-induced pH changes to achieve the formation of calcium carbonate only in the corresponding irradiated area. The crystallization was monitored in real-time by time-lapse imaging. The method is also shown to work in gels. Similarly, it was also shown to photo-activate locally the formation of barium carbonate biomorphs. In the last case, the morphology of these biomimetic structures was tuned by changing the irradiation intensity.


Assuntos
Carbonato de Cálcio , Carbonatos , Bário , Cristalização
20.
Environ Sci Technol ; 55(14): 10056-10066, 2021 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-34236189

RESUMO

Tailings dam failures can cause devastation to the environment, loss of human life, and require expensive remediation. A promising approach for de-risking brucite-bearing ultramafic tailings is in situ cementation via carbon dioxide (CO2) mineralization, which also sequesters this greenhouse gas within carbonate minerals. In cylindrical test experiments, brucite [Mg(OH)2] carbonation was accelerated by coupling organic and inorganic carbon cycling. Waste organics generated CO2 concentrations similar to that of flue gas (up to 19%). The abundance of brucite (2-10 wt %) had the greatest influence on tailings cementation as evidenced by the increase in total inorganic carbon (TIC; +0.17-0.84%). Brucite consumption ranged from 64-84% of its initial abundance and was mainly influenced by water availability. Higher moisture contents (e.g., 80% saturation) and finer grain sizes (e.g., clay-silt) that allowed for a better distribution of water resulted in greater brucite carbonation. Furthermore, pore clogging and surface passivation by Mg-carbonates may have slowed brucite carbonation over the 10 weeks. Unconfined compressive strengths ranged from 0.4-6.9 MPa and would be sufficient in most scenarios to adequately stabilize tailings. Our study demonstrates the potential for stabilizing brucite-bearing mine tailings through in situ cementation while sequestering CO2.


Assuntos
Sequestro de Carbono , Cimentação , Dióxido de Carbono , Carbonatos , Humanos , Hidróxido de Magnésio
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