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1.
Ecotoxicol Environ Saf ; 188: 109934, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31740234

RESUMO

Due to the presence of toxic pollutants, soils in former military areas need remedial actions with environmentally friendly methods. Greenhouse experiments were conducted to investigate the aided phytostabilization of multi-heavy metals (HMs), i.e. Cd, Cr, Cu, Ni, Pb, Zn, in post-military soil by Festuca rubra and three mineral amendments (diatomite, dolomite and halloysite). The amendments were applied at 0 and 3.0% to each pot filled with 5 kg of polluted soil. After seven weeks of the phytostabilization, selected soil properties, biomass yield of F. rubra and immobilization of HMs by their accumulation in plant and redistribution among individual fractions in soil were determined. In addition, ecotoxicology parameters of non-amended and amended soil were established using Phytotoxkit (Sinapsis alba) and Ostracodtoxkit (Heterocypris incongruens) tests. The addition of halloysite significantly increased F. rubra biomass. Diatomite significantly increased both the Cd, Cu, Pb and Cr concentrations in the roots and the pH of the soil. The application of halloysite significantly decreased the Cd and Zn contents of the soil after the completion of the experiment. Dolomite and halloysite were more effective in HM immobilization in soil by decreasing their content in an exchangeable fraction than diatomite. These soil amendments significantly differentiated the length of S. alba roots and had a positive effect on the development of H. incongruens.


Assuntos
Carbonato de Cálcio/química , Argila/química , Recuperação e Remediação Ambiental/métodos , Festuca/crescimento & desenvolvimento , Magnésio/química , Metais Pesados/análise , Instalações Militares , Poluentes do Solo/análise , Biodegradação Ambiental , Biomassa , Festuca/química , Raízes de Plantas/crescimento & desenvolvimento , Solo/química
2.
Chemosphere ; 239: 124741, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31518921

RESUMO

In many parts of the world, wastewater irrigation has become a common practice because of freshwater scarcity and to increase resource reuse efficiency. Wastewater irrigation has positive impacts on livelihoods and at the same time, it has adverse impacts related to environmental pollution. Hydrochemical processes and groundwater behaviour need to be analyzed for a thorough understanding of the geochemical evolution in the wastewater irrigated systems. The current study focuses on a micro-watershed in the peri-urban Hyderabad of India, where farmers practice intensive wastewater irrigation. To evaluate the major factors that control groundwater geochemical processes, we analyzed the chemical composition of the wastewater used for irrigation and groundwater samples on a monthly basis for one hydrological year. The groundwater samples were collected in three settings of the watershed: wastewater irrigated area, groundwater irrigated area and upstream peri-urban area. The collected groundwater and wastewater samples were analyzed for major anions, cations and nutrients. We systematically investigated the anthropogenic influences and hydrogeochemical processes such as cation exchange, precipitation and dissolution of minerals using saturated indices, and freshwater-wastewater mixtures at the aquifer interface. Saturation indices of halite, gypsum and fluorite are exhibiting mineral dissolution and calcite and dolomite display mineral precipitation. Overall, the results suggest that the groundwater geochemistry of the watershed is largely controlled by long-term wastewater irrigation, local rainfall patterns and water-rock interactions. The study results can provide the basis for local decision-makers to develop sustainable groundwater management strategies and to control the aquifer pollution influenced by wastewater irrigation.


Assuntos
Irrigação Agrícola/métodos , Água Subterrânea/química , Águas Residuárias , Ânions/análise , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Cátions/análise , Meio Ambiente , Monitoramento Ambiental/métodos , Água Doce/química , Água Subterrânea/análise , Hidrologia/métodos , Índia , Magnésio/química , Salinidade , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Qualidade da Água
3.
Chemosphere ; 240: 124860, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31542578

RESUMO

In order to increase the adsorption properties of sodium alginate gel beads, a series of SA@PF-beads (sodium alginate-based beads with different amount of pore-forming agent) were prepared with calcium carbonate as the pore forming agent. The experimental results showed that the adsorption capacity of Cu(Ⅱ) increased by at least two times (from 13.69 mg/g to 33.88 mg/g, treated with SA@PF-0 and SA@PF-2.0, respectively) with proper amount of calcium carbonate added, which is economical and effective. In the experiment, SEM was used to measure the morphology of gel beads with different amount of pore-forming agent. FTIR and XPS were used to analyze the variation of functional groups and bond energies in the adsorption process. Adsorption isotherms and kinetics were conducted and showed that the adsorption process was consistent with Langmuir model and Elovich kinetic model. The maximum Langmuir adsorption 229.746 mg/g. The effects of pH, temperature and solid-liquid ratio on adsorption capacity were also investigated. In brief, calcium carbonate is an efficient and convenient pore-forming agent, which can be used to improve the adsorption properties of alginate gel materials.


Assuntos
Alginatos/química , Cobre/isolamento & purificação , Microesferas , Adsorção , Carbonato de Cálcio/química , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente , Poluentes Químicos da Água/isolamento & purificação
4.
Chemosphere ; 239: 124823, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31726520

RESUMO

Several studies have demonstrated that gypsum (CaSO4·2H2O) and calcite (CaCO3) can be important hosts of arsenic in contaminated hydrogeological systems. However, the extent to which microbial reducing processes contribute to the dissolution and transformation of carbonate and sulfate minerals and, thereby, to arsenic mobilization is poorly understood. These processes are likely to have a strong impact on arsenic mobility in iron-poor environments and in reducing aquifers where iron oxyhydroxides become unstable. Anoxic batch bioassays with arsenate (As(V)) coprecipitated with calcite, gypsum, or ferrihydrite (Fe(OH)3) were conducted in the presence of sulfate or molybdate to examine the impact of bioprocesses (i.e. As(V), sulfate, and Fe(III)-reduction) on arsenic dissolution, speciation, and eventual remineralization. Microbial reduction of As(V)-bearing calcite caused an important dissolution of arsenite, As(III), which remained in solution up to the end of the experiment (30 days). The reduction of As(V) from gypsum-As(V) also led to the release of As(III), which was subsequently remineralized, possibly as arsenic sulfides. The presence of sulfate triggered arsenic dissolution in the bioassays with ferrihydrite-As(V). This study showed that although gypsum and calcite have a lower capacity to bind arsenic, compared to iron oxides, they can play a critical role in the biogeochemical cycle of arsenic in natural calcareous and gypsiferous systems depleted of iron since they can be a source of electron acceptors for reducing bioprocesses.


Assuntos
Arsênico/química , Bactérias/metabolismo , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Compostos Férricos/química , Arseniatos/química , Arsenicais/química , Arsenitos/química , Carbonatos/química , Água Subterrânea/química , Ferro/química , Molibdênio/química , Oxirredução , Solubilidade , Sulfatos/química , Sulfetos/química
5.
Sci Total Environ ; 702: 134993, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31726336

RESUMO

Since the establishment of the whole-contact sediment toxicity test using Heterocypris incongruens in 2012, this user-friendly method has been widely used for the assessment of many kinds of solid samples, such as sediment, soil, compost, and sewage sludge. There are two endpoints for this method: mortality and growth inhibition. Currently, there is no standard toxicity threshold established for the endpoint of growth inhibition. However, there is evidence showing that the calcite saturation state of the overlying water, which might be different among various samples, influences the growth and survival of H. incongruens. Thus, it is necessary to characterize the influence of the calcite saturation state to ensure that the test results are reliable and comparable among different samples. In the present study, we created artificial sediments comprised of quartz sand and 0-20% calcite particulates to manipulate the calcite saturation state in the overlying water and performed the test using H. incongruens for 6 d. The results show that a low calcite saturation state inhibited the growth of H. incongruens but had no effect on survival rate. The growth of ostracods was linearly related to the calcite saturation index of the overlying water. Additionally, a formula for artificial sediment consisting of 10% calcite and 90% quartz sand for the H. incongruens toxicity test was proposed. This study helps to distinguish H. incongruens growth inhibition caused by calcite saturation from that caused by toxicity.


Assuntos
Carbonato de Cálcio/química , Crustáceos/fisiologia , Poluentes Químicos da Água/toxicidade , Animais , Fenômenos Biológicos , Sedimentos Geológicos/química , Esgotos , Solo , Testes de Toxicidade , Poluentes Químicos da Água/normas
6.
Chemosphere ; 239: 124660, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31505445

RESUMO

The co-precipitation of Fe2+, Cu2+, Zn2+, Cd2+ and Ni2+ were investigated by a mechanochemical processing with CaCO3. The results showed that the synergies of the metal ions led to efficient co-precipitation. The precipitation of Fe2+, Cu2+ and Cd2+ are over 99% and that of Zn2+ and Ni2+ about 98.4% and 93.8%. A significant advantage of the process is that the moisture content of filter residue is much lower (less than 50%) than that using the lime neutralization (more than 80%), offering a potential solution to the sludge problem in wastewater treatment. A further advantage is the neutral pH (about 7.5) obtained by using CaCO3 rather than the highly alkaline pH (about 11) obtained using lime (Ca(OH)2) neutralization method.


Assuntos
Precipitação Fracionada/métodos , Metais Pesados/análise , Esgotos/química , Purificação da Água/métodos , Cádmio/análise , Carbonato de Cálcio/química , Cobre/análise , Dessecação/métodos , Concentração de Íons de Hidrogênio , Ferro/análise , Níquel/análise , Zinco/análise
7.
Environ Sci Pollut Res Int ; 26(32): 33607-33620, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31587163

RESUMO

This study aimed to improve the pore size, porosity, and hydrophobicity of polyvinylidene fluoride (PVDF) membranes for desalination by vacuum membrane distillation (VMD). New membranes were prepared via etching PVDF/calcium carbonate (CaCO3) composite membranes using hydrochloric acid (HCl), depending on the chemical reaction of CaCO3 and HCl. Etched membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), contact angle (CA), atomic force microscope (AFM), and scanning electron microscopy (SEM). The results showed that CaCO3 of composite membranes was completely reacted by 1.5 mol/L HCl after composite membranes had been etched 90 min. The crystallinity of etched membranes was the same as that of PVDF/CaCO3 composite membranes, and no new functional groups appeared in etched membranes, which indicated that etched membranes had good chemical stability. The surface roughness increased and led to the increase of contact angle, which means the hydrophobicity of etched membranes was enhanced. As a result, the increment of permeation flux had been improved in a VMD process. It was found that the maximum flux of etched membrane was enhanced and up to 1.65 times of composite membrane when the concentration of sodium chloride (NaCl) solution was 5.0 wt%, and the maximum flux reached up to 30.9 kg m-2 h-1.


Assuntos
Ácido Clorídrico/química , Membranas Artificiais , Polivinil/química , Carbonato de Cálcio/química , Destilação , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Varredura , Porosidade , Cloreto de Sódio , Espectroscopia de Infravermelho com Transformada de Fourier
8.
Chemosphere ; 235: 1015-1021, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561290

RESUMO

Phosphate is one of the main contaminations in water, so an effective method of decreasing or removing phosphate is needed. The main purpose of this paper is to synthesize CaFe-LDHs and MgFe-LDHs from the mixture of calcined dolomite and ferric chloride to remove orthophosphate and pyrophosphate. The study showed that removal of orthophosphate was attributed to the precipitation by Ca2+ and adsorption by MgFe-LDHs, where the former played a main role. As for pyrophosphate, it was mainly removed by precipitation at the initial pyrophosphate concentration ranging from 3.228 to 17.04 mmol/L. When the initial concentrations became relatively higher, the removal efficiency of pyrophosphate decreased because the complexation effects by Fe3+, Ca2+ and Mg2+ took place.


Assuntos
Carbonato de Cálcio/química , Cloretos/química , Difosfatos/análise , Compostos Férricos/química , Hidróxidos/química , Magnésio/química , Fosfatos/análise , Poluentes Químicos da Água/análise , Difosfatos/isolamento & purificação , Fosfatos/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos
9.
Nucl Med Rev Cent East Eur ; 22(2): 56-59, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31482557

RESUMO

BACKGROUND: 44Sc is becoming attractive as a PET radionuclide due to its decay characteristics. It can be produced from 44Ca present in natural calcium with 2.08% abundance. MATERIALS AND METHODS: The targets were mostly prepared from natural CaCO3 or metallic calcium in the form of pellets. After irradiation they were dissolved in 3 M hydrochloric acid and 44Sc was separated from excess of calcium by precipitation of scandium hydroxide using ammonia. Alternatively, targets were dissolved in 11 M hydrochloric acid and 44Sc was separated by extraction chromatography on UTEVA resin. As the next step, in both processes 44Sc was further purified on a cation exchange resin. Initially, the separation procedures were developed with 46Sc as a tracer. Gamma spectrometry with a high purity germanium detector was used to determine the separation efficiency. Finally, the CaCO3 pellet with 99.2% enrichment in 44Ca was activated with protons via 44Ca(p,n)44Sc nuclear reaction. RESULTS: Altogether twenty two irradiations and separations were performed. The working procedures were developed and the quality of separated 44Sc solution was confirmed by radiolabeling of DOTATATE. The chemical purity of the product was sufficient for preclinical experiments. At the end of around 1 hour proton beam irradiation of CaCO3 pellet with 99.2% enrichment in 44Ca the obtained radioactivity of 44Sc was more than 4.8 GBq. CONCLUSION: 44Sc can be produced inexpensively with adequate yields and radionuclidic purity via 44Ca(p,n)44Sc nuclear reaction in small cyclotrons. The recovery yield in both investigated separation methods was comparable and amounted above 90%. The obtained 44Sc was pure in terms of radionuclide and chemical purity, as shown by the results of peptide radiolabeling.


Assuntos
Elementos da Série Actinoide/química , Precipitação Química , Hidróxidos/química , Radioquímica/métodos , Radioisótopos/química , Radioisótopos/isolamento & purificação , Escândio/química , Escândio/isolamento & purificação , Urânio/química , Carbonato de Cálcio/química , Ciclotrons , Marcação por Isótopo , Radioquímica/instrumentação
10.
Nat Commun ; 10(1): 3580, 2019 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-31395889

RESUMO

Ocean acidification is expected to negatively impact calcifying organisms, yet we lack understanding of their acclimation potential in the natural environment. Here we measured geochemical proxies (δ11B and B/Ca) in Porites astreoides corals that have been growing for their entire life under low aragonite saturation (Ωsw: 0.77-1.85). This allowed us to assess the ability of these corals to manipulate the chemical conditions at the site of calcification (Ωcf), and hence their potential to acclimate to changing Ωsw. We show that lifelong exposure to low Ωsw did not enable the corals to acclimate and reach similar Ωcf as corals grown under ambient conditions. The lower Ωcf at the site of calcification can explain a large proportion of the decreasing P. astreoides calcification rates at low Ωsw. The naturally elevated seawater dissolved inorganic carbon concentration at this study site shed light on how different carbonate chemistry parameters affect calcification conditions in corals.


Assuntos
Aclimatação , Antozoários/fisiologia , Calcificação Fisiológica , Carbonato de Cálcio/metabolismo , Fontes Hidrotermais/química , Animais , Antozoários/química , Carbonato de Cálcio/análise , Carbonato de Cálcio/química , Geografia , Concentração de Íons de Hidrogênio , Isótopos , México , Água do Mar/química
11.
Curr Microbiol ; 76(11): 1298-1305, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31428805

RESUMO

Geobacillus thermoglucosidasius NY05 catalyzes calcite single crystal formation at 60 °C by using acetate and calcium. Endospores are embedded at the central part of the calcite single crystal and carbon atoms in the calcite lattice are derived from acetate carbon. Here, we synthesized 21-mer antisense DNA oligonucleotides targeting sporulation transcription factor, acetate-CoA ligase, isocitrate lyase, and malate synthase G mRNAs and evaluated the effect of these oligonucleotides on calcite formation in G. thermoglucosidasius NY05. G. thermoglucosidasius NY05 cells containing antisense DNA oligonucleotides targeting sporulation transcription factor, acetate-CoA ligase, isocitrate lyase, and malate synthase G mRNAs had reduced calcite single crystal formation by 18.7, 50.6, 55.7, and 82.3%, respectively, compared with cells without antisense DNA oligonucleotides. These results support that calcite formation needs endospores as the nucleus to grow, and carbon dioxide generated from acetate, which is metabolized via the glyoxylate pathway and glucogenesis, is supplied to the crystal lattice.


Assuntos
Proteínas de Bactérias/genética , Carbonato de Cálcio/metabolismo , Inativação Gênica , Geobacillus/genética , Acetatos/metabolismo , Proteínas de Bactérias/metabolismo , Cálcio/metabolismo , Carbonato de Cálcio/química , Geobacillus/química , Geobacillus/metabolismo , Glioxilatos/metabolismo , Isocitrato Liase/genética , Isocitrato Liase/metabolismo , Malato Sintase/genética , Malato Sintase/metabolismo
12.
Carbohydr Polym ; 223: 115054, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31427020

RESUMO

The interfacial structures and bonding mechanism of the adsorption of chitosan monomers (GlcN and GlcNAc) on calcite (104) surface are investigated using first principles molecular dynamics simulations. It is revealed that the strong coordination CaO bonds are formed between five-fold coordinated Ca atoms on calcite surface and O atoms of hydroxyl groups (OH) and acetyl groups of chitosan in the chitosan-calcite nanocomposites, improving the chemical compatibility between organic and inorganic phases at the interface in the natural occurring nacre. Although, the presence of interfacial hydrogen bonds is also confirmed by analyzing the valence electron density difference in terms of induced dipole, the evolution of the equilibrium adsorption geometry is found to be mainly governed interfacial CaO coordination bonds. The amide group (NH2) of chitosan binds with calcite at the interface mainly through the formation of weak hydrogen bond. The predicted interfacial electronic structure can be either conductive (GlcNAc) or insulating (GlcN). The frequencies of the characteristic peaks in the calculated total and partial vibrational densities of states of GlcN/calcite systems are found to be in agreement with the FT-IR spectrum of the experimentally prepared chitosan-calcite nanocomposites, crucially validating the modelling structures and computational methodology employed in current work. Theoretical results strongly indicate that the peculiar adsorption in FT-IR spectrum at 2500 cm-1 is related to the presence of free GlcN molecule due to the hydrolysis of chitosan in aqueous solution.


Assuntos
Carbonato de Cálcio/química , Quitosana/química , Nanocompostos/química , Adsorção , Ligações de Hidrogênio , Simulação de Dinâmica Molecular , Estrutura Molecular , Espectroscopia de Infravermelho com Transformada de Fourier , Eletricidade Estática
13.
Environ Pollut ; 254(Pt A): 112938, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31404731

RESUMO

In the present study, the competitive adsorption of Cu2+, Pb2+, and Cd2+ by a novel natural adsorbent (i.e., argillaceous limestone) modified with chitosan (C-AL) was investigated. The results demonstrated that both intraparticle diffusion and chemisorption marked significant contributions to the Cu2+ adsorption process by both raw argillaceous limestone (R-AL) and C-AL in mono-metal adsorption systems. Antagonism was found to be the predominant competitive effect for Cu2+, Pb2+ and Cd2+ adsorptions by C-AL in the multi-metal adsorption system. The three-dimensional simulation and FTIR analysis revealed that the presence of Cu2+ suppressed Pb2+ and Cd2+ adsorptions, while the effect of Cd2+ on Cu2+ and Pb2+ adsorptions was insignificant. The spectroscopic analyses evidenced that amide groups in C-AL played a crucial role in metal adsorption. The preferential adsorptions of Pb2+ > Cu2+ > Cd2+ were likely due to the different affinities of the metals to the lone pair of electrons on the N atom from the amide groups and/or the O atoms from the -OH and -COO- groups on C-AL. The interactions between C-AL and metal ions and between various metal species influenced their competitive adsorption behaviors. C-AL exhibited a superior metal adsorption capacity in comparison with that the capacities of other natural adsorbents reported during the last decade, suggesting its potential practical applications.


Assuntos
Cádmio/química , Carbonato de Cálcio/química , Quitosana/química , Cobre/química , Recuperação e Remediação Ambiental/métodos , Chumbo/química , Adsorção , Íons , Metais Pesados/química , Análise Espectral
14.
15.
Environ Sci Pollut Res Int ; 26(27): 28294-28308, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31368068

RESUMO

Stable Hg(II)-containing flue gas has been successfully simulated by the plasma oxidation of Hg(0), and an effective solution for Hg(0) mercury fumes was obtained by combining the plasma with a ceramic nanomaterial. Characterization tests showed that the ceramic nanomaterial was mainly composed of silicon dioxide (SiO2) with other minor constituents, including potassium mica (KAl3Si3O11), iron magnesium silicate (Fe0.24Mg0.76SiO3) and dolomite (CaMg(CO3)2). The nanomaterial had many tube bank structures inside with diameters of approximately 8-10 nm. The maximum sorption capacity of Hg(II) was 5156 µg/g, and the nanomaterial can be regenerated at least five times. During the adsorption, chemical adsorption first occurred between Hg(II) and sulfydryl moieties, but these were quickly exhausted, and Hg(II) was then removed by surface complexation and wrapped into Fe moieties. The pseudo-first-order kinetic model and the Langmuir equation had the best fitting results for the kinetics and isotherms of adsorption. This work suggests that the ceramic nanomaterial can be used as an effective and recyclable adsorbent in the removal of gaseous Hg(II).


Assuntos
Carbonato de Cálcio/química , Ferro/química , Magnésio/química , Mercúrio/análise , Nanoestruturas/química , Dióxido de Silício/química , Adsorção , Silicatos de Alumínio/química , Cerâmica/química , Gases , Cinética , Mercúrio/química , Minerais/química
16.
Artigo em Inglês | MEDLINE | ID: mdl-31337104

RESUMO

The Taiyuan formation limestone water in the Huaibei coalfield is not only the water source for coal mining, but also the water source for industry and agriculture in mining areas. Its hydrogeochemical characteristics and water quality are generally concerning. In this paper, conventional ion tests were carried out on the Taiyuan formation limestone water of 16 coal mines in the Sunan and Linhuan mining areas of the Huaibei coalfield. Piper trigram, Gibbs diagram and an ion scale coefficient map were used to analyze the hydrogeochemical characteristics of the Taiyuan formation limestone water. The water quality was evaluated in a fuzzy comprehensive manner. The results show that the main cation and anion contents in the Taiyuan formation limestone water were Na+ > Mg2+ > Ca2+ > K+, SO42- > HCO3- > Cl-. There were differences in the hydrogeochemical types of the Taiyuan formation limestone water in the two mining areas; HCO3-Na type water was dominant in the Sunan mining area and SO4·Cl-Na type water was dominant in the Linhuan mining area. The chemical composition of the Taiyuan formation limestone water is mainly affected by the weathering of the rock and is related to the dissolution of the evaporated salt and the weathering of the silicate. The fuzzy comprehensive evaluation results show that the V-type water accounts for a large proportion of the Taiyuan formation limestone water in the study area and the water quality is poor. This study provides a basis for the development and utilization of the Taiyuan formation limestone water and water environmental protection in the future.


Assuntos
Carbonato de Cálcio/química , Minas de Carvão , Poluentes Químicos da Água/análise , Qualidade da Água , Agricultura , China , Monitoramento Ambiental/métodos , Tempo (Meteorologia)
17.
Mater Sci Eng C Mater Biol Appl ; 103: 109734, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31349529

RESUMO

The present work reports the very first hydrothermal synthesis of 100% triclinic phase pure aragonite (A1) with microdumbbell microstructural architecture and Au Nanoparticle-decorated (AuNP-decorated) aragonites (A2, A3 and A4) with spherical, pentagonal/hexagonal and agglomerated AuNP-decorated microdumbbells having triclinic aragonite phase as the major and cubic AuNPs as the minor phase. Even in dark the AuNP-decorated aragonites (especially A2) show efficacies as high 90% against gram-negative e.g., Pseudomonas putida (P. putida) bacteria. Further the AuNP-decorated aragonites (A3) show anti-biofilm capability of as high as about 20% against P. putida. Most importantly the AuNP-decorated aragonites (A3) offer anti-cancer efficacy of as high as 53% while those of A1, A2, and A4 are e.g., 26%, 46% and 37%, respectively. For the very first time, based on detailed investigations, the mechanisms behind such advance antibiofilm and anticancer activities are linked to the generation of excess labile toxic reactive oxygen species (ROS). Thus, these materials show enormous potential as futuristic, multi-functional biomaterials for anti-bacterial, anti-biofilm and anti-cancer applications.


Assuntos
Antibacterianos , Antineoplásicos , Carbonato de Cálcio , Ouro , Nanopartículas Metálicas/química , Pseudomonas putida/crescimento & desenvolvimento , Antibacterianos/química , Antibacterianos/farmacologia , Antineoplásicos/química , Antineoplásicos/farmacologia , Carbonato de Cálcio/química , Carbonato de Cálcio/farmacologia , Ouro/química , Ouro/farmacologia
18.
J Appl Microbiol ; 127(5): 1479-1489, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31301204

RESUMO

AIMS: Development of biomineralization technologies has largely focused on microbially induced carbonate precipitation (MICP) via Sporosarcina pasteurii ureolysis; however, as an obligate aerobe, the general utility of this organism is limited. Here, facultative and anaerobic haloalkaliphiles capable of ureolysis were enriched, identified and then compared to S. pasteurii regarding biomineralization activities. METHODS AND RESULTS: Anaerobic and facultative enrichments for haloalkaliphilic and ureolytic micro-organisms were established from sediment slurries collected at Soap Lake (WA). Optimal pH, temperature and salinity were determined for highly ureolytic enrichments, with dominant populations identified via a combination of high-throughput SSU rRNA gene sequencing, clone libraries and Sanger sequencing of isolates. The enrichment cultures consisted primarily of Sporosarcina- and Clostridium-like organisms. Ureolysis rates and direct cell counts in the enrichment cultures were comparable to the S. pasteurii (strain ATCC 11859) type strain. CONCLUSIONS: Ureolysis rates from both facultatively and anaerobically enriched haloalkaliphiles were either not statistically significantly different to, or statistically significantly higher than, the S. pasteurii (strain ATCC 11859) rates. Work here concludes that extreme environments can harbour highly ureolytic active bacteria with potential advantages for large scale applications, such as environments devoid of oxygen. SIGNIFICANCE AND IMPACT OF THE STUDY: The bacterial consortia and isolates obtained add to the possible suite of organisms available for MICP implementation, therefore potentially improving the economics and efficiency of commercial biomineralization.


Assuntos
Álcalis/metabolismo , Carbonato de Cálcio/metabolismo , Sporosarcina/metabolismo , Ureia/metabolismo , Anaerobiose , Bactérias/metabolismo , Carbonato de Cálcio/química , Sedimentos Geológicos/microbiologia , Consórcios Microbianos , Sporosarcina/genética , Sporosarcina/isolamento & purificação
19.
ACS Appl Mater Interfaces ; 11(31): 28228-28235, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31310494

RESUMO

Enclosed films, also called capsules, bearing an ultrathin and robust nanoshell have sparked much interest for use in many applications, for which facile preparation methods are urgently pursued. Inspired by the pH-programmed adhesion/cohesion of mussel-secreted foot proteins, polyphenol/polyamine capsules with an ultrathin and robust nanoshell are fabricated through a pH-switched assembly on sacrificial calcium carbonate (CaCO3) templates. Polyphenols adhere to the templates at pH 6.0 and rapidly cohere with polyamines at pH 8.0. The pH-switched assembly process is accomplished in only a few minutes where multiple instances of electrostatic interactions and chemical conjugation between polyphenols and polyamines occur. As a result, the capsules exhibit a nanoshell thickness of ∼10 nm and a superior mechanical strength of ∼1.575 GPa (elasticity modulus). Cell mimics are prepared through encasing enzymes in the lumen and present an activity recovery of ∼70% along with little activity decline during reuse. Amine or phenolic groups on the nanoshell of capsules are then applied to induce the generation of titania or silver nanoparticles, which may expand the applications of the capsules to the photo- and biorelated realms. Our study not only deepens the understanding of the adhering process of mussels but also offers a generic method toward functional materials for diverse applications.


Assuntos
Materiais Biomiméticos/química , Bivalves , Nanoconchas/química , Poliaminas/química , Polifenóis/química , Animais , Carbonato de Cálcio/química , Concentração de Íons de Hidrogênio
20.
Chemosphere ; 235: 308-315, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31260871

RESUMO

This study evaluates the potential use of a new limestone calcined clay cement (LC3) for stabilization/solidification of zinc contaminated soil. LC3 is a new ternary blend manufactured by the replacement of 50% cement clinker by locally available two supplementary cementitious materials (SCMs) - limestone and calcined clay. The incorporation of LC3 is evaluated on the soil spiked with 0.5% and 1% of Zinc (Zn) at curing times of 3, 7, 14, 28 and 56 days. pH, strength and leachability properties of the solidified/stabilised soil are measured for both mechanical and environmental conditions. Additionally, sequential extraction procedure (SEP), X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) analysis are performed to elucidate the mechanisms of Zn immobilization in the soil. The results show that the leachable Zn concentrations in the stabilised soil are well below the corresponding hazardous waste management regulatory limit after the curing time of 14 days. The soil pH and unconfined compressive strength of the stabilised soil increase with curing time. The SEP results confirm that LC3 considerably reduces the acid soluble fraction (F1) and increase the residual fraction (F4). The XRD and SEM results indicate that formation of Tri-calcium Silicate 3CaO·SiO2, Portlandite Ca(OH)2, Ettringite Ca6Al2(SO4)3(OH)12.26 H2O and Wulfingite Zn(OH)2 are the primary mechanisms for the immobilization of Zn in the LC3 stabilised soil.


Assuntos
Carbonato de Cálcio/química , Argila/química , Poluentes do Solo/análise , Zinco/análise , Força Compressiva , Materiais de Construção , Resíduos Perigosos/análise , Minerais , Dióxido de Silício , Zinco/toxicidade
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