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1.
Monogr Oral Sci ; 28: 91-98, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31940633

RESUMO

Dental erosion is the partial demineralisation of the tooth surface caused by repeated exposure to acids. The loss of surface tissue, which results from simultaneous and/or subsequent exposure to mechanical forces is known as erosive tooth wear (ETW). Excessive consumption of acidic beverages and foods has been the main focus of research into erosion. Enamel dissolution is significantly associated with chemical parameters: pH, buffer capacity, titratable acidity, viscosity, as well as calcium, phosphate and fluoride concentrations in the beverages and foods. Some of these parameters are used to calculate the degree of saturation of a given substance, which represents its driving force to demineralise dental hard tissues. Undersaturated substances with low pH and high titratable acidity and high buffer capacity have greater erosive potential, while substances with high concentrations of Ca2+ and phosphate cause less demineralisation. Other physical parameters also modulate the demineralisation processes. Swishing drinks in the mouth tends to cause more erosion, since the Nernst layer is continuously renewed and does not reach saturation. Recent systematic reviews confirm that frequent consumption of carbonated/soft drinks are the main dietary factor associated with ETW. Vitamin C and frequent consumption of natural fruit juices and acidic snacks or sweets are also significantly associated with more ETW; whereas higher consumption of milk and yoghurt is a protecting factor. Patients presenting with ETW should have their dietary habits assessed by recording their complete dietary intake in a diet record sheet. Dentists should assess the erosive potential of the different beverages and foods, as well as the frequency of ingestion, then elaborate specific preventive measures and dietary interventions individually tailored to each patient.


Assuntos
Atrito Dentário , Erosão Dentária , Desgaste dos Dentes , Bebidas , Alimentos , Humanos , Concentração de Íons de Hidrogênio
2.
Chem Pharm Bull (Tokyo) ; 68(1): 70-76, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31902902

RESUMO

In this study, nickel-aluminium complex hydroxides at different molar ratios (nickel-aluminium = 1 : 2, 1 : 1, 2 : 1, 3 : 1, and 4 : 1, referred to as NA12, NA11, NA21, NA31, and NA41) were prepared, and their adsorption capability for chromium(VI) ion was investigated. Firstly, physicochemical characteristics (SEM images, X-ray diffraction (XRD) patterns, specific surface area, amount of hydroxyl groups, and surface pH) of nickel-aluminum complex hydroxide were evaluated. The amount of chromium(VI) ion adsorbed onto NA11 (15.3 mg/g) was greater than that adsorbed onto the other adsorbents. This research elucidated that the amount of chromium(VI) ion adsorbed using nickel-aluminium complex hydroxide was related to the adsorbent surface properties (r = 0.818-0.875). Subsequently, the adsorbent (NA11) surface before and after adsorption of chromium(VI) ion was evaluated, and chromium energy (577 and 586 eV) detected after adsorption onto the NA11 surface. These results revealed that the NA11 surface properties were very important for the removal of chromium(VI) ion from aqueous solution. In addition, the effects of pH, contact time, and temperature on the adsorption of chromium(VI) ion were evaluated. We confirmed a high recovery percentage of chromium(VI) ion when using sodium hydroxide solution at 10-1000 mmol/L (approximately greater than 80%) in this experimental condition. Thus, NA11 is a promising adsorbent for the removal of chromium(VI) ion from aqueous solution.


Assuntos
Alumínio/química , Cromo/química , Complexos de Coordenação/química , Hidróxidos/química , Níquel/química , Adsorção , Concentração de Íons de Hidrogênio , Íons/química , Temperatura Ambiente , Termodinâmica , Poluentes Químicos da Água/química
3.
Chemosphere ; 240: 124909, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31550590

RESUMO

Environmental pollution and human health issues due to unrestricted electronic waste (e-waste) recycling activities have been reported at a number of locations. Among different e-waste recycling techniques, open burning of e-waste releases diverse metal(loid)s into the environment, which has aroused concern worldwide. In human health risk assessments (HHRAs), oral ingestion of soil can be a major route of exposure to many immobile soil contaminants. In vitro assays are currently being developed and validated to avoid overestimation of pollutants absorbed by the human body when calculating total pollutant concentrations in HHRAs. In this study, Cu, As, Cd, Sb, and Pb bioaccessibility in polluted soils (n = 10) from e-waste open burning sites at Agbogbloshie in Accra, Ghana, was assessed using an in vitro assay, the physiologically based extraction test. A bioaccessibility-corrected HHRA was then conducted to estimate the potential health risks to local inhabitants. The in vitro results (%) varied greatly among the different metal(loid)s (Cu: 1.3-60, As: 1.3-40, Cd: 4.2-67, Sb: 0.7-85, Pb: 4.1-57), and also showed marked variance between the gastric phase and small intestinal phase. The particle sizes of soil samples and chemical forms of metal(loid)s also influenced bioaccessibility values. Using these bioaccessibility values, both the hazard index and carcinogenic risk were calculated. The hazard index was above the threshold value (>1) for 5/10 samples, indicating a potential health risk to local inhabitants.


Assuntos
Resíduo Eletrônico , Metaloides/análise , Medição de Risco , Poluentes do Solo/farmacocinética , Disponibilidade Biológica , Exposição Dietética/efeitos adversos , Exposição Dietética/análise , Exposição Ambiental/efeitos adversos , Exposição Ambiental/análise , Monitoramento Ambiental , Gana , Humanos , Concentração de Íons de Hidrogênio , Metaloides/farmacocinética , Metaloides/toxicidade , Metais/análise , Metais/farmacocinética , Metais/toxicidade , Tamanho da Partícula , Reciclagem , Solo/química , Poluentes do Solo/análise , Poluentes do Solo/toxicidade
4.
Chemosphere ; 240: 124916, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563104

RESUMO

Cadmium contamination in greenhouse vegetable fields greatly limited the sustainable production especially of leafy vegetables. Hydroxyapatite (HAP), as a common soil amendment, has been widely used in the remediation of Cd-contaminated soils, while its remediation efficiency greatly depends on its particle sizes. In this study, a rhizobag pot experiment was conducted to investigate the effects of HAP (<60 nm, <12 µm and <80 µm) on bioavailability of Cd to celery grown in acidic and slightly Cd-contaminated greenhouse soil. The results suggested that HAP with the largest particle size (<80 µm) had the best effectiveness in reducing Cd uptake especially by the edible part of celery. Specifically, the increase in HAP (<80 µm) addition from 0.5% to 3% prominently reduced Cd concentrations in celery shoot by 19.6%-76.8% as compared with the untreated group. Also, adding HAP (<80 µm) especially at 3% significantly decreased translocation factor (TF) of Cd from celery root to shoot by 30.6% and reduced bioconcentration factor (BCF) of Cd from rhizosphere soil to celery shoot by 76.4%. These were predominantly associated with the significantly increased soil pH and the subsequently decreased soil CaCl2-Cd concentration after adding HAP (<80 µm). Overall, although rhizosphere soil pH was the key factor in controlling Cd uptake by edible celery and regulating BCF and TF of Cd, insignificant root-induced acidification had limited effect on the immobilization efficiency of Cd by HAP (<80 µm). In conclusion, HAP (<80 µm) has good potential for the remediation of Cd-contaminated greenhouse soils.


Assuntos
Apium/efeitos dos fármacos , Apium/metabolismo , Cádmio/farmacocinética , Durapatita/farmacologia , Poluentes do Solo/farmacocinética , Solo/química , Apium/crescimento & desenvolvimento , Biodegradação Ambiental , Disponibilidade Biológica , Cádmio/análise , Durapatita/química , Concentração de Íons de Hidrogênio , Tamanho da Partícula , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/metabolismo , Rizosfera , Poluentes do Solo/análise
5.
Chemosphere ; 240: 124882, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726609

RESUMO

Biomimetic dynamic membrane (BDM) has been employed as a promising membrane separation technology regarding water/wastewater treatment (Model pollutant is methylene blue). Given its catalytic function on micro-pollutant removal and fouling control, detailed mechanism for impacts of fabrication method, carriers (CNT and GO) and laccase on the construction of biomimetic layer and enzyme immobilization have not been clear so far. In this work, the BDM performance with various fabrication methods, carriers and laccase were investigated and verified. The BDM fabrication tests demonstrated that BDM with mixed filtration method had better filtration performance (up to 120 L m-2 h-1 flux and 80% removal rate) than BDM with stepwise filtration method. Moreover, the laccases immobilized on GO exhibited a stronger laccase activity than those on CNT. Increasing CNT or GO dosage strengthened removal rate, but lowered flux, meanwhile flux and removal rate exhibited a significant fluctuation with certain laccase dosage. At 25 g m-2 CNT or GO dosage and 50 g m-2 laccase dosage, the optimized flux and removal rate values were obtained. Further study investigated the surface morphology and property of BDM, showing that BDM with mixed filtration method turned out to be the optimized enzyme immobilization mechanism and fabrication method. In addition, during multiple filtration cycles, with the optimized conditions, the removal rate, flux and laccase activity of BDM could maintain at high levels. On account of the finding of the present study, selecting a suitable fabrication method, appropriate CNT or GO dosage and laccase dosage can indeed optimize the structure of biomimetic layer and enzyme immobilization, expanding its possibility on sustainable operation.


Assuntos
Biomimética/métodos , Enzimas Imobilizadas/química , Filtração/métodos , Lacase/química , Membranas Artificiais , Purificação da Água/métodos , Catálise , Concentração de Íons de Hidrogênio , Azul de Metileno/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
6.
Food Chem ; 305: 125433, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31499293

RESUMO

Native high methoxy citrus pectin (NP) was de-esterified by pectin methyl esterase to produce modified pectins [MP (42, 37, and 33)] having different degrees of esterification. Complex coacervation between a pea protein isolate (PPI) and each pectin was investigated as a function of pH (8.0-1.5) and mixing ratio (1:1-30:1, PPI-pectin). Complex formation was found to be optimal for biopolymer-mixing ratios of 8:1, 8:1, 25:1 and 25:1 for PPI complexed with NP, MP42, MP37 and MP33, respectively, at pHs 3.6, 3.5, 3.9 and 3.9. And, the critical pHs associated with complex formation (accessed by turbidity) was found to shift significantly to higher pHs as the degree of esterification of the pectin decreased, whereas the shift in the pH corresponding to their initial interactions was minimal with degree of esterification. Complexation of PPI with NP and MP42 greatly improved the protein solubility.


Assuntos
Proteínas de Ervilha/química , Pectinas/química , Hidrolases de Éster Carboxílico/metabolismo , Citrus/enzimologia , Concentração de Íons de Hidrogênio , Pectinas/metabolismo , Solubilidade
7.
Food Microbiol ; 85: 103284, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31500712

RESUMO

The GAD system is widely present in several types of organisms and is known to play an important role in bacterial acid tolerance. There is only one account of this system playing a role in oxidative stress in bacteria and one in yeasts. Here we show for first time that it affects the oxidative stress resistance of a Gram-positive bacterium, (L. monocytogenes, tested in three strains; 10403S, EGD-e, and LO28). We found a statistically significant reduction in survival after H2O2 exposure in ΔgadD3 and ΔgadD2 of EGD-e and in ΔgadD1 of LO28. Furthermore, we observed a lag phase prolongation in ΔgadD3 of 10403S and EGD-e and a larger inhibition zone in disk diffusion assay for ΔgadD1 and ΔgadD3 of EGD-e upon H2O2 exposure. All GAD genes playing a role in oxidative stress resistance are part of GADi system and this occurs partly through catalase activity, while the most potent GADe system plays no role. The latter effects could occur through the GABA shunt, but we show here that mutants in succinate semialdehyde dehydrogenase do not show a phenotype suggesting that either effects are through the GABA transaminase or, this pathway is not involved. Our study highlights for first time the role of the GAD system in oxidative stress resistance of a Gram-positive bacterium, which could be used in Food Hurdle Technology to eliminate pathogens such as L. monocytogenes, while it gives an insight on the general mechanism.


Assuntos
Glutamato Descarboxilase/metabolismo , Peróxido de Hidrogênio/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/enzimologia , Estresse Oxidativo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Deleção de Genes , Regulação Bacteriana da Expressão Gênica , Glutamato Descarboxilase/genética , Concentração de Íons de Hidrogênio , Listeria monocytogenes/genética
8.
Chemosphere ; 238: 124675, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524615

RESUMO

A synergistic combination of chloride and copper powder was proposed as a new method to reductively remove arsenic from highly-acidic wastewater with high arsenic content (HAWA). As(III) was reduced to As(0) by copper powder in the presence of chloride and were effectively removed from HAWA. The procedure to remove arsenic was optimized as follows: initial H+ concentration of 5 mol L-1, Cu-to-As molar ratio of 8, Cl-to-As molar ratio of 10, a reaction temperature of 60 °C, copper powder particle size of 68-24 µm, and a stirring speed of 300 r min-1. Under these optimal conditions, the removal rate of arsenic was close to 100%. Kinetics results suggested that the arsenic removal process was controlled by both diffusion and chemical reactions with an apparent activation energy of 29.78 kJ mol-1. The XRD results showed that the removed arsenic in the residue existed primarily in the form of AsCu3 alloy.


Assuntos
Arsênico/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Cloretos/química , Cloro , Cobre/química , Concentração de Íons de Hidrogênio
9.
Chemosphere ; 238: 124690, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524625

RESUMO

Doxorubicin (DOX) originated from users' urine has been an emerging environmental pollutant due to its significant genotoxicity to mankind. Thus, urine source separation is a potential strategy to isolate DOX at a higher concentration and reduce the burden of downstream wastewater treatment. To develop highly efficient, easy separation and retrievable materials for individual patient to conveniently remove DOX from own urine, magnetic Cu3(PO4)2 nanoflowers were prepared through anchoring amino-functionalized magnetic nanoparticles on the Cu3(PO4)2 nanoflowers. Characterizations revealed the magnetic nanoflowers were spherical in shape with a mean size of 15 µm, and porous and hierarchical in structure. Magnetic nanoparticles located the surface of petals. Multibatch experiments were performed to assess the removal performance of DOX from aqueous solution. The magnetic nanoflowers exhibited excellent removal efficiency of DOX under weakly alkaline condition at ambient temperature. Linear and non-linear analyses were carried out to compare the best fitting kinetics and isotherms. Sorption kinetic data best fitted the pseudo-second order model. The Freundlich isotherm explained equilibrium sorption data with R2 = 0.993 higher than that for the Langmuir isotherm. When the pH of synthetic urine was adjusted to weakly alkaline (pH 8.0-9.0), over 95% of DOX (20 mg L-1) was removed by a little of magnetic nanoflowers (50 mg L-1) within 5 min. Meanwhile, the magnetic nanoflowers could be easily separated and recovered from the synthetic urine by a magnet. So, for individual urine source separation strategy, the magnetic nanoflower seems to be an efficient, convenient and inexpensive approach to remove DOX from human urine.


Assuntos
Cobre/química , Doxorrubicina/análise , Magnetismo/métodos , Urina/química , Purificação da Água/métodos , Adsorção , Humanos , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Nanopartículas/química , Fosfatos/química , Águas Residuárias/química
10.
Sci Total Environ ; 700: 134418, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31629269

RESUMO

Soil pH is an important predictor of bacterial community composition and diversity. Examining the effects of pH on diversity, structure, interaction, and function of rhizosphere bacterial communities in acidic crop soils provide valuable information for knowing potential role of rhizosphere bacteria in crop yield. Here, we collected soils from artificial greenhouses and applied Illumina Miseq sequencing, quantitative PCR techniques, multiple ecological analysis methods, including topological analysis and functional profiling to analyze our data and validate our hypotheses. We found that the soil physicochemical properties, species diversity, and rhizosphere bacterial community composition were significantly affected by the degree of soil acidification (pH < 5.5 and pH > 5.5) but not vegetation type. Additionally, bacterial absolute abundance increased with higher pH. The 18 soil samples were clustered into two distinct groups of pH < 5.5 and pH > 5.5 at the OTU level, and soil pH had more of an effect on bacterial community composition compared to the other physicochemical variables. In addition, rhizosphere bacteria might presented relatively less competition for survival in pH < 5.5 soils, and bacterial community functions, including nutrient (i.e., carbon, nitrogen, phosphorus, and sulphur) cycling-related enzymes and proteins, were downregulated in more acidic soils (pH < 5.5) based on sequence analysis. To our knowledge, this report is the first to show that pH is a key factor affecting the diversity, structure, interaction, and function of rhizosphere bacterial communities in acidic crop soil in artificial greenhouses. Our findings emphasize that community function and structure of rhizosphere bacteria are closely correlated in more acidic soils, and the decreased crop yield may be correlated with attenuation of the function of the rhizosphere bacterial community.


Assuntos
Rizosfera , Microbiologia do Solo , Solo/química , Bactérias , Biodiversidade , Sequenciamento de Nucleotídeos em Larga Escala , Concentração de Íons de Hidrogênio , Microbiota , Nitrogênio , Fósforo
11.
Sci Total Environ ; 700: 134464, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31689648

RESUMO

Ocean acidification (OA) and warming currently threaten coastal ecosystems across the globe. However, it is possible that the former process could actually benefit marine plants, such as seagrasses. The purpose of this study was to examine whether the effects of the seagrass Thalassia hemprichii can increase the resilience of OA-challenged coral reef mesocosms whose temperatures were gradually elevated. It was found that seagrass shoot density, photosynthetic efficiency, and leaf growth rate actually increased with rising temperatures under OA. Macroalgal growth rates were higher in the seagrass-free mesocosms, but the calcification rate of the model reef coral Pocillopora damicornis was higher in coral reef mesocosms featuring seagrasses under OA at 25 and 28 °C. Both the macroalgal growth rate and the coral calcification rate decreased in all mesocosms when the temperature was raised to 31 °C under OA. However, the variation in gross primary production, ecosystem respiration, and net ecosystem production in the seagrass mesocosms was lower than in seagrass-free controls, suggesting that the presence of seagrass in the mesocosms helped to stabilize the metabolism of the system in response to simulated climate change.


Assuntos
Antozoários/fisiologia , Recifes de Corais , Hydrocharitaceae/fisiologia , Animais , Mudança Climática , Concentração de Íons de Hidrogênio , Água do Mar/química , Temperatura Ambiente
12.
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
13.
Biosci Biotechnol Biochem ; 84(1): 143-153, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31549575

RESUMO

Brevinin-GR23 (B-GR23) was a brevinin-2 like antimicrobial peptide, which had antimicrobial activity against Staphylococcus aureus with minimum inhibitory concentration (MIC) of 16 µM. B-GR23 increased the bacterial membrane permeation, leading to the damage of membrane integrity and the leakage of genomic DNA, then causing the cell death. The peptide nearly inhibited all plantonic bacteria to start the initial attachment of biofilm at the concentration of 1 × MIC. Whereas the disruption rates on immature and mature biofilm decreased from 60% to 20%. B-GR23 reduced the production of extracellular polysaccharides (EPS) in the planktonic growth of S. aureus, which is a crucial structure of biofilm formation. B-GR23 with the concentration of ½ × MIC inhibited 50% water-soluble EPS, and 48% water-insoluble EPS, which contributed to the antibiofilm activity. B-GR23 had no significant toxicity to human blood cells under-tested concentration (200 µM), making it a potential template for designing antimicrobial peptides.


Assuntos
Proteínas de Anfíbios/farmacologia , Antibacterianos/farmacologia , Peptídeos Catiônicos Antimicrobianos/farmacologia , Biofilmes/efeitos dos fármacos , Staphylococcus aureus/fisiologia , Animais , Antibacterianos/síntese química , Peptídeos Catiônicos Antimicrobianos/síntese química , Peptídeos Catiônicos Antimicrobianos/química , Permeabilidade da Membrana Celular/efeitos dos fármacos , DNA Bacteriano/efeitos dos fármacos , DNA Bacteriano/metabolismo , Eritrócitos/efeitos dos fármacos , Hemólise/efeitos dos fármacos , Temperatura Alta , Humanos , Concentração de Íons de Hidrogênio , Testes de Sensibilidade Microbiana/métodos , Polissacarídeos Bacterianos/antagonistas & inibidores , Conformação Proteica em alfa-Hélice , Estabilidade Proteica/efeitos da radiação , Ranidae , Infecções Estafilocócicas/tratamento farmacológico
14.
Biosci Biotechnol Biochem ; 84(1): 17-24, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31566084

RESUMO

Human milk oligosaccharides (HMOs) have drawn attention for their contribution to the explosive bifidobacterial growth in the intestines of neonates. We found that bifidobacteria can efficiently metabolize lacto-N-biose I (LNB), the major building blocks of HMOs, and we have developed a method to synthesize LNB by applying this system. We produced LNB on a kilogram scale by the method. This proved that, among the enterobacteria, only bifidobacteria can assimilate LNB, and provided the data that supported the explosive growth of bifidobacteria in neonates. Furthermore, we were also able to reveal the structure of LNB crystal and the low stability for heating at neutral pH, which has not been clarified so far. In this paper, using bifidobacteria and LNB as examples, I describe the research on oligosaccharide synthesis that was conducted by utilizing a sugar metabolism.Abbreviations: LNB: lacto-N-biose I; GNB: galacto-N-biose; HMOs: human milk oligosaccharides; GLNBP: GNB/LNB phosphorylase; NahK: N-acetylhexosamine 1-kinase; GalT: UDP-glucose-hexose-1-phosphate uridylyltransferase; GalE: UDP-glucose 4-epimerase; SP: sucrose phosphorylase.


Assuntos
Acetilglucosamina/análogos & derivados , Bifidobacterium/metabolismo , Glucosiltransferases/química , Leite Humano/química , Oligossacarídeos/metabolismo , Sacarose/química , Acetilglucosamina/síntese química , Acetilglucosamina/química , Acetilglucosamina/metabolismo , Resinas de Troca de Ânions/química , Bifidobacterium/crescimento & desenvolvimento , Cristalização , Dissacaridases/metabolismo , Microbioma Gastrointestinal/fisiologia , Temperatura Alta , Humanos , Concentração de Íons de Hidrogênio , Recém-Nascido
15.
Chemosphere ; 240: 124962, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31574447

RESUMO

Pre-magnetized Fe0 (Pre-Fe0) was for the first time applied as heterogeneous catalyst to enhance the oxidation efficiency of electro-Fenton (EF) for the degradation of p-nitrophenol (PNP). The parameters including current, initial pH and pre-Fe0 dosage of Pre-Fe0/EF process were optimized and compared with other two processes (conventional Fe0/EF and electro-oxidation) to confirm its advantage. The rate constants of PNP removal were 1.40-3.82 folds of those by Fe0/EF process under various experimental conditions. The application of pre-Fe0 as catalyst could extend the working pH range from 3.0 to neutral conditions for PNP removal and reduce the Fe0 dosage from 2 to 0.5 mM corresponding to Fe0/EF, avoiding the second pollution of iron sludge. The superiority of Pre-Fe0/EF process was also verified to improve the degradation and mineralization of other phenols and antibiotics. Furthermore, a possible pathway of PNP degradation was revealed by the identification of intermediates and organic acids, and the possible mechanism of pre-Fe0 efficiently enhanced the EF efficiency was proposed. This work demonstrated that such a novel heterogeneous EF process using pre-Fe0 catalyst was clean and promising for the degradation of refractory organic pollutants.


Assuntos
Peróxido de Hidrogênio/química , Ferro/química , Campos Magnéticos , Nitrofenóis/metabolismo , Esgotos/química , Poluentes Químicos da Água/análise , Catálise , Concentração de Íons de Hidrogênio , Oxirredução
16.
Chemosphere ; 239: 124768, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31518917

RESUMO

There is a need for cheap but, efficient methods for the removal of precious metals from wastewaters, which are normally lost during mineral processing. Moreover, the disposal of yeast waste from brewing has been a problem in many parts of the world. In this study, the removal of Pt(IV) from aqueous solutions using the readily available bentonite clay functionalised with spent yeast from brewing was investigated. The maximum adsorption capacity of Pt(IV) with 100 mg yeast-functionalised bentonite at pH 2 within 90 min was 255 µg g-1 (98.5% efficiency) but, decreased as pH increased. The adsorption capacity of Pt(IV) was insignificantly (p > 0.05) affected by the presence of competing ions (Fe(III), Ca(II), Mg(II), K(I), Co(II), Ni(II), Hf(IV), Zn(II) and other platinum group metals (PGMs)). Moreover, most of these metals were significantly adsorbed along with Pt(IV). The indicative cost-benefit analysis showed that 1 kg of the yeast-functionalised bentonite can remove ∼700 g Pt(IV) in which a profit of more than USD20000 can be made. The bentonite functionalised with spent yeast from brewing has a potential to recover lost PGMs in wastewater. Since, this is a cheap process, the mining and other industries can make much profit from such recoveries.


Assuntos
Bentonita/química , Platina/isolamento & purificação , Saccharomyces cerevisiae/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Resíduos Industriais , Metais/química , Soluções , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias , Água/química
17.
Chemosphere ; 239: 124771, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520970

RESUMO

Sorption of radionuclides on mineral surfaces retards their migration in the environment of a repository. Presence of organic ligands, however, affects sorption and consequently influences their transport behavior. In this study, we quantify the sorption of Eu(III) onto quartz surfaces as a function of pH in the absence and presence of diethylenetriaminepentaacetic acid (DTPA). Batch sorption experiments show a pH-dependent sorption of Eu(III) on quartz. The presence of DTPA results in slightly higher sorption of Eu(III) at neutral to slightly acidic pH and considerably lower sorption at alkaline conditions. Sorption experiments were simulated using the Diffuse Double Layer Model (DDLM) with single sorption sites (≡QOH) and monodentate surface complexation. The reactions were established based on the aqueous speciation calculation under the experimental conditions, and the thermodynamic constants of surface reactions were obtained and refined by numerical optimization. Results of surface complexation modeling show the formation of a surface species ≡QOHEuDTPA2-, explaining the elevated sorption of Eu(III) at neutral to slightly acidic pH. In contrast, dissolved EuDTPA2- complex species are present at alkaline pH, resulting in an enhanced mobility of Eu(III).


Assuntos
Európio/química , Modelos Químicos , Ácido Pentético/química , Quartzo/química , Adsorção , Concentração de Íons de Hidrogênio , Poluentes Radioativos do Solo/química , Termodinâmica
18.
Chemosphere ; 239: 124765, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520981

RESUMO

In this study, palm shell activated carbon powder (PSAC) and magnesium silicate (MgSiO3) modified PSAC (MPSAC) were thoroughly investigated for fluoride (F-) adsorption. F- adsorption isotherms showed that PSAC and MPSAC over-performed some other reported F- adsorbents with adsorption capacities of 116 mg g-1 and 150 mg g-1, respectively. Interestingly, the MgSiO3 impregnated layer changed the adsorption behavior of F- from monolayer to heterogeneous multilayer based on the Langmuir and Freundlich isotherm models verified by chi-square test (X2). Thermodynamic parameters indicated that the F- adsorption on PSAC and MPSAC was spontaneous and exothermic. PSAC and MPSAC were characterized using FESEM-EDX, XRD, FTIR and XPS to investigate the F- adsorption mechanism. Based on the regeneration tests using NaOH (0.01 M), PSAC exhibited poor regeneration (<20%) while MPSAC had steady adsorption efficiencies (∼70%) even after 5 regeneration cycles. This is due to highly polarized C-F bond was found on PSAC while Mg-F bond was distinguished on MPSAC, evidently denoting that the F- adsorption is mainly resulted from the exchange of hydroxyl (-OH) group. It was concluded that PSAC would be a potential adsorbent for in-situ F- groundwater remediation due to its capability to retain F- without leaching out in a wide range pH. MPSAC would be an alternative adsorbent for ex-situ F- water remediation because it can easily regenerate with NaOH solution. With the excellent F- adsorption properties, both PSAC and MPSAC offer as promising adsorbents for F- remediation in the aqueous phase.


Assuntos
Carvão Vegetal/química , Fluoretos/isolamento & purificação , Silicatos de Magnésio/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Fluoretos/química , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Phoeniceae , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Resíduos , Poluentes Químicos da Água/química , Purificação da Água/métodos , Difração de Raios X
19.
J Enzyme Inhib Med Chem ; 35(1): 280-288, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31790614

RESUMO

Acidity, hypoxia and increased release of exosomes are severe phenotypes of tumours. The regulation of pH in tumours involves the interaction of several proteins, including the carbonic anhydrases which catalyze the formation of bicarbonate and protons from carbon dioxide and water. Among CA isoforms, CA IX is over-expressed in a large number of solid tumours, conferring to cancer cells a survival advantage in hypoxic and acidic microenvironment, but there isn't evidence that CA IX expression could have a real clinical impact. Therefore, in this study for the first time the expression and activity of CA IX have been investigated in the plasmatic exosomes obtained from patients with prostate carcinoma (PCa). For this purpose, the study was performed through different methodological approaches, such as NTA, western blot analysis, enzyme activity assay, Nanoscale flow cytometry, ELISA, confocal microscopy. The results showed that PCa exosomes significantly overexpressed CA IX levels and related activity as compared to healthy donors. Furthermore, CA IX expression and activity were correlated to the exosome intraluminal pH, demonstrating for the first time that PCa exosomes are acidic. Our data suggest the possible use of the exosomal CA IX expression and activity as a biomarker of cancer progression in PCa.


Assuntos
Antígenos de Neoplasias/biossíntese , Anidrase Carbônica IX/biossíntese , Exossomos/metabolismo , Neoplasias da Próstata/sangue , Idoso , Antígenos de Neoplasias/sangue , Anidrase Carbônica IX/sangue , Linhagem Celular , Humanos , Concentração de Íons de Hidrogênio , Masculino , Microscopia Confocal , Pessoa de Meia-Idade
20.
Water Res ; 170: 115362, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31841770

RESUMO

Boron (B), normally present in ground water and sea water, is a vital micronutrient for plants, but is also toxic in excessive amounts. Under typical conditions, aqueous boron is present as boric acid (H3BO3), which is uncharged, making B particularly challenging to remove by mechanisms commonly applicable to removal of trace constituents. Adsorption of B onto aluminum hydroxide solids (Al(OH)3(s)) generated using aluminum-based electrocoagulation (EC) is a promising strategy for B removal. Infrared spectroscopy analysis indicated complexation of B(OH)3 with aluminum hydroxide solids via surface hydroxyl groups, while X-ray and infrared spectroscopy results indicated that the structure of the Al(OH)3(s) was influenced both by EC operating conditions and by water quality. A linear adsorption model predicted B removal well when initial concentrations were lower than 50 mg/L, but fit the experimental data poorly at higher initial B concentrations. The Langmuir adsorption model provided a good fit for a broader range of initial B concentrations (5-1000 mg/L). Factors affecting B adsorption during the EC process, including current intensity, Al dissolution rate, boron concentration, pH, and total dissolved solid (TDS), were investigated. Increasing current intensity initially led to a higher Al dissolution rate, and therefore higher B adsorption, but there was a limit, as further increases in current intensity caused rapid formation of Al(OH)3(s) having a large particle size and a low capacity to complex B. Boron removal decreased as its concentration increased. The best removal of B occurred at pH 8, corresponding to a slightly positive zeta potential for aluminum hydroxide and a small but significant fraction of negatively charged B species. Higher TDS concentrations facilitated the use of higher current intensities, i.e., the limit on the effective Al dissolution rate increased with increasing TDS. Two real water samples (river water and oilfield produced water) spiked with B were treated using EC, resulting in up to 50% B removal from river water (C0 = 10 mg/L, current = 0.2 A) in 2 h, and 80% B removal from produced water (C0 = 50 mg/L, current = 1.0 A) in 2 h.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Boro , Eletrocoagulação , Concentração de Íons de Hidrogênio
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