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1.
Chemosphere ; 248: 125912, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006826

RESUMO

Novel meso-zero valent iron (mZVI) was investigated for treating complex wastewater containing toxic heavy metal Cr6+ and organic compound phenol. This study is first of its kind illustrating coupled removal in single-step with H2O2 playing a major role as an oxidant and reductant. The mechanism involved was electron transfer from Fe0/2+ to Cr6+ resulting in Fe2+/3+ which in turn was consumed for phenol oxidation returning as Fe2+ into the system for further Cr6+ reduction. While comparing, single-step simultaneous removal of Cr6+ and phenol showed better performance in terms of pollutant removal, Fe2+/3+ recurrent reaction and precipitation generation, double-tep sequential removal performed better in iron active-corrosion time. It was also observed that the entire redox cycle of Cr6+-Cr3+-Cr6+ was reusable for co-contaminant phenol degradation at all pH with the recurrence of Fe2+-Fe3+-Fe2+. The proposed technique was checked for its viability in a single batch reactor and the complex chemistry of the reactions are unfolded by conducting chemical speciation and mass balance study at every stage of reaction. The unique functioning of mZVI was proven with micro-analysis of ZVI's surface and compared with granular ZVI, cZVI. The results obtained from this study open the door for a safer and cleaner single treatment system in removing both toxic heavy metals and organic compounds from contaminated surface water, groundwater and many such industrial effluents.


Assuntos
Cromo/química , Fenol/química , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/química , Corrosão , Água Subterrânea/química , Peróxido de Hidrogênio/química , Ferro/química , Oxidantes/química , Oxirredução , Fenóis/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
2.
J Agric Food Chem ; 68(8): 2506-2515, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32013414

RESUMO

Thiol groups of cysteine (Cys) residues in proteins react with quinones, oxidation products of polyphenols, to form protein-polyphenol adducts. The aim of the present work was to quantify the amount of adduct formed between Cys residues and 4-methylcatechol (4MC) in minced beef. A Cys-4MC adduct standard was electrochemically synthesized and characterized by liquid chromatography-mass spectrometry (LC-MS) as well as NMR spectroscopy. Cys-4MC adducts were quantified after acidic hydrolysis of myofibrillar protein isolates (MPIs) and LC-MS/MS analysis of meat containing either 500 or 1500 ppm 4MC and stored at 4 °C for 7 days under a nitrogen or oxygen atmosphere. The concentrations of Cys-4MC were found to be 2.2 ± 0.3 nmol/mg MPI and 8.1 ± 0.9 nmol/mg MPI in meat containing 500 and 1500 ppm 4MC, respectively, and stored for 7 days under oxygen. The formation of the Cys-4MC adduct resulted in protein thiol loss, and ca. 62% of the thiol loss was estimated to account for the formation of the Cys-4MC adduct for meat containing 1500 ppm 4MC. Furthermore, protein polymerization increased in samples containing 4MC as evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the polymerization was found to originate from protein-polyphenol interactions as evaluated by a blotting assay with staining by nitroblue tetrazolium.


Assuntos
Cisteína/química , Guaiacol/química , Carne/análise , Fenol/química , Animais , Bovinos , Proteínas Musculares/química , Oxirredução , Quinonas/química , Espectrometria de Massas em Tandem
3.
J Phys Chem Lett ; 11(5): 1940-1946, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-32073271

RESUMO

We present vibrational and electronic photodissociation spectra of a model chromophore of the green fluorescent protein in complexes with up to two water molecules, prepared in a cryogenic ion trap at 160-180 K. We find the band origin of the singly hydrated chromophore at 20 985 cm-1 (476.5 nm) and observe partially resolved vibrational signatures. While a single water molecule induces only a small shift of the S1 electronic band of the chromophore, without significant change of the Franck-Condon envelope, the spectrum of the dihydrate shows significant broadening and a greater blue shift of the band edge. Comparison of the vibrational spectra with predicted infrared spectra from density functional theory indicates that water molecules can interact with the oxygen atom on the phenolate group or on the imidazole moiety, respectively.


Assuntos
Proteínas de Fluorescência Verde/metabolismo , Teoria da Densidade Funcional , Proteínas de Fluorescência Verde/química , Imidazóis/química , Oxigênio/química , Fenol/química , Água/química , Água/metabolismo
4.
Chemosphere ; 241: 125066, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31622888

RESUMO

A porous carbon aerogel (CA) was prepared to activate persulfate (PS) for the removal of phenol. The adsorption of phenol on CA and its removal in CA/PS system was fitted to a second-order model and first-order kinetic model, respectively. Influencing factors of CA/PS such as pH, CA dose, PS concentration, phenol concentration and temperature were investigated. CA/PS presented good performance on phenol removal over a pH range of 3-11 with the highest removal obtained at pH 7. Four kinds of organic pollutants including tetracycline, Rhodamine B, Safranine T and malachite green were investigated in the CA/PS system, proving that the adsorption of the contaminants benefitted their subsequent oxidation removal. The removal of aromatic compounds (phenol, p-diphenol, p-chlorophenol, and p-nitrophenol) in CA/PS system followed a decreasing order of hydroxyl > chlorine > nitro. The radical scavenging experiments suggested the removal of phenol was mainly through a non-radical pathway. The study presented the preparation and application of a green catalyst to activate PS, which is very promising for the development of the technology and the treatment of phenolic wastewater.


Assuntos
Carbono/química , Fenol/química , Poluentes Químicos da Água/química , Adsorção , Catálise , Clorofenóis , Radical Hidroxila/química , Cinética , Nitrofenóis , Oxirredução , Porosidade , Sulfatos/química , Tetraciclina , Águas Residuárias/química , Poluentes Químicos da Água/análise
5.
Chemosphere ; 239: 124686, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494321

RESUMO

Oxidative degradation of aniline in aqueous solution was performed by the sono-activated peroxydisulfate coupled with PbO process, wherein a dramatic synergistic effect was found. Experiments were carried out in the batch-wise mode to investigate the influence of various operation parameters on the sonocatalytic behavior, such as ultrasonic power intensity, peroxydisulfate anion concentrations and PbO dosages. According to the scavenging effect of ethanol, methanol and tert-butyl alcohol, the principal oxidizing agents were presumed to be sulfate radicals descended from peroxydisulfate anions, activated via ultrasound or sonocatalysis of PbO. Based on the results attained from gas chromatograph-mass spectrometer, it was hypothesized that aniline was initially oxidized into iminobenzene radicals, followed with formation of nitrosobenzene, p-benzoquinonimine and nitrobenzene respectively. Condensation of nitrosobenzene with aniline generated azobenzene. Phenol was detected as one of degradation intermediates, which was sequentially converted into hydroquinone and p-benzoquinone.


Assuntos
Compostos de Anilina/química , Chumbo/química , Óxidos/química , Fenol/química , Sulfatos/química , Compostos Azo/síntese química , Benzoquinonas/síntese química , Etanol/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Hidroquinonas/síntese química , Metanol/metabolismo , Nitrobenzenos/síntese química , Compostos Nitrosos/síntese química , Oxidantes , Oxirredução , Semicondutores , Ondas Ultrassônicas , terc-Butil Álcool/metabolismo
6.
Chemosphere ; 240: 124921, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726593

RESUMO

The interplay of phenolic molecules with 3d transition metals, such as Fe and Cu, and their oxide surfaces, provide important fingerprints for environmental burdens associated with thermal recycling of e-waste and subsequent generation of notorious dioxins compounds and phenoxy-type Environmental Persistent Free Radicals (EPFRs). DRIFTS and EPR measurements established a strong interaction of the phenol molecule with transition metal oxides via synthesis of phenolic- and catecholic-type EPFRs intermediates. In this contribution, we comparatively examined the dissociative adsorption of a phenol molecule, as the simplest model for phenolic-type compounds, on Cu and Fe surfaces and their partially oxidized configurations through accurate density functional theory (DFT) studies. The underlying aim is to elucidate the specific underpinning mechanism forming phenoxy- or phenolate-type EFPRs. Simulated results show that, the phenol molecule undergoes fission of its hydroxyl's O-H bond via accessible activation energies. These values are lower by 46.5-74.1% when compared with the analogous gas phase value. Physisorbed molecules of phenol incur very low binding energies in the range of -2.1 to -5.5 over clean Cu/Fe and their oxides surfaces. Molecular attributes based on charge transfer and geometrical features are in accord with the very weak interaction in physisorbed states. Thermo-kinetic parameters established over the temperature region of 300 and 1000 K, exhibit a lower activation energy for scission of phenolic's O-H bonds over the oxide surfaces in reference to their pure surfaces (24.7 and 43.0 kcal mol-1vs 38.4 and 47.0 kcal mol-1).


Assuntos
Radicais Livres/química , Fenol/química , Fenóis/química , Adsorção , Catecóis , Dioxinas , Radical Hidroxila , Oxirredução , Óxidos/química , Temperatura , Elementos de Transição
7.
Chemosphere ; 239: 124812, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31521932

RESUMO

Carbon-based materials have been studied as metal-free catalyst for persulfate activation. At present, the activation performance of carbon materials for persulfate is usually characterized by the removal efficiency of organic pollutants. However, the kinetics of persulfate activation by carbon materials has not been investigated. In this study, the kinetics of peroxymonosulfate (PMS) activation by reduced graphene oxide (RGO) and sludge-derived biochar (BC) were investigated. The experimental results showed that the kinetics of PMS activation followed the two-phase kinetic model (fast phase (a1) and slow phase (a2)). In the absence of organic pollutants, the a1 and a2 were calculated to be 0.320 and 0.0471 min-1 for BC, respectively, and 0.322 and 0.0850 min-1 for RGO, respectively. Based on the characterization of BC and RGO, it can be concluded that the fast phase was mainly due to the formation of surface-bound active species. Competitive adsorption between PMS and targeted pollutants decreased the kinetic constant for the first phase (a1) and the kinetic constant for the second phase (a2) for both BC and RGO. The value of a1 and a2 increased for BC after the addition of phenol, due to the enhanced PMS activation by surface adsorbed phenol. The increase of phenol concentration decreased slightly the value of a1 and a2. The increase of PMS concentration increased significantly the value of a1 and a2. The decrease of a1 and a2 in repeated use of carbon materials could be due to the decrease of oxygen-containing functional groups and defect intensity.


Assuntos
Carvão Vegetal/química , Grafite/química , Peróxidos/química , Adsorção , Carbono/química , Catálise , Cinética , Fenol/química
8.
J Chem Ecol ; 46(2): 150-162, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31872313

RESUMO

The botanical source of Brazilian green propolis (BGP) is Baccharis dracunculifolia DC, which interacts not only with Apis mellifera, but also with galling insects. In the last decade, because of green propolis´ important biologic activities, the international demand for BGP overcame the production capacity, consequently, new approaches are required to increase this production. Hence, the understanding of the chemical ecology interactions of B. dracunculifolia with galls and bees in field conditions may provide insights to increase BGP's production. A "bee pasture" experiment aiming to better understand this plant-insect interaction was therefore performed. For that, 48 B. dracunculifolia individuals, being 24 females and 24 males, were cultivated and investigated for the following parameters: (1) phenolic and volatile compounds in both B. dracunculifolia leaves and green propolis, (2) environmental variables, (3) visiting rate by bees, (4) time of resin collection, and (5) number of galls. Regression analyses by independent linear mixed-effect models were run to correlate phenolic and volatile compounds concentration with the environmental and field variables. Significant differences in chemical profile and field variables were observed between male and female plants. Male plants showed higher infestation by galling insects while female plants showed higher number of visiting bees, time of resin collection and terpenes concentration, contributing to the differences observed in the field. The obtained results suggest that increasing the percentage of female B. dracunculifolia plants in the field may attract more bees and therefore enhance propolis production.


Assuntos
Baccharis/química , Abelhas/fisiologia , Própole/química , Animais , Baccharis/metabolismo , Comportamento Animal/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Feminino , Masculino , Espectrometria de Massas , Fenol/análise , Fenol/química , Fenol/farmacologia , Folhas de Planta/química , Folhas de Planta/metabolismo , Tumores de Planta/parasitologia , Própole/análise , Própole/farmacologia , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/química , Compostos Orgânicos Voláteis/farmacologia
9.
Food Chem ; 309: 125673, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31784073

RESUMO

New types of precooked pasta products have been developed based on refined and wholegrain wheat and spelt flours. The resulting dry pasta was then assessed for chemical composition, including amino acids composition, phenolics content, as well as antioxidant activity. The precooked pasta quality was also evaluated for starch gelatinization degree, physical properties, hardness, color profile of dry and hydrated pasta, and sensory characteristics. We found that the application of the extrusion-cooking technique for wheat and spelt pasta processing allows to achieve instant products with good nutritional characteristics and high degree of gelatinization, as well as attractive quality and sensory profiles. Microstructure showed compact and dense internal structure with visible bran particles if wholegrain flours were used. Wholegrain wheat and wholegrain spelt precooked pasta were characterized by better nutritional composition and greater antioxidant potential, but lower firmness and increased adhesiveness when compared with refined flours.


Assuntos
Culinária/métodos , Farinha/análise , Triticum/química , Aminoácidos/análise , Antioxidantes/química , Dureza , Fenol/química
10.
Environ Sci Process Impacts ; 21(12): 2118-2127, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31667476

RESUMO

Although redox reactions of organic contaminants with manganese oxides have been extensively studied, the role of dissolved O2 in these processes has largely been overlooked. In this study, the oxidative degradation of phenol by δ-MnO2 was investigated under both oxic and anoxic conditions. Dissolved O2 inhibited phenol degradation due to its promoting role in the reoxidation and precipitation of reduced Mn(ii) to Mn(iii) on the δ-MnO2 surface, resulting in partial transformation of δ-MnO2 to "c-disordered" H+-birnessite at pH 5.5 and feitknechtite, manganite, and hausmannite at pH 7.0 and 8.5. The reformed Mn(iii) phases could reduce phenol oxidation by blocking reactive sites of δ-MnO2. In addition, dissolved O2 caused a higher degree of particle agglomeration and a more severe specific surface area decrease, and hence lower reactivity of δ-MnO2. These findings revealed that after reductive dissolution by phenol and reoxidation by dissolved O2 throughout continuous redox cycling, δ-MnO2 became less reactive rather than being regenerated. These results can provide new insights into the understanding of the oxidation of organic contaminants by manganese oxides in the natural environment.


Assuntos
Poluentes Ambientais/química , Compostos de Manganês/química , Modelos Teóricos , Óxidos/química , Oxigênio/química , Fenol/química , Poluentes Ambientais/análise , Cinética , Oxirredução , Fenol/análise , Solubilidade
11.
Molecules ; 24(20)2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31623084

RESUMO

In this work, we proved the efficient synthesis of a bio-based hyper-branched polyphenol from a modified lignin degradation fragment. Protocatechuic acid was readily obtained from vanillin, a lignin degradation product, via alkaline conditions, and further polymerised to yield high molecular weight hyperbranched phenol terminated polyesters. Vanillic acid was also subjected to similar polymerisation conditions in order to compare polymerisation kinetics and differences between linear and hyperbranched polymers. Overall, protocatechuic acid was faster to polymerise and more thermostable with a degradation temperature well above linear vanillic acid polyester. Both polymers exhibited important radical scavenging activity (RSA) compared to commercial antioxidant and present tremendous potential for antioxidant applications.


Assuntos
Técnicas de Química Sintética , Lignina/química , Fenol/química , Polímeros/química , Antioxidantes/síntese química , Antioxidantes/química , Fenol/síntese química , Polimerização , Polímeros/síntese química , Polifenóis/síntese química , Polifenóis/química , Termodinâmica , Termogravimetria
12.
Chemosphere ; 237: 124546, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31549658

RESUMO

The Fe-modified spherical meso-silica MCM-41 was synthesized via the base precipitation with Fe3+/urea, and the structure was characterized. Especially, the selective and enhanced adsorption characters and mechanism of the monosubstituted benzenes were investigated. The results showed that Fe modification increased the specific surface area of MCM-41 and retained the mesopore structure. Importantly, adsorption of the monosubstituted benzenes indicated that the adsorption behavior of the monosubstituted benzenes on the Fe-modified MCM-41 (Fe-MCM-41) was a monolayer adsorption on the heterogeneous surfaces, and it showed great selective adsorption towards aniline, and the maximum adsorption capacity of the Fe-MCM-41 towards aniline was 17.5 and 7.9 times of nitrobenzene and phenol. Additionally, the adsorption process and the isotherm of aniline conformed to the pseudo-second order kinetic mode and the Langmuir mode. The maximum adsorption capacity of the Fe-MCM-41 and the pure MCM-41 towards aniline were 17.9 and 1.9 mg g-1, which indicated that the Fe modification significantly enhanced the adsorption capacity of MCM-41 towards aniline. Mechanism analysis reveals that the selective adsorption of the monosubstituted benzenes was attributed to the electron donating/withdrawing capacity of the substituent groups on benzene ring. Due to the electron withdrawing capacity of O atom, the exposed Fe atom of the ferric oxide loaded in the Fe-MCM-41 gave a strong electrophilic surface, which electrostatically interacted with the electron donating group (amino) in aniline.


Assuntos
Derivados de Benzeno/química , Compostos Férricos/química , Dióxido de Silício/química , Adsorção , Compostos de Anilina/química , Benzeno/química , Nitrobenzenos/química , Fenol/química , Poluentes Químicos da Água/química
13.
Enzyme Microb Technol ; 130: 109365, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31421722

RESUMO

Layered double hydroxides (LDHs) are cheap materials suitable for immobilization of enzymes. In this study, we prepared Zn/Al-Cl LDHs with different Zn:Al molar ratios for immobilization of the lipase from Pseudomonas cepacia. The best values for activity retention (188%), immobilization efficiency (96%) and hydrolytic activity in organic medium (279 U g-1) were obtained with a molar ratio of Zn:Al of 4:1, a protein loading of 162 mg g-1 and Tris-HCl buffer (10 mmol L-1, pH 7.5) as the solvent for preparing the lipase solution. The immobilized lipase keeps its activity when stored at 4 °C during 30 days. The immobilized lipase gave a conversion of 50% in 1 h for the kinetic resolution of the alcohol rac-1-phenylethanol, with both ees and eep higher than 99% and E higher than 200. In the reutilization study, 30 successive 1-h kinetic resolutions were done with the same batch of immobilized enzyme. For all 30 resolutions, 50% conversion was maintained, with ees and eep higher than 99% and E higher than 200. These are promising results that lay the basis for further studies of immobilization of lipases onto LDHs for applications in organic media.


Assuntos
Alumínio/química , Compostos de Anilina/química , Burkholderia cepacia/enzimologia , Enzimas Imobilizadas/metabolismo , Lipase/metabolismo , Fenol/química , Álcool Feniletílico/química , Zinco/química , Hidrólise , Hidróxidos/química , Cinética
14.
Analyst ; 144(17): 5261-5270, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31364612

RESUMO

In this work, an enrichment approach for the profiling of N-linked glycans was developed by utilizing a highly porous 3D graphene composite fabricated from graphene oxide nanosheets and a phenol-formaldehyde polymer via graphitization and KOH activation. In tailoring the large surface area (ca. 2213 m2 g-1) and 3D-layered mesoporous structure, the 3D graphene composite demonstrated not only high efficiency in glycan enrichment but also the size-exclusion effect against residual protein interference. For a standard protein ovalbumin digest, 26 N-linked glycans were identified with good repeatability, and the detection limit was as low as 0.25 ng µL-1 with the identification of 13 N-linked glycans (S/N > 10). When the mass ratio of the ovalbumin digest to the interfering proteins, i.e., bovine serum albumin and ovalbumin was 1 : 2000 : 2000, 18 N-linked glycans could still be detected with sufficient signal intensities. From a 60 nL minute complex human serum sample, up to 53 N-linked glycans with S/N > 10 were identified after the 3D graphene enrichment, while only 20 N-linked glycans were identified by the porous graphitized carbon material used for comparison. In addition, the application of the 3D graphene composite in profiling the up-regulated and down-regulated N-linked glycans from the real clinical serum samples of ovarian cancer patients confirmed the potential of the 3D graphene composite for analyzing minute and complicated biological samples.


Assuntos
Grafite/química , Nanoestruturas/química , Ovalbumina/química , Polissacarídeos/análise , Albumina Sérica/química , Feminino , Formaldeído/química , Humanos , Neoplasias Ovarianas/sangue , Oxirredução , Fenol/química , Fenóis/química , Polímeros/química , Polissacarídeos/isolamento & purificação , Porosidade , Soro
15.
Environ Pollut ; 253: 1066-1078, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31434184

RESUMO

In this study, the synthesis of Fe3O4@GO@g-C3N4 ternary nanocomposite for enhanced photocatalytic degradation of phenol has been investigated. The surface modification of Fe3O4 was performed through layer-by-layer electrostatic deposition meanwhile the heterojunction structure of ternary nanocomposite was obtained through sonicated assisted hydrothermal method. The photocatalysts were characterized for their crystallinity, surface morphology, chemical functionalities, and band gap energy. The Fe3O4@GO@g-C3N4 ternary nanocomposite achieved phenol degradation of ∼97%, which was significantly higher than that of Fe3O4@GO (∼75%) and Fe3O4 (∼62%). The enhanced photoactivity was due to the efficient charge carrier separation and desired band structure. The photocatalytic performance was further enhanced with the addition of hydrogen peroxide, in which phenol degradation up to 100% was achieved in 2 h irradiation time. The findings revealed that operating parameters have significant influences on the photocatalytic activities. It was found that lower phenol concentration promoted higher activity. In this study, 0.3 g of Fe3O4@GO@g-C3N4 was found to be the optimized photocatalyst for phenol degradation. At the optimized condition, the reaction rate constant was reported as 6.96 × 10-3 min-1. The ternary photocatalyst showed excellent recyclability in three consecutive cycles, which confirmed the stability of this ternary nanocomposite for degradation applications.


Assuntos
Óxido Ferroso-Férrico/química , Nanocompostos/química , Fenol/química , Catálise , Luz , Modelos Químicos , Fenóis , Processos Fotoquímicos
16.
Environ Pollut ; 253: 1100-1106, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31434187

RESUMO

A polymer inclusion membrane (PIM) that contains a polyvinyl chloride (PVC) polymer matrix and 1-octanol (OCT) as specific carrier (PO-PIM) was prepared to investigate the mass transfer behaviour of phenol in aqueous solutions. Results showed that the mass transfer behaviour of the PO-PIM for phenol conformed to the first-order kinetics. In addition, the mass transfer efficiency for phenol reached the maximum when the OCT content was 82.8 wt%. The mass transfer activation energy (Ea) was 14.46 kJ mol-1, which indicated that intramembranous diffusion was the main controlling factor in the mass transfer process. The introduction of hydrophobic additives, such as kerosene, liquid paraffin and vegetable oil, into the PO-PIM could remarkably improve its stability. In an aqueous solutions of phenol ranging from 0 mg L-1 to 9000 mg L-1, the initial flux (J0) of kerosene/PVC/OCT-PIM (KPO-PIM) was positively correlated with the initial concentration of phenol. For a stripping solution with a feed solution pH of 2.0 and a sodium hydroxide concentration of 0.1 mol L-1, the maximum permeability coefficient during stable mass transfer reached 12.55 µm s-1. At a mass transfer area of 3.14 cm2, an enrichment factor (EF) of 3.5 for 200 mg L-1 of phenolic aqueous solution was achieved within 48 h through KPO-PIM.


Assuntos
Modelos Químicos , Fenol/química , Polímeros/química , Cloreto de Polivinila/química , 1-Octanol/química , Difusão , Querosene/análise , Cinética , Membranas Artificiais , Água
17.
Dalton Trans ; 48(41): 15613-15624, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31408065

RESUMO

The synthesis, structural and photophysical characterisation of four tricarbonyl rhenium(i) complexes bound to 1,10-phenanthroline and a tetrazolato ancillary ligand are reported. The complexes are differentiated by the nature (hydroxy or methoxy) and position (meta or para) of the substituent attached to the phenyl ring in conjugation to the tetrazole ring. The complexes exhibit phosphorescence emission from triplet charge transfer excited states, with the maxima around 600 nm, excited state lifetime decays in the 200-300 ns range, and quantum yield values of 4-6% in degassed acetonitrile solutions. The nature and position of the substituent does not significantly affect the photophysical properties, which remain unchanged even after deprotonation of the hydroxide group on the phenol ring. The interpretation of the photophysical data was further validated by resonance Raman spectroscopy and time-dependent density functional theory calculations. All the complexes are internalised within cells, albeit to variable degrees. As highlighted by a combination of flow cytometry and confocal microscopy, the species display diffuse cytoplasmic localisation except for the complex with the hydroxy functional group at the para position, which reveals lower accumulation in cells and more pronounced punctate staining. Overall, the complexes displayed low levels of cytotoxicity.


Assuntos
Complexos de Coordenação/química , Fenol/química , Rênio/química , Tetrazóis/química , Animais , Complexos de Coordenação/toxicidade , Ligantes , Camundongos , Modelos Moleculares , Conformação Molecular , Prótons , Teoria Quântica , Células RAW 264.7
18.
Int J Biol Macromol ; 138: 349-358, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31295480

RESUMO

Cigarette smoke contains a lot of harmful chemicals which cause different diseases like cancer, heart disease, bronchitis and ulcer etc. Ammonia and phenol are among those chemicals which cause cancer, fibrosis, respiratory disorder and pneumonia. So, to remove ammonia and phenol from cigarette smoke, five different types of carboxymethyl starch-g-polyacrylic acids (CMS-g-PAAs) were synthesized by using different initiators, different mole ratio of acrylic acid to CMS anhydroglucose unit (AGU) and different amount of water. Three types of modified CMSs, CMS-g-PAA1, CMS-g-PAA3 and CMS-g-PAA4 were selected for further characterization and application for ammonia and phenol adsorption. The 1H NMR and FT-IR spectroscopy confirmed the successful grafting of PAA on CMS. Crystallinity of CMS and three modified CMSs was checked by their XRD analysis. The XRD analysis showed that CMS had crystalline nature which was lost after modification. The thermal properties of CMS and the modified samples were checked by TGA and DTG which also gave information about the successful grafting on PAA on CMS. Finally the modified CMSs were further used for the adsorption applications of ammonia and phenol from the gaseous stream. It was found that CMS-g-PAA4 showed the highest adsorption efficiency towards ammonia (0.352 mmol/g) and phenol (0.18 mmol/g).


Assuntos
Resinas Acrílicas/química , Amônia/química , Amônia/isolamento & purificação , Fenol/química , Fenol/isolamento & purificação , Amido/análogos & derivados , Adsorção , Técnicas de Química Sintética , Análise Custo-Benefício , Poluentes Ambientais/química , Poluentes Ambientais/isolamento & purificação , Química Verde , Amido/química
19.
Food Chem ; 298: 125064, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260954

RESUMO

Edible films based on gelatin and chitosan have high gas and aroma barrier properties. This study focused on their capability to sorbed/retain aroma compounds (1-hexanal, 2-hexen-1-ol, 1-hexanol, 3-hexanone and phenol) at three relative humidity level (≤2%, 53% or 84% RH). Whatever the relative humidity condition, the order of sorption is keton (3-hexanone) < aldehyde (1-hexanal) < aliphatic alcohols (2-hexen-1-ol and 1-hexanol) < phenol. This order could be related to the intrinsic chemical properties of aroma compounds. The increase in moisture enhanced the sorption at the highest RH for all the aroma compounds. However, a competition between water and aliphatic alcohols is observed at 53%RH. All compounds have an ideal sorption behaviour (logarithmic increase) except 1-hexanal. The sorption of 1-hexanal, 1-hexanol, 2-hexen-1-ol and 3-hexanone induced an antiplasticization of the network by increasing the film Tg by more than 5 °C. On the contrary, phenol was an efficient plasticizer at least as high as moisture.


Assuntos
Quitosana/química , Gelatina/química , Compostos Orgânicos Voláteis/química , Adsorção , Álcoois/química , Varredura Diferencial de Calorimetria , Cromatografia Gasosa , Umidade , Cetonas/química , Cinética , Fenol/química , Temperatura
20.
J Environ Sci (China) ; 83: 183-194, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31221381

RESUMO

The photocatalytic activity of Fe-doped TiO2 nanoparticles is significantly increased by an acid-treatment process. The photocatalyst nanoparticles were prepared using sol-gel method with 0.5 mol% ratio of Fe:Ti in acidic pH of 3. The nanoparticles were structurally characterized by means of X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). It was observed that the photocatalytic activity suffered from an iron oxide contaminating layer deposited on the surface of the nanoparticles. This contamination layer was removed using an HCl acid-treatment process. The photocatalytic activity using 500 mg/L of Fe0.5-TiO2 in a 10 mg/L of phenol solution increased significantly from 33% to 57% (about 73% increase in the performance), within 90 min of reaction time under visible light irradiation. This significant improvement was achieved by removing the iron oxide contamination layer from the surface of the nanoparticles and adjusting pH to mild acidic and basic pHs.


Assuntos
Modelos Químicos , Fenol/química , Processos Fotoquímicos , Catálise , Luz , Fenóis , Espectroscopia Fotoeletrônica , Espectrometria por Raios X , Titânio/química , Difração de Raios X
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