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1.
Artigo em Inglês | MEDLINE | ID: mdl-33803950

RESUMO

The introduction of toxic chemicals into the environment can result in water pollution leading to the degradation of biodiversity as well as human health. This study presents a new approach of using metal oxides (Al2O3 and SiO2) modified with a plasmonic metal (silver, Ag) nanoparticles (NPs)-based nanofluid (NF) formulation for environmental remediation purposes. Firstly, we prepared the Al2O3 and SiO2 NFs of different concentrations (0.2 to 2.0 weight %) by ultrasonic-assisted dispersion of Al2O3 and SiO2 NPs with water as the base fluid. The thermo-physical (viscosity, activation energy, and thermal conductivity), electrical (AC conductivity and dielectric constant) and physical (ultrasonic velocity, density, refractive index) and stability characteristics were comparatively evaluated. The Al2O3 and SiO2 NPs were then catalytically activated by loading silver NPs to obtain Al2O3/SiO2@Ag composite NPs. The catalytic reduction of 4-nitrophenol (4-NP) with Al2O3/SiO2@Ag based NFs was followed. The catalytic efficiency of Al2O3@Ag NF and SiO2@Ag NF, for the 4-NP catalysis, is compared. Based on the catalytic rate constant evaluation, the catalytic reduction efficiency for 4-NP is found to be superior for 2% weight Al2O3@Ag NF (92.9 × 10-3 s-1) as compared to the SiO2@Ag NF (29.3 × 10-3 s-1). Importantly, the enhanced catalytic efficiency of 2% weight Al2O3@Ag NF for 4-NP removal is much higher than other metal NPs based catalysts reported in the literature, signifying the importance of NF formulation-based catalysis.


Assuntos
Nanopartículas Metálicas , Prata , Óxido de Alumínio , Catálise , Humanos , Nitrofenóis , Dióxido de Silício
2.
J Environ Manage ; 289: 112479, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33838465

RESUMO

Gypsum amendment is widely used to resolve alkalinity issues and implement sustainable management for bauxite residue disposal areas (BRDAs). Amended BRDAs under natural conditions suffer from long-term erosion processes. Nevertheless, the effect of erosion on amendment efficacy is rarely assessed. In this study, by integrating the geochemical modelling of PHREEQC and column leaching experiments, the dissolution of alkaline solids in bauxite residue (BR) and gypsum amendment, as well as their environmental behaviors, were determined through a 1-year simulated rainfall leaching experiment. The PHREEQC simulation results demonstrated that Na+ ion strength, CO2 partial pressure and rainfall, all affected the saturation index (SI) of calcite significantly and accelerated its corrosion, leading to the dissolution of gypsum and calcite in a relatively stable state. However, Na+ ion strength and rainfall significantly acted on the SI of gypsum, which lead to loss of Ca2+ and reduction of alkaline stability. In addition to the effects of Na+ and Ca2+ on the saturation concentration of gypsum and calcite solution, Na+ and Ca2+ also exhibited significant effects on the equilibrium of chemical species reactions. The column results confirmed that stability of gypsum and calcite was consistent with the simulation results of PHREEQC in the BRDAs environment. Furthermore, multiple linear regressions revealed differences in combined contributions of rainwater and atmospheric CO2 on the stability of calcite and gypsum. The PHREEQC simulation provides a new approach to predict long-term alkaline stability of BR as well as to establish sustainable remediation on BRDAs during erosion process.


Assuntos
Óxido de Alumínio , Sulfato de Cálcio , Solo
3.
Int J Oral Maxillofac Implants ; 36(2): 289-294, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33909718

RESUMO

PURPOSE: The objective of this study was to evaluate the influence of the oxide layer removal procedure using acid on the roughness and internal fit of overcast universal castable long abutments (UCLAs) for a taper connection. MATERIALS AND METHODS: For this, maxillary first premolars were waxed on the plastic sleeve of 15 UCLAs with a premachined interface. The specimens were overcast using the NiCr alloy, and the frameworks were randomly distributed to undergo one of two different oxide layer removal methods: blasting with 100-µm particles of aluminum oxide at 0.60-MPa pressure or bathing for 5 hours in 0.5% hydrofluoric acid. The surface roughness was evaluated by a light interferometer at the subcritical contour of each abutment. Next, the frameworks were attached to the respective analogs for internal fit evaluation. The central cross section of each assembly was exposed, and three regions were visualized by scanning electron microscopy (SEM): taper interface, axial wall, and index region. The premachined base was used as the control. The groups were compared using analysis of variance (ANOVA) and Tukey post hoc test (α = .05). RESULTS: The results showed that acid bathing produced intermediary roughness between premachined and blasted surfaces (P < .05). SEM images showed a sealed interface at the taper region of all groups, despite some irregularities after alumina blasting. Increased discrepancies at the axial wall and index region were found after the alumina blasting procedure (P < .05). CONCLUSION: It was concluded that acid bathing should be used, instead of blasting to remove the oxide layer, to produce a better fit and smoother surface on UCLAs.


Assuntos
Dente Suporte , Óxidos , Óxido de Alumínio , Teste de Materiais , Microscopia Eletrônica de Varredura , Propriedades de Superfície
4.
J Environ Manage ; 287: 112302, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33714045

RESUMO

Fly ash and arsenic species have been regarded as contaminants that pollute the environment. Herein, low alumina fly ash (LAFA) was utilized to fabricate the As(V) and As(III) adsorbent via combining the routes of alkali fusion and incipient-wetness impregnation. The characterization results suggested that the grafted ferric citrate was coordinated to LAFA by substituting a Si4+ to a Fe3+, and the compound monosodium citrate was observed. Based on the XPS analysis, the C-O and -COO- groups of monosodium citrate played the significant role in uptaking As(V) and As(III) species by chemical complexation, the FeOOH adsorbed As(V) and As(III) species via ion-exchange, and the Fe2O3 oxidize As(III) into As(V). Additionally, it was observed that the As(V) removal performance by adsorbent prepared with different modifiers was in the order of FeC6H5O7 (ca. 93.7%) > C6H8O7 (84%) > HCl (73%). And then, the optimal adsorbent synthesis condition for As(V) uptake was explored at ferric citrate loaded LAFA with 1:1 mass ratio (fly ash to NaOH) under temperature 923 K. The maximum monolayer adsorption capacities of the optimal adsorbent were 2725.0 µgAs(V)/g and 2281.9 µgAs(III)/g, and the removal efficiency of As(V) and As(III) was near 100% for their initial concentrations below 500 ppb, where the residual arsenic concentration met the required standard in drinking water (lower than 10 ppb).


Assuntos
Arsênico , Poluentes Químicos da Água , Purificação da Água , Adsorção , Óxido de Alumínio , Arsênico/análise , Cinza de Carvão , Compostos Férricos , Concentração de Íons de Hidrogênio , Cinética , Citrato de Sódio , Poluentes Químicos da Água/análise
5.
Environ Sci Technol ; 55(6): 3929-3939, 2021 03 16.
Artigo em Inglês | MEDLINE | ID: mdl-33646759

RESUMO

Bioneutralization of pH by microbial fermentation of added carbon substrates is a promising new method for remediation of the 1.7 GT/yr of alkaline mining tailings produced globally. Here, we present the first study to systematically compare and optimize the efficacy of microbial inocula of varying diversities, structures, and provenance and organic carbon substrates of varying complexities on the rate and extent of pH bioneutralization in alkaline bauxite residue tailings. Laboratory-scale bioreactors inoculated with soda lake sediments or with monosaccharide substrates added had a significantly lower minimum pH (<8) and a significantly higher maximum rate of pH neutralization (>0.02 µmol H+ day-1) and achieved these in significantly less time (<26 days) compared to bioreactors with other inocula or substrates. The soda lake sediment introduced a significantly higher-diversity microbial community with a distinct structure (dominated by Euryarchaeota and Bacteroidetes, rather than Acidobacteria and Actinobacteria), supporting higher acetate and formate-yielding fermentation pathways compared to other inocula. The strong performance of monosaccharides is attributed to widespread microbial capacity for efficient fermentation. Using either monosaccharide carbon substrates or soda lake sediments is recommended to maximize bioneutralization efficiency at the industrial scale.


Assuntos
Carbono , Microbiota , Óxido de Alumínio , Bactérias , Reatores Biológicos
6.
Ecotoxicol Environ Saf ; 213: 112003, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33588188

RESUMO

A green rust-coated expanded perlite (GR-coated Exp-p) microelectrode was synthesized and incorporated into a column-mode three-dimensional electrokinetic (3D-EK) platform to effectively pursue a continuous Cr(VI) removal from the aqueous solution. Brucite-like layers of GR were decorated onto the Exp-p material. The molar ratio of Fe(II) to Fe(III) played a most vital role among the three synthesis factors in influencing the performance of the particle electrode. For the equilibrium adsorption experiments, the target maximum adsorption capacity of 122 mg/g was predicted by a target optimizer and desirability function at the conditions following the pH of 4.7, the initial concentration of 172.4 mg/L, the dosage of 0.28 g/L, and the temperature of 28.96 °C, respectively. SO42-, Cl-, and NO3- fiercely competed with Cr(VI) anions in the acidic conditions for the locally positive sites. A low concentration and a slow flow were favored in the column-mode 3D-EK platform. The pseudo-first-order and Langmuir models were suitable for describing the kinetics and isotherms of the adsorption process, respectively. Cr(VI) anions were electrostatically attracted to the silanol groups and GR surface of the adsorbent, subsequently reduced in both heterogeneity and homogeneity, and finally immobilized by coordinating with silanediol groups and silanetriol groups.


Assuntos
Cromo/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Óxido de Alumínio , Ânions , Eletrodos , Compostos Férricos , Concentração de Íons de Hidrogênio , Cinética , Dióxido de Silício , Temperatura , Água , Poluentes Químicos da Água/análise
7.
Molecules ; 26(3)2021 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-33525515

RESUMO

Polymer templates play an essential role in the robust infiltration-based synthesis of functional multicomponent heterostructures with controlled structure, porosity, and composition. Such heterostructures are be used as hybrid organic-inorganic composites or as all-inorganic systems once the polymer templates are removed. Using iron oxide/alumina heterostructures formed by two-step infiltration of polystyrene-block-polyvinyl pyridine block copolymer with iron and aluminum precursors from the solution and vapor-phases, respectively, we show that the phase and morphology of iron oxide nanoparticles dramatically depend on the approach used to remove the polymer. We demonstrate that thermal and plasma oxidative treatments result in iron oxide nanoparticles with either solid or hollow morphologies, respectively, that lead to different magnetic properties of the resulting materials. Our study extends the boundaries of structure manipulations in multicomponent heterostructures synthesized using polymer infiltration synthesis, and hence their properties.


Assuntos
Nanopartículas/química , Nanoestruturas/química , Polímeros/química , Óxido de Alumínio/química , Compostos Férricos/química , Magnetismo/métodos , Nanotecnologia/métodos , Poliestirenos/química , Piridinas/química
8.
Molecules ; 26(4)2021 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-33562208

RESUMO

MgAl2O4-spinel has wide industrial and geological applications due to its special structural and physical-chemical features. It is presumably the most important endmember of complex natural spinel solid solutions, and therefore provides a structural model for a large group of minerals with the spinel structure. There exists a well known but still inadequately understood phenomenon in the structure of MgAl2O4-spinel, the Mg-Al cations readily exchanging their positions in response to variations of temperature, pressure, and composition. A large number of experiments were performed to investigate the Mg-Al cation order-disorder process usually quantified by the inversion parameter x (representing either the molar fraction of Al on the tetrahedral T-sites or the molar fraction of Mg on the octahedral M-sites in the spinel structure), and some thermodynamic models were thereby constructed to describe the x-T relation. However, experimental data at some key T were absent, so that the different performance of these thermodynamic models could not be carefully evaluated. This limited the interpolation and extrapolation of the thermodynamic models. By performing some prolonged annealing experiments with some almost pure natural MgAl2O4-spinel plates and quantifying the x values with single-crystal X-ray diffraction technique, we obtained some critical equilibrium x values at T down to 773 K. These new x-T data, along with those relatively reliable x values at relatively high T from early studies, clearly indicate that the CS94 Model (a model constructed by Carpenter and Salje in 1994) better describes the Mg-Al cation order-disorder reaction in MgAl2O4-spinel for a wide range of T. On the basis of the CS94 Model, a geothermometer was established, and its form is T-closure = 21362 × x3 - 12143 × x2 + 6401 × x - 10 (T-closure standing for the closure temperature of the Mg-Al cation exchange reaction). This geothermometer can be used to constrain the thermal history of the geological bodies containing MgAl2O4-spinel.


Assuntos
Alumínio/química , Magnésio/química , Óxidos/química , Óxido de Alumínio/química , Óxido de Magnésio/química , Minerais/química , Modelos Moleculares , Soluções/química , Temperatura , Termodinâmica , Difração de Raios X
9.
J Prosthet Dent ; 125(4): 703.e1-703.e7, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33551138

RESUMO

STATEMENT OF PROBLEM: High-performance thermoplastics have been adopted as an alternative restorative material to metal or ceramics. However, a straightforward surface modification process to provide a durable bond strength between the polymer and the veneering material is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the shear bond strength (SBS) of different veneering resin materials to polyetherketoneketone (PEKK) after different surface treatments. MATERIAL AND METHODS: Rectangular (7×7×2 mm) PEKK specimens (N=120) were randomly allocated to the following 6 groups (n=20): untreated (Cnt); nonthermal plasma (NTP) treated; tribochemical silica airborne-particle abrasion with 30-µm silica-modified Al2O3 (Tbc); abraded with a coarse-grit diamond rotary instrument (Ab); tribochemical silica airborne-particle abrasion + plasma treated (Tbc_NTP); abraded + plasma treated (Ab_NTP). After a bonding agent (PEKK Bond) was applied to the specimens, each group was divided into 2 subgroups according to the applied veneering resin materials: polymethylmethacrylate (PMMA) and nanohybrid composite resin (NHC, n=10). The specimens were stored in water for 24 hours at 37 °C and subjected to the SBS test by using a universal testing machine, and failure modes were evaluated using a stereomicroscope. Two-way analysis of variance (ANOVA) was performed followed by the Tukey honestly significant difference (HSD) test to statistically analyze the data (α=.05). RESULTS: The 2-way ANOVA showed that surface treatment methods, veneering material, and their interactions were significantly different on the SBS values (P<.001). The highest SBS values were determined for the Tbc and Tbc_NTP treatment groups not only for PMMA (10.71 to 11.63 MPa) but also for NHC (19.80 to 20.60 MPa) veneering resin materials (P<.05). CONCLUSIONS: The bonding capacity of PEKK to the PMMA and NHC veneering resin materials can be significantly improved by using tribochemical silica airborne-particle abrasion alone or with nonthermal plasma surface treatment techniques. Furthermore, using NHC veneering resin material is recommended over PMMA.


Assuntos
Colagem Dentária , Cimentos de Resina , Óxido de Alumínio , Benzofenonas , Análise do Estresse Dentário , Teste de Materiais , Polímeros , Resistência ao Cisalhamento , Propriedades de Superfície , Zircônio
10.
Chemosphere ; 273: 129723, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33524745

RESUMO

Over the past decades, inspired by the outstanding properties of clay minerals such as abundance, low-cost, environmental benignity, high stability, and regularly arranged silica-alumina framework, researchers put much efforts on the interface assembly and surface modification of natural minerals with bare photocatalysts, i.e. TiO2, g-C3N4, ZnO, MoS2, etc. The clay-based hybrid photocatalysts have resulted in a rich database for their tailor-designed microstructures, characterizations, and environmental-related applications. Therefore, in this study, we took a brief introduction of three representative minerals, i.e. kaolinite, montmorillonite and rectorite, and discussed their basic merits in photocatalysis applications. After that, we summarized the recent advances in construction of stable visible-light driven photocatalysts based on these minerals. The structure-activity relationships between the properties of clay types, pore structure, distribution/dispersion and light absorption, carrier separation efficiency as well as redox performance were illustrated in detail. Such representative information would provide theoretical basis and scientific support for the application of clay based photocatalysts. Finally, we pointed out the major challenges and future directions at the end of this review. Undoubtedly, control and preparation of novel photocatalysts based on clays will continue to witness many breakthroughs in the arena of solar-driven technologies.


Assuntos
Caulim , Minerais , Óxido de Alumínio , Bentonita , Argila
11.
J Environ Manage ; 284: 112052, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33540194

RESUMO

The fungal community and soil geochemical, physical and biological parameters were analyzed, respectively, in bauxite residues (BRs) treated with organic matter and vermiculite/fly ash by phylogenetic analysis of ITS-18 S rRNA, community level physiological profiles (CLPP) and so on. The results indicated that after amendment of the BR, microbial utilization of carbohydrates and their enzyme activities were significantly increased, but fungal compositions at the phylum level were similar and dominated by the phylum of Ascomycota (82.05-98.96%, RA: relative abundance) after one year of incubation. The fungal taxa in the amended BR treatments, however, show significantly less alpha and beta diversity compared with the reference soils, although they still harbor a substantial novel taxon. The combined amendment of organic matter (OM) and vermiculite/fly ash significantly increases the fungal taxa at the genus and species level compared with solely OM amendment. The results of the following canonical correspondence analysis found that, over 90% variation of the fungal community could be explained by pH, OM and mean weight diameter (MWD) of aggregates; but the biological indicators, including urease (UR), dehydrogenase (DHA) and the value of average well color development (AWCD) could explain only 50% variation of the fungal flora in BRs. This paper indicated that resilience of fungal community in BRs was positively correlated with the BRs' improvement in fertility as well as biogeochemical properties, but alkalinity must be firstly decreased to the target level of BRs' rehabilitation.


Assuntos
Cinza de Carvão , Microbiologia do Solo , Óxido de Alumínio , Silicatos de Alumínio , Filogenia , Solo
12.
Water Sci Technol ; 83(3): 727-738, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33600375

RESUMO

The current study focuses on a prime effect of pH changes in the catalytic ozonation process (COP) by using three main classes of catalysts such as zeolites (alumina-silicates), alumina (metal oxides), and activated carbons for decolorization of Reactive Red 241 (RR-241). The role of pH changes, point of zero charges and the effect of catalyst dose on pH change was studied. The results reveal that the overall removal efficiency of RR-241 in the case of COPs was the highest compared with single ozonation process (at pH = 7 the efficiency was 80, 65 65.5 and 60% for AC/O3, Al2O3/O3, Zeolite/O3 and O3 respectively). At initial acidic pH 4, the highest pH variations in COPs and ozonation processes were observed. Moreover, the pH changes were not found to be significant near the point of zero charges of materials (pHpzc = 6.8, 8.4 and 8.8 for zeolite, activated carbons and Al2O3, respectively. The COP in the presence of activated carbon shows the highest removal efficiency (82%) at pH 7. The material dose effect indicates that increasing the amount of catalyst (from 1 gm to 2 gm) significantly leads to a change in the pH of the solution. Results reveal the prominent effect and significance of pH changes on the efficiency of COP to determine true catalytic efficiency.


Assuntos
Ozônio , Poluentes Químicos da Água , Purificação da Água , Zeolitas , Óxido de Alumínio , Catálise , Carvão Vegetal , Concentração de Íons de Hidrogênio , Poluentes Químicos da Água/análise
13.
Dent Mater ; 37(3): 516-522, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33461761

RESUMO

OBJECTIVE: The airborne-particle abrasion of zirconia with alumina particle (APA) has been reported to result in the durable bonding of appropriate adhesive luting systems. However, whether a delay between APA and the application of the adhesive luting material might affect the resulting bond strength and its durability is unknown. METHODS: A total of 140 disc-shaped zirconia specimens were divided according to the elapsed time between the APA of zirconia and its bonding into 5 test groups (15 min, 1 h, 4 h, 24 h, and 72 h). The specimens were airborne-particle abraded with 50-µm Al2O3, and then stored at room temperature according to the test group (n = 28/group). Surface free energy (SFE) was measured for 12 specimens per group using a goniometer. For each group 16 Plexiglas tubes filled with composite resin were bonded to the zirconia specimens with an adhesive luting resin (Panavia 21). Tensile bond strength (TBS) was tested for subgroups of 8 specimens after water storage for 3 days and for 150 days with 37,500 thermal cycles. RESULTS: SFE decreased significantly within 24 h after APA. TBS after 3 days of water storage ranged from 38.3 (1 h) to 28.4 MPa (24 h) and after 150 days with thermocycling from 38.3 (15 min) to 24.8 MPa (24 h). SIGNIFICANCE: Based on these results, the time between the APA of zirconia and the application of adhesive materials should be minimized when bonding nonretentive zirconia restorations clinically.


Assuntos
Colagem Dentária , Óxido de Alumínio , Cerâmica , Análise do Estresse Dentário , Teste de Materiais , Cimentos de Resina , Propriedades de Superfície , Resistência à Tração , Zircônio
14.
Chemosphere ; 271: 129610, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33465623

RESUMO

This study reports on an easy and scalable synthesis method of a novel magnetic nanocomposite (GO/ZIF-8/γ-AlOOH) based on graphene oxide (GO) nanosheets decorated with zeolitic imidazolate framework-8 (ZIF-8), pseudo-boehmite (γ-AlOOH), and iron oxide (Fe3O4) nanoparticles by combining solvothermal and solid-state dispersion (SSD) methods. The nanocomposite was successfully applied to remove of diclofenac sodium (DCF) - a widely used pharmaceutical - from water. Response Surface Methodology (RSM) was used to optimize the adsorption process and assess the interactions among the influencing factors on DCF removal efficiency; including contact time, adsorbent dosage, initial pH, solution temperature, and DCF concentration. Adsorption isotherm results showed a good fitting with the Langmuir isotherm model with an exceptional adsorption capacity value of 2594 mg g-1 at 30 °C, which was highly superior to the previously reported adsorbents. In addition, kinetic and thermodynamic investigations further illustrated that the adsorption process was fast (equilibrium time = 50 min) and endothermic. The regeneration of GO/ZIF-8/γ-AlOOH nanocomposite using acetic acid solution (10% v/v) after a simple magnetic separation was confirmed in five consecutive cycles, which eliminate the usage of organic solvents. The nanocomposite has also shown a superior performance in treating a simulated hospital effluent that contained various pharmaceuticals as well as other organic, and inorganic constituents.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Zeolitas , Adsorção , Hidróxido de Alumínio , Óxido de Alumínio , Diclofenaco , Grafite , Hospitais , Cinética , Poluentes Químicos da Água/análise
15.
Artigo em Inglês | MEDLINE | ID: mdl-33499727

RESUMO

In the present study, the adsorption behavior of ciprofloxacin (CIP) from aqueous solution onto MWCNTs/Al2O3 was studied using batch experiments. Physical characterization of MWCNTs/Al2O3 was determined by SEM, XRD, and BET. The effective parameters investigated included: initial CIP concentration, contact time, MWCNTs/Al2O3 mass, and temperature. Based on experimental results and correlation coefficients, the rate of CIP adsorption followed the pseudo-second-model kinetics. Complete compatibility of the adsorption isotherm process was achieved with the Langmuir model, and the maximum adsorption capacity reached 41.73 mg/g under the optimized conditions (pH = 7, MWCNTs/Al2O3 dose = 1.2 g/L, contact time = 60 min, initial concentration = 10 mg/L, and temperature= 45 °C). The adsorption capacities based on the Langmuir model at different temperatures, 273, 288, 303, and 318 K, were equal to 72.18, 75.92, 79.65, and 83.47 mg/g, respectively. The determined parameters of the thermodynamic studies demonstrated the endothermic and spontaneous nature of the biosorption. The mean free energy was estimated from D-R isotherm model to be 0.316-0.707 KJ/mol, which clearly proved that the adsorption experiment followed a physical process. The data suggest that MWCNTs/Al2O3 could be used as a highly effective adsorbent material with a high capacity for the removal of antibiotics from water and wastewater.


Assuntos
Óxido de Alumínio/química , Antibacterianos/química , Ciprofloxacino/química , Nanotubos de Carbono/química , Poluentes Químicos da Água/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Temperatura , Termodinâmica , Águas Residuárias , Purificação da Água/métodos
16.
Food Chem ; 347: 129040, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33484960

RESUMO

An Ultra High-Performance Liquid chromatography method quadruple time-of-flight mass spectrometry has been developed for the analysis of 11 cyclic polyesters oligomers, following a modified QuEChERS clean-up with alumina/primary secondary amine, in pasta. Target analytes were polyethylene terephthalate (PET) 1st series cyclic dimer to heptamer, polybutylene terephthalate (PBT) dimer to pentamer and a polyurethane oligomer. Standard addition method was applied for the calibration, and the limits of quantification ranged from 3.2 to 17.2 ng g-1. Recoveries ranged from 86.4 to 109.8%, RSDs were lower than 12% for all analytes, and matrix effect never exceeded ± 2.5%. The method was successfully applied to real commercial pasta samples, where the PET 1st series cyclic trimer was the most abundant oligomer, being found in all tested samples. The 1st series PET cyclic dimer and tetramer, as well as 1,4,7-trioxacyclotridecane-8,13-dione, were found in considerable amounts. Traces of the 2nd and 3rd series PET cyclic dimers were also found.


Assuntos
Análise de Alimentos/métodos , Espectrometria de Massas/métodos , Poliésteres/química , Polietilenotereftalatos/química , Óxido de Alumínio/química , Cromatografia Líquida de Alta Pressão , Dimerização , Farinha/análise , Poliésteres/análise , Polietilenotereftalatos/análise , Polimerização , Dióxido de Silício/química
17.
Chemosphere ; 273: 129678, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33515960

RESUMO

Electrostatic and complexation effects have been considered as the primary adsorption mechanisms for defluorination using aluminum based materials, while the effect of ion exchange between anions and fluorine ion has been mostly ignored, although synthesized alumina materials usually contain a large amount of anions, such as SO42-, NO3-, and Cl-. In this study, the effect of anions exchanges and its key role on defluorination were systematically investigated for adsorption by aluminas loaded with various typical anions (SO42-, NO3- and Cl-). Experimental results showed that SO42-- loading alumina had the best defluorination performance (94.5 mg/g), much higher than NO3- (45.0 mg/g) and Cl- (19.1 mg/g). The contribution ratio of ion exchange between SO42- and F- was as high as 20-60% in all potential defluorination mechanisms. By using Density Functional Theory calculation, the detailed mechanism revealed that the ion exchange process was mainly driven by the tridentate chelation of SO42- which reduced the exchange energy ( [Formula: see text] 4.8 eV). Our study clearly demonstrated that ion exchange between SO42- and F- is a critical mechanism in defluorination using aluminum-based materials and provides a potential alternative method to enhance the adsorption performance of modified alumina.


Assuntos
Óxido de Alumínio , Adsorção , Ânions , Concentração de Íons de Hidrogênio , Troca Iônica , Cinética
18.
Plant Physiol Biochem ; 159: 335-346, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33429191

RESUMO

Aluminum oxide (Al2O3) nanoparticles (NPs) are among the nanoparticles most used industrially, but their impacts on living organisms are widely unknown. We evaluated the effects of 50-1000 mg L-1 Al2O3 NPs on the growth, metabolism of lignin and its monomeric composition in soybean plants. Al2O3 NPs did not affect the length of roots and stems. However, at the microscopic level, Al2O3 NPs altered the root surface inducing the formation of cracks near to root apexes and damage to the root cap. The results suggest that Al2O3 NPs were internalized and accumulated into the cytosol and cell wall of roots, probably interacting with organelles such as mitochondria. At the metabolic level, Al2O3 NPs increased soluble and cell wall-bound peroxidase activities in roots and stems but reduced phenylalanine ammonia-lyase activity in stems. Increased lignin contents were also detected in roots and stems. The Al2O3 NPs increased the p-hydroxyphenyl monomer levels in stems but reduced them in roots. The total phenolic content increased in roots and stems; cell wall-esterified p-coumaric and ferulic acids increased in roots, while the content of p-coumaric acid decreased in stems. In roots, the content of ionic aluminum (Al+3) was extremely low, corresponding to 0.0000252% of the aluminum applied in the nanoparticulate form. This finding suggests that all adverse effects observed were due to the Al2O3 NPs only. Altogether, these findings suggest that the structure and properties of the soybean cell wall were altered by the Al2O3 NPs, probably to reduce its uptake and phytotoxicity.


Assuntos
Óxido de Alumínio , Parede Celular , Lignina , Nanopartículas , Soja , Óxido de Alumínio/toxicidade , Parede Celular/efeitos dos fármacos , Lignina/química , Lignina/metabolismo , Nanopartículas/toxicidade , Soja/efeitos dos fármacos
19.
Nat Commun ; 12(1): 140, 2021 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-33420061

RESUMO

Solid-state nanopores allow high-throughput single-molecule detection but identifying and even registering all translocating small molecules remain key challenges due to their high translocation speeds. We show here the same electric field that drives the molecules into the pore can be redirected to selectively pin and delay their transport. A thin high-permittivity dielectric coating on bullet-shaped polymer nanopores permits electric field leakage at the pore tip to produce a voltage-dependent surface field on the entry side that can reversibly edge-pin molecules. This mechanism renders molecular entry an activated process with sensitive exponential dependence on the bias voltage and molecular rigidity. This sensitivity allows us to selectively prolong the translocation time of short single-stranded DNA molecules by up to 5 orders of magnitude, to as long as minutes, allowing discrimination against their double-stranded duplexes with 97% confidence.


Assuntos
DNA de Cadeia Simples/metabolismo , Ensaios de Triagem em Larga Escala/métodos , Nanoporos , Imagem Individual de Molécula/métodos , Óxido de Alumínio/química , Ensaios de Triagem em Larga Escala/instrumentação , Polímeros/química , Imagem Individual de Molécula/instrumentação , Propriedades de Superfície
20.
Bioresour Technol ; 323: 124634, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33422792

RESUMO

The efficient depolymerization and hydrodeoxygenation of enzymatic hydrolysis lignin are achieved in cyclohexane solvents over a gamma-alumina supported nickel molybdenum alloy catalyst in a single step. Under initial 3 MPa hydrogen at 320 °C, the highest overall cycloalkane yield of 104.4 mg/g enzymatic hydrolysis lignin with 44.4 wt% selectivity of ethyl-cyclohexane was obtained. The reaction atmosphere and temperature have significant effects on enzymatic hydrolysis lignin conversion, product type and distribution. The conversion of enzymatic hydrolysis lignin was also investigated over different nickel and molybdenum-based catalysts, and the gamma-alumina supported nickel molybdenum alloy catalyst exhibited the highest activity among those catalysts. To reveal the reaction pathways of alkylphenol hydrodeoxygenation, 4-ethylphenol was tested as a model compound. Complete conversion of 4-ethylphenol into cycloalkanes was achieved. A two-step mechanism of 4-ethylphenol dihydroxylation - hydrogenation is proposed, in which the benzene ring saturation is deemed as the rate-determining step.


Assuntos
Cicloparafinas , Lignina , Ligas , Óxido de Alumínio , Catálise , Hidrólise , Molibdênio , Níquel
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