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1.
J Environ Manage ; 267: 110582, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32364130

RESUMO

A major action to reduce CO2 emissions is replacing fossil fuels by renewable energy sources. Matching the energy supply and demand by the mostly intermittent renewable resources (wind, solar, wave) is hence a hot topic, and energy storage has become crucial. Thermo-chemical energy storage (TCES) has a higher energy density than sensible and latent heat storage, and allows energy to be stored in the reaction products for multiple reuse and even off-site application. Design parameters are the equilibrium temperature, the reaction heat and the reaction rate, as obtained from both thermodynamic and kinetic assessments. Equilibrium temperatures of the selected metal oxides, Mn2O3/Mn3O4 and Co3O4/CoO are between 1115 K and 1179 K. The present research studies both redox reactions as examples. Commercial Mn2O3 and Co3O4 were previously investigated in detail, and suffer from incomplete reversibility. The present study investigates the use of self-made Mn2O3 and Co3O4 mesoporous particles, of micrometer or nanometer scale, respectively. The average particle size of self-made Mn2O3 particles is < 5 µm, with a BET surface area of 239.7 m2/g, and Teq of 1177 K at ambient pressure. Self-made Co3O4 was of nano size, with average size of about 100 nm, a BET surface area of 54.2 m2/g, and Teq of 1109 K at ambient pressure. The redox reactions of these ultrafine particles are fast and nearly fully reversible. The effect of adding inert Al2O3 or Fe2O3 was also studied, but proven to offer no kinetic benefit, while reducing the reaction heat due to their inert additive character. The findings were used in the design of a 10 kW TCES pilot plant that is currently being tested in a concentrated solar furnace.


Assuntos
Temperatura Alta , Óxidos , Tamanho da Partícula , Temperatura , Termodinâmica
2.
Mutat Res ; 850-851: 503149, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32247558

RESUMO

Cadmium oxide nanoparticles (CdO NPs) are among some of the most studied and industrially used metal oxide NPs. They have been widely used for industrial application, such as paint pigments and electronic devices, and medical therapeutics. With increasing use of CdO NPs and concerns for their potential adverse effects on the environment and public health, evaluation of the cytotoxicity and genotoxicity of CdO NPs becomes very important. To date, there is a limited understanding of the potential hazard brought by CdO NPs and a lack of information and research, particularly on the genotoxicity assessment of these NPs. In this study, 10 nm CdO core-PEG stabilized NPs were synthesized, characterized and used for evaluation of CdO NPs' cytotoxicity and genotoxicity. Release of cadmium ions (Cd+2) from the CdO NPs in cell culture medium, cellular uptake of the NPs, and the endotoxin content of the particles were measured prior to the toxicity assays. Cytotoxicity was evaluated using the MTS assay, ATP content detection assay, and LDH assay. Genotoxicity was assessed using the Ames test, Comet assay, micronucleus assay, and mouse lymphoma assay. The cytotoxicity of cadmium chloride (CdCl2) was also evaluated along with that of the CdO NPs. The results showed that endotoxin levels within the CdO NPs were below the limit of detection. CdO NPs induced concentration-dependent cytotoxicity in TK6 and HepG2 cells with the MTS, ATP and LDH assays. Although the genotoxicity of CdO NPs was negative in the Ames test, positive results were obtained with the micronucleus, Comet, and mouse lymphoma assays. The negative response of CdO NPs with the Ames test may be the result of unsuitability of the assay for measuring NPs, while the positive responses from other genotoxicity assays suggest that CdO NPs can induce chromosomal damage, single or double strand breaks in DNA, and mutations. The toxicity of the CdO NPs results from the NPs themselves and not from the released Cd+2, because the ions released from the NPs were minimal. These results demonstrate that CdO NPs are cytotoxic and genotoxic and provide new insights into risk assessment of CdO NPs for human exposure and environmental protection.


Assuntos
Compostos de Cádmio/toxicidade , Nanopartículas Metálicas/toxicidade , Testes de Mutagenicidade , Mutagênicos/toxicidade , Óxidos/toxicidade , Animais , Compostos de Cádmio/farmacologia , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Ensaio Cometa , Dano ao DNA/efeitos dos fármacos , Humanos , Nanopartículas Metálicas/química , Camundongos , Mutagênicos/farmacologia , Óxidos/farmacologia
3.
J Adhes Dent ; 22(2): 207-214, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32322841

RESUMO

PURPOSE: To synthesize tantalum oxide quantum dots (Ta2O5QDs) using an imidazolium ionic liquid as a precursor and evaluate the effect of its addition to an experimental adhesive resin on the degree of conversion (DC) and antibacterial activity. MATERIALS AND METHODS: Ta2O5QDs was synthesized from the hydrolysis of an imidazolium ionic liquid (1-n-decyl-3-methylimidazolium hexachlorotantalate [DMI.TaCl6]) and evaluated by transmission electron microscopy (TEM). The adhesive was formulated with 66.7 wt% bisphenol A-glycidyl methacrylate (bis-GMA), 33.3 wt% 2-hydroxyethyl methacrylate (HEMA) with a photoinitiator/co-initiator system. In one group, Ta2O5QDS was added to the adhesive at 1 wt% Ta2O5QDs) and one group remained without Ta2O5QDS as control (CTRL). The adhesives were evaluated for DC by Fourier Transform Infrared spectroscopy. Direct contact inhibition assay was used to evaluate the antibacterial activity of the experimental adhesive resins against biofilm formation and planktonic bacteria. RESULTS: Ta2O5QDs had a particle size distribution of 1.52 ± 0.73 nm. DC was 50.91 ± 4.94% for CTRL and 55.4 ± 4.58% for Ta2O5QDs (p = 0.310). Ta2O5QDs showed less Streptococcus mutans biofilm formation on adhesive surfaces (p = 0.013). There was no statistically significant difference in terms of antibacterial activity against planktonic bacteria (p = 0.079). CONCLUSION: Non-agglomerated Ta2O5QDs synthesized from an imidazolium ionic liquid provided antibacterial activity to the experimental adhesive resin against biofilm formation of Streptococcus mutans.


Assuntos
Líquidos Iônicos , Pontos Quânticos , Antibacterianos , Cimentos Dentários , Óxidos , Tantálio
4.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 38(2): 133-138, 2020 Apr 01.
Artigo em Chinês | MEDLINE | ID: mdl-32314884

RESUMO

OBJECTIVE: This work aimed to determine the expression changes in LIM domain only protein 1 (LMO1) in gene transcription and protein levels during oral squamous cell carcinoma (OSCC) development. METHODS: The tissues in this study were taken from our team's previous animal model building, and we performed hematoxylin-eosin (HE) staining on 49 cases. The pathological classification of the experiment group was determined on the basis of the abnormal epithelial hyperplasia degree. The expression part of LMO1 was determined by immunohistochemistry staining. The mRNA and protein LMO1 expression levels in five groups were detected by real-time fluorescent quantitative of nucleotide polymer chain reaction (RT-qPCR) and Western blot, respectively. RESULTS: HE staining determined 7 cases of the control group, 6 cases of mild epithelial dysplasia, 11 cases of moderate epithelial dysplasia, 9 cases of severe epithelial dysplasia, and 16 cases of OSCC. Immunohistochemistry results: LMO1 expression was localized in the cytoplasm, and the positive expression rates of the protein LMO1 in the control and experiment groups were 14.3% for normal buccal mucosal tissue, 33.3% for mild epithelial dysplasia, 81.8% for moderate epithelial dysplasia, 88.9% for severe epithelial dysplasia, and 93.8% for OSCC. RT-qPCR results: mRNA expression was lowest in the control group and highest in the OSCC group, the difference between the mild dysplasia and control groups was not significant (P>0.05). Pairwise comparison among other groups showed statistically significant differences (P<0.05). Western blot results: with the aggravation of the pathological degree, the protein LMO1 expression level increased gradually. The OSCC group expressed the highest LMO1 expression level. CONCLUSIONS: The oral mucosa carcinogenesis models showed abnormal the mRNA and protein LMO1 expression levels, and the mRNA and protein expression levels were positively correlated with the degree of abnormal proliferation.


Assuntos
Carcinoma de Células Escamosas , Neoplasias Bucais , Quinolinas , Animais , Carcinogênese , Mucosa Bucal , Óxidos , Ratos , Ratos Sprague-Dawley
5.
Water Sci Technol ; 81(2): 228-240, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32333656

RESUMO

A magnetic graphene oxide nanocomposite modified by the ionic liquid 1-amino-3-methylimidazole chloride (LI-MGO) was prepared by the chemical coprecipitation method as a phenol adsorbent for the treatment of contaminated aqueous environments. The structure of the prepared nanocomposite was investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The prepared nanoparticles exhibited a BET (Brunauer-Emmett-Teller) specific surface area of 110.44 m2 g-1 and total pore volume of 0.2839 cm3 g-1. The results revealed that the adsorption process had the highest phenol removal percentage (95.3%) under optimum conditions (pH = 3, nanocomposite concentration = 0.04 g/l at room temperature). Kinetic studies showed a significant fit to the pseudo-second-order kinetic model (R2 > 0.9997) giving an equilibrium rate constant (K2) of 0.000119 gmg-1 min-1 for phenol loaded. The experimental adsorption data were better fitted with the Langmuir isotherm model than with the Freundlich isotherm model. To further investigate the phenol removal optimization process of the modified magnetic nanoparticles, and to determine the effect of each parameter on the adsorption process, the Taguchi optimization approach was used. The adsorption of these synthesized nanocomposites is among the low-cost, high-efficiency processes that can be used for the reduction/elimination of environmental pollutants, especially in aqueous environments.


Assuntos
Grafite , Líquidos Iônicos , Nanocompostos , Nanopartículas , Poluentes Químicos da Água , Adsorção , Cinética , Fenômenos Magnéticos , Óxidos , Fenol , Espectroscopia de Infravermelho com Transformada de Fourier
6.
Nature ; 580(7804): 458-459, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32322075
7.
Science ; 368(6488)2020 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-32299920

RESUMO

Rolston et al suggest through a convective heating scheme that the mechanism of light-induced lattice expansion is from light-induced thermal heating. We bring out key differences in the physical observables that are not discussed and different from what is observed in the original paper by Tsai et al.


Assuntos
Compostos de Cálcio , Luz Solar , Óxidos , Titânio
8.
J Clin Pediatr Dent ; 44(2): 84-89, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32271667

RESUMO

Introduction: the study aimed to evaluate Enterococcus Faecalis colonization in the pulp chamber in pulpotomized extracted human teeth filled by different pulpotomy base materials (PBMs), using confocal laser scanning microscopy (CLSM). Study design: Cavity preparations were made in 70 extracted primary molars. The pulp chambers were filled using either Intermediate restorative material (IRM), Mineral Trioxide Aggregate (MTA) or Glass ionomer (GI). Twenty-five teeth served controls. The specimens were sterilized, and coronally filled with bacterial suspension for 21 days. The specimens were cut through the furcation area, stained using LIVE/DEAD BacLight Bacterial Viability Kit and evaluated using CLSM. Results: The extent of fluorescent staining was larger in the GI group, compared to the IRM and MTA groups, and larger in the IRM group compared to the MTA group (P<0.05). The minimal and maximal bacterial penetration depths into the dentinal tubules were 55 and 695μm, respectively (mean 310μm), without differences between the materials (GI, IRM, MTA, p>0.05). The ratio of live bacteria to dead bacteria within the evaluated areas was higher in the GI group compared to the IRM and the MTA groups, and higher in the IRM group compared to the MTA group (P<0.05). There were no differences between the mesial, distal and apical parts in any of the evaluations (p>0.05). Conclusions: bacteria colonize the interface between the PBM and dentin and penetrate deeply into the dentinal tubules. The extent and the vitality of the colonized bacteria may be affected by the type of PBM.


Assuntos
Compostos de Cálcio , Pulpotomia , Compostos de Alumínio , Proliferação de Células , Combinação de Medicamentos , Humanos , Microscopia Confocal , Dente Molar , Óxidos , Silicatos , Dente Decíduo
9.
Chemosphere ; 250: 126133, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234615

RESUMO

The metal-organic frameworks MOF-525 and MOF-545 comprised of Zr-oxide clusters and porphyrin moieties in different geometries were synthesized solvothermally and applied for the adsorptive removal of the broadly used organic contaminant sulfamethoxazole (SMX) from water. Both MOFs were found highly efficient for the adsorption of SMX with the maximum adsorption capacities of 585 and 690 mg/g for MOF-525 and MOF-545, respectively. The latter value is the highest adsorption capacity reported so far for the adsorption of SMX molecules on any adsorbent. The adsorption equilibrium could be modeled successfully by the Langmuir model, which showed close to matching with the experimental data. Their adsorption equilibriums were attained within 120 and 30 min for MOF-525 and MOF-545, respectively. MOF-545 with mesopores demonstrated superior adsorption kinetics to MOF-525 with micropores, and the simulation by the pseudo-second-order kinetic model indicated ca. 20 times faster adsorption by MOF-545 than MOF-525. Both showed pH-dependent adsorption of SMX with a gradual reduction at high pH due to the repulsion between negatively charged adsorbent and SMX. The adsorption of SMX conducted over a group of representative MOFs with different physicochemical properties and detailed characterization confirmed that the high adsorption capacity of the porphyrin MOFs is achieved by H-bonding between the SMX molecule and the N-sites of the porphyrin units in the MOFs, π-π interaction, and the high surface area. The adsorbents were easily regenerated by simple washing with acetone and reusable with >95% efficiency during 4 repeated adsorption-desorption cycles.


Assuntos
Sulfametoxazol/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Cinética , Estruturas Metalorgânicas , Óxidos , Água , Poluentes Químicos da Água/análise
10.
J Environ Manage ; 261: 110169, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32148261

RESUMO

The bioremediation of an oily sludge (321 ± 30 mg of polycyclic aromatic hydrocarbons/kgDRY SLUDGE and 13420 ± 1300 mg of aliphatic hydrocarbons/kgDRY SLUDGE) by mixture with contaminated soil (23 ± 2 mg of polycyclic aromatic hydrocarbons/kgDRY SOIL and 98 ± 10 mg of aliphatic hydrocarbons/kgDRY SOIL) was studied. Furthermore, the effect of oxidative pretreatments (persulfate and permanganate) on the performance of the global process was examined. The treatments reached contamination levels lower than the original residues, indicating the presence of synergic processes between a highly contaminated sludge and soil with a selected hydrocarbon-degrading community. Pretreatment with permanganate significantly improved biodegradation, possibly due to the increase in bioavailability and biodegradability of petroleum hydrocarbons. Two months of incubation was enough to reach the complete elimination of polycyclic aromatic hydrocarbons and 92% elimination of aliphatic hydrocarbons. Monitoring using five parameters (concentration of total petroleum hydrocarbons, total cultivable heterotrophic bacteria count, lipase and dehydrogenase activities, and polycyclic aromatic hydrocarbon-degrading bacteria count) as an approach for a preliminary scanning of the effectiveness of a treatment is proposed based on principal components analysis.


Assuntos
Petróleo , Hidrocarbonetos Policíclicos Aromáticos , Poluentes do Solo , Biodegradação Ambiental , Hidrocarbonetos , Compostos de Manganês , Óxidos , Esgotos , Solo , Microbiologia do Solo
11.
J Indian Soc Pedod Prev Dent ; 38(1): 56-63, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32174630

RESUMO

Objective: The quest for ideal pulp capping materials has given rise to the development of newer materials such as light cure mineral trioxide aggregate (MTA). The bond strength of the pulp capping materials with overlying restoration is one among the several factors that are critical for the success of vital pulp therapy. Hence, we conducted this study to evaluate and compare the shear bond strength (SBS) of light cure MTA and light cure calcium hydroxide with nanofilled composite. Materials and Methods: Thirty acrylic blocks each with a central hole were prepared to uniform dimensions and randomly distributed into two equal groups. In Group I, light cure MTA, and in Group II, light cure calcium hydroxide was used as pulp capping materials. After the application of adhesive system, nanofilled composites were applied onto the pulp capping material using a cylindrical plastic matrix. The SBS was tested on a universal testing machine (Instrom 3366, UK) at a crosshead speed of 0.5 mm/min. The samples were examined under stereomicroscope and scanning electron microscope to analyze different modes of failure. Results: The results were statistically analyzed using independent sample t-test. Light cure MTA attained the mean SBS of 6.54 MPa and light cure calcium hydroxide attained the mean SBS of 6.56 MPa. There was no significant difference statistically in SBS of both the materials (P < 0.05). The modes of failure were predominantly mixed failure followed by cohesive failure within the restorative material in both Group I and II. Conclusion: The results of the study suggest that the SBS of light cure MTA and light cure calcium hydroxide is comparable. The modes of failure analyzed in both light cure MTA and light cure calcium hydroxide are not significantly different statistically. Hence, both materials can be successfully used as pulp capping material with nanofilled composite.


Assuntos
Hidróxido de Cálcio , Colagem Dentária , Compostos de Alumínio , Compostos de Cálcio , Resinas Compostas , Capeamento da Polpa Dentária , Combinação de Medicamentos , Microscopia Eletrônica de Varredura , Óxidos , Silicatos
12.
Chemosphere ; 249: 126126, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32142984

RESUMO

Arsenic (As) and fluoride (F-) are the two most conspicuous contaminants, in terms of distribution and menace, in aquifers around the world. While the majority of studies focus on the individual accounts of their hydro-geochemistry, the current work is an effort to bring together the past and contemporary works on As and F- co-occurrence. Co-occurrence in the context of As and F- is a broad umbrella term and necessarily does not imply a positive correlation between the two contaminants. In arid oxidized aquifers, healthy relationships between As and F- is reported owing desorption based release from the positively charged (hydr)oxides of metals like iron (Fe) under alkaline pH. In many instances, multiple pathways of release led to little or no correlation between the two, yet there were high concentrations of both at the same time. The key influencer of the strength of the co-occurrence is seasonality, environment, and climatic conditions. Besides, the existing primary ion and dissolved organic matter also affect the release and enrichment of As-F- in the aquifer system. Anthropogenic forcing in the form of mining, irrigation return flow, extraction, recharge, and agrochemicals remains the most significant contributing factor in the co-occurrence. The epidemiological indicate that the interface of these two interacting elements concerning public health is considerably complicated and can be affected by some uncertain factors. The existing explanations of interactions between As-F are indecisive, especially their antagonistic interactions that need further investigation. "Multi-contamination perspectives of groundwater" is an essential consideration for the overarching question of freshwater sustainability.


Assuntos
Arsênico/análise , Monitoramento Ambiental , Fluoretos/análise , Água Subterrânea/química , Poluentes Químicos da Água/análise , Água Doce , Metais , Minerais , Mineração , Óxidos
13.
Chemosphere ; 249: 126564, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32213389

RESUMO

Pb-based perovskite nanoparticles (PbPNPs) are amongst others used within highly efficient solar cells. PbPNPs can be released into the environment during their production, recycling or waste processing. In this study we investigated the fate and toxicity of PbPNPs on soil bacterial community under simulated natural environmental conditions across a range of pH, humic acid, and divalent cation concentrations. Increasing pH decreased PbPNPs-particle aggregation as well as Pb-ion release. The presence of only humic acid (HA) prevented the aggregation of PbPNPs-particles, whereas the presence of only divalent cations promoted the aggregation of PbPNPs-particles. The amount of Pb-ions released from the PbPNPs-particles was reduced in the presence of either HA or the divalent cations. Results of toxicity testing of PbPNPs by determining the metabolic potential of a bacterial community indicated that increasing pH alleviated particle toxicity. The presence of only HA reduced the toxicity of PbPNPs, while the presence of only divalent cations enhanced the particle toxicity. The coexistence of HA and divalent cations enhanced PbPNPs aggregation and reduced toxicity, with both Pb-ions and the interaction between the PbPNPs-particles and bacterial cells contributing to the toxic effects. Our study emphasized that environmental conditions play important roles that influencing the fate and toxicity of PbPNPs.


Assuntos
Bactérias/efeitos dos fármacos , Compostos de Cálcio/química , Nanopartículas/toxicidade , Óxidos/química , Microbiologia do Solo , Poluentes do Solo/toxicidade , Titânio/química , Cátions Bivalentes , Substâncias Húmicas/análise , Concentração de Íons de Hidrogênio , Íons , Chumbo , Solo , Poluentes do Solo/análise , Testes de Toxicidade
14.
Bratisl Lek Listy ; 121(3): 192-198, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32115976

RESUMO

AIM: The study was designed to evaluate the possible adverse effects and consequences of metal oxide nanoparticles used on some major body organ functions and health parameters. MATERIALS AND METHODS: Thirty albino rats, allocated randomly into three groups for experimental period of 20 days post-administration were used. Different effects of metal oxide nanoparticles were targeted including, thyroid, parathyroid, kidney, calcium, phosphate, hematological parameters and indices, as well as oxidative stress markers of the red blood cells and their membranes as alpha tocopherol and GSH, by using different analytical methods. RESULTS: Data revealed thyroid and parathyroid hormonal disturbances; kidney dysfunction in the form of accumulation of some waste products as BUN, creatinine, and uric acid. A decrease in the calcium and phosphate and an increase in the potassium and phosphate concentrations was recorded.  A marked decrease in the indices of anemia and diminished oxidative stress indicators were also evident, associated with marked increase in the total leukocyte count. CONCLUSION: The present study confirmed the health risks of the use of metal oxide nanoparticles in the medical field without precautions and supervision; and may encourage application of nanoparticles from alternative origins, such as plants, algae, or microorganisms instead (Tab. 5, Fig. 4, Ref. 30) Keywords: nanoparticles, thyroid, parathyroid, kidney, oxidative stress, blood, green, alternative.


Assuntos
Nanopartículas Metálicas , Estresse Oxidativo , Animais , Nanopartículas Metálicas/toxicidade , Metais , Estresse Oxidativo/efeitos dos fármacos , Óxidos , Ratos , Distribuição Tecidual
15.
Sci Total Environ ; 719: 137455, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32120101

RESUMO

A multi-season field trial was carried out to investigate the effect of the amendment of biochar, lime, ash and washed biochar on the growth of maize. A degraded, strongly acidic Ultisol (pHKCl 3.60), with a relatively high exchangeable aluminium content (2.4 cmolc/kg) and a low exchangeable calcium content (0.99 cmolc/kg), was used. Soil was treated once at the beginning of the field trial and crop growth was monitored over seven planting seasons (PS). All treatments increased maize yield. The average increases were; seven times for biochar, five times for lime, five times for washed biochar and eight times for ash treatment, when compared to the control across all PS. The effect of biochar, lime and ash treatments on maize yield were sustained over the seven PS. Soil pHKCl was significantly increased (p < 0.05 level) following the addition of all of the amendment materials. All treatments significantly reduced the concentration of Al3+ when compared to the control (p < 0.05), with the lowest concentrations for the lime and ash treatments. The ash treatment also increased the concentration of macronutrients (K, P and Mg) to the greatest extent. Results showed that there was a clear liming effect at play. The better performance of biochar compared to lime, despite lime having the highest pH and the lowest Al3+ concentration, can be explained by the additional K, Mg and P the biochar adds to the soil. Results also showed a clear nutrient addition effect where ash added the most nutrients. Overall, this work supports the fact that small scale farmers in Indonesia should produce biochar from their waste agricultural materials. Doing so not only provides an increase in crop productivity, but also sequesters carbon resulting in the best overall environmental benefit.


Assuntos
Zea mays , Compostos de Cálcio , Carvão Vegetal , Indonésia , Óxidos , Solo
16.
Chemosphere ; 250: 126329, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32126334

RESUMO

The increasing contamination of lead ions (Pb(II)) in groundwater has become a serious environmental issue, which provides the impetus for intense research on Pb(II) removal. ε-MnO2 nanoflowers were successfully fabricated through a simple decomposition reaction. And the obtained ε-MnO2 nanoflowers were employed to remove Pb(II) from water. The detailed microstructure and surface properties of ε-MnO2 were systematically characterized. The results indicate that the pure ε-MnO2 phase was obtained and the specific surface area is 96.33 m2 g-1. Batch adsorption experiments of Pb(II) were carried out, and the ε-MnO2 nanoflowers exhibited outstanding adsorption performance. The maximum adsorption capacity for Pb(II) and Cd(II) achieved to 239.7 mg g-1 and 73.6 mg g-1 at the dosage of 0.2 g L-1. Besides, the prepared ε-MnO2 nanoflowers show much higher removal efficiency toward Pb(II) compared with commercial MnO2. The XRD results reveal the stability of ε-MnO2 nanoflowers, and the XPS results suggest that both the electrostatic interaction and structural tunnels are responsible for the removal mechanisms of Pb(II). This work finds a facile method to synthesize ε-MnO2 nanoflowers, showing great potential for Pb(II) removal.


Assuntos
Chumbo/química , Compostos de Manganês/química , Nanoestruturas/química , Óxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Água Subterrânea , Íons , Propriedades de Superfície , Águas Residuárias/química , Água , Poluentes Químicos da Água/análise
17.
Water Res ; 175: 115679, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32172054

RESUMO

The removal of phosphate (nutrient) and E. coli (pathogen) from secondary effluent is of great importance to control the water quality of the receiving water bodies. In this study, magnetic porous NiLa-layered double oxides (NiLa-LDOs/Fe3O4) were synthesized using a simple co-precipitation method. NiLa-LDOs/Fe3O4 exhibited a high phosphate adsorption capacity of 203.10 mg g-1 in batch adsorption experiments, which can mostly be maintained within the pH range (5.5-8.5) and ionic strength range (5-20 mM) of secondary effluent, and in the presence of commonly co-existing species (anions and organics). NiLa-LDOs/Fe3O4 were further evaluated in real secondary effluent and the homogenous surface diffusion model (HSDM) was used to predict the performance in field applications. Under typical conditions, NiLa-LDOs/Fe3O4 can last for ∼1845-2448 bed volumes (BVs) before the phosphate concentration in the effluent exceeds the monthly average limit of 1 mg L-1 P. Good regeneration capacities were also demonstrated in cyclic adsorption-desorption runs in both synthetic solution and secondary effluent. In addition, the presence of Ni and La species greatly enhanced the antibacterial performance of the NiLa-LDOs/Fe3O4 toward E. coli. Results obtained from this study indicate porous NiLa-LDOs/Fe3O4 can be a promising multifunctional material for the treatment of secondary effluent.


Assuntos
Fosfatos , Purificação da Água , Adsorção , Antibacterianos , Escherichia coli , Fenômenos Magnéticos , Óxidos , Porosidade
18.
Phys Chem Chem Phys ; 22(14): 7537-7545, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32219231

RESUMO

Understanding how electrons and protons move in a coupled manner and affect one another is important to the design of proton-electron conductors and achieving biological transport in synthetic materials. In this study, a new methodology is proposed that allows for the quantification of the degree of coupling between electrons and protons in tyrosine-rich peptides and metal oxide hybrid films at room temperature under a voltage bias. This approach is developed according to the Onsager principle, which has been thoroughly established for the investigation of mixed ion-electron conductors with electron and oxide ion vacancies as carriers at high temperatures. Herein, a new device platform using electron-blocking electrodes provides a new strategy to investigate the coupling of protons and electrons in bulk materials beyond the molecular level investigation of coupled proton and electron transfer. Two Onsager transport parameters, αi* and σe', are obtained from the device, and the results of these transport parameters demonstrate that the coupled transport of electrons and protons inside the hybrid film plays an important role in the macroscopic-scale conduction. The results suggest that an average of one electron is dragged by one proton in the absence of a direct driving force for electron movement ∇ηe.


Assuntos
Técnicas de Química Analítica/instrumentação , Transporte de Elétrons/fisiologia , Elétrons , Compostos de Manganês/química , Óxidos/química , Peptídeos/química , Prótons , Transporte Biológico/fisiologia
19.
Chemosphere ; 250: 126251, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32113100

RESUMO

Sorption onto clays (montmorillonite and kaolinite), oxidation and sorption by manganese oxides (synthesized MnO and natural MnO), and coupled sorption-oxidation experiments were conducted for the removal of antibiotics sulfadiazine (SDZ) and ciprofloxacin (CIP) at pH 5 and 8. Individual sorption and oxidation modelling were carried out using the first-order kinetic model. A coupled sorption-oxidation kinetic model was developed to predict the simultaneous sorption and oxidation process. The coupled sorption-oxidation enhanced the antibiotic sorption, with the first-order sorption rate constants in the simultaneous presence of clays and manganese oxides (ksorp) being higher than those with clays only (ksorp0). In contrast, a depression was observed; the first-order oxidation and sorption combination rate constants in the simultaneous presence of manganese oxides and clays (kMnO) were lower than those with manganese oxides only (kMnO0). In the coupled sorption-oxidation reaction, 13.5-62.5% of SDZ and CIP removal was attributed to the sorption. The SDZ and CIP species distributions at pH 5 affected the coupled sorption and oxidation systems more than those at pH 8. The best removal efficiency was achieved by the montmorillonite-synthesized MnO combination, mainly due to the higher surface area (ABET) and pore size of montmorillonite and synthesized MnO combination compared to other clays and manganese oxides combinations.


Assuntos
Ciprofloxacino/química , Compostos de Manganês/química , Modelos Químicos , Óxidos/química , Sulfadiazina/química , Adsorção , Antibacterianos/química , Bentonita , Argila/química , Recuperação e Remediação Ambiental/métodos , Caulim , Cinética , Manganês , Oxirredução
20.
Eur J Paediatr Dent ; 21(1): 23-28, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32183524

RESUMO

AIM: Single-session apexification treatment with MTA is an alternative to the root-canal treatment of immature teeth. Since its results are far from ideal, research with MTA-derivative biomaterials continues; however, the number of studies is limited as of yet. This study aimed to compare the fragilities of in vitro-simulated immature teeth in single-session apexification with MTA and newly-developed calcium-silicate-based MTA derivatives. MATERIALS AND METHODS: Two hundred seventy human permanent upper incisors were randomly divided into study (n = 180), positive control (Ca (OH)2) (n = 45), and negative control (NC-intact) (n = 45) groups. The study groups used ProRoot MTA (MTA-PR), MM-MTA, NeoMTA-Plus, and Biodentine (BD). Two-week, two-month, and one-year follow-ups data were recorded. A fracture resistance (FR) test was performed at the end of each period. The results of the biomaterials at the different follow-up timepoints were statistically analysed and compared. RESULTS: The two-week FR medians were significantly lower in MM-MTA, NEO, MTA-PR, and Ca (OH)2 groups (p<0.001, p<0.001, p=0.003, and p<0.001. respectively), compared to NC. The two-month FR medians were significantly lower in BD, MM-MTA, NEO, MTA-PR, and Ca (OH)2, (p=0.005, p<0.001, p<0.001, p<0.001, and p<0.001, respectively) compared to NC. The one-year FR medians were significantly lower in the BD, MM-MTA, NEO, MTA-PR, and Ca (OH)2 groups (p=0.002, p<0.001, p<0.001, p<0.001, and p<0.001, respectively) compared to NC. For all groups, FR at the one-year mark was significantly lower compared to the two-week and two-month marks (p<0.001, p<0.001). STATISTICS: All groups were compared with each other regarding fracture resistance at two weeks, two months, and one year. Also, for each group follow-up data on fracture resistance were compared. CONCLUSIONS: Since FR was significantly higher at the two-week and the two-month mark compared to the one-year mark for each material, filling the root canal completely with biomaterials used in our study leads to tooth denaturation over time, with effects like Ca (OH)2.


Assuntos
Hidróxido de Cálcio , Materiais Restauradores do Canal Radicular , Compostos de Alumínio , Apexificação , Materiais Biocompatíveis , Compostos de Cálcio , Combinação de Medicamentos , Humanos , Óxidos , Silicatos
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