Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 16.747
Filtrar
1.
Monogr Oral Sci ; 28: 48-58, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31940626

RESUMO

Ultratrace element is a relatively new term, and is defined as those elements with an established, estimated, or suspected dietary requirement of minute amount, generally of the order of µg/day. This chapter focuses on fluorine (F), aluminium (Al), molybdenum (Mo), and cobalt (Co). Whilst diet is the principal source of Al, Mo, and Co found in the body, inadvertent ingestion of dental hygiene products accounts for a significant proportion of F intake. Apart from F, the influence of other ultratrace elements on oral health, and in particular dental caries, has not been fully established. The calcified tissues contain 99% of body F. During tooth development, ingested (systemic) F is incorporated into the apatite crystals of the developing tooth which helps in improving resistance to acid demineralisation. However, the presence of low but constant levels of topical F in the fluid phase at the tooth enamel surface are more important in controlling tooth decay in people of all ages. An adequate intake, from all dietary and non-dietary sources, is estimated as 0.05 mg/kg body weight/day for children older than 6 months and adults, based on estimated intakes that have been shown to reduce the incidence of dental caries while minimising adverse health effects such as dental fluorosis. An inverse relationship between incidence of dental caries and levels of Al in drinking water, food, and soils has been indicated by some epidemiological studies. Co and Mo, whilst occasionally showing potential beneficial oral health effects in laboratory experiments, do so at concentrations much higher than found in vivo.


Assuntos
Cárie Dentária , Molibdênio , Adulto , Alumínio , Criança , Cobalto , Fluoretos , Humanos , Lactente
2.
Chem Pharm Bull (Tokyo) ; 68(1): 70-76, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31902902

RESUMO

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


Assuntos
Alumínio/química , Cromo/química , Complexos de Coordenação/química , Hidróxidos/química , Níquel/química , Adsorção , Concentração de Íons de Hidrogênio , Íons/química , Temperatura Ambiente , Termodinâmica , Poluentes Químicos da Água/química
4.
Environ Technol ; 41(3): 329-338, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29993344

RESUMO

Tea trees (Camellia sinensis) can take in fluorine from soil and the content of fluorine in tea increases with maturity, leading to high content of fluoride in tea leaves and tea products. Long-term consumption of high fluoride tea products could result in chronic fluoride intoxication. Confining the fluoride in the earth with absorbents to reduce the fluoride accumulation of the tea trees during the growth period which could radically control the fluoride level in tea product. Humic acid (HA), a kind of organic matter in the earth was used as raw material to prepare adsorbent aluminum humate (HAA) by aluminum modification. The HAA absorbent presented excellent absorption performance to the fluoride in a wide pH range (4-10), and the maximum adsorptive capacity can reach to 62.5 mg/g. The absorption isotherm demonstrated the adsorption of fluoride was the monomolecular adsorption and the absorption was in accordance with the pseudo-second order kinetic equation. Fluoride content in real soil solution decreased significantly by 53.03% by using the HAA absorbent. The utilization of HAA adsorbent in the culture and field plots experiments also obviously adsorb the soluble fluoride in solution and soil, which could significantly suppress the fluoride accumulation in tea leaves. In September, the fluoride accumulation in tea leaves has been reduced 74.29% in the field plots experiments.


Assuntos
Alumínio , Fluoretos , Adsorção , Folhas de Planta , Chá
5.
Waste Manag ; 102: 677-685, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31790926

RESUMO

Bottom ash from waste incineration is heterogeneous and contains different materials. Previous studies on the material composition of bottom ash provide only limited information as to composition, because large pieces present in bottom ash were not investigated nor were all materials were separated and analysed. The objective of the present study is to provide the complete and detailed composition of bottom ash encompassing and extensive range of different materials. Altogether, nine bottom ash samples with a mass of 3000 kg each were sieved to eight size fractions, whereby small particles adhering to larger pieces were separated by water and added to the respective size fractions. In the sorting analysis of all size fractions, the materials enclosed in molten mineral material and materials present as composites (e.g. transformers and batteries) were considered. The material characterisation revealed that the size fraction > 50 mm contains most of the iron (up to 50% of the total iron) and copper (about 20% of the total copper), while batteries, coins, silver and gold are almost exclusively present between 16 and 50 mm. The fractions between 8 and 16 mm show the highest share of aluminium (up to 50% of the total aluminium) and glass (up to 60% of the total glass). While the metal content is underestimated, if large pieces of material are disregarded, the multi-step approach applied in this study enables a complete determination of materials in bottom ash, which is essential for optimising material recovery in bottom ash treatment.


Assuntos
Incineração , Resíduos Sólidos , Alumínio , Cinza de Carvão , Metais
7.
Food Chem Toxicol ; 135: 110974, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31743745

RESUMO

During tea preparation mineral elements are extracted from the dried leaves of tea (Camellia sinensis (L.) Kuntze) plants into the solution. Micro-particle induced X-ray emission was employed to investigate the spatial distribution of magnesium (Mg), calcium (Ca) and manganese (Mn) in the young and old leaves of tea plants grown in the absence and presence of aluminium (Al) in the substrate. Results revealed that in tea leaves the largest concentrations of Mg occurred in the epidermis, of Ca in oxalate crystals and of Mn in epidermis and oxalate crystals; there was a leaf-age effect on tissue-specific concentrations of Mg, Ca and Mn with all tissues of old leaves containing larger concentrations of Mg, Ca and Mn than young leaves; supplementation of substrate with Al reduced concentrations of Mg, Ca and Mn in the old leaves, and a link between the distribution of Mg, Ca and Mn in the tea leaves with the extraction efficiencies of these elements into the tea was possible. We conclude that old leaves of tea plants cultivated under conditions of low Al availability will have the largest concentrations of Mg, Ca and Mn and may represent most acceptable ingredient for the preparation of tea.


Assuntos
Cálcio/metabolismo , Camellia sinensis/química , Magnésio/metabolismo , Manganês/metabolismo , Folhas de Planta/química , Chá/química , Alumínio/metabolismo , Cálcio/análise , Magnésio/análise , Manganês/análise , Extração em Fase Sólida , Espectrometria por Raios X , Distribuição Tecidual
8.
J Forensic Sci ; 65(1): 318-322, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31433869

RESUMO

Electrocution injuries represent a severe occupational hazard. Those at work usually ignore the importance of safety training and safe practices while the electric source is nearby the work area. Death due to electrocution can occur with or without any electric mark on the body. Limbs are the commoner site for electric entry and exit wounds. Various uncommon sites for electric exit wounds have also been reported in the literature. We report a rare case of fatal electrocution, where a 28-year-old male carpenter sustained electric injuries at the worksite. Multiple exit wounds were present over the back of the chest, an uncommon site for the exit wounds, and notably, both entry and exit wounds showed evidence of metallization. The present case emphasizes on the significance of death scene investigations in the reconstruction of events and need for complete autopsy supplemented with chemical and histopathological examination of the electric wounds.


Assuntos
Alumínio/análise , Traumatismos por Eletricidade/patologia , Íons/análise , Pele/química , Adulto , Evolução Fatal , Patologia Legal , Humanos , Masculino , Traumatismos Ocupacionais/patologia , Pele/patologia
9.
Ecotoxicol Environ Saf ; 187: 109828, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31639644

RESUMO

Different forms of aluminum (Al) in soil can be toxic to plants and the bacterial community. In our previous study, the distribution and toxicity to plants of soil Al species and soil labile Al fractions were examined. However, the toxicity of different forms of Al on the bacterial community has not been completely studied. In this study, five soil samples (pH: 4.92, 6.17, 6.62, 6.70, 8.51) were collected from Lichuan, China. Tall fescue was planted in rhizosphere boxes with those soils for 120 days. The toxicity of soil Al species and soil labile Al fractions on the bacterial community of near-rhizosphere (NR) soils and far-rhizosphere (FR) soils were analyzed. The effect of different forms of Al on bacterial community between NR and FR soils was small, but the difference was obvious according to the different spatial distribution of samples. An individual bacterial community has eosinophilia, and most bacterial communities are tolerant of heavy metals (e.g., Cu, Zn, Cd). The toxicity of exchangeable Al has a strong effect on the bacterial community. Meanwhile, the toxicity of Al3+ to the bacterial community is strong. In this study, the key finding was that the toxicity of the Al-F- complex toward the bacterial community and plants was different. AlF2+, AlF2+, AlF3, and AlF4- are toxic for the bacterial community, and the correlation decreases with the addition of F-. This finding is of considerable significance to the treatment of acid-contaminated soil and the study of the tolerance mechanism of plants toward Al.


Assuntos
Alumínio/toxicidade , Festuca/microbiologia , Microbiota/efeitos dos fármacos , Microbiologia do Solo , Poluentes do Solo/toxicidade , Alumínio/química , Biodegradação Ambiental , Festuca/metabolismo , Concentração de Íons de Hidrogênio , Metais Pesados/metabolismo , Rizosfera , Solo/química , Poluentes do Solo/química
10.
Ecotoxicol Environ Saf ; 187: 109813, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31644989

RESUMO

To explore the relationship between charge characteristics of rice roots and aluminum (Al) tolerance of rice, roots of 47 different rice genotypes were obtained by hydroponic experiment. The zeta potentials of roots were determined by streaming potential method, and the Al tolerance and the functional groups of rice were measured by relative root elongation and infrared spectroscopy (ATR-FTIR), respectively. The exchangeable, complexed and precipitated Al(III) sorbed on the root surface of rice was extracted with 1 mol L-1 KNO3, 0.05 mol L-1 EDTA-2Na and 0.01 mol L-1 HCl, respectively. There was a significant correlation between the zeta potentials and the relative elongation of rice roots, indicating that the zeta potentials of rice roots could be used to characterize rice tolerance to Al toxicity. Twelve Al-tolerant rice varieties, 25 medium Al-tolerant rice varieties, and 10 Al-sensitive rice varieties were obtained. The Al-tolerant rice varieties sorbed less complexed Al(III) and total Al(III) because there was lower negative charge on their roots compared to less tolerant genotypes. A correlation analysis showed that there were significant negative correlations between the zeta potential, relative root elongation, and the total Al(III) sorption capacity of the roots, which further confirmed the reliability of using the root zeta potential to characterize rice tolerance to Al toxicity. The results of this paper provide a new method for screening Al-tolerant rice varieties.


Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Alumínio/toxicidade , Oryza/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Poluentes do Solo/toxicidade , Solo/química , Adaptação Fisiológica/genética , Eletroquímica , Genótipo , Concentração de Íons de Hidrogênio , Oryza/genética , Oryza/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Especificidade da Espécie , Propriedades de Superfície
11.
Chemosphere ; 239: 124720, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31499313

RESUMO

Cathodic protection by galvanic anodes (GACP) is often used to protect immerged metallic structures in harbor environments, especially GACP employing aluminum-based anodes. To follow a previous study that was performed in a laboratory on Al-anode, two monitoring periods were performed in parallel, one in an in situ environment (in the Port of Calais) for 42 months and the other in a laboratory for 18 months, to evaluate the transfer of metals constituting the Al-anode towards the sedimentary compartment. During each monitoring, two conditions of agitation of water (weak and strong) were compared, and different factors of sediment quality were used to assess the enrichment and potential toxic effects of these released metals. The results showed that the dissolution of Al-anode-induced a greater Zn enrichment of sediment than an Al enrichment. This is in contrast with the abundance of these elements present in the composition of the anode and suggested a potential toxic effect for marine organisms with regards to the discovered Zn level, especially in confined areas.


Assuntos
Alumínio , Eletrodos/efeitos adversos , Monitoramento Ambiental/métodos , Sedimentos Geológicos/análise , Organismos Aquáticos , Sedimentos Geológicos/química , Metais Pesados/análise , Poluentes Químicos da Água/análise , Zinco/análise , Zinco/toxicidade
12.
Chemosphere ; 239: 124832, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31726524

RESUMO

Aqueous arsenate [As(V)] was removed using an aluminum-based adsorbent (ABA) and coal mine drainage sludge coated polyurethane (CMDS-PU) prepared using alum and coal mine sludge, respectively. Their As(V) removal efficiencies were compared with each other and granular ferric hydroxide (GFH). The mineralogy and surface chemistry of materials were determined using wavelength dispersive X-ray fluorescence (WD XRF) and Fourier transform infrared spectroscopy (FTIR), respectively. The angle-resolved X-ray photoelectron spectroscopy (AR-XPS) studies confirmed As(V) retention on the adsorbent surfaces. The adsorption kinetics data were fitted to pseudo second-order rate equation. The faster As(V) uptake kinetics of GFH and ABA (GFH > ABA > CMDS-PU) were attributed to their large pore volume and mesoporous nature. Langmuir adsorption capacities of 22, 31 and 10 mg/g, were achieved for GFH, ABA and CMDS-PU, respectively. As(V) adsorption on GFH, ABA and CMDS-PU was endothermic. GFH and ABA were efficient over a wide pH range (3-10). In column studies, GFH, ABA, and CMDS-PU successfully treated 23625, 842, and 158 bed volumes (BVs) and 2094, 6400, and 17 BVs of As(V)-contaminated water with 9.5 and 27 EBCT, respectively (at pH = 6.0, Asi = 600 µg/L). The GFH and ABA have a potential to be used at large-scale aqueous phase As(V) remediation.


Assuntos
Alumínio/química , Arseniatos/análise , Compostos Férricos/química , Poliuretanos/química , Esgotos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Indústria do Carvão Mineral , Minas de Carvão , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia Fotoeletrônica , Água/química
13.
Chemosphere ; 240: 124986, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726592

RESUMO

Alkaline activation is of great potential in the solidification of municipal solid waste incineration (MSWI) fly ash, but the metallic aluminum in the ash inhibits its application. This work studies the effects of residual metallic aluminum on the expansion and microstructure of alkali-activated MSWI fly ash-based pastes. Based on the results obtained, an optimized preparation process is suggested. Characterizations of the pastes include expansion ratio, morphology (SEM), mechanical strength and microstructure (XRD and FTIR). It is confirmed that MSWI fly ash could be solidified through alkaline activation when using a small amount of coal fly ash to adjust the reactive silica and aluminum ratios. In the optimized preparation, sodium hydroxide was added separately, so that expansion in the pastes was significantly mitigated, the formation of geopolymer gel was improved and the compressive strength of the pastes increased.


Assuntos
Alumínio/química , Cinza de Carvão/química , Incineração , Eliminação de Resíduos/métodos , Resíduos Sólidos , Álcalis/química , Força Compressiva , Dióxido de Silício
14.
Chemosphere ; 238: 124541, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31422313

RESUMO

Quantifying variation of metals in urban soils is crucial for efficient environmental and public health management. Prior to the interferences of human activities, regional topsoil geochemical distributions were generally primarily controlled by the underlying parent materials (PMs). With the rapid urbanisation, urban topsoil geochemical distributions have been modified with different levels. Three metals, aluminium (Al), calcium (Ca) and lead (Pb), were chosen to investigate the different levels of geogenic and anthropogenic controls in urban topsoil of Greater London Authority (GLA) area. These three metal elements clearly demonstrated the different spatial distribution affected by human activities using analysis of variance (ANOVA) and GIS-based spatial analysis. The high values of Al were in the clay which is located in the north and south GLA area; Pb accumulated in built-up areas and near traffic roads, which was likely associated with leaded paints and leaded petrol, respectively; the high Ca concentrations were in the Chalk bedrock of the southern GLA area and historical deconstruction and reconstruction sites in the city centre. Based on spatial interpolation and hot spot analysis (local Moran's I), this study reveals the different levels of geogenic and anthropogenic controls on different chemicals in urban soils: while the spatial distribution of Pb, which is more easily affected by human activities, can be significantly changed, the inert element Al may still be able to maintain its natural spatial distribution even in the heavily urbanized GLA area, and Ca demonstrates the mixed spatial distribution affected by both natural factors and human activities.


Assuntos
Alumínio/análise , Cálcio/análise , Monitoramento Ambiental , Chumbo/análise , Poluentes do Solo/análise , Solo/química , Análise Espacial , Cidades , Humanos , Londres
15.
J Sci Food Agric ; 100(2): 803-810, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31612503

RESUMO

BACKGROUND: New evidence has shown that arbuscular mycorrhizal (AM) fungi can contribute to the aluminum (Al3+ ) tolerance of host plants growing in acidic soils with phytotoxic levels of Al3+ . The aim of this study was to investigate the role of AM fungi isolated from naturally occurring Al3+ acidic soils in conferring host tolerance to Al3+ toxicity in three wheat cultivars differing in Al3+ sensitivity. The experiment was conducted in a soilless substrate (vermiculite/perlite, 2:1 v/v) using two Al3+ -tolerant wheat genotypes and one Al3+ -sensitive wheat genotype. The wheat was colonized with a consortium of AM fungi isolated from an Andisol, with or without Al3+ at a concentration of 200 µmol L-1 . RESULTS: The response of wheat to Al3+ in the medium was dependent on both the plant genotype and AM colonization. The benefits of the AM fungi to the wheat cultivars included an increased P concentration and relatively low Al3+ accumulation in the plants. This was achieved through two mechanisms. First, the metal-chelating capacity of the AM fungi was clear in two of the cultivars ('Tukan' and 'Porfiado'), in which the enhanced extraradical mycelium development was able to retain Al3+ in the glomalin and hyphae. Second, the increased AM-induced acid phosphatase activity in the rhizosphere of the other cultivar ('Atlas 66') increased host nutrition possibly by hyphae-mediated nutrient uptake and glomalin-related soil protein. CONCLUSION: The results suggest that the role of AM fungi in cultivar-specific Al3+ detoxification can be achieved by increased extraradical mycelial filters and enhanced bioavailability of P in the host rhizosphere. © 2019 Society of Chemical Industry.


Assuntos
Alumínio/metabolismo , Micorrizas/metabolismo , Fósforo/metabolismo , Poluentes do Solo/metabolismo , Triticum/microbiologia , Alumínio/análise , Alumínio/toxicidade , Hifas/crescimento & desenvolvimento , Hifas/metabolismo , Micélio/crescimento & desenvolvimento , Micélio/metabolismo , Micorrizas/crescimento & desenvolvimento , Fósforo/análise , Poluentes do Solo/análise , Poluentes do Solo/toxicidade , Triticum/crescimento & desenvolvimento , Triticum/metabolismo
16.
Forensic Sci Int ; 307: 110076, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31862657

RESUMO

The recovery of fingermarks and DNA from the same location at a crime scene can be problematic because of contamination issues associated with powdering or laboratory-based visualisation processes and/or the perceived destructive impact of commonly employed 'swabbing' approaches to DNA recovery. Previous research in a controlled environment demonstrated that it was possible to recover DNA and latent fingermarks from the same location on various substrates when an adhesive approach to DNA recovery was used. The aim of this research was to conduct a pseudo-operational trial into the dual recovery of DNA and fingermarks using gel lifters for DNA recovery. Participants were asked to voluntarily and anonymously donate a wide variety of porous and non-porous substrates post handling. No instruction as to fingermark deposition nor environmental storage was provided. BVDA gel lifters were applied to the substrates to replicate DNA recovery followed by the application of fingermark visualisation processes. The number and quality of the fingermarks was established using a grading approach. Application factors were also investigated to consider the effects of user variation. The results demonstrated that it was possible to recover DNA and fingermarks considered to be capable of supporting an identification. Fingermark quality post lifting was dependant on the substrates used. The weight applied to the gel during its application was a lesser contributing factor than the duration of its contact with the surface. There was a greater chance of leaving the fingermarks unaltered with the application of a low weight and instantaneous retraction.


Assuntos
DNA/isolamento & purificação , Dermatoglifia , Ciências Forenses/métodos , Alumínio , Cianoacrilatos , Géis , Humanos , Indicadores e Reagentes , Ninidrina , Porosidade , Pós , Manejo de Espécimes/instrumentação , Propriedades de Superfície , Volatilização
17.
Water Sci Technol ; 80(6): 1099-1106, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31799953

RESUMO

Chlorophenols are extremely toxic to the environment and recalcitrant to biological degradation. Herein chemical degradation of 4-chlorophenol (4-CP) from aqueous solutions by zero-valent aluminum (Al), zero-valent iron (Fe), Al and Fe mixtures (Al/Fe mass ratio 90/10, labeled as Al/Fe10) and Al-Fe alloy (Al/Fe mass ratio 90/10, labeled as Al-Fe10) were investigated. No removal was found for 50 mg·L-1 4-CP under anoxic conditions at initial pH 2.5 during a period of 10 hrs while 56%, 83%, 78% and 99% of 4-CP were removed by Fe, Al, Al/Fe10 and Al-Fe10, respectively under aeration conditions. The removal of 4-CP by Al/Fe10 mixtures was primarily in the Fe mode in the beginning 4 h and then transitioned to the Al mode. The removal of 4-CP by Al-Fe10 alloy was accomplished via two intermediate products, hydroquinone (HQ) and 4-chlorocatechol (4-CC), and it was speculated that reactive oxygen species and hydroxyl radicals (·OH) play an important role in the degradation of 4-CP and that Al-Fe intermetallic compounds might catalyze the reactions. This study demonstrates that alloying Al with Fe offers a promising strategy for developing new materials for water and wastewater remediation.


Assuntos
Clorofenóis , Poluentes Químicos da Água , Ligas , Alumínio , Ferro , Oxirredução , Água
18.
Water Sci Technol ; 80(6): 1163-1173, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31799960

RESUMO

This work presents the study of tris(2-butoxyethyl) phosphate advanced oxidation in TiO2-containing systems. Titania was immobilized on aluminum surfaces from recyclable materials and the results were compared with the suspension system. The initial concentration of photocatalyst and the oxidizing agent was optimized in a 23 experimental design and a kinetic study of the reactions was performed in the selected conditions. The experimental data were fitted to the pseudo-first-order model (rate constants estimated at 0.0129 ± 0.0009 and 0.0079 ± 0.0006 min-1 for the systems with TiO2 in suspension and immobilized, respectively). Artificial neural networks were also employed to model the experimental data and they presented correlation coefficients superior to 0.98 in all the training operations. After five cycles of degradation, the TiO2-aluminum meshes exhibited a very low decrease in photocatalytic activity (inferior to 2%). Acute phytotoxicity assays demonstrated that the byproducts of the oxidation of TBEP molecules are less toxic than the raw samples regarding lettuce seeds. For both TiO2 systems, COD decreased considerably as a consequence of the degradation. The immobilized TiO2 system achieved similar degradation rates when compared with the suspension system.


Assuntos
Alumínio , Fosfatos , Catálise , Organofosfatos , Compostos Organofosforados , Titânio
19.
Chem Commun (Camb) ; 56(2): 217-220, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31803869

RESUMO

Herein, we evaluate the suitablity of polystyrenes with thiol, dithioester and trithiocarbonate end-groups for the synthesis of Al nanocrystals. Both the end-groups and molecular weight of the polymer ligands play important roles for controlling the size and shape of the Al nanocrystals. A general criterion for evaluating polymers as the ligand for the synthesis of Al nanocrystals is proposed.


Assuntos
Nanopartículas/química , Poliestirenos/química , Alumínio/química , Cristalização , Teoria da Densidade Funcional , Ligantes , Modelos Químicos , Peso Molecular , Tamanho da Partícula , Compostos de Sulfidrila/química
20.
Environ Monit Assess ; 191(12): 722, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31696322

RESUMO

Monitoring of groundwater is fundamentally important due to it has emerged as a major source of drinking water and also used for irrigation purposes in many places in the world. Arsenic contamination in surface water and groundwater resources is a major concern due to its presence at high concentration and associated adverse health effects. Thus, the remediation of As in water resources, alongside other chemical species including fluoride, lithium, vanadium aluminium and nitrate is necessary. We have designed a hybrid [polyethyleneimine (PEI)-supported Fe3+-attached poly-(HEMA-co-GMA)] column for the reduction of arsenic (III and V) and other groundwater chemicals from natural groundwater as a potential contribution to water resource management. Swelling behaviour and scanning electron microscopy (SEM) were performed for the characterization of hybrid material. For the optimization of experimental conditions, the effects of pH and initial arsenic concentrations on adsorption were studied using arsenic solutions. Maximum adsorption capacity in equilibrium was 11.44 and 5.79 mg/g polymer for As(III) and As(V), respectively at pH 7. The reduction of metalloids and other subsurface chemicals were carried out with natural groundwater samples obtained from local sources. The mean concentrations of arsenic were recorded between 44.96 and 219.04 µg/L and of which 71.3-95.4 % (0.32-1.22 mg/g) were removed. The average removals were determined as F-1 50-86%, Li+ 43.2-99.7%, Al+3 83.8-91.4%, NO3- 48.4-72.2% and V 91.3-95.7. Chemical-loaded hybrid columns were regenerated successfully 15 times with only a loss of 5% in adsorption capacity by 0.01 M NaCl- treatment for potential adaptation into water industry. No pre-oxidation of As species was performed for the treatment of ground water samples prior to the hybrid column testing.


Assuntos
Arsênico/análise , Filtração/métodos , Água Subterrânea/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Alumínio , Monitoramento Ambiental , Fluoretos , Água/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA