Comparative effects of macro-sized aluminum oxide and aluminum oxide nanoparticles on erythrocyte hemolysis: influence of cell source, temperature and size

Al2O3 is the most abundantly produced nanomaterial and has been used in diverse fields, including the medical, military and industrial sectors. As there are concerns about the health effects of nanoparticles, it is important to understand how they interact with cells, and specifically with red blood cells. The hemolysis induced by three commercial nano-sized aluminum oxide particles (nanopowder 13 nm, nanopowder <50 nm and nanowire 2-6 nm × 200-400 nm) was compared to aluminum oxide and has been studied on erythrocytes from humans, rats and rabbits, in order to elucidate the mechanism of action and the influence of size and shape on hemolytic behavior. The concentrations inducing 50% hemolysis (HC50) were calculated for each compound studied. The most hemolytic aluminum oxide particles were of nanopowder 13, followed by nanowire and nanopowder 50. The addition of albumin to PBS induced a protective effect on hemolysis in all the nano-forms of Al2O3, but not on Al2O3. The drop in HC50 correlated to a decrease in nanomaterial size, which was induced by a reduction of aggregation Aluminum oxide nanoparticles are less hemolytic than other oxide nanoparticles, and behave differently depending on the size and shape of the nanoparticles. The hemolytic behavior of aluminum oxide nanoparticles differs from that of aluminum oxide.

Adsorção de glifosato sobre solos e minerais

Glyphosate, an enzyme inhibitor herbicide, has been widely used around the world in agriculture. Dr. John Franz from Monsanto Corporation (USA) discovered glyphosate in 1970. It has been showed that glyphosate is strongly adsorbed by inorganic soil components especially aluminium and iron oxides, and the phosphate group is involved in this interaction. The inactivation of glyphosate in soils can last for days or even months depending on soil characteristics. The addition of phosphate from fertilizers can displace glyphosate from the soils and this could be the cause of decreased productivity of some crops.

Typen oksidien mittausepävarmuuden määrittäminen ilmanlaatumittauksille

Euroopan unionin direktiiveissä ja kansallisessa lainsäädännössä on asetettu tavoitteita, velvoitteita ja raja-arvoja ilmanlaadun mittauksille. Ilmanlaatua on seurattava, ilmanlaatumittaukset on tehtävä laadukkaasti sekä luotettavasti ja mittaustuloksista on tiedotettava väestölle. Mittausten epävarmuus on tunnettava ja sen on oltava alle 15 %, jotta epävarmuudelle asetettu kriteeri täyttyy. Tässä työssä perehdyttiin Euroopan unionin ilmastopolitiikkaan ja kansalliseen ilmanlaatua koskevaan lainsäädäntöön, käytiin läpi menetelmiä ja tapoja, joilla ilmanlaadusta tiedotetaan väestölle sekä selvitettiin ilmanlaadun mittausjärjestelmiä koskevia vaatimuksia. Ennen varsinaista mittausepävarmuuden selvittämistä käytiin läpi tutkimuksen kohteena olevan typen oksidien analysaattorin mittausperiaate ja merkittävimmät komponentit. Mittausepävarmuus määritettiin standardia SFS-EN 14211 noudattamalla. Mittausepävarmuuden selvittämiseksi analysaattorille tehtiin erilaisia sen toimintaa kuvaavia testejä Ilmatieteen laitoksen kalibrointilaboratoriossa. Saatujen tuloksien perusteella voitiin laskea analysaattorin mittausepävarmuus, joka tuntiraja-arvopitoisuudessa oli 15,5 % ja vuosiraja-arvopitoisuudessa 10,5 %. Kaikkia testejä ei voitu tehdä standardissa määrätyllä tavalla, joten tuloksiin pitää suhtautua kriittisesti. Tulosten perusteella mittausepävarmuus tuntiraja-arvopitoisuudessa ei aivan täytä direktiivin kriteeriä, mutta vuosiraja-arvopitoisuudessa kriteeri täyttyy (< 15 %).

Síntese e caracterização de perovskitas LaNi(1-x)Co xO3 como precursores de catalisadores para a conversão do metano a gás de síntese pela reforma com CO2

LaNiO3 perovskite was modified by partial substitution of nickel by cobalt in order to increase the stability and resistance to carbon deposition during the methane CO2 reforming. The results showed that a suitable combination of precipitation and calcination steps resulted in oxides with the desired structure and with important properties for application in heterogeneous catalysis. The partial substitution of Ni by Co resulted in lower rates of conversion of both the reactants, but the catalyst stability was highly increased. The LaNi0.3Co0.7O3 catalyst, calcined at 800 ºC, was the most active under the reaction conditions.

Diagramas de Ellingham e de Van't Hoff: algumas considerações

The main subject of this article is to show the parallelism betwen the Ellingham and Van't Hoff diagrams. The first one is a graphic representation of the changes in the standard Gibbs free energy (deltarGtheta) as a function of T and was introduced by Ellingham in 1944, in order to study metallurgic processes involving oxides and sulphides. On the other hand, the Van't Hoff diagram is a representation of the function ln K versus (1/T). The equivalence between both diagrams is easily demonstrated, making simple mathematical manipulations. In order to show the parallelism between both diagrams, they are presented briefly and two examples are discussed. The comparison of the both diagrams surely will be helpful to students and teachers in their learning and teaching activities, and will certainly enrich important aspects of chemical thermodynamics.

Redução catalítica seletiva de óxidos de nitrogênio sobre hematita contendo cobre

The activity of copper-doped hematite in the SCR with propane, in the presence of oxygen, was evaluated in this work. It was found that copper sulfate led to the production of solids with different specific surface areas depending on the amount of copper. The sulfur and copper species were mainly located on the surface. The copper-containing catalysts were more active in the reduction of nitrogen oxides and less active in the propane oxidation as compared to pure hematite. This behavior was assigned to an association of both sulfur and copper species to produce new sites active for NO reduction.

Estudo da oxidação total do etanol usando óxidos tipo perovskita LaBO3 (B= Mn, Ni, Fe)

The present work investigated the effect of coprecipitation-oxidant synthesis on the specific surface area of perovskite-type oxides LaBO3 (B= Mn, Ni, Fe) for total oxidation of ethanol. The perovskite-type oxides were characterized by X-ray diffraction, nitrogen adsorption (BET method), thermogravimetric analysis (TGA-DTA), TPR and X-ray photoelectron spectroscopy (XPS). Through method involving the coprecipitation-oxidant was possible to obtain catalysts with different BET specific surface areas, of 33-51 m²/g. The results of the catalytic test confirmed that all oxides investigated in this work have specific catalytic activity for total oxidation of ethanol, though the temperatures for total conversion change for each transition metal.

Compósitos magnéticos baseados em hidrotalcitas para a remoção de contaminantes aniônicos em água

In this work the adsorption features of hydrotalcites (Al, Mg- CO3) and the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. The magnetic hydrotalcites were characterized by XRD, magnetization measurements, N2 adsorption isotherms and Mössbauer spectroscopy. These magnetic adsorbents show remarkable adsorption capacity for anionic contaminants in water.

Uma estratégia adaptada para síntese de magnetita

Chemical reactions in the solid state are often not included in undergraduate chemistry curricula, due to requirements for special laboratory facilities such as ovens and precision weighing balances. This work aims to describe novel and relatively simple magnetite chemical syntheses in dry medium, which could also be used as an alternative for freshmen chemistry experiments. The proposed reaction was carried out in a muffle furnace by heating (i) a sol-gel preparation and (ii) natural hematite, under nitrogen atmosphere at 400 ºC. The synthesized magnetite was characterized with powder X-ray diffraction and Mössbauer spectroscopy. Results show that magnetite samples have chemical properties as well as crystalline structure quite similar to those of standard natural magnetite.

Nióbia magnética como adsorvente de contaminantes orgânicos em meio aquoso: efeito da temperatura e do pH

This work describes novel materials based on pure iron oxide and iron oxide/niobia composite to produce a magnetic adsorbent. These materials were prepared with synthetic iron oxide and characterized by powder XRD, SEM, FTIR, TPR and Mössbauer spectroscopy. Results showed that the main iron oxides formed were goethite (aFeOOH) and maghemite (gFe2O3) with small particle size. The iron oxide and iron oxide/niobia composite showed high adsorption ability for organic compounds. The positive enthalpy indicated an endothermic adsorption process suggesting physical adsorption.

Estudo sobre a utilização da lama vermelha para a remoção de corantes em efluentes têxteis

Red mud is the principal residue of the alumina (Al2O3) industry. Generated during the Bayer process, it is characterized by strong alkalinity and ion exchange. Iron oxides are the principal component (30 to 60%). Annually millions of tons of red mud are generated in the world. Red mud disposal is responsible for a large part of the cost of alumina production. On the other hand, textile industry wastewaters containing dyes have a great impact on the environment and on human health. In this paper the possibility of applying red mud for the removal of dyes was investigated by two processes: adsorption and degradation by the Fenton reagent.

Arsenic mobilization from sulfidic materials from gold mines in Minas Gerais State

Acid drainage results from exposition of sulfides to the atmosphere. Arsenopyrite is a sulfide that releases arsenic (As) to the environment when oxidized. This work evaluated the As mobility in six sulfidic geomaterials from gold mining areas in Minas Gerais State, Brazil. Grained samples (<2 mm) were periodically leached with distilled water, during 70 days. Results suggested As sorption onto (hydr)oxides formed by oxidation of arsenopyrite. Low pH accelerated the acid generation, dissolving Fe oxihydroxides and releasing As. Presence of carbonates decreased oxidation rates and As release. On the other hand, lime added to a partially oxidized sample increased As mobilization.

Fracionamento de metais pesados em solo contaminado antes e após cultivo de arroz

The objective of the present work was to evaluate the distribution of Cd, Cu, Mn, Pb and Zn among the different fractions of contaminated soil, before and after rice cultivation. Seven soil samples with different degrees of contamination were studied using a randomized experimental design, with four replicates. Using an ICP-OES we analyzed the contents of heavy metals in fractions of soil, the organic matter therein, the oxides and the residual content before and after rice cultivation. The largest concentrations of Cd, Cu, Mn and Zn in the soil are found in the fractions with stable chemical bonds.

Espectroscopia Mössbauer na caracterização de compostos ferrosos em solos e sua relação com retenção de fósforo

The chemical role of iron-bearing compounds on the dynamics of phosphorus in selected Brazilian latosols was investigated. The iron oxides were characterized in an attempt to assess their main chemical-mineralogical properties influencing the ion sorption mechanisms in those pedosystems. It was found that increasing total iron contents tend to increase the phosphorus adsorption capacity in the selected soils. 110 K-Mössbauer data reveal that the dominant iron oxides are hematite and goethite. Particularly for the yellower soil samples some prominent doublets, more certainly due to superparamagnetic relaxation, may be assigned to corresponding fractions of relatively small-sized particles.

Parâmetros bioquímicos foliares das espécies Licania tomentosa (Benth.) e Bauhinia forficata (Link.) para avaliação da qualidade do ar

Foliar analysis of biochemical parameters were carried out in order to investigate the influence of air pollutants on two tropical tree species (Licania tomentosa (Benth.) and Bauhinia forfícata (Link.)). Special attention was given to tropospheric ozone due to the fact that concentration levels in the region were found to be up to 140 µg m-3 for a 4 h average time, which is well above the value that can cause injuries to orchides and tobacco (59 µg m-3). Other pollutants such as nitrogen and sulphur oxides were measured and their ambient concentrations were also associated to biochemical alterations in the investigated species.