Magnesium Arsenate Research Articles

Composition of Gases in the Interporous Space of Technogenic Bodies

Abstract —We present results of studies of inclusions in secondary sulfates (antlerite and a mixture of copiapite and coquimbite) and arsenates (erythrite and picropharmacolite) formed on the surface of technogenic bodies, such as stored waste from the enrichment of sulfide (Belovo and Ursk waste heaps) and arsenide (disposal maps of the Tuvakobalt plant) ores. A wide range of components were identified in the gas–liquid inclusions, the main ones being water and carbon dioxide. Hydrocarbons, oxygen-containing organic compounds, and nitrogen- and sulfur-containing gases were found in smaller but measurable amounts. Arsine H3As was also detected in inclusions in picropharmacolite (calcium and magnesium arsenate–arsenite). The gas–liquid inclusions in secondary minerals reflect the composition of the interporous space in the waste body, filled with particular atmospheric gases entering the body in free form and with seasonal precipitation. The combination of in situ generated and penetrating gases determines the diversity of inorganic and biotic interactions in technogenic bodies. The presence of hydrocarbons and oxygen-containing organic compounds is, most likely, associated with bacterial transformations of organic matter (residual vegetation, wood, microalgae, and fungi). At the same time, carbon disulfide and sulfur dioxide are indicators of active inorganic reactions of decomposition of the sulfide matrix.

Simultaneous Removal of Arsenate and Fluoride Using Magnesium-Based Adsorbents

In this study, arsenate, As(V), and fluoride (F) were simultaneously removed from contaminated water using MgO, Mg(OH)2, and MgCO3 as Mg-based adsorbents, as existing studies only focus on their individual removal. The removal performance of As(V) and F followed the order MgCO3 < Mg(OH)2 < MgO. Under the test conditions, MgO and Mg(OH)2 met the environmental standards for As and F (0.01 and 0.8 mg/L, respectively), but MgCO3 did not. The As(V) removal performance was not significantly affected by an increase in the initial F concentration. It was concluded that As(V) was adsorbed and removed more preferentially than F by Mg-based adsorbents because a considerable amount of F remained even when the majority of As(V) was removed. Most arsenic (As)-adsorption data for MgO fit the Langmuir and Freundlich models, whereas those for Mg(OH)2 did not fit either model well. Additionally, the As-adsorption data for MgCO3 fit the Freundlich model but not the Langmuir model. Most of the F-adsorption data for the Mg-based adsorbents fit the Langmuir and Freundlich models. The removal mechanisms of As(V) and F using Mg-based adsorbents were assumed to be predominantly caused by ion-exchange and chemical-adsorption reactions on the adsorbent surface because no magnesium arsenate, magnesium fluoride, or magnesium hydroxide fluoride species were observed in the X-ray diffraction analysis. This research advances the sustainable As–F simultaneous treatment method using inexpensive adsorbents.

Effect of slag composition on the distribution and separation behavior of arsenic between CaO-based slag and liquid copper

To determine the effects of slag basicity and oxygen potential on the distribution of arsenic (As) between slag and liquid copper, high-temperature experiments were conducted using a Kanthal-Super electric furnace. The thermodynamic driving force of As removal from liquid copper was found to increase as the slag basicity increased because the excess free energy of As2O3 decreased with increasing basic oxide content in the slag. The addition of a small amount of Na2O improved As removal efficiency from the liquid copper. In the case of acidic (i.e., low basicity) slag, the As was minimally distributed to slag phase due to the low activity of CaO in the slag. As a result, the basicity of slag should be carefully controlled for the efficient removal of As. In addition, As was segregated and stabilized in the (Mg,Fe)O monoxide as well as in crystalline phases (magnesium arsenate, Mg3(AsO4)2 and ferric arsenate, FeAsO4) formed due to the high contents of MgO and FeO in the slag, from which it was concluded that As enrichment and separation can be achieved during cooling process.

Microanalyses and Spectroscopic Techniques for the Identification of Pigments and Pictorial Materials in Monet's Pink Water Lilies Painting.

In this work, the technique and the pictorial materials employed by Claude Monet in Pink Water Lilies, presently housed at the National Gallery of Modern and Contemporary Art in Rome, were investigated. The painting underwent noninvasive investigations such as energy-dispersive X-ray fluorescence and visible reflectance spectroscopies. The combined use of these techniques allowed us to identify most of the inorganic pigments such as cobalt blue and violet, zinc oxide, cadmium yellow, vermilion, and mixtures. Particularly, the spectrophotometric curves allow for the detection of the anhydrous and hydrated chromium greens. Two micro-fragments of the painting were also examined with micro-Fourier transform infrared spectroscopy and the cross-sections obtained were analyzed with the optical microscope and with scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS). Fourier Transform Infrared spectroscopy analyses allowed us to recognize the animal glue used for priming the canvas, which was covered with a ground layer consisting of calcite and lead white mixed with an oil binder. A lipidic binder was also detected in the color layer. Optical microscopy and SEM-EDS were useful to retrieve information about the stratigraphy, the distribution of pigments, and a more complete palette identification of phosphate, arsenate, and magnesium arsenate cobalt violets, and the red lake was possible.

A novel scheme for safe disposal and resource utilization of arsenic-alkali slag

As solid waste posing a great threat to the environmental system, the disposal of arsenic-alkali slag has become the top priority in the development of the antimony industry. In this paper, a novel technological scheme combining the advantages of chemical precipitation and fractional crystallization is proposed for the safe disposal and resource utilization of arsenic-alkali slag. The scheme is mainly composed of three parts, namely, leaching of arsenic-alkali slag, selective removal of arsenic in the arsenic-alkali solution, and evaporation crystallization of alkali solution. In the leaching part, the optimum leaching parameters are determined by orthogonal tests. In the arsenic and alkali separation part, based on thermodynamic analysis, the selective removal of arsenic from arsenic-alkali solution is realized by forming ammonium magnesium arsenate (MgNH4AsO4) precipitation. In the evaporation crystallization part, the crystalline product with sodium carbonate (Na2CO3) content of 89.87% is obtained by the evaporation crystallization experiment. The whole process does not produce secondary pollution and realizes the reuse of wastewater. The final products are leaching residue, arsenic slag, and sodium carbonate with an arsenic content of 0.83%, 24.93%, and 0.18%, respectively.

Comprehensive utilization and safe disposal of hazardous arsenic-alkali slag by the combination of beneficiation and metallurgy

The accumulation of hazardous arsenic-alkali slag poses a great threat to the environment and human health due to the high content of soluble sodium arsenate. In this paper, a novel process scheme is proposed for the comprehensive utilization and safe disposal of arsenic-alkali slag by the combination of beneficiation and metallurgy. The new technology is novel since every procedure of high arsenic content is run at room temperature, which guarantees good occupational health. The valuable alkali and antimony were recovered efficiently without any secondary pollution. The separation of arsenic and alkali is the most difficult and critical section of the process, where magnesium salt and ammonium salt were added to the arsenic alkali solution in certain manner to selectively precipitate arsenic in the form of MgNH4AsO4·6H2O (magnesium ammonium arsenate) and Mg3(AsO4)2·8H2O (magnesium arsenate). By controlling the addition of ammonium salt and magnesium salt, arsenic slag with high arsenic content, good sedimentation performance, and high crystallinity was produced. The arsenic slag can be stored by rigid landfill for the future development. The whole process is relatively simple and safer than existing approaches, providing an alternative solution for the treatment of hazardous arsenic-alkali slag.

Arsenic(V) removal from enargite leach solutions by precipitation of magnesium ammonium arsenate

ABSTRACTThis study investigated a potential method for the removal of arsenic from enargite leach solution containing 5.86 g/L As(V) by precipitation of magnesium ammonium arsenate (MAA). The experimental results showed the As(V) concentration can be reduced to 1.8 mg/L under the optimum conditions. The molar ratio NH4/Mg/As in precipitates formed at different pH values was checked by wet chemical analysis, indicating that some of by-products such as Mg3(AsO4)2, Mg(OH)2, and MgHAsO4 will be formed at the solution pH above or below pH 9.5. Notably, this study indicated MAA has a better ability for arsenic removal than magnesium arsenate. The precipitates also were characterized by XRD and SEM.

The green grass was never green: How spectroscopic techniques should have assisted restoration works

This paper presents the results of a multidisciplinary research based on the use of different diagnostic techniques for the study of wall paintings that belong to the late Gothic period and are preserved in the church of Saint Stephen in Ribera de Valderejo (Álava, Basque Country). Portable Raman and X-ray fluorescence spectroscopy measurements carried out in-situ allowed to characterize the plaster composition, the colour palette used by the artists and the materials employed during the restoration works in recent times. The analyses were focused especially on some areas that appear unusually grey. Apparently, the results obtained by both techniques seem to be contradictory and it was necessary to perform a selective sampling in some areas of interest which were analyzed in the laboratory. Raman spectroscopy and scanning electron microscope, coupled with energy dispersive X spectroscopy, applied on the cross-section of micro samples, made possible to clarify some important issues, showing the inadequacy of the restoration works carried out in previous years and the presence of a potentially dangerous material too (magnesium arsenate), whose use was not documented. The results demonstrated the importance of using diagnostic tools for the identification of the materials belonging to Cultural Heritage, especially before restoration works in order to choose the most appropriate methodology and to respect the original appearance of the paintings.

Selective removal of arsenic(V) from a molybdate plant liquor by precipitation of magnesium arsenate

Precipitation of Mg 3(AsO 4) 2 for the removal of arsenic (As) from a molybdenum oxide processing plant liquor containing 70.9 g/L Mo(VI) and 469 mg/L As(V) was performed. The Stabcal software was used to model the speciation and solubility equilibria, and to identify the pH conditions at which optimum precipitation can be carried out. The optimum pH range for As(V) removal is between pH 7.5 and 10.2. This avoids the need to adjust the liquor pH to affect the precipitation. By adding magnesium chloride or sulphate at a Mg:As molar ratio of at least 2:1, As(V) could be removed to less than 5 mg/L at pH 10.2 resulting in a pure Mo(VI) liquor from which a high purity product of 99.9% MoO 3 could be produced by acidification.

Mg7(AsO4)2(HAsO4)4: A New Magnesium Arsenate with a very Strong Hydrogen Bond.

AbstractFor Abstract see ChemInform Abstract in Full Text.

砒酸塩の生成速度についての研究 (第1報)

When As2O3is heated at the temperature higher than 700°C, it tends to dissociate and produce (As4O6and O2) gas mixture. The mechanism of the arsenate formation was studied by observing the reaction between CaO or MgO and dissociated gas of As2O5at various temperature. The X-ray diffraction measurement and X. M. A. analysis of reaction products showed the existence of 3CaO·As2O5and 3MgO·As2O5. Infra-red absorption spectra of the products also gave the characteristic band due to (AsO4) group. The results obtained by Pt marker method and measurement of the effect of gas pressure on the reaction velocity indicated that Ca2+, Mg2+and O2+ions are main diffusing species. The activation energies for the formation of calcium and magnesium arsenate are about 38Kcal/mole and 32Kcal/mole respectively.

The crystal structure of magnesium arsenate, Mg 8.5As 3O 16

Single crystals of magnesium arsenate have been grown from a PbOAs 2O 5 eutectic by flux crystallization of a ceramic preparation having an initial composition of 6MgO·As 2O 5. The crystals are rhombohedral, space group R 3m , with hexagonal unit cell parameters a = 6.0278(6) and c = 27.600(3) Å. A three-dimensional structural analysis using automatic diffractometer data has been completed and refined by full-matrix least-squares procedures to a residual R = 0.049 ( R w = 0.059) with a data-parameter ratio of 36 in the final anisotropic refinement. The structure analysis indicated that magnesium arsenate has the composition Mg 8.5As 3O 16 and is isostructural with the previously reported Co 8As 3O 16. The structure is based upon a cubic close-packed oxygen array with charge balance achieved in magnesium arsenate through partial occupancy of a unique magnesium site occurring in an arsenic-substituted MgO-type layer.

Photoresistors for ultraviolet radiation

The UV is converted to visible light with a phosphor (magnesium arsenate, halophosphate, or magnesium fluorosilicate), which works into a CdS photoresistor. This gives large currents with erythemal and bactericidal lamps, which provides the basis for convenient and portable equipment.

Efficiency of Eu3+ Fluorescence in Oxygen-Dominated Host Lattices

The efficiency of Eu3+ fluorescence in a variety of rare-earth oxygen-dominated host materials was measured under excitation by 2537 Å uv at 25°C. It was found to be of the same order as that of the commercial phosphor, magnesium arsenate:Mn in all such hosts. To account for the high efficiency and particularly for the insensitiveness of efficiency to the nature of the host lattice, it is proposed that europium—oxygen states are excited directly and that the corresponding absorbtion coefficient is of a magnitude to make this the dominant absorption process.

PLANT GROWTH AND THE AERIAL ENVIRONMENT

SummaryThe apparent efficiency of conversion of incident light energy (ɛapp/i) by whole plants of Im‐patiens parviflora in a range of natural and artificial light climates has been calculated from growth analysis data. It was found that it ranged from 1.3% in full natural daylight to 7.5% in extreme shade (metal shades transmitting 7% daylight). The corresponding figures for real efficiency, i.e. corrected for respiration losses, ɛtrue/i were 3.0% and 12.5% respectively. In the growth cabinets with light intensities roughly equivalent to 7—15% daylight a combination of two Blue/six De Luxe Warm White fluorescent tubes gave values of ɛapp/i averaging 7.4% for plants grown at 15°C, 5.9% for those at 10°C and 6.5% at 20°C. Four Daylight/four De Luxe Warm White averaged 5.8% at 20°C and Red (magnesium arsenate) at 20°C was highest with 7.7%. Blue tubes gave 6.0% apparent efficiency with plants at 15°C. In all the cabinet experiments and in the extreme shade in natural daylight the plants were small with leaves scarcely overlapping. In more open, natural daylight sites some self‐shading would have occurred. When the efficiency was expressed on a quantum basis, rather than on total energy, and correction for temperature differences applied, there was little difference between Blue, Blue‐white and Red, with Daylight‐white somewhat lower. On the basis of assimilation for a given number of lamps the combinations two Blue/six De Luxe Warm White and four Daylight/four De Luxe Warm White were the best.

PLANT GROWTH AND THE AERIAL ENVIRONMENT

SummaryA comparison was made between the rooting conditions used previously in this series of investigations (sandy loam with added fertilizers) and a mixture of vermiculite, sand and gravel with culture solution. The principal effect of vermiculite was to increase the leaf weight by 25% for a given total dry weight. This was mainly compensated for by a lower root weight. The specific leaf area of vermiculite plants was 5% lower than for plants of comparable size and unit leaf rate in sandy loam. The overall result was a rise of 20% in leaf area ratio. The unit leaf rate was unaffected by the rooting condition so there was a resultant 20% increase in relative growth rate over that in sandy loam. The second comparison was with Red light from magnesium arsenate tubes (6000–7000 Å). Red light from germination gave excessively spindly plants, but plants grown initially for 10 days in Daylight‐white grew well subsequently in Red. There was no effect of Red light on leaf weight/total dry weight distribution. The specific leaf area and relative growth rate were marginally lower. Red light was converted 20% more efficiently on an incident energy/apparent assimilation basis.

Some aspects of the activation of phosphors by tetravalent manganese

Tetravalent manganese is known to give a characteristic red emission in phosphors such as magnesium fluogermanate and magnesium arsenate. Spectral energy distribution measurements have been obtained for a number of similar phosphors, including a new phosphor magnesium lithium antimony fluo-silicate. The outstandingly good temperature characteristics of magnesium fluogermanate and magnesium arsenate may be associated with their special emission characteristics which have not been observed with the other phosphors which have been examined.

Dosage du cuivre, du mercure et de l'arsénic en présence prédominante du fer

Methods are recommended for the determination of copper, mercury and arsenic, in the presence of a preponderance of iron. This problem arises in technological analysis, for example, of pigments used for antifouling marine paints. These methods are chosen so as to simplify or even to avoid preliminary separation; a separate weight of sample is taken for each determination. Mercury is determined as the Reineckate, and copper by means of salicylaldoxime. Arsenic is separated as the ammonium magnesium arsenate, then determination selectively by iodometry.

Relative Toxicities to Insects of Acid Lead Arsenate,Calcium Arsenate and Magnesium Arsenate

Relative Toxicities to Insects of Acid Lead Arsenate,Calcium Arsenate and Magnesium Arsenate

Insecticides for the Control of the Mexican Bean Beetle

Field tests over a period of three years indicate that potassium hexafluoaluminate and synthetic cryolite are satisfactory for the control of the Mexican bean beetle ( Epilachna corrupta Muls.) when used as sprays at the rate of 3 pounds to 50 gallons of water. Barium fluosilicate (80 per cent) must be used at the rate of 5 pounds to 50 gallons of water to give satisfactory control, and is considered too expensive to be recommended. These compounds have not given satisfactory control when used as dusts. There appears to be no advantage in changing current recommendations for the use of magnesium arsenate except that the dosage should be increased from 1 pound to 2 pounds to 50 gallons of water where the infestation is heavy. If fluorine compounds are used, the problem of poisonous residues on green beans is not avoided, and green beans should not be sprayed with any of the above compounds after the pods have set.