Arsenic Volatilization Research Articles

Heterogeneous hydride generation in a packed membrane cell

Volatilization of arsenic, selenium and antimony for sample introduction in atomic absorption spectrometry has been performed by pumping an acidic sample through an anion exchanger in the tetrahydroborate (III) form packed as a bed in the liquid channel of a gas-liquid separation membrane cell. The hydrides generated in the heterogeneous reaction between bound tetrahydroborate (III) ions and the analytes are rapidly transferred with the aid of the concomitantly generated hydrogen gas through the gas-permeable membrane into the gas phase and swept to the spectrometer by an additional hydrogen gas flow. This instant transfer of the hydrides to the gas phase kinetically discriminates the reaction of the hydride with metal borides and metal colloids, whose formation by reaction with tetra-hydroborate (III) is slower than the hydride reaction. The susceptibility to interference by transition metal ions is thus markedly reduced, as compared with both batch hydride generation methods and a previously presented heterogeneous reaction scheme. The detection limits for arsenic, selenium, and antimony were 1.2, 3.7, and 10 μg/l, respectively. The calibration graphs were linear from the detection limit up to 125 μg/l for arsenic, 150 μg/l for selenium, and 250 μg/l for antimony. The relative standard deviations at concentration levels of 10 and 100 μg/l were 1.8 and 0.7% for arsenic and 2.3 and 1.2% for selenium. Corresponding figures for 50 and 100 μg/l antimony were 2.5 and 1.6%.

Comparison and origin of electronic states of the free GaAs (100) surface and the GaAs/CaF2 interface

An in situ assessment technique has been used on forming a metal-insulator-semiconductor structure in which the vacuum of the molecular-beam epitaxy system is used as the insulating film. The electrical characteristics of the metal-vacuum-semiconductor structure were measured in situ at room temperature using the capacitance-voltage (C-V) technique. Investigations were also carried out on the effect of the arsenic volatility on such structures. These results were compared to those obtained on a true MIS capacitor where CaF2 was used as insulator. The C-V hysteresis phenomena recorded on most of the Al/CaF2/GaAs diodes were investigated using a computer program. The results suggest that slow surface states rather than fast ones were responsible for the hysteresis phenomena and an insulator deposited under carefully controlled conditions might reduce defects at the GaAs surface, presumably through structural reordering.

Thermodynamics for arsenic and antimony in copper matte converting—computer simulation

Thermodynamic data for arsenic and antimony and their sulfide and oxide gases have been critically reviewed and compiled. The entropy values for AsS(g), SbS(g), and BiS(g) have been recalculated based on a statistical thermodynamic method. The standard heat of formation and entropy of As2O3(g) have been newly assessed to be △H 298 0 = −81,500 cal/mole and S 298 0 = 81.5 cal/deg/mole. Copper matte converting has been mathematically described using the stepwise equilibrium simulation technique together with quadratic approximations of oxygen and magnetite solubilities in molten mattes. A differential equation for the volatilization of arsenic and antimony has been derived and solved for successive reaction microsteps, whereby the volatilization, slagging, and alloying of the minor elements in copper matte converting have been examined as functions of reaction time and other process variables. Only the first (slag-making) stage of converting is responsible for the elimination of arsenic and antimony by volatilization. Arsenic volatilizes mainly as AsS(g) and AsO(g), with As2(g) also contributing when initial mattes are unusually rich in arsenic (above 0.5 pct arsenic). Antimony volatilizes chiefly as SbS(g), and the contributions of other gases such as SbO(g) and Sb(g) always remain negligibly low. The results of the stepwise equilibrium simulation compare favorably with the industrial operating data.

Volatilization of tin as stannane in anoxic environments

Recent reports of volatilization of metals from the aquatic environment demonstrate a previously unsuspected loss from the aquatic metal budget. Volatilization can occur by various mechanisms. Arsenic volatilizes from the aquatic environment as trimethyl- and dimethylarsine formed by biomethylation1; plants and soils form volatile selenium compounds2; volatilization of mercury from the oceans might rival that of anthropogenic origin3; maritime air can contain a significantly higher fraction of alkyl-lead compounds to total lead than continental or urban air4. Finally, increasing evidence suggests the potential importance of tin volatilization through formation of tetramethyltin by chemical or biological methylation in the environment5–7. We recently described possible formation of tetramethyltin by the macroalgae Enteromorpha sp. under oxic conditions6. Here we examine the contribution of decaying algal material to environmental cycling of tin by describing formation of volatile stannane (SnH4) in anoxic environments.

Environmental bioremediation for organometallic compounds: Microbial growth and arsenic volatillization from soil and retorted shale

AbstractNutrient effects on microbial growth and arsenic volatilization from retorted oil shale and soil were evaluated in a laboratory study. Dimethylarsinic acid (DMAA), methanearsonic acid (MAA) and sodium arsenate amendments were used with added nutrients, or with retort process water added to simulate possible co‐disposal conditions. In experiments with soil and retorted shale, dimethylarsinic acid showing the highest cumulative arsenic releases, in comparison with added inorganic sodium arsenate (SA). Low but detectable amounts of innate arsenic present in retorted shale could be volatilized with added organic matter. In soil, arsenic volatilization showed a direct relationship to nutrient levels and microbial growth. With shale, in comparison, a threshold response to available nutrients was evident. Distinct increases in fungal community development occurred with nutrients available at a level of 2.5% w/v, which also allowed incresed arsenic volatization. Codisposal of retort process waters with shale allowed arsenic volatilization without the addition of other nutrients. The presence of retort process water limited arsenic volatilization from the added organometallic compounds DMAA and MAA, but not from SA or innate arsenic. These differences should be useful in the definition of permissive and non‐permissive environmental conditions for arsenic volatilization in bioremediation programs.

Arsenic speciation in solid biological specimens by temperature-controlled pyrolysis and NAA

A pyrolysis-neutron activation analysis (NAA) procedure has been developed and applied to the speciation of arsenic in solid biological samples. The method involves the retention of the inorganic arsenic in the pyrolysis boat by the addition of NaOH, the volatilization and trapping of the organic arsenic on a cation exchange resin and the subsequent NAA of the resin for the determination of the trapped arsenic. The method, developed with the aid of radiochemically labelled arsenic compounds, has been applied to the determination of the ratio of inorganic to organic arsenic species in commercical shrimps as well as in NBS standard reference materials such as oysters and orchard leaves. The results show different relative amounts of inorganic arsenic content in the samples analysed. In the shrings the fraction of inorganic arsenic was of the order of 20%, in the oysters the inorganic arsenic consfituted 60% of the total arsenic concentration while in the samples of vegetable origin more than 98% of the arsenic was of inorganic nature.

Reduction of effects of structured non-specific absorption in the determination of arsenic and selenium by electrothermal atomic absorption spectrometry

The presence of iron and phosphates in biological matrices causes deuterium arc background-correction systems to overcompensate at several arsenic and selenium resonance lines. The addition of platinum as matrix modifier has a significant effect on both the absorbance/time profile of iron and the formation of gaseous phosphate decomposition products. A nickel/platinum matrix modifier is shown effectively to control the problems in the determination of selenium arising both from thermal instability and spectral interferences. The same combination eliminates the spectral interferences found at the arsenic resonance lines. Remaining problems are the thermal stabilization of organometallic arsenic compounds present in biological samples. When radioactived-labelled 74As compounds prepared in vivo were applied, none of the tested matrix modifiers (Ni, Cu, Ag, Pd, Zr, Ce, Ce + magnesium nitrate) showed a significant influence on the volatility of arsenic in whole blood and urine from rats.

Heteronuclear compounds of arsenic and antimony

Volatilization of secondary metals such as arsenic, antimony, and bismuth, during the smelting of copper ores, is important because of environmental and resource considerations. The Bureau of Mines, United States Department of the Interior, has been studying copper concentrate roasting in conjunction with the volatility of these minor constituents. Some unusual vaporization behavior initiated this supplemental paper which shows that when the mixed sulfides of arsenic and antimony are heated, the volatilization of arsenic is retarded and the volatilization of antimony increased. Mixed oxides of arsenic and antimony also exhibit exceptional volatilization behavior. These anomalous vaporization behaviors are attributed to the formation of heteronuclear compounds of arsenic and antimony, but the colligative properties of solutions may also be a factor.

Differential pulse polarographic determination of chromium in gallium arsenide

The proposed method for the determination of Cr in gallium arsenide is based on the catalytic activity of chromium(VI)-DTPA complex in the presence of nitrate ions. After dissolution of gallium arsenide with hydrochloric and nitric acids and volatilization of arsenic, chromium is oxidised to chromate with potassium chlorate in nitric acid. After nitric acid removal, the 0.012 M DTPA — 2.5 M LiNO3 supporting electrolyte buffered with 0.2 M CH3COONa — 0.05 M CH3COOH is directly added to the residue. Differential pulse polarography of this solution provides a detection limit of about 100 ng g−1, with a relative standard deviation of ±2–5% and a reproducible calibration curve up to at least 1 μg of Cr(VI) ml−1.

Effects of organic and inorganic binding on the volatilization of trace elements during coal pyrolysis

The volatility of bromine, chlorine, vanadium, managanese, selenium, arsenic, chromium, and cobalt during coal pyrolysis was determined. Volatility was determined for both hydrogenated and nonhydrogenated coal, and for coal spiked and unspiked with inorganic and organic forms of the trace elements. Volatilization of selenium and arsenic was higher when those elements were present as inorganic sulfide salts. The importance of chemical forms of elements to rates of volatilization during pyrolysis is established. (1 diagram, 9 references, 4 tables)

Arsenic Distribution and Control in Copper Smelters

Arsenic emissions from primary copper smelters are currently being reviewed by the U.S. Environmental Protection Agency to help establish the best available control technology. Relatively little information is available in the literature concerning the actual distribution of arsenic throughout the copper smelting processes. In addition, smelting process parameters which specifically affect arsenic distribution have not been clearly defined. This paper presents a general summary of arsenic distributions based on data from foreign and domestic copper smelters utilizing different smelting processes. The distribution of arsenic is presented on a 100% input basis for the various smelting configurations as well as for the individual process units. The general trends of arsenic volatilization and slagging for different process units are examined and probable effects are discussed. The effectiveness of control devices such as electrostatic precipitators and fabric filters in the control of arsenic emissions from copper smelters is also discussed.

Volatilization of arsenic(III, V), antimony(III, V), and selenium(IV, VI) from mixtures of hydrogen fluoride and perchloric acid solution: application to silicate analysis

Volatilization of arsenic(III, V), antimony(III, V), and selenium(IV, VI) from mixtures of hydrogen fluoride and perchloric acid solution: application to silicate analysis

I. On the combustion of hydrogen and carbonic oxide in oxygen under great pressure

In a former communication to the Royal Society I described some researches on the effect of a diminution of pressure on some of the phenomena of combustion, and deduced therefrom the law that the diminution in illuminating-power is directly proportional to the diminution in atmospheric pressure . Further experiments, made more than a year ago, on the nature of the luminous agent in a coal-gas flame, led me to doubt the correctness of the commonly received theory first propounded by Sir Humphry Davy, that the light of a gas-flame and of luminous flames in general is due to the presence of solid particles. In reference to gas- and candle-flames, it is now well known that the fuliginous matter produced when a piece of wire- •gauze is depressed upon such flames, and the sooty deposit which coats a piece of white porcelain placed in a similar position, are not pure carbon, but contain hydrogen, which is only completely got rid of by prolonged exposure to a white heat in an atmosphere of chlorine. On pursuing the subject further, I found that there are many flames possessing a high degree of luminosity which cannot possibly contain solid particles. Thus the flame of metallic arsenic burning in oxygen emits a remarkably intense white light; and as metallic arsenic volatilizes at 180° C., and its product of combustion (arsenious anhydride) at 218° C., whilst the temperature of incandescence of solids is at least 500° C., it is obviously impossible here to assume the presence of ignited solid particles in the flame. Again, if carbonic disulphide vapour he made to hum in oxygen, or oxygen in carbonic disulphide vapour, an almost insupportably brilliant light is the result. Now fuliginous matter is never present in any part of this flame, and the boiling-point of sulphur (440° C.) is below the temperature of incandescence, so that the assumption of solid particles in the flame is here also inadmissible. If the last experiment be varied by the substitution of nitric oxide gas for oxygen, the result is still the same; and the dazzling light produced by the combustion of these compounds^ is also so rich in the more refrangible rays, that it has been employed in taking instantaneous photographs, and for exhibiting the phenomena of fluorescence.

The working processes for the reduction of the gray copper (Tetrahedrite) ores ckt stefanshutte, in the comitat (County) of Zips, in Hungary

The possible arsenic tolerance mechanisms were explored in Arundo donax L. under various supplied arsenic concentrations. The treatments included control (no metal) and five doses of arsenic trioxide i.e., 0, 50, 100, 300, 600 and 1000 μg L−1 As to A. donax. The phytoextraction ability of A. donax L. plants was assessed using both the translocation and bioaccumulation factors. The transpirates were collected to analyze the arsenic concentration volatilized along-with study of anatomical characteristics of the plant parts. In general, the arsenite and arsenate accumulation linearly increased in roots, shoot and leaves with the increasing supplied arsenic levels i.e., from 2.348, 2.775 and 3.25 μg g−1 at 50 μg L−1 to 50, 53.125 and 64.25 μg g−1 arsenite, at 1000 μg L−1, from 4.075, 5.425 and 13.56 μg g−1 at 50 μg L−1 to 71, 62.02 and 436.219 μg g−1 arsenate at 1000 μg L−1, respectively. The order of arsenic accumulation in A. donax L. was: solution As(III) < Root As(III) < Shoot As(III) < Leaf As(III) < Solution As(V) < Root As(V) < Shoot As(V) < Leaf As(V). The range of arsenic volatilization by A. donax L. was 7.2–22% at higher supplied arsenic (300–1000 μg L−1). Volatilization was an important mechanism to avoid toxic effects of arsenic by A. donax L. in addition to bioaccumulation.