Benjamin Greene

New Mexico State University, Las Cruces, New Mexico, United States

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Publications (8)27.04 Total impact

  • J.W. II Watkins · R.C. Elder · Benjamin Greene · Dennis W. Darnall
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    ABSTRACT: The alga Chorella vulgaris has been shown to have a high affinity for both gold(I) and gold(III) species in aqueous solutions. The accumulation of gold may approach 10% or more of the algae dry weight. X-ray absorption spectroscopy was used to investigate Au-algae samples prepared from aqueous solutions of the antiarthritic drug Myochrisine (sodium gold(I) thiomalate) and the gold complexes dicyanoaurate(I) and tetrachloroaurate(III). The oxidation state of the algae-bound gold and the structure of the gold coordination sphere that results upon binding have been determined. These results indicate that chemical reaction, not simply electrostatic interaction, is involved in the binding of the gold to the algae. The predominant oxidation state in algae complexes is Au(I). For samples derived from Au(I) complexes, the ligating atom appears to be sulfur while, for the samples prepared from Au(III), the product appears to bind Au(I) to a nitrogen moiety. 22 references, 2 figures, 2 tables.
    No preview · Article · Apr 1987 · Inorganic Chemistry
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    ABSTRACT: Chlorella vulgaris accumulates both gold(I) and gold-(III) from aqueous solutions with high affinity. The degree of gold adsorption strongly depends on competing ligands present in the solution. Tetrachloroaurate(III) and gold(I) sodium thiomalate are rapidly adsorbed by the algal cells over a wide pH range, whereas dicyanoaurate(I) is bound more slowly and in a highly pH-dependent manner, with maximum binding observed near pH 3.0. Inhibition and reversal of gold binding by strong competing ligands (mercaptoethanol, cyanide, and thiourea) are also pH dependent. Under certain conditions, the level of gold accumulation by Chlorella vulgaris approaches 10% of the organism's dry weight. Experiments suggest that the alga rapidly reduces gold(III) to gold(I) and that the algal-bound gold is slowly reduced to gold(0).
    No preview · Article · Jun 1986 · Environmental Science and Technology
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    ABSTRACT: Freeze-dried preparations of Chlorella vulgaris will accumulate U(Vl) from alkaline, bicarbonate-containing waters collected from uranium mill process streams, provided that the pH is pre-adjusted to between 4.0 and 6.0. Bicarbonate ion complexes the uranyl ion in these waters and seriously interferes with the binding of U(Vl) to the algal cells at pH values above 6.0. No binding of U(Vl) to the algae occurred at the natural pH of 8.0 when Chlorella vulgaris was suspended in untreated mull-waters containing up to 2.5 x 10/sup -4/M U(Vl). However, when the pH of these waters was lowered from 8.0 to near 5.0, with nitric acid, nearly quantitative binding of U(Vl) to the alga was achieved. Binding is rapid and largely unaffected by ions including Na/sup +/, Cl/sup -/, NO/sub 3//sup -/, /sup -/OAc, and SO/sub 4//sup 2 -/. Our results indicate that provided steps are taken to eliminate bicarbonate interference, such as adjustment of the pH to near 5.0, dried algal biomass could prove useful for the removal and recovery of U(Vl) from high carbonate-containing waters.
    Preview · Article · May 1986 · Biotechnology and Bioengineering
  • Benjamin Greene · Peter G. Mitchell · Joseph Sneddon

    No preview · Article · Mar 1986 · Spectroscopy Letters
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    ABSTRACT: The accumulation of Au(0) by lyophilized preparations of the alga Chlorella vulgaris has been investigated. Gold is bound to the algae upon suspending dried algal cells in solutions containing hydrogen tetrachloroaurate (III). Relative amounts of ionic and atomic algal-bound gold were determined by thiourea extraction. It was found that the amount of algal-bound atomic gold produced from ionic gold increased with time. The effect of algal-bound gold concentration on the rate and extent of gold reduction was observed. It is suggested that at least three different classes of sites are available for gold binding and reduction. The effect of Au(0) accumulation on the binding ability of gold-bound algae was also investigated, and an apparent enhancement of gold binding ability is reported.
    No preview · Article · Mar 1986 · Inorganica Chimica Acta
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    ABSTRACT: In determining the abilities of microorganisms to remove metal ions from water, a number of investigators have shown that different metal ions bind to cell walls of bacteria, fungi, and algae. We have observed that the pH dependence of the binding of Au3+, Ag+, and Hg2+ to the algae Chlorella vulgaris is different than the binding of other metal ions. Between pH 5 and 7, a variety of metal ions bind strongly to the cell surface. Most of these algal-bound metal ions can be selectively desorbed by lowering the pH to 2; however, Au3+, Hg2+, and Ag+ are all bound strongly at pH 2. Addition of a strong ligand at different pHs is required to elute these ions from the algal surface. Algal-bound gold and mercury can be selectively eluted by using mercaptoethanol. An elution scheme is demonstrated for the binding and selective recovery of Cu2+, Zn2+, Au3+, and Hg2+ from an equimolar mixture.
    No preview · Article · Feb 1986 · Environmental Science and Technology
  • Peter G. Mitchell · Benjamin Greene · Joseph Sneddon
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    ABSTRACT: A study on the use of electrothermal vaporization for introduction of solid samples into a direct-current plasma is presented. The solid samples investigated were milligram masses of an alga exposed to various mercury solutions. The results are independent of the algal mass in the 0.6–9 mg range, and give acceptable calibration curves up to 20 mg of mercury absorbed on 5-mg masses of the alga; the relative standard deviation was 7.4% for nine successive samples of 100g of mercury absorbed by a mass of approximately 3 mg of algal cells. Various mercury compounds gave more than one peak, with different appearance times. Addition of sulphur-containing algal cells or cysteine modified the mercury signal, making it the same (for the compounds tested) irrespective of the mercury compound originally present.
    No preview · Article · Jan 1986 · Microchimica Acta
  • Benjamin Greene · Adriana Uranga · Joseph Sneddon
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    ABSTRACT: This paper reports observations on the determination of uranium in ground and mine waters by direct current argon plasma emission spectrometry. An enhancement effect due to different concentrations of six sodium salts and calcium nitrate was characterized. When the salt concentration of the waters was greater than the aqueous uranium standards, an erroneous uranium signal was found. The method of standard additions showed that direct calibration with aqueous uranium standards containing 0.05M sodium acetate was satisfactory. The use of matrix matched uranium standards is recommended to compensate for large enhancements in the uranium emission signal that may result from the presence of naturally occurring salts. Concentrations of uranium in ground waters ranged from 5 ppm to 16 ppm depending on sampling site and in mine waters from 2 ppm to several hundred ppm.
    No preview · Article · Jul 1985 · Spectroscopy Letters