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  • Springer  (117)
  • American Geophysical Union  (33)
  • Molecular Diversity Preservation International  (19)
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  • 1
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    Lability of DOC transported by Alaskan rivers to the Arctic Ocean (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 35 (2008): L03402, doi:10.1029/2007GL032837.
    Description: Arctic rivers transport huge quantities of dissolved organic carbon (DOC) to the Arctic Ocean. The prevailing paradigm is that DOC in arctic rivers is refractory and therefore of little significance for the biogeochemistry of the Arctic Ocean. We show that there is substantial seasonal variability in the lability of DOC transported by Alaskan rivers to the Arctic Ocean: little DOC is lost during incubations of samples collected during summer, but substantial losses (20–40%) occur during incubations of samples collected during the spring freshet when the majority of the annual DOC flux occurs. We speculate that restricting sampling to summer may have biased past studies. If so, then fluvial inputs of DOC to the Arctic Ocean may have a much larger influence on coastal ocean biogeochemistry than previously realized, and reconsideration of the role of terrigenous DOC on carbon, microbial, and food-web dynamics on the arctic shelf will be warranted.
    Description: This material is based on work supported by the National Science Foundation under grant numbers OPP-0436106, OPP- 0519840, and EAR-0403962, and is a contribution to the Study of Environmental Arctic Change (SEARCH).
    Keywords: DOC ; Arctic ; Rivers
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: text/plain
    Format: application/pdf
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    PAPER (OA)
  • 2
    Electronic Resource
    Electronic Resource
    Determination of arsenic(III) in caustic melts (1992)
    Springer
    Journal of applied electrochemistry 22 (1992), S. 581-584 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Voltammetric and potentiometric methods were evaluated for the determination of As(III) levels in molten sodium hydroxide at 450°C. Because of the crystallization of As(V) salts on the working electrode, voltammetric measurements were limited to less than 3 wt% As(III) in melts containing up to 6 wt% total arsenic and only 2 wt% in melts containing up to 12 wt% total arsenic. Potentiometry has maximum sensitivity when the As(III)/As(V) ratio was near 1: 1 at 12 wt% total arsenic. The applicability of the two methods for control of an As(III) to As(V) oxidation process was evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01024101
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of low-temperature cryolite-based electrolytes for aluminium smelting (1995)
    Springer
    Journal of applied electrochemistry 25 (1995), S. 1098-1104 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Aluminium was smelted in a laboratory-scale cell at temperatures down to 850 °C from cryolite-based electrolytes with bath ratios in the range 0.75–1.50. Electrolyses were conducted for 1–2h using a current density of 1 A cm−2 on 5 cm2 electrodes with an anode-cathode distance of 2 cm. Current efficiencies of up to 95% were recorded. In low bath ratio electrolytes, operation at alumina concentrations of ≥ 3 wt% sometimes resulted in the aluminium deposit breaking into globules which clustered around the cathode. Under constant current conditions, the critical alumina concentration for the onset of anode effect was found to be ∼2 wt%. The bubble evolution characteristics (i.e., size and frequency) which affect mass transfer and cell voltage were also evaluated. Overall, low-temperature cryolite-based electrolytes may offer a viable alternative to conventional compositions for aluminium smelting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242536
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  • 4
    Electronic Resource
    Electronic Resource
    Investigation of the aluminium electrodeposition process in cryolite-based melts using a rotating ring-disc electrode: evidence for the existence of a subvalent intermediate species (1996)
    Springer
    Journal of applied electrochemistry 26 (1996), S. 249-254 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The rotating ring-disc electrode technique has been used to investigate the reaction mechanism of the aluminium electrodeposition process in cryolite-based electrolytes. Laboratory studies using high temperature gold-molybdenum and platinum-molybdenum rotating ring-disc electrodes have provided evidence for the existence of a subvalent intermediate species (Al (I)). In a cryolite-alumina electrolyte (bath ratio: 1.5), two well separated convective-diffusion controlled oxidation processes were observed at both a gold and a platinum ring during aluminium electrodeposition at the disc. On the basis of the data presented, a reaction scheme involving reduction of A1(III) to A1(0) via A1(I), followed by chemical dissolution of A1(0) into the bulk electrolyte was proposed. The loss of current efficiency in aluminium smelting was primarily attributed to the chemical dissolution of A1(0), rather than to the formation of a subvalent intermediate species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242093
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  • 5
    Electronic Resource
    Electronic Resource
    The estimation of the coulombic efficiency of zinc electrodeposition by measurement of current efficiencies at a rotating ring disc electrode (1986)
    Springer
    Journal of applied electrochemistry 16 (1986), S. 387-392 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The rotating ring disc electrode (RRDE) offers a simple method for the determination of the current efficiency (CE) of zinc electrodeposition in acidic zinc sulphate electrolytes. The hydrogen evolved during zinc deposition can be detected at the ring. This allows estimation of the current due to hydrogen formation at the disc and hence CE for electrodeposition of zinc can be calculated. Investigations of the conditions under which reliable measurements of CE can be obtained are described. A correlation between CE, determined using the RRDE, and the coulombic efficiency (QE), determined by weighing the zinc deposit obtained after 2 h electrodeposition at constant current, is established for a range of electrolyte compositions. It is suggested that measurement of CE at a Pt−Zn RRDE provides an efficient means of estimating QE for zinc electrolytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01008849
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  • 6
    Electronic Resource
    Electronic Resource
    Identification of optimum conditions for zinc electrowinning in high-purity synthetic electrolytes (1987)
    Springer
    Journal of applied electrochemistry 17 (1987), S. 453-462 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The optimum conditions for zinc electrowinning in synthetic acidic zinc sulphate electrolytes (0.8 M ZnSO4+1.07 M H2SO4) were determined using response surface statistical analysis. The coulombic efficiency (QE) was optimized with respect to temperature (T), current density (J) and electrode rotation rate (n). For an electrolyte prepared from AR zinc sulphate and Aristar sulphuric acid, containing trace lead and nickel, QE reached a maximum of 98.8% on a zinc substrate under the following conditions:T=50°C,J=500 A m−2,n=35s−1. For a very-high-purity electrolyte, prepared by dissolution of 99.9999% zinc in Aristar sulphuric acid, a maximum QE of 98.4% was predicted and obtained at:T≃61°C,J≃890 A m−2,n≃38s−1. Using a statistical response surface model calculated during the optimization process, QE contours giving an overall view of electrolyte performance were constructed. The QE responses were determined principally byT andJ, with significant interaction betweenn andJ orT andJ, depending on the impurity composition of the electrolyte. The model was also used to predict the QE response of the above electrolytes under conditions similar to industrial practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01084118
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of certain impurities on zinc electrowinning in high-purity synthetic solutions (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 583-589 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The individual effects of lead, copper, nickel, cobalt and antimony on zinc electrowinning were evaluated by measurements in high-purity synthetic solutions, free from additives. The coulombic efficiency (QE) of zinc electrodeposition was determined over 2h under mass transfer-controlled conditions at a temperature of 35°C and a current density of 400 A m−2 in a solution of 0.8 M ZnSO4+1.07 M H2SO4. Antimony had a very detrimental effect on QE causing decrease of ∼ 5 and 50% at 4 and 14 μg l−1, respectively. Antimony also exerted a strong grain-refining effect and changed the deposit orientation from random to (112) to (004) with increasing concentration. Lead had a small beneficial effect on QE at the electrode rotation rate employed (20 s−1). It also exerted a grain-refining effect and changed the deposit orientation from random to (102), (103), (104), to strong basal (004), (002) with increasing concentration. Copper, nickel and cobalt had minor effects on QE, with reductions at 5 mg l−1 of 0.8, 0.3 and 0.3%, respectively. The effects of copper on morphology and orientation were very concentration dependent, but with a general trend towards grain-refining and random orientation. Nickel promoted coarse-grained deposits and changed the orientation from random to (114), (102) to (204), (102) with increasing concentration. Cobalt had the least effect on the morphology of the deposit, although it gradually increased the basal plane orientation with increasing concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01022254
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  • 8
    Electronic Resource
    Electronic Resource
    The electrodeposition of gallium from synthetic Bayer-process liquors (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 134-141 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Gallium was electrodeposited from a synthetic Bayer solution comprising 4.5m NaOH/0.2m Na2CO3/0.3m NaCl/1.7m Al(OH)3. Hydrogen evolution occurred in parallel with gallium deposition, the latter process being in part controlled by mass transfer and in part by the electron transfer step. Combined coulometric and voltammetric measurements allowed estimation of a diffusion coefficient for Ga (III) of 3.6×10−6 cm2 sec−1 at 40° C. The coulombic efficiency for gallium deposition was a function of current density, deposition time, electrode rotation rate, temperature and gallium concentration. Values of up to 11% were obtained on a copper electrode from a solution containing 3.2×10−3 m Ga (III). Heavy-metal impurities, such as iron and vanadium, usually found in these liquors, promote the hydrogen evolution reaction, completely inhibiting gallium production if present above certain critical concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01016217
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  • 9
    Electronic Resource
    Electronic Resource
    Operational characteristics of laboratory scale alumina reduction cells with wettable cathodes (1993)
    Springer
    Journal of applied electrochemistry 23 (1993), S. 933-942 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The operational characteristics of a laboratory-scale alumina reduction cell incorporating a wettable cathode were evaluated by electrolyses in a 10 wt% alumina/cryolite melt at 975° C. It was shown that as the anode—cathode distance (a.c.d.) decreased, the mass transfer rate increased and the current efficiency decreased. The contribution to cell resistance from the anode bubble-layer at small a.c.d.'s was found to be significant. The ohmically corrected cell voltage decreased with decreasing a.c.d., increasing anode immersion and increasing anode rotation rate, indicating a substantial influence of mass-transfer on cell operation. Digital analysis of cell voltage and resistance data was used to characterize bubble behaviour over a range of operating conditions. The frequency spectra varied over the course of a run due to the cessation of the regular formation and detachment of large bubbles. Bubble behaviour was strongly dependent on anode geometry, current density and anode rotation rate, tending towards smaller bubbles at high angles of inclination, low current density and high rotation rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251030
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  • 10
    Electronic Resource
    Electronic Resource
    Development of a rotating ring-disc electrode for high temperature studies in cryolite-based melts (1995)
    Springer
    Journal of applied electrochemistry 25 (1995), S. 456-461 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A compact rotating ring-disc electrode incorporating a molybdenum disc, gold ring and boron nitride insulator has been designed, constructed and evaluated in molten cryolite-based electrolytes at temperatures up to 1000°C and rotation rates between 0 and 2000 rpm. The electrode design is extremely versatile and relatively maintenance free, with no visible evidence of melt leakage at the ring-insulator and disc-insulator interfaces. The operating performance of the gold-molybdenum rotating ring-disc electrode was evaluated from collection efficiency measurements based on the dissolution of the disc surface and subsequent detection of soluble species transported to the ring. The observed collection efficiency was less than the theoretical value determined from the geometry of the electrode, primarily because of noncoplanarity of the electrode surface at the working temperature. The results confirm that the electrode should be useful for mechanistic studies in high temperature molten fluoride electrolytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260688
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