James H. Ephraim

Linköping University, Linköping, Östergötland, Sweden

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Publications (11)3.14 Total impact

  • Maria Nordén, James Ephraim, Bert Allard
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    ABSTRACT: The complexation of an aquatic fulvic acid, FA, with Sr2+ and Eu3+ was studied using an ultrafiltration technique and an ion exchange distribution method. The total amount of bound metal (Sr2+ and Eu3+) was measured as a function of pH at low metal concentrations (trace levels) and constant FA concentration. In the Sr-FA system the bound metal fraction increased slightly with pH, and the values obtained from the two experimental techniques were comparable. For Eu-FA, according to the ultrafiltration data, the fraction of bound metal ion was relatively insensitive to pH changes, whereas values from the ion exchange measurements showed a strong and positive dependence on pH. The results are discussed in the light of possible intrinsic problems of the two methods.
    10/2006: pages 297-303;
  • Environmental Science & Technology - ENVIRON SCI TECHNOL. 04/2002; 23(3).
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    ABSTRACT: Partial least squares (PLS) modeling was applied to investigate number-average molecular weights (Mn) and weight-average molecular weights (Mw) of fulvic acids (FAs) in relation to the corresponding UV/VIS spectra. The Mn and Mw values were determined by size exclusion chromatography (SEC). The impact of pH control, wavelength range and density as well as smoothing and derivation of spectra were tested. It was found that PLS models based on absorbance spectra can be a fast and powerful complement to existing techniques employed for determination of molecular weights of FAs. Control of pH of the FA solutions is important for the performance of the models. The models were also compared with the best univariate alternatives.
    Chemosphere 03/1999; 38(4):783-94. · 3.14 Impact Factor
  • C. Pettersson, J. Ephraim, B. Allard
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    ABSTRACT: Fulvic and humic acids were collected from groundwater and surface waters by an isolation procedure utilizing DEAE-cellulose, a weak anion exchange resin. DEAE-cellulose was selected since it can adsorb himics without any pH adjustment of the sampled water (in the pH range 4–8), thus making the method well suited for isolation of groundwater humic substances in the field. Characterization of general parameters (elemental composition, molecular weight, acidity, absorptivity, 14C-age) was performed on these humic substances as well as on humics isolated by other procedures. The humic weights and were divided into three categories on the basis of calculated atomic ratios, molecular weights and absorptivity: humic acids (high molecular weight) and fulvic acids (low molecular weight) from groundwater and surface waters, respectively. The similarities of the humics within each group, despite variations in age and origin, support the contention that humic substances have more properties in common than they have differences.
    Organic Geochemistry. 01/1994;
  • James H. Ephraim, Bert Allard
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    ABSTRACT: Despite the considerable number of publications in the literature, the interaction between humic substances and the Cu2+ metal ion is still of interest because the stability of the resultant complex coupled with the high reliability of the Cu2+-selectrode offers the possibility of obtaining very reliable data to facilitate modeling of the metal-humate systems. In this paper, the results of Cu2+ binding by a well characterised aquatic fulvic acid are presented in such a manner as to allow comparison with previously reported studies. In addition, these results obtained as a function of ionic strength (0.010 mol and 0.100 mol NaClO4) and fulvic acid to metal ion concentration ratios (FA/Cu2+ = 30, 6, 1) have been interpreted by considering the identified predominant ligand sites to give credence to the functionality assigned to them. Chemical speciation distributions have been obtained using MICROQL, a chemical equilibrium computer program.
    Environment International. 01/1994;
  • James H. Ephraim
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    ABSTRACT: Zinc binding by a well characterized fulvic acid was studied by the ion-exchange distribution technique and ultrafiltration method at 0.100 M NaClO4 using trace amounts of zinc (≤ 10−1 M) and two different fulvic acid concentrations (6.2 × 10−4 and 1.2 × 10−3 M). The results were interpreted by considering the various acidic sites envisaged from potentiometric titrations in aqueous and non-aqueous media. In addition to calculating the overall complex formation function, literature-based constants for the complexation between the metal ion and the ascribed functional group were employed to account for the observed binding patterns as a function of pH. This supported the interpretation of the functional groups assigned to the envisaged acidic sites. Results from the ultrafiltration method were in agreement with those obtained from the ion-exchange distribution technique.
    Analytica Chimica Acta. 01/1992;
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    ABSTRACT: An ultrafiltration technique has been adapted to obtain information on the binding of cadmium by a fulvic acid extracted from a deep groundwater. The results obtained are compared to those obtained by the ion-exchange distribution method (Schubert's approach) and an ion selective electrode method. The data obtained have been analyzed taking into consideration the heterogeneity of the fulvic acid sample. Results from the comparison indicate that with a proper design and conditioning of the diaflo membrane, the ultrafiltration technique offers a promising approach with respect to obtaining meaningful information on the binding of trace metals by natural organic acids.
    Science of The Total Environment - SCI TOTAL ENVIR. 01/1989;
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    ABSTRACT: Fulvic acids have been recovered from three deep groundwaters and one surface water and characterized with respect to elemental composition, molecular weight, acid capacity and 14C-age. The corresponding waters are also characterized in detail. All of the fulvic acids, with ages varying from 0 to 5250 years, are very similar. The onlu significant difference between fresh and old materials are lower content of oxygen and nitrogen and higher COOH/OH-ratios for the materials from the old waters. Dating of the water using 14C-analysis of the dissolved organic material is probably better than using the carbonate as the 14C-source.
    Science of The Total Environment - SCI TOTAL ENVIR. 01/1989;
  • H. Xu, J. Ephraim, A. Ledin, B. Allard
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    ABSTRACT: The effects of fulvic acids on the adsorption of cadmium on alumina has been studied by a batch distribution technique and with variation of pH (3 – 10), cadmium concentration (10−4 – 10−8 M) and fulvic acid concentration (0, 1, 10 and 50 mg/l). Two fulvic acids of different origin (surface water and deep groundwater) were used. The presence of fulvic acid generally enhanced the adsorption at pH below PZC (pH 7.8) and reduced the adsorption above this pH. Linear adsorption isotherms were obtained at cadmium concentration below 10−6 M. The presence of fulvic acids at concentration levels representative of surface waters would be expected to have a significant impact on the distribution and mobility of cadmium in the environment.
    Science of The Total Environment. 01/1989;
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    ABSTRACT: Insight into the functional group heterogeneity of an aquatic fulvic acid has been gained via carefully designed acid-base titrations in aqueous and nonaqueous media and a newly developed derivatization technique. Results of the acid-base titrations in an aqueous medium and in the presence of heavy metals (eg. Cu(II) and La(III) indicate the presence of salicylic acid-like and catechol-like moieties in the fulvic acid molecule. The total acidic capacity can be separated into contributions from a weak acid of carboxylic functionality and a still weaker acid of -OH type by acid-base titrations in a nonaqueous medium in the presence of an internal reference standard. An organic derivatization technique in conjunction with high resolution gas chromatography has facilitated the determination of the total number of hydroxyl groups in the fulvic acid sample. The results obtained from the derivatization technique are compared with those obtained from the acid-base titrations in aqueous and nonaqueous systems.
    Science of The Total Environment - SCI TOTAL ENVIR. 01/1989;
  • James H. Ephraim, Catharina Pettersson, Bert Allard
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    ABSTRACT: The overall acid-base properties of humic substances have been postulated to be affected by the functional group heterogeneity and heterogeneity in molecular size leading to an ionic strength effect. In this paper, the acidic properties of various molecular size fractions (500, 1000, 5000, 10 000 daltons as per ultrafiltration) of an aquatic fulvic acid (Rådsla FA) are determined and correlated to other physicochemical parameters such as UV, FTIR, and molecular weight determinations by gel-filtration chromatography. There was a positive correlation between the size cut-off as per ultrafiltration and the molecular weight determinations from the gel-filtration chromatography. The acid-base titrations of the filtrates and retentates corroborate the hypothesis that ionic strength effects are significantly larger for samples with higher molecular weight moieties.
    Environment International. 22(5):475–483.