In situ study of binding of copper by fulvic acid: Comparison of differential absorbance data and model predictions | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS


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  In situ study of binding of copper by fulvic acid: Comparison of differential absorbance data and model predictions

Type de publication:

Journal Article


WATER RESEARCH, Elsevier Ltd, Volume 47, Nombre 2, p.588–596 (2013)





This study examined the binding of copper(II) by Suwannee River fulvic acid (SRFA) using the method of differential absorbance that was used at environmentally-relevant concentrations of copper and SRFA. The pH- and metal-differential spectra were processed via numeric deconvolution to establish commonalities seen in the changes of absorbance caused by deprotonation of \SRFA\ and its interactions with copper(II) ions. Six Gaussian bands were determined to be present in both the pH- and Cu-differential spectra. Their maxima were located, in the order of increasing wavelengths at 208 nm, 242 nm, 276 nm, 314 nm, 378 nm and 551 nm. The bands with these maxima were denoted as A0, A1, A2, A3, \A4\ and A5, respectively. Properties of these bands were compared with those existing in the spectra of model compounds such as sulfosalicylic acid (SSA), tannic acid (TA), and polystyrenesulfonic acid-co-maleic acid (PSMA). While none of the features observed in differential spectra of the model compound were identical to those present in the case of SRFA, Gaussian bands A1, \A3\ and possibly \A2\ were concluded to be largely attributable to a combination of responses of salicylic- and polyhydroxyphenolic groups. In contrast, bands \A4\ and \A5\ were detected in the differential spectra of \SRFA\ only. Their nature remains to be elucidated. To examine correlations between the amount of copper(II) bound by \SRFA\ and changes of its absorbance, differential absorbances measured at indicative wavelengths 250 nm and 400 nm were compared with the total amount of SRFA-bound copper estimated based on Visual İNTEQ\ calculations. This examination showed that the differential absorbances of \SRFA\ in a wide range of pH values and copper concentrations were strongly correlated with the concentration of SRFA-bound copper. The approach presented in this study can be used to generate in situ information concerning the nature of functional groups in humic substances engaged in interactions with metals ions. This information can be useful for further elaboration and development of detailed theoretic models that describe the complexation of metals in the environment.