کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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6367684 | 1316853 | 2013 | 9 صفحه PDF | دانلود رایگان |
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 208Â nm, 242Â nm, 276Â nm, 314Â nm, 378Â nm and 551Â 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 250Â nm and 400Â nm were compared with the total amount of SRFA-bound copper estimated based on Visual MINTEQ 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.
162Highlights⺠Change of SRFA spectra at varying pHs and Cu is deconvoluted into six Gaussian bands. ⺠Some bands in SRFA are similar to those observed for selected model compounds. ⺠Differential absorbance at 400 nm is correlated with the amount of Cu bound to SRFA.
Journal: Water Research - Volume 47, Issue 2, 1 February 2013, Pages 588-596