STUDY OF THE COMPLEXATION OF CU(II) BY FULVIC-ACIDS EXTRACTED FROM A SEWAGE-SLUDGE AND ITS COMPOST

The complexation of Cu(II) by two samples of fulvic acids (FA) extract ed from the raw sewage sludge (RsFA) of a waste water processing plant and from the composted sludge (CsFA) obtained upon aerobical digestio n was studied at pH 6.0. Synchronous molecular fluorescence spectrosco py was used to monitor the association of FA with Cu(II) and a self-mo delling mixture analysis method (SIMPLISMA) was used to preprocess the spectral data to calculate the number of components with different qu enching profiles as function of the Cu(II) concentration and their spe ctra. The stability constants and a rough estimation of the binding si te concentrations were obtained by a Stern-Volmer analysis, by a non-l inear least-square method and by a linear procedure. The analysis of t he SyF spectra allowed the identification of two binding sites for bot h samples. The logarithm of the conditional stability constant corresp onding to the 1:1 complex formed between the stronger binding site and Cu(II) is about 4 for both samples.