Humic acids metal complexes

Jambu, R, Dupuis,T., and Garais, M. (1975a). Use of differential thermal-analysis to characterize fulvic acid metal complexes and humic acid metal complexes. 2. Application to natural organometallic complexes. J. Therm. Anal. 8(2), 231-237. 

Horseradish peroxidase, 704 Human serum albumin technetium-99 labelled lung profusion techniques, 994 Humboltine structure, 849 Humic acids metal complexes geochemistry, 857-861 minerals, 849 stability, 859... 

Senesi, N., Saiz-Jimenez, C., and Miano,T. M. (1992). Spectroscopic characterizaton of metal-humic acid-like complexes of earthworm-composted organic wastes. Sci. Total Environ. 117/118,111-120. 

Montavon G, Mansel A, Seibert A, Keller H, Kratz JV, Trautmaim N (2000) Complexation studies of U02 with humic acid at low metal ion concentrations by indirect speciation methods. Radiochim Acta 88 17-24... 

Stevenson F.J. Nature of divalent transition metal complexes of humic acids as revealed by a modified potentiometric titration method. Soil Sci 1977 123 10-17. 

Organic matter is also the essential component of natural soils and its association with microorganisms may influence the behavior and fate of toxic metals. A variety of batch complexation experiments were performed by Borrok et al. (2007) in single, binary and ternary systems for the three components natural organic matter (NOM), bacterium (B. subtilis) and metals (Pb, Cu, Cd, and Ni) to determine the significance of ternary complexation. They found that the formation of bacteria-metal-NOM complex is a rapid, fully-reversible chemical process. The stability of bacteria-metal-NOM complexes increases with the decrease of pH. All NOM fractions form ternary complexes to similar extents at circumneutral pH, but humic acid becomes the dominant NOM fraction in ternary complexes at low pH. The abundance of humic acid in ternary form is greatest with Ni or Cd systems and less with Pb and Cu systems. Their results suggest that... 

Batley and Farrah [ 120] and Gardner and Yates [118] used ozone to decompose organic matter in samples and thus break down metal complexes prior to atomic absorption spectrometry. By this treatment, metal complexes of humic acid and EDTA were broken down in less than 2 min. These observations led Gardner and Yates [ 118 ] to propose the following method for the determination of cadmium in seawater. 

Magni et al. [857] studied the optimisation of the extraction of metal-humic acid complexes from marine sediments. Polyarylamide gels have been... 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

Vitamin B12 catalyzed also the dechlorination of tetrachloroethene (PCE) to tri-chloroethene (TCE) and 1,2-dichloroethene (DCE) in the presence of dithiothreitol or Ti(III) citrate [137-141], but zero-valent metals have also been used as bulk electron donors [142, 143]. With vitamin B12, carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction cis-l,2-DCE, ethene, and ethyne were the main products [138, 139]. Using Ni(II) humic acid complexes, TCE reduction was more rapid, leading to ethane and ethene as the primary products [144, 145]. Angst, Schwarzenbach and colleagues [140, 141] have shown that the corrinoid-catalyzed dechlorinations of the DCE isomers and vinyl chloride (VC) to ethene and ethyne were pH-dependent, and showed the reactivity order 1,1-DCE>VC> trans-DCE>cis-DCE. Similar results have been obtained by Lesage and colleagues [146]. Dror and Schlautmann [147, 148] have demonstrated the importance of specific core metals and their solubility for the reactivity of a porphyrin complex. 

Wang, Z.-J., and W. Stumm (1987), "Heavy Metal Complexation by Surfaces and Humic Acids A Brief Discourse on Assessment by Acidimetric Titration", Netherlands J. of Agricult. Sci. 35, 231 -240. 

---