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On-site characterization of humic-rich hydrocolloids and their metal loading by means of mobile size-fractionation and exchange techniques.
- Source :
-
Fresenius' journal of analytical chemistry [Fresenius J Anal Chem] 2001 Nov; Vol. 371 (5), pp. 660-9. - Publication Year :
- 2001
-
Abstract
- Humic-rich hydrocolloids and their metal loading in selected German bog-waters have been characterized by a novel on-site approach. By use of an on-line multistage ultrafiltration (MST-UF) unit equipped with conventional polyethersulfone (PES)-based flat membranes (nominal cut-off 0.45, 0.22, and 0.1 microm, or 100, 50, 10, 5, 3 kDa) the hydrocolloids could be fractionated on-site in both sub-particulate and macromolecular size ranges. Characterization (dissolved organic carbon (DOC), metals) of the colloid fractions obtained this way was performed off-site by use of conventional instrumental methods (carbon analyzer, AAS, ICP-OES, and TXRF (total reflection X-ray fluorescence)). Major DOC fractions of the hydrocolloids studied were found to be in the size range <5 kDa. The assessed metals (Al, Cu, Fe, Mn, Pb, and Zn) were, however, predominantly enriched in the macromolecular and sub-particulate range, depending on the metal and the sample, respectively. In addition, metal species bound to these hydrocolloids were kinetically characterized on-site by use of competitive ligand (EDTA (ethylenediaminetetraacetate)) and metal (Cu(II)) exchange; the EDTA complexes formed and the metal ions exchanged were separated by means of a small time-controlled tangential-flow UF unit (cut-off 1 kDa). Bound metal fractions, in particular Al and Fe, reacted only slowly (500 to 1000 min) with EDTA; the conditional availability was 60-99%, depending on the hydrocolloid. In contrast, the Cu(II) exchange of colloid-bound metal species approached equilibrium within 5-10 min, with characteristic exchange constants, Kex, of the order of 0.01 to 90 for the metals (Fe<Al<Zn<Mn approximately/= Ca approximately/= Mg). The results were clearly dependent on the water investigated. Thus detailed information on the conditional kinetic and thermodynamic stability of colloid-bound metal species could be obtained from competitive EDTA and Cu(II) exchange under on-site conditions.
- Subjects :
- Chelating Agents chemistry
Colloids chemistry
Copper chemistry
Edetic Acid chemistry
Fresh Water chemistry
Germany
Humic Substances chemistry
Kinetics
Spectrophotometry, Atomic
Spectrophotometry, Ultraviolet
Ultrafiltration
Colloids analysis
Humic Substances analysis
Metals, Heavy analysis
Water Pollutants, Chemical analysis
Subjects
Details
- Language :
- English
- ISSN :
- 0937-0633
- Volume :
- 371
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Fresenius' journal of analytical chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 11767893
- Full Text :
- https://doi.org/10.1007/s002160101013