Extraction and exchange behavior of metal species in therapeutically applied peat characterised by competitive extractants

Luciane P. C. Romão, Ângelo Augusto M J. Silva, Fabiana A. Lobo, Danielle Goveia, Leonardo F. Fraceto, Julio C. Rocha, Peter Burba and André H. Rosa

After Wise Use – The Future of Peatlands, Proceedings of the 13th International Peat Congress: Peat Balneology

balneological-peat, dissolved-organic-matter, extractants, extraction-kinetics, metal

Romão et al. 2008: Extraction and exchange behavior of metal species


The binding and availability of metals (Al, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb) in therapeutically applied peat was characterised by means of a versatile extraction approach. Aqueous extracts of peat were obtained by a stan- dardized batch equilibrium procedure using high-purity water (pH 4.5 and 5.0), 0.01 mol/L ethylenediaminete- traacetic acid and 0.01 mol/L diethylenetriaminepenta-acetic acid solution as metal extractants. Metal determinations were performed by atomic spectrometry methods and dissolved organic matter (DOM) was char- acterised by UV/VIS. Of the extractants studied Ca, Mg and Mn were the most available metals, in contrast to peat-bound Fe and Al. A pH increase favored the extraction of metals and DOM from peat revealing complex ex- traction kinetics. Moreover, a competitive exchange between peat-bound metal species and added Cu(II) ions showed that >100 mg of Cu(II) per 50 g wet peat were necessary to exchange the maximum of bound metals.