Selective effect of exchangeable cations on the pyrolysis patterns of natural and laboratory-prepared metal adducts of fulvic acids

Natural and laboratory-prepared metal adducts of soil fulvic acids (FA) were subjected to flash pyrolysis to assess the effect of cations in the products released. Striking differences were found as regards the type, concentration and speciation form of the metal (Fe, Al, Mn and Cr). Long-chain alkylbenzenes were characteristically released from the natural and laboratory- prepared metal adducts of Fe and Al. The cation-induced effects were not observed in physical mixtures of FA with the corresponding oxides or salts. The results suggest processes as (a) formation of non-volatile organometallic adducts, (b) metal-catalysed alkylation of aromatic fragments, and/ or (c) cation-dependent changes in the thermal stability of the three-dimensional, paracrystalline structures of the FA.Peer Reviewe