P. Arfaioli et al., Influence of clay minerals and exchangeable cations on the formation of humic-like substances (melanoidins) from D-glucose and L-tyrosine, CLAY MINER, 34(3), 1999, pp. 487-497
The ability to produce humic-like polymeric compounds, with D-glucose and L
-tyrosine as starting materials, was evaluated in different mineral systems
: (1) Ca-, Al- and Cu(II)-saturated montmorillonite; (2) Ca-, Al- and Cu(II
)-saturated kaolinite; (3) quartz in the presence of two different amounts
of the same cations (according to the cation exchange capacity of the clays
); and (4) untreated quartz (as control). All systems proved to be effectiv
e in the formation of humic-like compounds, particularly quartz, in the pre
sence of cations. The effectiveness in promoting humification reactions was
strictly related to the amounts of added cations. In the reaction conditio
ns considered, the humification appears to be due more to the cations than
to the type of clay minerals. The clayey systems synthesized more complex (
aromatic) substances than the quartz ones.