Effects of pH, anions and cations on the dissolution kinetics of humic acid particles

BRIGANTE, M.; ZANINI, G.; AVENA, M.

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS

ELSEVIER SCIENCE BV

Año: 2009 vol. 347 p. 180 - 186

0927-7757

The dissolution kinetics of solid humic acid (HA) particles under different conditions is reported and analyzed. The dissolution rate at pH 4 and 5 is very slow and several years may take to achieve equilibration. The rate is strongly increased by increasing pH, and at pH 11 complete dissolution is achieved in 30 min. The dissolution rate is also markedly increased by the presence of monocarboxylic acids and anionic her- bicides such as glyphosate and 2,4-D. On the contrary, the rate is decreased by inorganic divalent cations Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ). The divalent cation paraquat has a dual behavior, decreasing the dissolution rate at pH >7 but increasing it at pH