Influence of humic acid on sorption of Co(II), Sr(II), and Se(IV) on goethite

Abstract

-This work examined the influence of a leonardite humic acid on the sorption of Co(II), Sr(II), and Se(IV) onto goethite as a function of pH. The sorption of humic acid and ions alone was first studied. The humic acid sorbs appreciably to the goethite surface according to a reversible process, with a maximum sorption of 19 mg of total organic carbon per g of goethite reached at lower pH values (≈ 5). Cobalt and selenium are significantly sorbed on goethite while strontium is only weakly sorbed. In the presence of humic acid, the cobalt sorption is enhanced in acidic media due to the humic acid sorption on goethite, which modified the surface properties by making it more negative. However, it decreases in alkaline media due to the complexation of Co(II) by soluble humic acid. The sorption of Sr(II) is significantly increased in the presence of humic acid even in alkaline media. The sorption of selenite ions (SeO 3 2-) decreases in the presence of humic acid because a competition with humate ions occurs at the surface sites of the goethite. The results presented here constitute a good set of data for modelling the effect of humic acid on the sorption of ions on goethite.sorption / humic acid / goethite / cobalt / strontium / selenium Résumé -Influence de l'acide humique sur la sorption de Co(II), Sr(II) et Se(IV) sur une goethite. Dans ce travail est examinée l'influence de l'acide humique leonardite sur la sorption de Co(II), Sr(II) et Se(IV) sur une goethite en fonction du pH. La sorption de l'acide humique et de chaque ion a été étudiée séparément en premier lieu. L'acide humique est sorbé de façon non négligeable sur la goethite, selon un mécanisme réversible, avec un maximum sorbé de 19 mg de carbone organique total par g de goethite observé aux valeurs de pH les plus faibles (pH ≈ 5). Le cobalt et le sélénium présentent une bonne aptitude à se sorber sur la goethite tandis que le strontium n'est que faiblement retenu. En présence d'acide humique, la sorption de Co(II) est favorisée en milieu acide car la sorption de l'acide humique sur la goethite rend la surface du minéral plus négative. En milieu basique, au contraire, la sorption est diminuée en raison de la complexation des ions cobalt par l'acide humique soluble. La sorption de Sr(II) augmente en présence d'acide humique, Agronomie 20 (2000) [525][526][527][528][529][530][531][532][533][534][535] 525

Adsorption of cadmium on different granulometric soil fractions: Influence of organic matter and temperature

“…OM favors indeed adsorption and many works are in accordance with this conclusion. So, for Masset et al (2000), humic substances enhance the sorption of positive ions by making the surface more negative.…”

Transport of Kaolinite Colloids through Quartz Sand: Influence of Humic Acid, Ca2+, and Trace Metals

“…The adsorption of organic matter on the solid surfaces (oxides or clay surfaces) is due to electrostatic interactions and specific adsorption via ligand exchange (23,24). Several authors have already observed this particular effect of humic or fulvic acid on the charge and the stability of mineral colloids (25)(26)(27). For concentration values of humic acid lower than 0.2 mg/L, the suspension is slightly destabilized and the corresponding absolute value of zeta potential slightly diminishes.…”

Adsorption of a soil humic acid at the surface of goethite and its competitive interaction with phosphate

“…Many of the studies investigating the role of organic matter in adsorption processes on mineral surfaces (Du et al, 1999;Lenhart and Honeyman, 1999;Masset et al, 2000) have focused on metal cations, particularly those that occur as contaminants in natural environments. These types of systems are complex, because as well as the interactions of the cations and organic matter with the surface, there also exist interactions between the cations and either the dissolved organic matter or the organic matter that is adsorbed on the mineral surface.…”