The removal of humic acids (HA) from natural waters is a very old yet modern problem : humic substances are at the origin of the coloration of water but also, they give off nocive trihalomethanes during chlorination.
Humic acids are also known to be a metal micropollutant vector and their behavior is not well defined when there is coadsorption.
The purpose of this work was to study the effect of an anionic surfactant, sodium dodecyl sulphate (SDS), on the adsorption on powdered activated carbon (PAC) of humic substances from a commercial source, as a function of the pH (7.0 or 10.5), as well as the effect of the order of introduction of the coadsorbate.
Results (fig. 1 to 3 and fig. 6) showed an inhibition of the adsorption for both HA and SDS in the presence of the coadsorbate. The inhibition was more significant for a pH = 7.0.
Results of the influence of the order of introduction of the coadsorbate on the adsorption (fig. 4 and 5) showed a more significant inhibition of HA adsorption when HA were introduced into the equilibrium suspension SDS-PAC (the contact lime was 24 hours).
Table 1 gives parameter values of the Langmuir equation for the adsorption on PAC of HA atone or with SDS.
All these results suggest that a competition on the same sites occurs during the adsorption on PAC of HA and SDS.
Sodium dodécylsulphate (SDS), adsorption, humic acids, powdered activated carbon.
Mazet, M., Laboratoire de génie chimique traitement des eaux, Faculté des Sciences, 123, Avenue Albert Thomas, 87060 Limoges Cedex - France