Geoscience Reference
In-Depth Information
Fig. 8.31 Isotherms for the adsorption of paraquat a by H
+
-humic acid, b by Ca
2+
-humate in
water and 0.335 M CaCl
2
solution, and c by Na
+
-humate solution in water and dilute NaCl
solutions (Burns et al.
1973
)
increasingly anionic as pK
a
is reached and exceeded. Table
8.9
shows the
adsorption from aqueous solution of a series of compounds from the s-triazine
family onto Na
+
-smectites, as affected by the solution pH. Hayes and Mingelgrin
(
1991
) emphasize that, under low pH conditions, prometone adsorption can take
place through association of triazine with carboxyl groups in the humic substances,
followed by electrostatic binding to the conjugate carboxylate base of the proton
donor.
