Adsorption of Terbutryne on Metal Humates*

Adsorption of terbutryne (2-methyl thio, 4-ethyl amino, 6-tertiary butyl amino-S-triazine) on Ca-, Zn-, H- and Cu-humates of humic acids from five soil samples of Tarai area, Nainital, Uttar Pradesh is reported. Adsorption was significantly influenced by the nature of cation present and followed the order Ca->H->Cu-> and Zn- humate. The partial molar free energy of adsorption also followed the same order. Desorption was only partially reversible and was accompanied by hydrolysis of terbutryne. Adsorption and desorption studies indicate that the mode of binding of the herdicide may be different depending on the nature of cation.