Adsorption of Metsulfuron and Bensulfuron on a Cationic Surfactant-Modified Paddy Soil1

Adsorption isotherms of metsulfuron and bensulfuron on a hexadecy ltrimethylammonium (HDTMA) bromide-modified paddy soil under different ionic strengths, with divalent cation Cu2+, or having different pH were studied to describe their adsorptive behavior, and to try to explain the adsorption process of a sulfonylurea compound with a carbamoylsulfamoyl group in the modified soil environment. All the adsorption isotherms fitted the Freundlich equation well, and the HDTMA treatment of paddy soil dramatically enhanced adsorption capacity of metsulfuron or bensulfuron. Also, an increase of ionic strength and the addition of divalent heavy metal cation Cu2+ on the HDTMA-modified paddy soil increased the adsorption of metsulfuron or bensulfuron. Additionally, for metsulfuron and bensulfuron in the aqueous phase, adsorption capacity of the HDTMA-modified paddy soil gradually increased with decreasing pH.