Cosorption of Glyphosate and Copper (Ii) on Goethite

Herbicides and some heavy metals are frequently added together to agricultural crops. However, few studies on the phenomena that may take place in such systems have been carried out. We studied the adsorption of the herbicide glyphosate (GPS) and copper (Cu) on a synthetic goethite (Gt), in order to determine the relative contribution and mutual effect of both components on the availability of GPS and Cu in soils. The adsorption of GPS reached a maximum at 99 μmol g−1. In the presence of Cu, the adsorption of GPS on goethite increased about 9%. The reason for this behavior is the formation of Cu-GPS complexes and their higher tendency to be adsorbed compared with free GPS. Cu adsorption on goethite also increased in the presence of GPS. This higher Cu adsorption can be due to its adsorption through the formation of bonds with GPS previously adsorbed, and the adsorption of the Cu-GPS complexes formed in solution.