ADSORPTION OF AMITRAZ BY A RIVER SEDIMENT - APPARENT THERMODYNAMIC PROPERTIES

The adsorption/desorption of amitraz by suspended river sediment parti cles in an aqueous medium was studied in terms of a model wh;ch assume s the adsorption/desorption equilibrium nX + S <(partial derivative)ov er bar>i SXn(w) <(partial derivative)over bar>i SXn(sed), where X and S represent the pesticide molecule and suspended particle respectively , SXn(w) is the pesticide-particle complex tin suspension), and n is t he number of pesticide molecules associated with a single adsorption s ite. According to this model the apparent adsorption/desorption equili brium constant, K', is given by In [X](ads) = In (nK') + nln ([X](e) [SXn](w)) where [X](ads) is the concentration of X in the adsorbed st ate in suspension found in the sediment after settling, [X](e) is the concentration of X in solution at equilibrium, and [SXn](w) is the con centration of the pesticide-adsorption site complex in suspension at e quilibrium. Values of 111 '' 19, 0.26 '' 0.03 and -11.6 '' 0.5 KJmole( -1) were obtained for K', n, and DG' (the apparent adsorption/desorpti on flee energy) for the adsorption of amitraz by the river sediment us ed.