Effect of Co-pesticide on Adsorption- Desorption Process on Agricultural Soils
Abstract
This work aim is to study the effect of different copesticides as Atrazine and propanil on adsorption processes on agricultural soil samples. The co-pesticides as Atrazine on adsorption behavior of metolachlor [ 2-chloro-N- (2-ethyl-6-methylphenyl)-N-(2-methoxy-1methylethyl) acetamide)] which is nonionic herbicide, and propanil on adsorption behavior of 2,4-D (2,4dichlorophenoxyacetic acid) as anionic herbicide have been preformed, using batch equilibrium experiments on six agricultural soil samples. Linear and Freundlich models were used to describe the competitive sorption between the pair herbicides. Variation in adsorption affinities of the soils to the pesticides was observed. Freundlich coefficient KF values for adsorption process varied between 0.079- 2.282 mlg-1 and 0.058- 0.720 mlg-1 for metolachlor/atrazine and 2, 4-D/propanil respectively. The sorption strength of the herbicides decreased with increasing solution concentration. A nonionic surfactant was tested for its desorption potential and was found to be fairly effective at critical micelles concentration cmc concentration with removal of more than 65 % sorbed pair competitive herbicides. Freundlich coefficient for desorption process KFdes for desorption process varied between 0.209- 0.523 and 0.926- 1.296 mlg-1 for metolachlor/atrazine and 2,4-D/propanil respectively. To investigate the effect of adsorption-desorption in the presence of cmc concentration of the nonionic surfactant for each pesticide alone also performed by using batch equilibrium experiments on six agricultural soil samples. The Freundlich coefficient KF in the presence of the nonionic surfactant for metolachlor and 2,4-D ranged between 0.337-0.437 and 0.001-1.012 mlg-1 for adsorption processes. The Freundlich coefficient KFdes values for desorption process in presence of the nonionic surfactant ranged from 0.209 to 0.689 mlg-1 and 0.238 to 1.442 mlg-1 for metolachlor and 2,4-D respectively.