Research
Effect of Cadmium ion on Adsorption-Desorption Behavior of Simazine on Agricultural Soils
The effect of cadmium (Cd) on adsorptiondesorption behavior of Simazine [2-chloro-4, 6 bis (ethylamine)-1,3,5-triazine] which is anionic herbicide were investigated at three different temperature 10, 25 and 40 ±1˚C on six agricultural soil samples which has different texture. The first order rate law was most fitted with the best correlation factor, the Linear, Freundlich and Langmuir models also were applied to describe the adsorption-desorption affinities to the soil samples. Values of adsorption rate constant ka were in the range 0.836 - 1.818 h-1 while desorption rate constant kdes were in the range 0.779 - 1.376 h-1. The activation energy Ea * for adsorption processes followed the range 11.041- 17.684 KJmol-1. Values of equilibrium constant lnKo were in the range 0.048 - 0.278. The standard free energy change ΔGo values were in the range -0.126 to -0.655 KJmol-1. Values of the standard enthalpy change ΔHo followed the range -2.702 to - 4.850 KJmol-1. The value of standard entropy change ΔSo followed the range-7.557 to-14.965 Jmol-1k-1. The negative values revealed that the adsorption-desorption processes spontaneously, exothermic and physical in nature to some extent and chemical in others. The distribution coefficient Kd values for adsorption-desorption process varied between 2.369 - 2.611 mlg-1, 5.556- 22.85 mlg-1 respectively. Freundlich coefficient KF ranged between 0.180-0.506 mlg-1 for adsorption processes. The value Freundlich coefficient for desorption process KFdes ranged from 0.107 to0.498 mlg-1. Langmuir coefficient KL for adsorption process varied between 0.027 - 0.064 mlg-1. Langmuir coefficient KLdes values for desorption process from 0.014 to 0.067 mlg-1. All desorption isotherms exhibited hysteresis.
Kinetic and Thermodynamic study for Adsorption a Desorption of Diazinon with copper in the presence of Surfactant
In the present work change in the adsorption-desorption processes of Diazinon[O,Odiethylo-( 2-isopropyl-6-methyl4pyrimidinyl) phosphorothioate] which is nonionicorganophosphorous pesticide, preformed by using batch equilibrium experiments on six agricultural soil samples. The kinetics study for adsorption processes investigated that first order rate law and power function equation model provided the best correlation with experiment results. The isothermal models Linear, Freundlich, and Langmuir were applied to describe the adsorption-desorption affinities to the soils. Thermodynamic parameters (ΔG, ΔH and ΔS) were also calculated according to the values of binding Langmuir constant KL at 10, 25, 40 ±1ºC. Linear coefficient Kd values for adsorption process of diazinon varied between 3.261 - 6.413 mlg- 1. Freundlich coefficient KF values for adsorption process varied between 1.194 - 1.506 mlg-1. Langmuir coefficient KL for adsorption process varied between 0.017 - 0.020 mlg-1. The negative values for each of ΔG, ΔH and ΔS constants confirmed that diazinon adsorption processes more at lower temperature and done via enthalpy effect.
