Adsorption Kinetics, Isotherms, and Desorption of Monocrotophos and Dichlorvos on Various Indian Soils

Pesticide sorption on to the soil has a significant role in deciding the fate and behavior of pesticides in soil and aquatic environment. The present study investigates the adsorption of monocrotophos (MCP) and dichlorvos (DDVP) on the three soils of Malwa region of Punjab, India under different conditions. Batch adsorption experiments were preformed in replicates using 2?g of air-dried soil and varying concentrations of pesticides and 20?mL of 0.01?M CaCl2 as background electrolyte. The results revealed high adsorption of MCP and DDVP in soil B with kf-values 0.1261 and 0.0498 and n-values 2.7345 and 1.831, respectively. The adsorption isotherms obtained were analyzed and the data was subjected to classical Langmuir, Freundlich, and Temkin models. The experimental data best fitted to the logarithm form of Freundlich and Temkin model. Kinetics analyses were performed using pseudo-first order, pseudo-second order, and intraparticle diffusion models. The regression results showed that the experimental data fitted very well with the pseudo-second order kinetic model as correlation coefficient value is very closer to 1 and also followed the intraparticle diffusion model, whereas, diffusion is not only the rate controlling step. The percentages desorption with tap and distilled water is 3264% for MCP and 2548% for DDVP.