Removal of an insecticide (methomyl) from aqueous solutions using natural clay

Adsorption of an insecticide (methomyl) onto natural clay have been investigated as a possible alternative method for its removal from aqueous solutions. The study was aimed to use low cost material as a step towards cleaner environment. The influence of system variables, such as particle size (d_p) and temperature on the adsorption capacity have been studied. It was found that natural clay reached equilibrium with methomyl solution in time less than 3 h. The experimental data were fitted to equilibrium isotherm models, Langmuir, Freundlich and Redlich–Peterson. Adimensionless separation factor, widehat{R} , was used to judge the favorable adsorption. The results indicated that percentage of insecticide removal ranged from 27.6 to 32.9 for initial concentration varied from 43.71 to 19.99 mg/l. The effect of temperature showed the exothermic nature of the process. The enthalpy change (ΔH) of adsorption has been evaluated and it has a value of, 17.54 kJ/mol. The Langmuir model fit the experimental data significantly better than Freundlich and Redlich–Peterson models. A chart based on material balance using single batch adsorber was constructed for different percentage of methomyl removal using the Langmuir isotherm where the mass of natural clay required to treat a specified volume of solution is calculated.