Removal of Chlorpyrifos (Dursban) Pesticide from Aqueous Solutions using Barley Husks

The removal of chlorpyrifos pesticide from aqueous solutions was achieved by adsorption using low cost agricultural residue as adsorbent surface; barley husks. Several variables that affect the adsorption were studied including contact time, adsorbent weight, pH, ionic strength, particle size and temperature. The absorbance of the solution before and after adsorption was measured by using UV-Visible spectrophotometer. The equilibrium data was suitable with Langmuir model of adsorption and the linear regression coefficient R2 = 0.9785 at 37.5°C was used to knowledge the best fitting isotherm model. The general shape of the adsorption isotherm of chlorpyrifos on barley husks consistent with (H3-type) on the Giles classification. Several thermodynamic functions such as (Gibb s free energy, enthalpy and entropy) of the on-going adsorption process have also been estimated. (ΔH°=0.0080/mol) (Δs°=+16.7778j/mol.) and (ΔG°+-5.2015kJ/mol),The results of the pesticide adsorption process on barley husks indicated that the adsorption process is endothermic. The positive ΔG° values of propose the increasing randomized. The negative values indicated the spontaneous process of adsorption.