Publisher: Chemical Society of Nigeria

Adsorption Studies of Chlorpyrifos and Endosulfan Pesticides From Aqueous Solution Using Coconut Fibre

J. C. Igwe, N. E. Okoronkwo, E. A. Okoli
KEYWORDS: Adsorption, environment, isotherm, kinetics, pesticides

ABSTRACT:

The adsorption removal of Chlorpyrifos and Endosulfan pesticides from aqueous solution using activated and unactivated coconut fibre was investigated in this study. The coconut fibre was cut into pieces, powdered in a grinder and was activated with 2% nitric acid for 24 hrs. Sorption experiments were performed at concentration range of 10-100 mg/L and contact time of 10-120 mins. The pesticide concentrations were monitored using UV-Visible absorption spectrophotometer. The amount of pesticides adsorbed increased as the contact time and initial concentration was increased. Adsorption equilibrium was reached at about 60 mins contact time. Activation of the adsorbent enhanced the sorption capacity of the adsorbent. The sorption of both pesticides was better for the activated coconut fiber than the unactivated fiber with chlorpyrifos showing higher sorption capacities. Pseudo-second order equation gave a better fit to the kinetic experimental data with rate constant (K2) values ranging from 1.94 x10-3 to 3.66 x 10-3 (g.mg-1.min-1) and the sorption process was found to be particle diffusion controlled. The equilibrium data was modeled using four isotherm equations namely Langmuir, Freundlich, Dubin-Radushkevich and Temkin isotherms. The maximum sorption capacity qmax (mg/g) gave 78.740 and 59.880 for chlorpyrifos and 37.313 and 62.893 for Endosulfan on activated and unactivated coconut fiber respectively. Freundlich isotherm gave a better fit to the equilibrium experimental data with linear correlation coefficient (R2) values ranging from 0.8524 to 0.9950. The sorption process was found to follow chemisorption mechanism as was seen from the mean sorption energy values of 288.68 to 1118.03 KJ/mol. Therefore activated and unactivated coconut fibre was used as an effective adsorbent for Chlorpyrifos and Endosulfan adsorption from aqueous solution


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