Adsorption of Glimepiride on activated charcoal and Iraqi kaolin from aqueous solution

Treatment of acute poisoning due to drug overdose in general depends on the prevention of further absorption of the drug and acceleration of elimination , using a specific antidotes. Drugs adsorption of significant importance in physical pharmacy for the preparation of physical antidotes.
Objective The purpose of this study is to investigate the adsorption of glimepiride from aqueous solution on two adsorbents (activated charcoal and Iraqi kaolin) . Method UV – Spectrophotometric technique was used to obtain the quantitive adsorption data at different conditions of pH and temperature. Results The ability of Activated charcoal to adsorb the Glimepiride drug was better than that of kaolin, in all conditions of pH and temperature. The adsorbed quantities of the drug adsorbed at pH=1 and 37°C were 0. 2 mg/g on kaolin and 1.25 mg/g on activated charcoal. The equilibrium time for the adsorption of Glimepiride on activated charcoal and kaolin were 30 min at pH =1 and at 37°C. Adsorption isotherms of glimepiride on both surfaces were consistent with Freundlich adsorption isotherm. The increase in pH cause an increase in the amount of the adsorbate that is adsorbed on the activated charcoal and Iraqi kaolin at (37ºC) and at pH=1 the quantity adsorbed of Glimepiride drug on Iraqi kaolin was 0.2mg/g whereas, at pH=7 the quantity adsorbed of Glimepiride drug on Iraqi kaolin was 0. 95 mg/g , at pH=1 the quantity adsorbed of Glimepiride drug on activated charcoal was 1.25 mg/g whereas, at pH=7 the quantity adsorbed of Glimepiride drug on activated charcoal was 1.95 mg/g. However,the amount of the adsorbate that is adsorbed on the activated charcoal and Iraqi kaolin was decreased at pH 7 andtemperature25–30 ºC.The quantities of glimepiride adsorbed on activated charcoal and kaolin were increased with decreasing temperature. Thermodynamic functions (∆G,∆H and ∆S) were useful in describing the spontaneity of the adsorption process. The thermodynamic parameters associated with the adsorption processes can be calculated from the variation of thermodynamic equilibrium constant (K ) with change in temperature, during the adsorption reaction, at pH=1 and 37 ºC , ∆G =+2178.72 (J/ mol) , ∆H= +811.50(J/ mol) and ∆S= -4.41 (J/ mol k) on activated charcoal whereas, ∆G=+2705.74(J/ mol) , ∆H=+1191.08 (J/ mol) and ∆S=-4.88(J/ mol k) on kaolin. Conclusion The quantity of the drug that is adsorbed on activated charcoal was higher than that adsorbed on kaolin surface therefore , the activated charcoal is a better antidote