English abstract
Abstract
Dehydrated and activated carbons were prepared from date palm leaflets. Dehydrated carbon (DC) was prepared via sulfuric acid treatment at 150 °C in air for 24 hours. DC was transformed to activated carbon (AC) at 500 °C under nitrogen atmosphere for an hour. Dehydrated carbon is loaded with carbon-oxygen functional groups and exhibits low surface area (48 m'g'), whereas, activated carbon possesses high surface area (405 m' g*), with less carbon-oxygen functional groups on its surface. X-Ray Diffraction showed that both carbon are amorphous, however, activated carbon possesses little graphitization. The developed carbons were tested for the removal of two antihistamine drugs: fexofenadine (FEX) and diphenhydramine (DPH) from aqueous solutions in terms of kinetics and equilibrium. The adsorption of FEX and DPH was tested at different initial pH, time, drug concentration, temperature salt in addition to column studies. Optimum adsorption of FEX was pH 4.0, however, for DPH, it was pH 8.0. Kinetic and equilibrium studies were carried out at their optimal initial pH values. ~ 48 hours were used as equilibrium time for the removal of both drugs on the carbons under investigation. Adsorption data were found to follow the pseudo second order kinetic model. Adsorption rate was found to increase with temperature rise with activation energy in the range of 12-17 kJ mol'; indicating the physical nature of drug adsorption. Activated carbon showed faster kinetics than dehydrated carbon. The equilibrium studies show very good fitting with Langmuir isotherm more than Freundlich. Equilibrium adsorption was found to increase with temperature rise in the range 25-45 °C. Dehydrated carbon, even with little surface area, still shows comparable drug adsorption capacities to that of activated carbon. Thermodynamic parameters showed that removals of FEX and DPH are spontaneous and endothermic in nature with physical adsorption dominating their removal from aqueous solution. The presence of salt increases the adsorption efficiency due to the salting out effect. Dynamic adsorption studies shows good breakthrough curves for the removal of both drugs. From this study, dehydrated carbon proved to be as efficient as activated carbon in removing pharmaceutical drugs from aqueous solution, however, with better desorption properties.
