Adsorption Equilibrium Studies Of Lignocellulosic Sawdust For Separation Of Aqueous Ethanol Mixture
Keywords:
Ethanol, zeolite, sawdust, adsorption capacity, calcium chloride, isothermAbstract
This study investigated the effects of initial water concentration on the adsorption capacity of lignocellulosic sawdust in Southwestern Nigeria. The performance of these adsorbents in aqueous ethanol purification was also evaluated with a view to finding cheap and readily available alternatives to the costly commercial zeolites. Liquid phase batch equilibrium experiments were conducted on hardwood (Khaya senegalensis) and softwood (Annona senegalensis) sawdust pretreated with 25% (w/w) calcium chloride (CaCl2). Modified Khaya senegalensis (M25C) was observed to be more suitable for dehydration than 3A zeolite at 15% (w/w) initial water concentration due to equilibrium mechanism. The performance of the sawdust measured by the Freundlich (1/Nf) and Sips (1/Ns) isotherms was favourable in ranges 0.4531 - 0.8884 and 0.5622 – 0.9399, respectively. The system became more heterogeneous as the values approached zero and the performance improved upon chemical modification with CaCl2. The surface areas as determined by the BET isotherm for modified Khaya senegalensis and Annona senegalensis were 736 and 286 m2/g, respectively. These results indicated that Khaya senegalensis sawdust adsorbed water better than Annona senegalensis on chemical modification. It was concluded that Sips isotherm with the highest coefficient of determination (R2 = 0.9726) was the most suitable isotherm for designing the adsorption process.
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