Adsorption thermodynamics of phenobarbital sodium on powdered garcinia kola seeds

Effective remedy for common ailments associated with poisoning from environment, foods, drugs and cosmetics has gone beyond total dependence on orthodox medicines. Such ailments could require immediate attention which orthodox medicines (if available) might not provide before irreversible damages are done. The people of South Eastern Nigeria have been using Garcinia kola seeds as an antidote for the management of poison-related ailments. This research investigated the adsorptivity potential of the Garcinia kola seeds for weakly acidic antidepressant- phenobarbital sodium. Adsorption experiments were carried out by standard methods. The adsorption data were fitted to different isotherm models (Freundlich, Langmuir and Dubinin-Radushkevich) and the thermodynamic parameters (∆Hº, ∆Gº and ∆Sº) of adsorption were determined. The parameters were compared to those obtained with a standard adsorbent- activated charcoal. The adsorption parameters (Qmax, RL, E and pHZPC) for Garcinia kola seed were 5.67 mg/g, 0.098, 2.26 KJ/mol and 7.12 respectively. The R2 values of the linear plots were>0.9 while n constant of Freundlich isotherm was >1. The thermodynamic parameters, ∆Gº, ∆Hº, and ∆Sº at 298 K were 1.165 KJ/mol, 18.308 KJ/mol and -0.058 KJ/mol.K respectively. The results show that maximum adsorption of Garina kola occurred below pH of 7.12. The adsorption and thermodynamics parameters showed that the adsorption processes of phenobarbital sodium onto Garcinia kola and charcoal were physisorption, favourable and non spontaneous at temperatures 298-318 K. Garcinia kola is a powerful adsorbent for phenobarbital and could be useful as an antidote for systemic barbiturate overdose.