Adsorción de fenobarbital en carbones activados comerciales. Equilibrio cinético e isotermo de adsorción

Abstract

The in vitro adsorption of phenobarbital by different adsorbents in simulated gastric fluid (SGF) at pH 1.2 and 310 K, was determined on three types of commercial samples of activated carbon (AC): Norit USP XX, Ch3J (both used as antidotes) and M1. The equilibrium isotherms for the adsorption of phenobarbital were analyzed by four models: Langmuir (Type I and II), D-R, Freundlich and Temkin isotherms equations and the kinetic curves obtained were fitted using seven equations (Elovich, pseudo-first order, pseudo-second order, zero order, first order, second order and the intraparticle model) to determine kinetic parameters of adsorption. The pseudo-second order and the Langmuir model respectively showed the best fittings. The pseudo-second order suggered that the overall rate of the adsorption was controlled by chemisorption which involved valency forces through sharing or exchange of electrons between the sorbent and adsorbate The correlation coefficients (R2) obtained from Langmuir model for the linear regression in all cases were higher than 0.99. Kinetic studies showed that the adsorption of phenobarbital on the three adsorbents obtained the best results with the pseudo-second order model TI (R2 > 0.98) and TII (R2 ≥ 0.92) respectively. The variation of the free Gibbs energy (ΔG < 0), in all cases, explained the spontaneous character of the adsorption process. Despite the different behaviors all materials tested have potential for treating phenobarbital intoxications.