Abstract

REY-MAFULL, Carlos A; CESAR-LLOPIZ, Julio; HOTZA, Dachamir  and  GARCIA-GALLARDO, Raquel. Thermodynamic process of theophylline adsorption in vitro on to activated carbon in simulated gastric fluid. Rev Cub Quim [online]. 2016, vol.28, n.2, pp.625-644. ISSN 2224-5421.

The in vitro adsorption of theophylline onto seven selected materials (NB, NE, BDH, Ch3J, Merck, Panreac, ML) was studied in simulated gastric fluid at pH 1.2 and 4 h by using shaker water bath within a temperature range 300 to 317 K in batch experiments. The experimental adsorption was fitted by eight isotherms models: Langmuir Type I and II, DR, Halsey, Freundlich, Harkins-Jura, Temkin and BET. Materials were characterized by pH_zpc, and N₂77 K. The best linear (R²=098) and non linear (R²=0.95, RAMSE=43) fittings of isotherms models were obtained with Langnuir TI which assumes monolayer adsorption and specific interactions. The theophylline adsorption was controlled by chemisorptions and exothermically process (ΔH = -36.81-88.70 kJ/mol) with maximal capacity, q_m (316-587 mg/g). The ΔG<0 indicate the spontaneous character and more favourable at lower temperature. ΔS<0 suggests a decrease in the order of the adsorbed system with losses of freedom willingly.

Keywords : activated carbon; theophylline; thermodynamic parameters; adsorption isotherms.

        · abstract in Spanish     · text in English     · English ( pdf )