Estudio de la cinética y el equilibrio del proceso de adsorción sobre bagazo de caña de azúcar y zuro de maíz de los fármacos sulfametoxazol, diclofenaco y ciprofloxacina

Abstract

In order to study the adsorption process, both in discontinuous and continuous processes, of the drugs sulfamethoxazole, ciprofloxacin and diclofenac on sugarcane bagasse and corn cob, several kinetic and equilibrium models were applied to the previously obtained experimental data by the Center for Environmental Studies (CEA) of the University of Cuenca. Within the discontinuous process study, kinetics and equilibrium were studied. In the study of kinetics, Pseudo-first order, Pseudo-second order, Weber & Morris and Elovich models were applied. The Pseudo-Second order model was satisfactorily adjusted to the experimental data indicating that the adsorption process of the three drugs on the two biomasses presents physical-chemical interactions.On the other hand, the Weber & Morris and Elovich models established that adsorption of drugs occurs by external diffusion with heterogeneity of the active sites on the surface of the adsorbents. In the equilibrium study, the isotherms obtained show a subgroup 3 type L behavior according to Giles' classification. Langmuir, Freundlich, Dubinin-Radushkevich, Brunauer Emmett & Teller (BET), Temkin and Sips models were applied for the equilibrium study. The BET model presents the best linear fit describing the formation of multilayers. The parameters obtained for the Dubinin-Radushkevich, Temkin and Sips models indicate physical adsorption processes with an exothermic character that are favorable for the two biomasses. The calculated thermodynamic parameters show spontaneous adsorption with exothermic character and with low randomness at the adsorbent / dissolution interface. To describe the behavior in a fixed-bed column of the adsorption process of the three drugs on sugarcane bagasse, the kinetic parameters were calculated, where when working at a flow rate of 2 cm3 / min, a higher performance of the column is obtained due to at the lowest linear speed and longest contact time. The kinetic models that were applied are Bohart-Adams, Yoon-Nelson, Thomas, Dose-Response and BDST. The Dose-Response model presents the best fit for the representation of the breakdown curve. The calculated mass transfer coefficients are low indicating low drug transfer at the solid-liquid interface.