Non-linear kinetic, equilibrium, and thermodynamic studies of 5-fluorouracil adsorption onto chitosan–functionalized graphene oxide

Abstract

In the present study, the performance of loading and release of 5-Fluorouracil (5-FU, a potent chemotherapeutic agent) was investigated by using chitosan–functionalized graphene oxide (CS/GO) composite in aqueous media. CS/GO were loaded with 5-FU through the adsorption method. π–π electron donor-acceptor interactions and hydrogen bonds may be possible mechanisms of 5-FU adsorption on to CS/GO. Batch adsorption experiments were carried out to evaluate the influences of main experiment parameters such as initial solution pH, contact time, temperature, and initial 5-FU concentration on the adsorption capacity of CS/GO. The results showed that kinetic data well followed a pseudo-first-order model and equilibrium data were closely fitted by Langmuir model. The activation energy of 2.75 kJ mol–1 indicated that the 5-FU adsorption physically controlled process. The maximum adsorption capacity of CS/GO for 5-FU, calculated from Langmuir model, was 44.29 mg g–1 at pH 5.0 and 293 K, and the adsorption capacity decreased with the increase in temperature. Thermodynamic studies revealed an exothermic and spontaneous adsorption process in nature. Almost, 58% of 5-FU was released from CS/GO in the simulated blood fluid (at pH 7.4 and the temperature of 37 °C) in the first 30 min and the next 30% of 5-FU was smoothly delivered over a period of 4 h. Therefore, the prepared CS/GO may be a satisfactory adsorbent for loading of 5-FU in potential delivery systems.