Interfacial Engineering of Fe3O4-Decorated Activated Carbon for 5-Fluorouracil Loading and Diffusion-Controlled Release

This study aimed to develop a magnetic activated carbon (MAC) composite by combining activated carbon with magnetite nanoparticles (Fe3O4–NPs) green-synthesized using citrus peel waste, an abundant agro-industrial byproduct, and to evaluate its potential as a drug delivery material using 5-fluorouracil (5-FU) as a model anticancer drug. The synthesized MAC composite was characterized by SEM, EDX, XRD, FTIR, DLS, VSM, ζ potential, and N2 adsorption–desorption analyses. The adsorption of 5-FU onto MAC was optimized using response surface methodology, with pH, temperature, adsorbent concentration, and initial 5-FU concentration as the experimental variables. The MAC composite exhibited a high saturation magnetization of 25.5 emu/g, a ζ potential of 29.1 mV, a specific surface area of 538.2 m2/g, a mesopore diameter of 5.16 nm, and a total pore volume of 0.350 cm3/g. The optimum adsorption conditions were pH 6, 25 °C, 1 g/L MAC, and an initial 5-FU concentration of 80 mg/L. The Langmuir isotherm best described the equilibrium data, with a maximum adsorption capacity of 72.5 mg/g (R2 = 0.991). The adsorption kinetics agreed with both the pseudo-second-order kinetic model, indicating electrostatic and chemical interactions between 5-FU molecules and the MAC surface, and the Weber-Morris model, which shows intraparticle diffusion. In 5-FU release studies conducted in phosphate buffer medium after drug loading onto the MAC, it was observed that 27.8% of the loaded drug was released into the solution immediately, after which a steady drug concentration was maintained. Drug release results demonstrate diffusion-controlled kinetics, with the best fit to the first-order, Korsmeyer-Peppas, and Kopcha models. Overall, the fabricated MAC showed strong potential as a drug delivery carrier. Overall, the results demonstrate that the green-synthesized Fe3O4/activated carbon composite combines magnetic separability with substantial 5-FU adsorption capacity, highlighting its potential as a magnetic carrier for drug delivery applications.