The selection of suitable mass transfer models that fit the adsorption of a mixture of antibiotics in aqueous solution onto activated carbon derived from Delonix Regia Pods (DRPs) was examined in this study. The ripe DRPs were cleaned, activated with KOH and then carbonised at 350 °C. The surface chemistry of the raw and the modified DRPs were characterised using Fourier Transform Infrared (FTIR), before being subjected to batch adsorption of a mixture of Amoxicillin (AMO), Tetracycline (TETRA) and Ampicillin (AMP)  under the effect of time (0-240 mins), and concentration (20-100 mg/l). The adsorption diffusion mechanisms of the process were analyzed. The spectra of the raw and modified DRP indicate the existence of hydroxyl groups alkanes, unconjugated ketone, carbonyl, and ester groups.  McKay has the highest  (0.9445) for the mass transfer diffusion model. This indicates that the adsorption rate of the selected antibiotics in the wastewater is regulated and monitored by the internal mass transport processes in accordance with a pore diffusion mechanism.