Mesoporous (2 - 50 nm pore diameter) and non-porous SiO₂ and Al₂O₃ adsorbents were reacted with the fluoroquinolone carboxylic acid ofloxacin over a range of pH values (2 - 10) and initial concentrations (0.03 - 8 mM) to investigate the effects of adsorbent type and intraparticle mesopores on adsorption/desorption. Maximum ofloxacin adsorption to SiO₂ surfaces occurs slightly below the pKa₂ (pH 8.28) of the antibiotic and sorption diminishes rapidly at pH > pKa₂. For Al₂O₃, maximum sorption is observed at pH values slightly higher than the adsorbent's point of zero net charge (p.z.n.c.) and less than midway between the pKa values of ofloxacin. The effects of pH on adsorption and ATR-FTIR spectra suggest that the zwitterionic compound adsorbs to SiO₂ solids through the protonated N₄ in the piperazinyl group and, possibly, a cation bridge; whereas the antibiotic sorbs to Al₂O₃ solids through the ketone and carboxylate functional groups via a ligand exchange mechanism. Sorption edge and isotherm experiments show that ofloxacin exhibits a higher affinity for mesoporous SiO₂ and non-porous Al₂O₃, relative to their counterparts. It is hypothesized that decreased ofloxacin sorption to mesoporous Al₂O₃ occurs due to electrostatic repulsion within pore confines. In contrast, it appears that the environment within SiO₂ mesopores promotes sorption by inducing formation of ofloxacin-Ca complexes, thus increasing electrostatic attraction to SiO₂ surfaces.