Uptake of ofloxacin antibiotic from aqueous solution on Co3O4/SBA-15 adsorbent by an adsorption process: Evaluation of isotherm, kinetics, and thermodynamic studies

Abstract

In this study, the Co₃O₄/SBA-15 adsorbent was very effective in removing ofloxacin from the aqueous solution. An impregnation method was used to prepare the adsorbent. TGA, low-angle XRD, wide-angle XRD, DRS-UV-Visible, FT-IR, FESEM with EDX, HRTEM, BET, Raman, contact angle, and XPS analysis were used to characterize the Co₃O₄/SBA-15 (2 wt%, 4 wt%, and 6 wt%) and SBA-15, respectively. At a pH of around 5, the adsorbent dosage of Co₃O₄/SBA-15 (4 wt%) (20 mg), the contact time (70 min), the concentration of the ofloxacin solution (10 mg/L), and the temperature (room temperature) showed outstanding results in removing ofloxacin from aqueous solution. With a high value of the regression coefficient (r² = 0.9999), the Freundlich isotherm model fits the best experimental data, suggesting a multi-layer or cooperative adsorption process. Ofloxacin’s maximum adsorption capacity is 149.25 mg/g, and its kinetics may be described by a pseudo-second-order equation with a rate constant of k₂ = 0.0006 g mg⁻¹ min⁻¹. According to the results of the thermodynamic analysis, the adsorption process occurred spontaneously and was exothermic in nature. In the reusability testing after the fourth cycle, ofloxacin was effectively removed. Therefore, Co₃O₄/SBA-15 (4 wt%) can be a very good adsorbent for the removal of industrial and environmental wastewater samples.