Batch and continuous fixed-bed adsorption of antibiotics from aqueous solution using stearic acid-activated carbon composite

The use of water containing antibiotics can result in adverse effects on humans and other living organisms. Therefore, it is essential to remove them from water. Adsorption is a promising method for their efficient removal since it is inexpensive and effective. In this study, the efficiency of an adsorbent prepared from kaolinite clay, coconut husk and stearic acid (SMC) for the removal of ciprofloxacin and tetracycline from aqueous solution was investigated. In batch adsorption, 99% of both ciprofloxacin and tetracycline were removed in 120 min at a pH of 6; SMC dose of 0.05 g; and initial concentration of 40 mg/L. Experimental data best fit the Brouers–Sotolongo isotherm with maximum adsorption capacities of 88.1 mg/g and 93.4 mg/g for ciprofloxacin and tetracycline, respectively. Kinetic data fitted best the fractal kinetics ( R 2 = 0.995) and the intraparticle diffusion ( R 2 = 0.970) models for ciprofloxacin and tetracycline adsorption, respectively. The results demonstrate that adsorption occurred via more than one interaction on active sites with different energies, while intraparticle diffusion played a significant role in the adsorption. The regeneration studies performed on SMC revealed that at the beginning of the third cycle of adsorption–desorption, the adsorbent maintained 97% efficiency. This shows that SMC is easily regenerated and can be reused multiple times while maintaining a high adsorption capacity. SMC which is prepared from readily available, low-cost materials is a highly sustainable alternative adsorbent for the effective removal of ciprofloxacin and tetracycline from wastewater.