The effect of two activation routes, ball milling and ultrasonic, on the adsorption performance of fly ash towards oxytetracycline

Abstract Background This research sheds light on one of the contaminants of the emerging concern, oxytetracycline (OTC), a commonly used antibiotic used to treat infections and diseases caused by bacteria. Numerous studies have shown that despite the use of various removal mechanisms, trace amounts of this antibiotic remain in water. The accumulation of these trace amounts can negatively impact water quality and both microscopic and macroscopic organisms. Methods This study utilizes adsorption as a successful and cost-effective method for removing OTC compounds using industrial waste, fly ash (FA). Ball milling and sonication have been applied to improve the adsorption capacity towards OTC. The developed materials were characterized using Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption isotherms, and X-ray diffraction (XRD) techniques. The performance of OTC adsorption onto FA and its modified forms has been optimized using different parameters (solution pH, adsorbent dose, contact time, and OTC initial concentration). Results It is noticed that under the optimum conditions (pH 8, adsorbent mass 0.001 g and contact time 30 min), the ball milling has improved the adsorption capacity of OTC to 6040.6 mg/g compared to pristine FA (5615 mg/g). This is because surface of MFA1 has become more active as is evident from the FTIR and Nitrogen adsorption/desorption isotherms studies. On the other hand, the sonication approach is not effective due to the washing of the main functional groups during the sonication process. The supercolossial adsorption capacity of both FA and MFA1 towards OTC is attributed to the involvement of hydrogen bonding, OTC hydrophobicity, electrostatic attraction, complexation, and pore filling in the adsorption process. Moreover, the nanoconfinement plays a significant role in enhancing the multi-layer adsorption of OTC onto the modified FA. Conclusions Therefore, this study is considered an environmentally friendly model where FA has been recycled to remove OTC, achieving sustainable water treatment and the circular economy.