Removal of four antibiotics from the aqueous phase using Polyethylene adsorbent: Mechanistic understanding and reusability potential

The release of pollutants of emerging concerns like antibiotics in the environment is posing serious threats to ecosystems. The aim of this study was to remove four antibiotics from the aqueous phase using polymer-based adsorbent in its raw form for antibiotic removal coupled with a mechanistic understanding of the process. Polyethylene, post-cleaning, served as an adsorbent, characterized for surface area, pore size, and structure. Two-week batch experiments at 25°C and pH 7 were conducted at a laboratory scale. Polyethylene demonstrated over 90 % removal efficiencies for all the selected antibiotics. Data fitting into various models revealed Langmuir isotherm and Elovich kinetic model governed the adsorption. Antibiotics, excluding ciprofloxacin, followed second-order kinetics; ciprofloxacin was governed by pseudo-first-order kinetics. Pseudo-second-order kinetics had R² values of 0.9855, 0.9746, and 0.9997 for ofloxacin, sulfamethoxazole, and oxytetracycline, respectively. Elovich had R² values over 0.90 for all the antibiotics, with the order of values as oxytetracycline>ofloxacin>sulfamethoxazole> ciprofloxacin. Langmuir Isotherm indicated the R² value of 0.9777, 0.9902, 0.9551, and 0.9959 for ofloxacin, ciprofloxacin, sulfamethoxazole, and oxytetracycline, respectively. Regeneration results exhibited that all antibiotics had greater than 80 % removal efficiencies in the first two cycles while the regeneration capacity of ciprofloxacin and sulfamethoxazole reduced to 75 % and 50 %, respectively at the fourth cycle. The effective removal of antibiotics indicates its usefulness and potential for widespread application compared to the costly and chemical-intensive adsorbents. These findings highlight the potential of selected adsorbents for real-time applications as the lab-scale studies mimicked the real environment by using a mixture of antibiotics.