Sustainable adsorbent design: ZnSA@PEG from agricultural waste for environmental remediation

Antibiotic drugs have the potential to induce persistent impairment to the ecosystem within soil and natural water bodies. To address this issue, this study utilized ofloxacin (OFL) as the research subject; ZnSA@PEG was synthesized employing agricultural waste-derived peanut shell biochar as the primary material, with sodium alginate (SA) serving as the substrate. The biochar was activated using ZnCl₂, followed by the incorporation of polyethylene glycol (PEG) into the SA, and subsequently cross-linked with CaCl₂. The effect of ZnSA@PEG on OFL removal efficiency was investigated under different influencing conditions. The results showed that ZnSA@PEG had the best removal effect on OFL at pH = 8, with an adsorption amount of 68.57 mg/g (with OFL 50 mg/L, and the ZnSA@PEG was 100 mg), which was 13 times higher than that before unmodified. The adsorption kinetics followed the pseudo-first-order model. The isothermal adsorption data fitted the Langmuir model, with a maximum adsorption capacity of 103.803 mg/g. The adsorption mechanism was primarily attributed to the π-π interactions, hydrogen bonding, and complexation. ZnSA@PEG demonstrated exceptional stability in reusability, which keep the adsorption capacity remained at 39.78 mg/g even after five cycles. In summary, ZnSA@PEG is a highly efficient and reusable adsorbent material with promising applications in antibiotic wastewater.