Preparation of magnetic biochar with different magnetization sequences for efficient removal of oxytetracycline from aqueous solution

Magnetic modification has been widely applied to solve the difficulty of separating the powdered material from an aqueous medium after use. But knowledge on magnetization sequence to the properties of materials and their performance is still inadequate. To make up for this vacancy, in this study, the magnetic biochars with different magnetization sequences (Pre-MCS and Post-MCS) were prepared and employed in the adsorptive removal of oxytetracycline (OTC) wastewater. Characterizations, adsorption performance and mechanisms, as well as cycle performance of the prepared biochar were investigated. Results indicated that the Post-MCS not only had the highest OTC adsorption capacity (21.8 mg/g) but also exhibited the best separation performance. Mechanism analysis revealed that the chemisorption dominated the adsorption process of OTC on the studied biochars, besides, the electrostatic attraction and physisorption also had a certain contribution to the adsorption mechanism. Furthermore, the optimized biochar (Post-MCS) had acceptable reusability and remained similar to 61.9% of the adsorption capacity of fresh Post-MCS biochar. Therefore, the Pre-MCS can be considered as a promising adsorbent for the removal of OTC due to its high adsorption capacity and good separation performance.

Automated summary

This study prepared magnetic biochars with different magnetization sequences for the adsorptive removal of oxytetracycline wastewater. The Post-MCS biochar showed the highest OTC adsorption capacity and best separation performance, dominated mainly by chemisorption with contributions from electrostatic attraction and physisorption. The optimized biochar displayed acceptable reusability and retained a significant portion of its adsorption capacity after multiple cycles.