Tetracycline removal from an aqueous solution using bimetallic-impregnated activated carbon synthesized via one-step dry-pyrolysis of hawthorn kernels

A novel bimetallic Fe-Mn-impregnated activated carbon (Fe: Mn: AC) composite was synthesized via the one-step dry pyrolysis method and is applied to tetracycline (TC) removal from aqueous solution. Characterization results revealed a mesoporous structure with various functional groups on the Fe: Mn: AC adsorbent. The impacts of solution pH, adsorption time (kinetics), and initial TC concentration on equilibrium in batch adsorption were studied. The highest TC removal efficiency using Fe: Mn: AC occurred at a pH of 6. The kinetic analysis using various models revealed that the data best fit the Elovich model, highlighting the significance of external diffusion (film diffusion) during the adsorption process. The equilibrium data aligned well with the Langmuir isotherm, which predicted a maximum adsorption capacity of 463.040 mg/g for TC adsorption at 25 °C. The primary mechanisms of adsorption included Hydrogen bonding, surface complexation with metal functional groups (M-π), Lewis acid-base interactions, π-π interactions, and pore filling. Continuous mode experiments in five cycles confirm the high adsorption capacity of the Fe: Mn: AC adsorbent for effectively removing pharmaceutical contaminants from aqueous media (27.5% reduction in adsorption ability).