Kryptofix 222‐Based Modified Lignin as a Novel Adsorbent to Eliminate Pb(<scp>II</scp>) Ions From Water‐Based Media

ABSTRACT A novel adsorbent was developed by modifying lignin with 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8] hexacosane (Kryptofix 222, abbreviated as LK‐222). The successful synthesis of LK‐222 was confirmed through characterization techniques, including FTIR, FE‐SEM, and EDX, which revealed appropriate functional groups, morphology, and structural features for effective adsorption. The material was then evaluated for its ability to remove lead (Pb(II)) ions from aqueous solutions. Key parameters influencing adsorption efficiencies—such as solution pH, temperature, adsorbent dosage, contact time, and initial metal ion concentration—were systematically studied. Kinetic analysis indicated that the adsorption followed a pseudo‐second‐order model, while equilibrium data fitted well with the Langmuir isotherm model. The maximum adsorption capacity of Pb(II) onto LK‐222, as predicted by the Langmuir model, was 454.55 mg/g. Thermodynamic studies revealed that the adsorption process was spontaneous and exothermic in the temperature range of 25°C–55°C. Additionally, the adsorbent was effectively regenerated using 0.1 N HCl and reused in successive adsorption cycles with minimal performance loss.