Highly Stable Lignin-Based Magnetic Composites for Efficient Removal of Pb(II) from Wastewater

In this study, a novel lignin-based magnetic composite with a shell-and-core structure and high saturated magnetic strength has been developed for the efficient removal of Pb(II) from wastewater. The adsorbent was fabricated through the introduction of silica–amino groups and a cross-linking complex with lignin, utilizing Fe-Fe2O3 as a magnetic source. The paramagnetic characteristics enabled its rapid separation from the aqueous solution within merely 15 s. Batch adsorption experiments demonstrated that the adsorbents could reach equilibrium for Pb(II) adsorption within 30 min. When the concentration of Pb(II) is in the low range of 0 to 200 mg/L, the removal rate of Pb(II) approaches 100%, and the theoretical maximum adsorption capacity is as high as 384.2 mg/g. The mechanism analysis indicated that the adsorption process was primarily characterized as monolayer chemisorption. Notably, the resultant bio-composites demonstrated a high level of stability even after eight consecutive adsorption and desorption cycles, with the removal rate of Pb(II) still reaching 82.3%. This work outlines a novel approach for designing highly efficient lignin-derived adsorbents toward wastewater treatment.