Tailoring Functionalized Lignin-Based Spherical Resins as Recyclable Adsorbents for Heavy Metal Uptake

A novel mesoporous spherical chelating lignin-based adsorbent was successfully synthesized via inverse suspension polymerization using sulfate pine pulping black liquor as raw material, followed by graft copolymerization with acrylonitrile and subsequent amination. The obtained aminated cyanoethyl spherical lignin resin (ACSLR) exhibited a well-defined porous morphology and abundant active sites, as confirmed by SEM and FT-IR. Adsorption experiments demonstrated high Pb²⁺ uptake capacity (63.98 mg·g^-1) under optimal conditions (pH = 5.5, 2.0 g·L^-1 adsorbent dosage, and 150 mg·L^-1 initial concentration of Pb²⁺ solution). The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetics, indicating monolayer chemisorption dominated by amino and cyano groups. This work provides a sustainable strategy for valorizing industrial lignin waste into efficient adsorbents for heavy metal removal, highlighting its potential for practical wastewater treatment applications.