Tailor-made sulfonated lignin derivatives with controllable anionic charge and enhanced aqueous solubility for the fabrication of uniform microspheres

초록

A sustainable route was developed to convert lignin into a practical and recyclable adsorbent by tailoring the anionic charge through sulfonation and shaping the lignin into recoverable microspheres. Sulfonated lignin derivatives with controllable anionic charges were synthesized from kraft lignin using 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt hydrate (CPSA). The introduction of ionizable sulfonate groups increased the negative charge and markedly improved aqueous solubility, providing a charge-engineered lignin platform suitable for water-based processing. Both kraft lignin and sulfonated lignin were subsequently materialized into lignin-based microspheres via emulsion crosslinking, and the microsphere size was readily tuned by adjusting the agitation speed (rpm), yielding particles in the range of similar to 400-800 mu m. The microspheres exhibited efficient removal of ionic dyes, and the uptake behavior was governed by the combined contributions of electrostatic interactions, pi-pi stacking between aromatic lignin domains and dye chromophores, and hydrogen bonding. Adsorption proceeded rapidly in the initial stage and gradually approached equilibrium, indicating the presence of accessible binding sites within the microsphere network. The equilibrium data were well described by monolayer-type adsorption, reflecting strong affinity and effective site utilization. This study established a derivatization-materialization strategy that translated charge-tailored lignin into size-controllable microsphere adsorbents with practical separability and promising potential for wastewater treatment applications.

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