Preparation of economical and reusable novel multi-chemically modified lignin-based adsorbent for efficient adsorption of lead ions.

In this work, through sequential demethylation, amination and esterification, a novel multi-chemically modified lignin-based adsorbent (NMCL) was developed to remove lead ions (Pb) from wastewater. These modifications significantly enhanced lignin's reactivity and introduced diverse active sites, thereby improving its adsorption performances. The adsorption studies revealed that NMCL's adsorption followed the Langmuir isotherm model and Pseudo-second-order kinetics, confirming a monolayer chemical adsorption process. Thermodynamic analysis indicated the whole process was spontaneous, entropy-driven and endothermic. NMCL demonstrated exceptional adsorption capacity (334.8 mg/g) and high selectivity and reusability, retaining 92 % efficiency after ten cycles. In addition, the related adsorption mechanism studies highlight the potential of NMCL for wastewater treatment via mechanisms involving electrostatic attraction and coordination with -NH and -CSS groups. This study offers a novel idea on the high value utilization of lignin and provides a new method for the removal of Pb from wastewater.