Dual-Modified Lignin-Assembled Multilayer Microsphere with Excellent Pb²⁺ Capture.

Area of Science:

• Materials Science
• Environmental Science
• Chemistry

Background:

• Lignin-based sorbents face limitations in spherical form and high adsorption capacity for heavy metals like lead (Pb2+).
• Modification and assembly of alkali lignin (AL) are crucial for enhancing adsorption active sites and improving performance.
• Developing efficient and selective adsorbents is vital for environmental remediation.

Purpose of the Study:

• To synthesize and characterize novel lignin-based multilayer microspheres (LMM) for enhanced Pb2+ adsorption.
• To investigate the adsorption mechanism, kinetics, and isotherms of the LMM for Pb2+.
• To evaluate the selectivity and reusability of the LMM for heavy metal removal.

Main Methods:

• Dual-modified lignin (DML) was prepared and assembled with sodium alginate (SA) and dopamine to form LMM.
• Physicochemical properties including specific surface area (2.14 m2/g) and average pore size (8.32 nm) were analyzed.
• Adsorption experiments were conducted to determine capacity, kinetics, isotherms, selectivity, and recyclability.

Main Results:

• The LMM exhibited a high adsorption capacity of 250 mg/g for Pb2+, following Freundlich isotherm and second-order kinetic models.
• Adsorption mechanism involves electrostatic attraction and surface complexation.
• Selective adsorption order was Pb2+ (187.4 mg/g) > Cu2+ (168.0 mg/g) > Mn2+ (166.5 mg/g), with 69.34% Pb2+ removal after three cycles.

Conclusions:

• The developed LMM demonstrates significant potential as an efficient and selective adsorbent for Pb2+ removal from aqueous solutions.
• The spherical structure and abundant active sites contribute to the high adsorption capacity and performance.
• The LMM shows good reproducibility, indicating its viability for practical environmental applications.