A review of lignin-based adsorbent materials: Synthesis and applications in the remediation of heavy metal/ antibiotic-containing wastewater

Lignin, often regarded as an agricultural waste, possesses notable advantages such as renewability, degradability and non-toxicity, enabling it as an emerging and promising adsorbent for wastewater remediation. Native lignin is typically modified to enhance its removal performance. This review provides an overview of lignin's versatility, discusses chemical modifications for its functionalization, and summarizes the potential interaction mechanisms of lignin-based adsorbents in wastewater remediation. After that, based on the guidance of aforementioned mechanisms, different synthesis methods for lignin-modified adsorbent materials, including organic (anionic and cationic surfactants), inorganic (iron and other metal component modification), and composite modification, are summarized. Subsequently, applications of lignin-based adsorbent materials in wastewater treatment are reviewed, including the removal of heavy metals, antibiotics and the combined pollutants. Finally, the review identifies current challenges and explores future development directions for lignin-based adsorbent materials. • Overview lignin and lignin biochar as adsorbents for wastewater treatment. • Summarize synthesis methods for lignin-based materials. • Analyze removal capabilities for heavy metals and antibiotics. • Elucidate removing mechanisms by lignin-based materials.