# Upcycling Lignin into Porous Hybrid Beads and Sponges for Efficient Removal of Organic and Biological Contaminants from Water

## TL;DR

This paper introduces a sustainable method to create biodegradable materials from lignin and chitosan for removing pollutants and bacteria from water.

## Contribution

A novel lignin-chitosan composite is developed for efficient removal of both organic and biological contaminants from water.

## Key findings

- The lignin-chitosan sponge achieved complete E. coli adsorption with a 4 log reduction.
- The composite showed high adsorption capacity for the organic dye methyl orange.
- Cross-linking with chitosan reversed lignin's surface charge, improving its affinity for anionic pollutants.

## Abstract

Modern industrialization leads to the widespread discharge
of pollutants,
such as organic dyes and bacterial contamination, into water streams,
necessitating efficient and sustainable treatment strategies. To address
this challenge, we report the fabrication of biodegradable adsorbents
for efficient adsorption of chemical pollutants while reducing the
microbial load. Herein, kraft lignin (KL) is cross-linked with chitosan
to produce highly porous spherical beads, while EDC/NHS ((N-ethyl-N′-(3-(dimethylamino)­propyl)­carbodiimide/hydroxysuccinimide)
coupling chemistry enabled the formation of microporous sponges and
alginate-integrated beads. Cross-linking with chitosan induced a surface
charge reversal of lignin from negative (−37 mV) to positive
(+51 mV), enhancing its affinity for anionic contaminants. The resulting
materials exhibited promising adsorption capacity for an organic pollutant
(methyl orange). Furthermore, the composites demonstrated efficient
bacterial adsorption, achieving complete adsorption of E. coli (∼4 log reduction) using the lignin–chitosan
sponge. These results highlight the potential of lignin–chitosan
architectures as sustainable and multifunctional materials for advanced
water purification.