# Covalently Linked Poplar and Ayous Lignin-Based Hydrogels: Sustainable Materials for Water Remediation

## TL;DR

This study creates sustainable hydrogels from lignin in Poplar and Ayous wood to effectively remove pollutants like methylene blue from water.

## Contribution

Ayous lignin-modified hydrogels show significantly improved methylene blue removal compared to commercial lignin and unmodified hydrogels.

## Key findings

- Ayous lignin-based hydrogels achieved 88% methylene blue removal efficiency.
- Chemical crosslinking reduced lignin leaching and improved hydrogel stability.
- The hydrogels offer a sustainable solution for wastewater treatment.

## Abstract

Lignin-based materials
are attracting increasing attention
for
their effectiveness in treating polluted water. In this study, special
emphasis is placed on hydrogels modified with lignin extracted from
Poplar and Ayous (Alpi Spa wood waste) which were developed for the
removal of organic dyes, using methylene blue as a model pollutant.
The two types of wood differ notably in their characteristics. Poplar
is a medium-density hardwood with a relatively low lignin content,
higher water repellence, and good ability to be shaped and glued.
Ayous is a tropical wood; its lignin has a different chemical makeup,
offering greater resistance to microbial degradation. However, Ayous
is more prone to moisture absorption and less durable outdoors if
untreated. The lignins covalently incorporated into polyvinyl alcohol
(PVA)-based hydrogel via direct esterification with polyamide epichlorohydrin
(PAE) were investigated. This chemical crosslinking strategy significantly
reduced lignin leaching. The resulting hydrogels were thoroughly characterized
by ATR-FTIR spectroscopy, thermogravimetric analysis, and scanning
electron microscopy to elucidate their structure and morphology. Batch
adsorption experiments revealed that hydrogels incorporating lignin
from Ayous hardwood waste achieved remarkable methylene blue removal
efficiency (up to 88%), a substantial improvement over both hydrogels
incorporating commercial lignin (64%) and unmodified hydrogel (9%).
By integrating lignin’s adsorption capabilities with the porosity
and recoverability of the hydrogel matrix, the Ayous lignin-modified
hydrogels present a highly promising and sustainable solution for
eliminating organic pollutants from wastewater. This innovative approach
not only enhances pollutant removal but also promotes environmental
sustainability and aligns with circular economy principles.