Green Preparation of Waste-Derived Nanocellulose/Chitosan/Ag Aerogels for Multifunctional Water Treatment

Summary

This study presents recoverable nanocellulose/chitosan aerogels embedded with green-synthesized silver nanoparticles derived from sugarcane bagasse. The optimized composite exhibits balanced multifunctionality, delivering robust antibacterial activity, efficient catalytic 4-nitrophenol reduction, and enhanced dye and heavy metal adsorption with highly controlled silver release.

Abstract

​Waste-derived nanocellulose aerogels offer a sustainable route for converting lignocellulosic residues into functional porous materials, but balancing antibacterial activity, catalytic performance, adsorption capacity, and Ag-release control remains challenging. In this study, sugarcane bagasse was used as a biomass source to prepare waste-derived nanocellulose through alkaline treatment, hydrogen peroxide bleaching, high-pressure homogenization, and sonication. The nanocellulose was combined with chitosan to form porous aerogels by freezing and freeze-drying, followed by in situ green loading of Ag nanoparticles using standardized green tea extract as the reducing medium. The optimized Ag-WNC/CS-A-3 aerogel retained high porosity, improved mechanical stability, and a BET surface area of 66.4 ± 5.2 m²/g. It showed strong antibacterial activity against Escherichia coli and Staphylococcus aureus, efficient 4-nitrophenol reduction with an apparent rate constant of 0.184 ± 0.017 min⁻¹, and enhanced adsorption toward methylene blue and Pb(II), with equilibrium capacities of 118.7 ± 7.1 mg/g and 72.4 ± 6.3 mg/g, respectively. Although higher Ag loading slightly improved antibacterial and catalytic performance, it reduced adsorption balance and increased Ag release. Overall, Ag-WNC/CS-A-3 provided the most balanced combination of structural integrity, multifunctional activity, reuse stability, and Ag-release control. This work supports a sustainable design strategy for recoverable bio-based aerogels in antibacterial, catalytic, and water-treatment applications.

Introduction

The conversion of agricultural waste into functional materials has become an important direction in sustainable materials science. Sugarcane bagasse is particularly attractive because it is generated in large quantities during sugar and juice processing and contains a high proportion of cellulose that can be recovered for value-added applications. Recent work has emphasized that sugarcane bagasse is a low-cost and environmentally relevant biomass source, although efficient cellulose extraction, functionalization, and scalable nanostructure production remain key technical challenges¹. This makes bagasse-derived nanocellulose a suitable platform ....

Protocol

Materials and experimental design

Sugarcane bagasse was used as the lignocellulosic waste source for nanocellulose preparation. Fresh bagasse was washed with tap water and deionized water, dried at 60 °C for 24 h, cut into 1–2 cm fragments, milled, and passed through a 40-mesh sieve. The dried powder was stored in sealed polyethylene bags with silica gel at room temperature and used within 1 month. All the reagents, materials, and equipment used in this study are listed in the Table of Materials file.

Unless otherwise specified, all chemicals were analytical grade and used as recei....

Results

Recovery of cellulose-rich pulp and preparation of waste-derived nanocellulose

The pretreatment process effectively converted sugarcane bagasse into cellulose-rich pulp. After alkaline treatment and hydrogen peroxide bleaching, the biomass changed from brown fibrous powder to a pale cellulose-rich pulp, indicating progressive removal of lignin-rich and hemicellulosic fractions. The cellulose content increased from 42.6% ± 1.8% in raw bagasse to 78.6% ± 2.4% in bleached pulp, w.......

Discussion

This study demonstrates that waste-derived nanocellulose can serve as a structurally viable platform for constructing multifunctional aerogels with antibacterial, catalytic, and adsorption functions. The value of this design lies not only in converting sugarcane bagasse into a porous material, but also in using the nanocellulose network as a carrier for chitosan reinforcement and green AgNP immobilization. Recent reviews have emphasized that nanocellulose-based materials are attractive for water-pollutant removal because.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
100 µm nylon mesh	Commercial laboratory supplier		Used to filter chitosan solution before aerogel fabrication.
Acetic acid	Sigma-Aldrich	695092
Antibiotic disc positive control	Thermo Fisher	https://www.thermofisher.com/search/browse/category/us/en/90222069	Select according to the bacterial strain and local antibacterial testing standard.
BET surface area and porosity	Micromeritics ASAP 2460	ASAP 2460	Micromeritics describes the ASAP 2460 as a surface area and porosimetry analyzer with expandable high-throughput ports.
Calcium chloride	Sigma-Aldrich	946664	Report hydrate state according to the purchased reagent.
Carbon-coated copper TEM grids	Ted Pella	https://www.tedpella.com/grids_html/	Use actual grid specification in final table.
CasaXPS version reference	CasaXPS 2.3.25 or current installed version	https://casaxps.com/
Chitosan	Sigma-Aldrich	448869
Cylindrical polypropylene molds	Commercial laboratory supplier		Used for aerogel monolith molding.
Data analysis and plotting	OriginPro 2024
Escherichia coli	ATCC	ATCC 25922
Ethanol	Sigma-Aldrich	459844
Folin–Ciocalteu reagent	Sigma-Aldrich	F9252
Freeze dryer	Labconco FreeZone	https://www.labconco.com/category/freeze-dry-evaporation/freeze-dry-systems
FTIR	Thermo Scientific Nicolet iS50	912A0760	FTIR Spectrometer or equivalent
Gallic acid	Sigma-Aldrich	G7384	Use as calibration standard for Folin–Ciocalteu assay; product source should be checked against the lab’s actual purchase record.
Green tea leaves	Local supplier	Local supplier	Use batch record, brand, collection/purchase date, and total phenolic standardization instead of only a commercial webpage.
Hydrochloric acid	Sigma-Aldrich	258148
Hydrogen peroxide	Sigma-Aldrich	386790
ICP-OES	Agilent 5110	5110	PerkinElmer Avio 500 / equivalent
Image analysis	ImageJ 1.54	ImageJ/Fiji version should be reported according to the actual software package installed in the laboratory.
LB broth and LB agar	Thermo Fisher	10855001	Use actual supplier and catalog number from microbiology lab inventory.
Lead nitrate	Sigma-Aldrich	NIST928
Magnesium chloride	Sigma-Aldrich	M8266	Report hydrate state according to the purchased reagent.
Methylene blue	Sigma-Aldrich	M9140
Nitric acid	Sigma-Aldrich	438073	Use trace-metal grade if available for ICP-OES workflows.
PBS	Thermofisher Scientific	https://www.thermofisher.com/order/catalog/product/10010023	Used as antibacterial assay control/dilution medium.
Ready-to-use E. coli QC organism	Thermo Fisher Culti-Loops	Cat. No. R4607050	Alternative format for ATCC 25922
SEM	Hitachi SU8010 / ZEISS Sigma / equivalent	https://www.hitachi-hightech.com/global/en/products/microscopes/sem-tem-stem/sem/
Silver nitrate	Sigma-Aldrich	209139
Sodium borohydride	Sigma-Aldrich	452882	Sigma-Aldrich lists sodium borohydride 452882 as powder, ≥98.0%.
Sodium carbonate	Sigma-Aldrich	223530
Sodium chloride	Sigma-Aldrich	S9888
Sodium hydroxide	Sigma-Aldrich	221465
Staphylococcus aureus	ATCC	ATCC 25923	ATCC identifies S. aureus 25923 as a quality-control strain used for CLSI disk diffusion and media testing.
Prism 10	GraphPad	Version 10	Statistical analysis
Sterile filter-paper discs	Whatman		Used for disc-diffusion controls and aerogel-disc comparison.
Sugarcane bagasse	Local supplier	Local juice-processing source	Use collection record rather than supplier webpage; report location, date, drying method, and storage condition.
Syringe filters	Millipore	https://www.merckmillipore.com/US/en/products/filtration/laboratory-syringe-filters/syringe-filters	Match membrane material to solvent system and actual purchase record.
TEM	JEOL JEM-2100	JEM-2100
TGA	TA Instruments Q500	Q500
Universal testing machine	Instron 5943	5943
UV–Vis spectroscopy	Shimadzu	UV-2600i Plus
XPS data processing	CasaXPS	https://casaxps.com/
XRD	Bruker D8 Advance	https://www.bruker.com/en/products-and-solutions/diffractometers-and-x-ray-microscopes/x-ray-diffractometers.html	Rigaku SmartLab / equivalent