EXTENDED ABSTRACT
Introduction

Water hyacinth (Eichhornia crassipes) is one of the most aggressive invasive aquatic plants worldwide and has become a major environmental concern in many freshwater ecosystems. Due to its rapid vegetative propagation and exceptional adaptability, this floating macrophyte can quickly cover large areas of rivers, lakes, reservoirs, irrigation canals, and wetlands. The uncontrolled spread of water hyacinth causes severe ecological, environmental, and socio-economic problems. Dense plant mats formed on water surfaces block sunlight penetration, thereby reducing photosynthetic activity in submerged aquatic plants and disrupting aquatic food chains. In addition, decomposition of the accumulated biomass significantly decreases dissolved oxygen concentration, leading to hypoxic conditions that negatively affect fish populations and aquatic biodiversity. The obstruction of waterways also interferes with irrigation systems, fisheries, hydroelectric facilities, and navigation. Furthermore, stagnant water beneath the dense vegetation provides suitable breeding habitats for mosquitoes and other disease vectors.
Despite these negative impacts, water hyacinth has recently gained attention as a promising lignocellulosic biomass resource. The plant contains relatively high cellulose content and comparatively low lignin levels, which facilitate cellulose extraction and reduce the severity of pretreatment processes compared with conventional lignocellulosic resources such as wood. These characteristics make water hyacinth an attractive renewable feedstock for nanocellulose production.
Nanocellulose, including cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), is considered one of the most important bio-based nanomaterials due to its remarkable physicochemical and mechanical properties. These materials possess high tensile strength, low density, large specific surface area, biodegradability, renewability, and tunable surface chemistry. Such unique characteristics have led to increasing interest in their applications in sustainable packaging, advanced composites, paper reinforcement, environmental remediation, energy storage, biomedical materials, and flexible electronics. In this context, converting invasive water hyacinth into high-value nanocellulose represents an environmentally sustainable approach that simultaneously addresses biomass management and renewable material production within the framework of circular economy principles. This review aims to summarize recent advances in the extraction, characterization, modification, and industrial applications of nanocellulose derived from water hyacinth. In addition, the study discusses the environmental significance of utilizing this invasive biomass and highlights future research opportunities for developing sustainable nanocellulose-based technologies.


Materials and methods
This review study summarizes published research on the extraction, characterization, and applications of nanocellulose derived from water hyacinth, while also highlighting the environmental threats caused by the uncontrolled spread of this invasive aquatic plant. It critically evaluates major production methods, including acid hydrolysis, enzymatic, mechanical, and combined chemical-mechanical treatments. The structural and functional properties of the produced nanocelluloses, as well as their applications in composites, packaging, paper, energy, environmental remediation, and advanced materials, are discussed. Research gaps and future development opportunities are also highlighted.

Results and discussion
The reviewed studies demonstrate that water hyacinth is a highly promising lignocellulosic resource for nanocellulose production due to its relatively high cellulose content and low lignin concentration. These characteristics facilitate cellulose purification and reduce the intensity of chemical pretreatments required during nanocellulose extraction. As a result, water hyacinth can serve as a sustainable alternative to conventional cellulose sources such as wood and agricultural residues. Structurally, nanocellulose derived from water hyacinth exhibits nanoscale dimensions, high specific surface area, and high aspect ratio, which are important parameters for reinforcement applications. The crystallinity index of water-hyacinth-derived nanocellulose is typically reported between 68% and 73%, indicating relatively ordered crystalline structures. High crystallinity contributes significantly to improved stiffness, tensile strength, dimensional stability, and thermal resistance. Thermogravimetric analyses reported in the literature indicate thermal degradation temperatures ranging between 300 and 320 °C, demonstrating suitable thermal stability for various industrial applications. Moreover, the large number of hydroxyl groups present on nanocellulose surfaces enables strong hydrogen bonding interactions and facilitates surface functionalization. Various chemical modification techniques, including TEMPO- oxidation, acetylation, and graft polymerization, have been investigated to improve compatibility with hydrophobic polymer matrices and introduce additional functionalities such as conductivity or adsorption capacity.
In packaging applications, incorporation of nanocellulose into biodegradable polymer films significantly improves tensile strength, elastic modulus, thermal stability, and barrier properties against oxygen and water vapor. These improvements are essential for the development of environmentally friendly alternatives to petroleum-based plastic packaging. In composite systems, nanocellulose acts as an efficient reinforcing nanofiller due to its high aspect ratio and strong interfacial interactions with polymer matrices.
In the pulp and paper industry, the addition of water-hyacinth-derived nanocellulose to recycled pulp improves inter-fiber bonding, sheet density, tensile strength, burst resistance, and overall paper quality. This application is particularly important because recycled fibers often experience mechanical degradation after repeated recycling cycles.
The reviewed studies also highlight the potential of water-hyacinth nanocellulose in energy-related applications. Cellulose nanofibers have been successfully used as separators in rechargeable batteries due to their porous structure, electrolyte wettability, ion transport capability, and thermal stability. In addition, surface-modified nanocellulose combined with conductive polymers has enabled the fabrication of lightweight conductive materials suitable for sensors, supercapacitors, and flexible electronic devices.
Environmental remediation is another important application area. The nanoscale structure and abundant functional groups of nanocellulose provide high adsorption capacity for heavy metals, dyes, oils, and other contaminants. Several studies have reported efficient removal of pollutants such as lead, cadmium, and chromium from wastewater using modified nanocellulose adsorbents derived from water hyacinth. Hydrophobic modifications have also enabled efficient oil–water separation systems for environmental cleanup applications.
Although significant progress has been achieved, several challenges still limit commercial scale utilization of water-hyacinth-derived nanocellulose. High moisture content of the biomass, variability in chemical composition, energy-intensive drying processes, and chemical consumption during extraction remain important concerns. Therefore, future studies should focus on developing greener extraction technologies, reducing production costs, improving process scalability, and conducting comprehensive life cycle and techno-economic assessments.


Conclusion
The findings of this review clearly demonstrate that water hyacinth, despite being one of the world’s most problematic invasive aquatic weeds, can be effectively converted into a valuable renewable feedstock for nanocellulose production. The produced nanocellulose exhibits favorable structural, mechanical, thermal, and surface properties, making it suitable for a wide range of advanced industrial applications including packaging, composites, paper reinforcement, environmental remediation, energy storage, and functional materials.
The valorization of water hyacinth biomass into high-value nanomaterials represents a practical example of sustainable development and circular economy principles, where an environmental problem is transformed into a renewable industrial resource. Such an approach not only contributes to invasive species management but also reduces dependence on fossil-based and non-renewable materials. Globally, water-hyacinth-derived nanocellulose shows strong potential for future multifunctional bio-based technologies. However, further research is still required to optimize environmentally friendly extraction methods, improve economic feasibility, scale up industrial production, and expand commercial applications. With continued technological advancements, nanocellulose derived from water hyacinth may become an important sustainable material for next-generation green industries.