Turning Rice Husk Waste into High-Performance Bio-Based Hydrogels: Taguchi Optimization for Sustainable Materials Engineering

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Agricultural waste is increasingly recognized as a valuable source of renewable raw materials for advanced engineering applications. Among these resources, rice husk is produced in enormous quantities worldwide but is frequently discarded through open burning or landfilling, creating environmental concerns. The reviewed study investigates an alternative valorization pathway by converting rice husk-derived cellulose into a fully bio-based cellulose–phosphate hydrogel. Using the Taguchi optimization method, the researchers systematically evaluated the influence of synthesis parameters on hydrogel swelling performance while characterizing the resulting material through Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The research demonstrates how statistical optimization and sustainable material design can be integrated to produce environmentally friendly absorbent materials without relying on synthetic monomers or complex grafting processes.

Bibliographic Information

Item Information
Article Title Optimization of bio-based cellulose-phosphate hydrogel production from rice husk waste using the Taguchi method
Authors Selvia Aprilyanti; Irnanda Pratiwi; Winny Andalia; Tine Aprianti; Hariman Al Faritzie
Journal Teknomekanik
Volume 9
Issue 1
Publication Date February 2026
Pages 77–90
DOI https://doi.org/10.24036/teknomekanik.v9i1.47172
Publisher Universitas Negeri Padang
License Creative Commons Attribution 4.0 International (CC BY 4.0)
e-ISSN 2621-8720
p-ISSN 2621-9980
Keywords cellulose; extraction; hydrogel; rice husk; Taguchi method

1. Research Background

  • Bio-based hydrogels are attracting increasing attention as sustainable absorbent materials. Their three-dimensional crosslinked polymer networks can absorb and retain substantial amounts of water, making them useful in agriculture, wastewater treatment, biomedical devices, and controlled-release applications. Their biodegradable nature provides an environmentally preferable alternative to conventional synthetic hydrogels.
  • Most commercial absorbent hydrogels remain dependent on petrochemical polymers. Widely used materials such as polyacrylamide and acrylic acid derivatives provide excellent swelling performance but rely on non-renewable resources and exhibit limited biodegradability, raising long-term sustainability concerns.
  • Agricultural biomass offers an abundant renewable feedstock. Agricultural residues are inexpensive, widely available, and rich in cellulose. Rice husk, one of the largest by-products of rice milling, represents a promising raw material because of its substantial cellulose content and widespread availability.
  • Rice husk disposal continues to create environmental problems. Large quantities of rice husk are frequently discarded through open burning or landfilling. These disposal practices contribute to environmental pollution while simultaneously wasting a renewable biomass resource that could be converted into value-added engineering materials.
  • Existing cellulose-based hydrogels often require synthetic grafting agents. Although cellulose hydrogels derived from biomass have demonstrated promising absorbent properties, many published approaches still depend on synthetic monomers, multiple crosslinking agents, or complicated chemical modification processes that reduce environmental compatibility and increase manufacturing complexity.
  • Optimization of synthesis parameters remains insufficiently explored. Previous studies have generally focused on maximizing swelling capacity without systematically investigating how processing variables influence hydrogel structure, crosslink formation, and absorbent performance.
  • Phosphoric acid provides an environmentally compatible crosslinking alternative. As a single crosslinking agent, phosphoric acid can simultaneously introduce hydrophilic phosphate groups and create stable three-dimensional cellulose networks without requiring synthetic polymerization chemistry.
  • The study addresses both sustainability and process optimization. The research combines biomass valorization, environmentally friendly chemistry, and statistical optimization through the Taguchi method to establish an efficient route for producing cellulose–phosphate hydrogels from rice husk waste.

2. Research Objective

  • To develop a fully bio-based cellulose–phosphate absorbent hydrogel using cellulose extracted from rice husk waste.
  • To optimize hydrogel synthesis using the Taguchi L16 (45) orthogonal experimental design by evaluating the effects of cellulose content, reaction time, heating temperature, and phosphoric acid volume.
  • To determine the synthesis conditions that maximize hydrogel swelling performance while minimizing experimental variability.
  • To characterize the chemical structure of the synthesized hydrogel using Fourier Transform Infrared Spectroscopy (FTIR).
  • To investigate the hydrogel morphology using Scanning Electron Microscopy (SEM).
  • To demonstrate a simple, environmentally friendly, and scalable approach for converting agricultural waste into functional absorbent materials without synthetic monomers or grafting agents.

3. Why This Research Matters

  • Supports sustainable materials engineering. The study transforms agricultural waste into high-value engineering materials, contributing to circular economy principles and sustainable resource utilization.
  • Reduces dependence on petrochemical polymers. Developing entirely bio-based hydrogels helps reduce reliance on fossil-derived raw materials commonly used in commercial absorbent products.
  • Demonstrates practical biomass valorization. Rice husk, traditionally considered waste, becomes a functional cellulose source for advanced polymeric materials with engineering applications.
  • Introduces systematic statistical optimization. Rather than relying on trial-and-error experimentation, the research employs the Taguchi method and ANOVA to identify influential synthesis parameters efficiently.
  • Promotes environmentally compatible hydrogel synthesis. The hydrogel is produced without synthetic monomers or complex grafting chemistry, simplifying manufacturing while improving environmental compatibility.
  • Provides insight into structure–property relationships. Combining optimization with FTIR and SEM characterization improves understanding of how synthesis conditions affect hydrogel network formation and water absorption.
  • Supports future industrial implementation. The proposed synthesis route offers a scalable approach for producing sustainable absorbent materials suitable for agricultural, environmental, and potentially biomedical applications.

4. Research Methodology

  • Research Design

    The study employed an experimental research design to develop and optimize a fully bio-based cellulose–phosphate hydrogel derived from rice husk waste. A Taguchi Design of Experiments (DOE) based on an L16 (45) orthogonal array was implemented to evaluate the influence of four synthesis variables while minimizing the total number of experimental runs. The swelling ratio of the hydrogel served as the primary response variable for optimization.

  • Raw Materials

    Rice husk collected from a local rice milling facility in Palembang, Indonesia, served as the cellulose source. Analytical-grade sodium hydroxide (NaOH), sodium sulfite (Na2SO3), nitric acid (HNO3), acetic acid (CH3COOH), phosphoric acid (H3PO4, 85 wt%), distilled water, and ethanol were used throughout the extraction and hydrogel synthesis processes.

  • Cellulose Extraction

    Cellulose was extracted through sequential chemical treatments designed to remove hemicellulose, lignin, and other non-cellulosic components. Rice husk was first treated using nitric acid and acetic acid under controlled heating. Delignification was subsequently performed using sodium hydroxide and sodium sulfite. After repeated washing with distilled water and ethanol, the extracted cellulose was dried at 60 °C until constant weight was achieved before being used for hydrogel synthesis.

  • Experimental Factors

    Four controllable synthesis parameters were investigated, each at four experimental levels:

    • Cellulose content (1–4 g)
    • Reaction time (2–5 minutes)
    • Heating temperature (30–60 °C)
    • Phosphoric acid volume (6–12 mL)

    The Taguchi L16 orthogonal array enabled efficient evaluation of these variables while substantially reducing the experimental workload compared with a full factorial design.

  • Hydrogel Synthesis

    Extracted cellulose was first dispersed in distilled water and allowed to swell for twenty-four hours. Phosphoric acid was subsequently introduced as the crosslinking agent according to the experimental design. Microwave-assisted heating was applied under controlled temperature and reaction time conditions. After completion of the reaction, the hydrogel was cooled, filtered, repeatedly washed to remove unreacted species, dried to constant weight, and stored for subsequent characterization.

  • Performance Evaluation

    Hydrogel absorbency was evaluated through swelling ratio measurements. Dried hydrogel samples were immersed in distilled water until equilibrium swelling was reached. The swelling ratio was calculated from the difference between swollen and dry weights, and all measurements were performed in triplicate to improve experimental reliability.

  • Optimization Method

    The Taguchi optimization employed the "larger-the-better" Signal-to-Noise Ratio (SNR) criterion because maximizing water absorption represented the primary engineering objective. Signal-to-noise analysis was used to determine the optimal parameter combination while minimizing experimental variability.

  • Statistical Analysis

    Analysis of Variance (ANOVA) was conducted to determine the statistical significance of each synthesis parameter on hydrogel swelling performance. The analysis quantified the contribution of cellulose content, reaction time, heating temperature, and phosphoric acid volume while identifying the dominant factor governing absorbent behavior.

  • Material Characterization

    Fourier Transform Infrared Spectroscopy (FTIR) was used to identify functional groups and verify phosphate ester bond formation after crosslinking. Scanning Electron Microscopy (SEM) was employed to examine pore morphology, surface architecture, and network connectivity of the optimized hydrogel, allowing relationships between microstructure and swelling behavior to be evaluated.

5. Key Findings

Rice Husk Successfully Produced a Fully Bio-Based Cellulose–Phosphate Hydrogel

The study successfully converted rice husk waste into a phosphate-crosslinked cellulose hydrogel using phosphoric acid as the sole crosslinking agent. Unlike many previously reported cellulose hydrogels, the developed material required neither synthetic monomers nor grafting agents, demonstrating a simpler and more environmentally compatible synthesis route.

Optimal Synthesis Conditions Produced Excellent Water Absorption Performance

Among the sixteen experimental runs, the optimal hydrogel formulation achieved a maximum swelling ratio of 91.25 g/g. This performance was obtained using 3 g of cellulose, a reaction time of 3 minutes, a heating temperature of 60 °C, and 10 mL of phosphoric acid. Although the swelling capacity remained lower than some synthetic superabsorbent polymers, it represents substantial absorbency for a completely bio-based hydrogel produced without synthetic polymer chemistry.

Taguchi Optimization Efficiently Identified the Best Processing Conditions

The Taguchi experimental design effectively reduced the number of required experiments while systematically evaluating four important synthesis variables. Signal-to-Noise Ratio analysis identified the experimental condition that simultaneously maximized swelling performance and minimized process variability, demonstrating the effectiveness of statistical optimization in sustainable materials development.

Cellulose Content Was the Most Influential Processing Parameter

Analysis of Variance revealed that cellulose content exerted the greatest influence on hydrogel swelling behavior. With an F-value of 10.12 and a p-value of 0.045, cellulose concentration was the only synthesis parameter that exhibited statistical significance at the 95% confidence level. Reaction time, heating temperature, and phosphoric acid volume showed comparatively smaller contributions within the investigated parameter ranges.

FTIR Confirmed Successful Phosphate Crosslinking

FTIR characterization demonstrated clear chemical evidence of hydrogel formation. Following crosslinking, the O–H stretching band broadened and decreased in intensity, indicating participation of hydroxyl groups in esterification reactions. Additional phosphate-related absorption bands corresponding to P=O and P–O–C stretching vibrations confirmed the successful formation of phosphate ester linkages between cellulose chains.

SEM Revealed a Porous Three-Dimensional Network

Scanning Electron Microscopy showed that the optimized hydrogel possessed a porous, interconnected internal structure. This network morphology provides pathways for water diffusion while enabling efficient water retention, explaining the hydrogel's high swelling capability. The observed pore architecture supports the relationship between microstructure and absorbent performance proposed by the authors.

The Study Demonstrated an Effective Agricultural Waste Valorization Strategy

Beyond hydrogel optimization, the research demonstrated that rice husk can be transformed from an agricultural by-product into a functional engineering material through a relatively simple synthesis process. The combination of biomass utilization, environmentally friendly chemistry, and statistical optimization illustrates a practical approach toward sustainable material manufacturing.

6. Scientific Contribution

  • Introduces a fully bio-based cellulose–phosphate hydrogel synthesized entirely from rice husk-derived cellulose using phosphoric acid as the only crosslinking agent.
  • Demonstrates efficient application of the Taguchi method for optimizing hydrogel synthesis while minimizing experimental effort.
  • Establishes cellulose content as the dominant synthesis parameter governing hydrogel swelling performance through statistical ANOVA evaluation.
  • Confirms successful phosphate ester crosslink formation using FTIR characterization and validates hydrogel morphology using SEM analysis.
  • Provides a scalable biomass valorization strategy that transforms agricultural waste into functional absorbent materials without relying on synthetic polymerization.
  • Strengthens understanding of structure–property relationships by linking synthesis conditions, chemical crosslinking, pore morphology, and water absorption performance.

7. Industrial Implications

  • Provides a sustainable alternative for hydrogel manufacturing. The developed cellulose–phosphate hydrogel demonstrates that renewable agricultural biomass can replace petroleum-derived polymers in absorbent material production, supporting greener manufacturing practices.
  • Promotes agricultural waste valorization. Rice husk, which is commonly discarded through open burning or landfilling, can be transformed into a high-value engineering material. This conversion reduces environmental waste while creating new opportunities for biomass-based industries.
  • Supports environmentally friendly production processes. The synthesis route eliminates the need for synthetic monomers and complicated grafting reactions by using phosphoric acid as a single crosslinking agent, simplifying production while reducing environmental impact.
  • Offers potential applications in sustainable agriculture. Owing to its high water absorption capability, the hydrogel may serve as a soil moisture retention material capable of improving irrigation efficiency and supporting water conservation in agricultural systems.
  • Creates opportunities for wastewater treatment materials. The porous hydrogel structure provides a foundation for future development of environmentally friendly absorbent materials intended for contaminant adsorption and water purification technologies.
  • Supports the development of biodegradable absorbent products. The cellulose-based hydrogel may contribute to environmentally compatible absorbent materials for packaging, horticulture, environmental remediation, and related engineering applications where biodegradability is desirable.
  • Demonstrates the value of statistical process optimization. The successful implementation of the Taguchi method illustrates how Design of Experiments (DOE) can reduce experimental costs while improving manufacturing efficiency during material development.
  • Provides a scalable platform for biomass-based material industries. The relatively simple synthesis procedure suggests that agricultural biomass can become a practical feedstock for future bio-based polymer manufacturing with reduced dependence on fossil resources.

8. Research Limitations

  • The optimization focused exclusively on four synthesis variables—cellulose content, reaction time, heating temperature, and phosphoric acid volume. Other potentially influential processing parameters were beyond the scope of the investigation.
  • Hydrogel performance was evaluated primarily through swelling ratio measurements. Other engineering properties such as mechanical strength, biodegradation behavior, cyclic swelling stability, thermal stability, and long-term durability were not investigated.
  • Material characterization was limited to FTIR and SEM analyses. Additional characterization techniques could provide a more comprehensive understanding of the hydrogel's physicochemical properties.
  • The statistical optimization was conducted within predefined experimental ranges established by the Taguchi design. Conditions outside these investigated ranges were not evaluated.
  • Although the hydrogel demonstrated promising absorbent performance, the study did not include application-specific performance testing under practical agricultural, environmental, or industrial operating conditions.
  • Economic feasibility, production cost analysis, scale-up considerations, and industrial manufacturing assessments were not addressed within the objectives of the research.

9. Future Research Opportunities

  • Investigate additional synthesis variables, including microwave power, cellulose particle size, drying conditions, and alternative crosslinking concentrations, to further improve hydrogel performance.
  • Evaluate the mechanical properties, compressive strength, elasticity, and structural stability of the hydrogel for engineering applications requiring long-term mechanical integrity.
  • Study biodegradability, environmental degradation behavior, and life-cycle performance to assess long-term sustainability under practical operating conditions.
  • Investigate adsorption capabilities for heavy metals, dyes, fertilizers, and other pollutants to explore wastewater treatment and environmental remediation applications.
  • Evaluate controlled-release behavior for fertilizers, nutrients, pesticides, or other agricultural additives to determine suitability for smart agriculture.
  • Compare phosphoric acid crosslinking with alternative environmentally compatible crosslinking systems to optimize hydrogel structure and functional performance.
  • Expand biomass utilization by investigating cellulose extracted from other agricultural residues, including corn stalks, sugarcane bagasse, coconut husks, and oil palm biomass.
  • Apply advanced optimization approaches such as Response Surface Methodology (RSM), Grey Relational Analysis (GRA), machine learning, or artificial intelligence to complement Taguchi optimization.
  • Conduct pilot-scale manufacturing studies to evaluate industrial scalability, production economics, and process sustainability.
  • Assess long-term performance under real agricultural and environmental operating conditions to validate practical implementation of the developed hydrogel.

10. Potential for Public Policy Citation (Overton)

This article demonstrates strong potential for citation within public policy documents related to sustainable materials engineering, agricultural waste management, biomass utilization, and circular economy initiatives. By presenting a practical approach for converting rice husk waste into value-added bio-based absorbent materials, the study directly addresses environmental challenges associated with agricultural residue disposal while supporting resource efficiency and renewable material development.

Government agencies responsible for agriculture, environmental protection, waste management, industrial innovation, and sustainable manufacturing may find the research particularly relevant. The proposed synthesis strategy aligns with broader policy objectives promoting biomass valorization, waste reduction, renewable materials, and environmentally friendly industrial technologies.

Although the study primarily focuses on laboratory-scale material development rather than policy implementation, its engineering methodology provides a scientific foundation that could inform future technical guidelines, national biomass utilization strategies, sustainable manufacturing programs, and circular economy roadmaps. Consequently, the article possesses moderate-to-high potential for future citation in policy-oriented literature related to green materials and sustainable resource management.

11. Who Should Read This Paper?

  • Materials scientists working on sustainable polymers and bio-based materials.
  • Chemical engineers developing environmentally friendly polymer synthesis technologies.
  • Researchers specializing in cellulose-based materials and biomass valorization.
  • Industrial engineers interested in statistical process optimization using the Taguchi method.
  • Agricultural engineers developing water-retention materials for sustainable farming.
  • Environmental engineers investigating biodegradable absorbent materials.
  • Researchers working in waste management and circular economy initiatives.
  • Graduate students studying materials engineering, polymer science, and green manufacturing.
  • Industrial practitioners interested in sustainable absorbent material production.
  • Policy makers supporting biomass utilization, renewable materials, and sustainable industrial development.

12. Final Thoughts

This study presents a well-designed integration of sustainable materials engineering and statistical process optimization by transforming rice husk waste into a functional cellulose–phosphate hydrogel. Through the application of the Taguchi experimental design, the authors systematically identified synthesis conditions that maximize swelling performance while minimizing experimental variability. The research demonstrates that environmentally compatible hydrogel production can be achieved without synthetic monomers or complex grafting chemistry, representing an important contribution toward renewable polymer development.

One of the principal strengths of the work lies in its combination of experimental optimization and material characterization. Statistical analysis through Signal-to-Noise Ratio evaluation and ANOVA identifies cellulose content as the dominant processing factor, while FTIR and SEM analyses confirm successful phosphate crosslinking and the formation of a porous three-dimensional network responsible for efficient water absorption. Together, these complementary approaches provide a clear understanding of the relationships between synthesis parameters, chemical structure, and hydrogel performance.

Beyond its technical findings, the study demonstrates a practical strategy for agricultural waste valorization that supports circular economy principles and sustainable manufacturing. By converting an abundant agricultural by-product into a biodegradable absorbent material using relatively simple processing techniques, the research offers valuable insights for future developments in biomass-based polymers, green materials engineering, and environmentally responsible industrial production.



13. Suggested Citations

Teknomekanik (UNP) Style

Aprilyanti S, Pratiwi I, Andalia W, Aprianti T, Al Faritzie H. Optimization of bio-based cellulose-phosphate hydrogel production from rice husk waste using the Taguchi method. Teknomekanik. 2026;9(1):77–90. https://doi.org/10.24036/teknomekanik.v9i1.47172

APA (7th Edition)

Aprilyanti, S., Pratiwi, I., Andalia, W., Aprianti, T., & Al Faritzie, H. (2026). Optimization of bio-based cellulose-phosphate hydrogel production from rice husk waste using the Taguchi method. Teknomekanik, 9(1), 77–90. https://doi.org/10.24036/teknomekanik.v9i1.47172

IEEE Style

S. Aprilyanti, I. Pratiwi, W. Andalia, T. Aprianti, and H. Al Faritzie, "Optimization of bio-based cellulose-phosphate hydrogel production from rice husk waste using the Taguchi method," Teknomekanik, vol. 9, no. 1, pp. 77–90, Feb. 2026, doi: 10.24036/teknomekanik.v9i1.47172.

Harvard Style

Aprilyanti, S., Pratiwi, I., Andalia, W., Aprianti, T. and Al Faritzie, H., 2026. Optimization of bio-based cellulose-phosphate hydrogel production from rice husk waste using the Taguchi method. Teknomekanik, 9(1), pp.77–90. Available at: https://doi.org/10.24036/teknomekanik.v9i1.47172.

Vancouver Style

Aprilyanti S, Pratiwi I, Andalia W, Aprianti T, Al Faritzie H. Optimization of bio-based cellulose-phosphate hydrogel production from rice husk waste using the Taguchi method. Teknomekanik. 2026;9(1):77–90. doi:10.24036/teknomekanik.v9i1.47172.

Chicago (Author–Date)

Aprilyanti, Selvia, Irnanda Pratiwi, Winny Andalia, Tine Aprianti, and Hariman Al Faritzie. 2026. "Optimization of Bio-Based Cellulose-Phosphate Hydrogel Production from Rice Husk Waste Using the Taguchi Method." Teknomekanik 9 (1): 77–90. https://doi.org/10.24036/teknomekanik.v9i1.47172.

MLA (9th Edition)

Aprilyanti, Selvia, et al. "Optimization of Bio-Based Cellulose-Phosphate Hydrogel Production from Rice Husk Waste Using the Taguchi Method." Teknomekanik, vol. 9, no. 1, 2026, pp. 77–90. Crossref, https://doi.org/10.24036/teknomekanik.v9i1.47172.

14. Editorial Note

This review is based exclusively on the scientific content presented in the published research article. The discussion summarizes the study's objectives, methodology, experimental findings, scientific significance, industrial relevance, and future research directions while preserving the authors' original scientific intent. The review is intended for educational and scholarly communication purposes and does not replace the original peer-reviewed publication. Readers are encouraged to consult the original article for complete experimental details, data interpretation, figures, and references.

15. SEO Meta Description

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16. SEO Keywords

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