Preparation of Chitin Nanofibers from Shrimp Shell Waste by Partial Deacetylation and Mechanical Treatment

ABSTRACT

Chitin is one of the most abundant biopolymers in nature. Herein, we report the successful preparation of chitin nanofibers (ChNFs) from shrimp shell waste using a partial deacetylation process with NaOH and high-speed blending. The effects of the deacetylation reaction with NaOH concentrations (0–40 wt%) on the degree of acetylation (DA), crystallinity, zeta potential, thermal stability, and morphology of the ChNFs were investigated. With the more aggressive deacetylation reaction (higher NaOH concentration), ChNFs had the lower DA, crystallinity degree, and thermal stability, and their widths and lengths became smaller and shorter. The presence of amino groups in the chitin molecule caused by deacetylation generated repulsive forces with aids of acetic acid, efficiently leading to the individualization of ChNFs using high-speed blending. The individualized ChNFs deacetylated with 30 wt% NaOH had an average width of 8.07 ± 1.80 nm and length of less than 500 nm, whereas bundles of aggregated fibers with widths in the range of 30–100 nm and lengths of up to several μm were extracted from chitin without deacetylation. Additionally, the deacetylation with 40 wt% NaOH completely converted chitin to chitosan. The ChNFs could be efficiently used for composites, biomaterials, and packaging applications.

摘要

甲壳素是自然界中含量最丰富的生物聚合物之一. 在此，我们报道了利用NaOH脱乙酰工艺和高速共混，从虾壳废料中成功制备甲壳素纳米纤维（ChNFs）. 研究了NaOH浓度（0–40 wt%）下的脱乙酰反应对ChNFs的乙酰化程度（DA）、结晶度、ζ电位、热稳定性和形态的影响. 随着更积极的脱乙酰反应（更高的NaOH浓度），ChNFs具有更低的DA、结晶度和热稳定性，并且它们的宽度和长度变得越来越小和更短. 脱乙酰基化导致的几丁质分子中氨基的存在在乙酸的帮助下产生了排斥力，有效地导致了使用高速共混的ChNFs的个性化. 用30 wt%NaOH脱乙酰的个性化ChNFs的平均宽度为8.07 ± 1.80 nm，长度小于500 nm，而从几丁质中提取的聚集纤维束的宽度在30–100 nm范围内，长度可达数μm，而没有脱乙酰. 此外，用40 wt%的NaOH脱乙酰作用将甲壳素完全转化为壳聚糖. ChNF可以有效地用于复合材料、生物材料和包装应用

KEYWORDS:

• Shrimp shells
• protonation
• morphology
• thermal stability
• deacetylation
• blending
• mechanical treatment
• surface charges

关键词:

• 关键词
• 质子化
• 形态学
• 热稳定性
• 脱乙酰
• 混合
• 机械处理
• 表面电荷

Highlights

• Chitin nanofibers (ChNFs) with an average width of 8.07 ± 1.80 nm and length of less than 500 nm were successfully prepared from shrimp shell waste.

• Effects of deacetylation conditions with various NaOH concentrations (0–40 wt%) on properties of ChNFs were investigated.

• A decrease in crystallinity degree and thermal stability was observed for deacetylated ChNFs.

• Deacetylation facilitated individualization of ChNFs using high-speed household blending.

• The aggressive deacetylation reaction with a higher concentration of NaOH caused a reduction in the length of ChNFs.

Acknowledgements

This project is funded by National Research Council of Thailand (NRCT) (Grant No. N41A640090). The authors also gratefully acknowledge the support from the department of Materials Science, Faculty of Science, Chulalongkorn University and Learning Institute, King Mongkut’s University of Technology Thonburi. S. Tanpichai would like to thank Thailand Toray Science Foundation for the financial support of the science and technology research grant (28^th TTSF, 2021) and express gratitude to Mstr. Skoravit Tanpichai and Mstr. Monapicha Tanpichai for their invaluable curiosity and support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Ethical approval

The research does not involve any human or animal-welfare-related issues.

Additional information

Funding

This work was supported by the National Research Council of Thailand (NRCT) under Grant No. N41A640090