Development and Characterization of Chitin-based Hydrogel Nanocomposites from Animal Shells for Sustainable Agriculture

Abstract

This paper presents a report on the design and performance testing of a nano-chitin-source-based hydrogel (Portunus pelagicus crab) shell-derived nano-hydrogel in support of sustainable agricultural uses in terms of its potential to be used in water retention and urea release. Using a multi-step acid hydrolysis method, nano-chitin could be extracted and introduced into a NaOH/urea aqueous solution whereby a hydrogel was formed. The prepared hydrogel was expected to minimize the loss of nutrients and increase the moisture holding capacity of soil in arid and semi-arid environments. The Fourier transform infra red spectra proved the existence of typical N-H and amide functional groups at 3257 cm⁻¹ and 1631 cm⁻¹, respectively. In X-ray diffractograms crystalline peaks were observed at 9.35° and 23.2° which revealed that nano-chitin is partially de-crystallized after hydrogel formation. The scanning electon microscopic images exhibited about 55.5 nm wide semi-crystalline nanofibrilsand nanopores on the surface of the fibres favouring high water-retention capacity and nutrient loading capacity. Application of soil trials showed 50% higher water holding capacity and 88% urea release, which results in long-lasting nutrient. In a plant growth experiment using Vigna radiata, it was observed that plant seed germination and their initial growth are enhanced and therefore the gels are agronomically viable. Soil analysis of the soil before and after hydrogel addition showed that there was an improvement in the soil ammoniacal nitrogen and moisture content.