Naturally Derived Superabsorbent Quaternized Chitosan/Clay Hydrogels for Water Retention in Agriculture

To increase the agricultural productivity in severely water-constrained areas affecting about one-sixth of the world’s population the development of effective and environmentally friendly superabsorbent hydrogels is imperative. This study aims to develop superabsorbent hydrogels based on two naturally derived components, quaternized chitosan (QCS) and montmorillonite (MMT) clay. Positively charged QCS interacts strongly with negatively charged MMT, leading to clay exfoliation, as was demonstrated by X-ray powder diffraction, infrared spectroscopy, thermogravimetric analysis and field-emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The potential of QCS/MMT gels for use in agriculture was verified through measurements of their swelling ability, mechanical properties, and water retention. It was shown that these gels can absorb up to 200 times their own weight in water. MMT particles were found to provide a two-fold increase in the Young’s modulus of hydrogels, which can help them withstand the pressure from surrounding soil particles during swelling inside the soil. As was shown by water retention studies on gel/sand mixtures, this leads to an enhanced water holding capacity and an increased water range available for plants for MMT-containing gels compared to pristine QCS gels. These findings are valuable for the research and development of bio-based superabsorbents for agricultural applications.