A sustainable synthesis of cellulose hydrogels for agriculture with repurpose of solvent as fertilizer

Rapid population growth, combined with abrupt climate changes, significantly threatens global food security. Water-efficient agricultural practices are crucial to achieving global sustainability goals. A novel and sustainable methodology was developed to produce biodegradable cellulose hydrogels for agricultural applications by repurposing the salts from cellulose solvent (NaOH/urea) as nitrogen fertilizers. The recyclability of the solvent used in the synthesis (methyl ethyl ketone - MEK) was also evaluated over five cycles. The hydrogels were synthesized by crosslinking the prepared 3-allyloxy-2-hydroxy-propyl-cellulose (AHP-cellulose) derivatives via UV free radical polymerization (FRP). The effect of the crosslinking density on the hydrogel properties was investigated, and a maximum swelling degree of ~2500 % was attained in deionized water. The cellulose hydrogel exhibited significant resistance to pH and salinity. Under soil conditions, with only 1.0 wt% of hydrogel, the water retention capacity of the soil increased by ~20 %. The hydrogels demonstrated a delayed release of fertilizer salts for more than seven days and were biodegradable within 90 days. This environmentally sustainable approach aligns with sustainability goals and demonstrates the potential of allylic cellulose derivatives for the development of eco-friendly hydrogels for rapidly increasing agricultural applications.