Cellulosic hydrogels are widely used in various applications, as they are natural raw materials and have excellent degradability. However, their poor mechanical properties restrict their practical application. This study presents a facile approach for fabricating cellulosic hydrogels with high strength by synergistically utilizing salting-out and ionic coordination, thereby inducing the collapse and aggregation of cellulose chains to form a crosslinked network structure. Cellulosic hydrogels are prepared by soaking cellulose in an Al2(SO4)3 solution, which is both strong (compressive strength of up to 16.99 MPa) and tough (compressive toughness of up to 2.86 MJ/m3). The prepared cellulosic hydrogels exhibit resistance to swelling in different solutions and good biodegradability in soil. The cellulosic hydrogels are incorporated into strain sensors for human-motion monitoring by introducing AgNWs. Thus, the study offers a promising, simple, and scalable approach for preparing strong, degradable, and anti-swelling hydrogels using common biomass resources with considerable potential for various applications.

Soil and water pollution are current global environmental and agricultural challenges, adversely affected by ineffective industrial waste treatment before discharging into the environment combined with inefficient long-term inputs of fertilizers. The development of targeted fertilizers delivery vehicles, sufficient soil/water remediation, and contamination detection systems using eco-friendly technologies become critically important. Due to their high specific surface area, biocompatibility, easiness of operation, and high performance, nanomaterials-based controllable soil fertility promoters, adsorbents, sensors, and photocatalysts are promising tools for soil/water pollution prevention, remediation, and monitoring. Altogether, crystallinity, hydrophilic-tunable surface chemistry, and 3D forming ability of nanocellulose (NC), in addition to biodegradability, regeneration ability, and mechanical properties of NC nanocomposite hydrogels (NCHs), lead to advancing promising soil/water nanohydrogels-based targeted fertilizers delivery vehicles, adsorbents, co-adsorbents/co-sensors, and co-adsorbents/co-photocatalysts. In these systems, NCHs introduce 3D rigid porous scaffolds for homogenous dispersing/fixing of functional groups, fertilizers, fluorescence sources, and photocatalysts. Also, they present stimuli-responsive networks for fertilizer regulation in soil, and matrixes with extra active sites enabling contaminates immobilization/degradation. This review outlines an update of the most recent potential utilization of functionalized NCHs-based soil/water adsorbents, photocatalysts, sensors, and slow/targeted fertilizers release vehicles. An in-depth discussion of surface pretreatments-modifications used to improve their performance, fabrication methods, application properties, and working mechanisms was discussed. The potential limitations and future perspectives on using NCHs in fertilizer/water management, soil/water remediation, and detection are highlighted.