Eutrophication and ecosystem damage result from phosphate pollution. Competing ions make extracting trace phosphate under 2.0 mg/L from treated wastewater difficult. However, if the phosphate could be sustainably recovered or reused in agriculture, considerable savings in fertilizer could be made. On the other hand, agricultural waste, which is a menace, contains a significant amount of cellulose that finds interesting applications as a biodegradable material. This study synthesized a cellulose-based adsorbent with iron hydroxide nanoparticles from nano-fibrillated cellulose (CNF) from agricultural waste and carboxymethyl cellulose (CMC). It selectively removed phosphate from secondary treated wastewater. Fe(OH)3@CNF/CMC (FCC) removed 3 mg/g phosphate. The hydrogel-like material quickly absorbed 40 g/g of water and slowly released it for a week when dry. Soil burial test indicates microorganisms biodegraded 80 % of the hydrogel in 3 months. After these findings, we delivered plant nutrients using the phosphate-rich exhausted FCC adsorbent. Results showed that phosphate-rich FCC improved seed germination and plant growth. Phosphate-loaded FCC adsorbent promoted better plant growth than single super-phosphate and control samples. This study creates a circular economy-based slowrelease fertilizer from agricultural waste and secondary-treated wastewater. This approach uses the 3 R rule-recycle, recover, and reuse-to benefit society ecologically and economically.

An imbalance between available resource reserves generated by human activities and disposal measures causes a series of harmful problems related to water, soil and human health, such as those from hazardous metal ions (HMs) and their carrier materials (LMs). As excellent intermediates with adjustable spatial structures and many active sites, geopolymers can be directly used as adsorbents to remove HMs from wastewater or produced by LMs via in situ stabilization/solidification methods. This paper first reviews the common methods used to optimize the pore structures of geopolymers and then reports the common methods for optimizing LM-based geopolymers. For geopolymers-based adsorbents, the pore structure is vital in the adsorption of the target ions, and the application of functional auxiliary materials among adsorbents has been summarized. The feasibility of using geopolymers for in situ stabilization/solidification of HMs is highlighted, but instability and low mechanical strength remain significant factors hindering their development. Finally, the mechanism for bonding between HMs and geopolymers is summarized, and future developments, challenges, and possible solutions are briefly described.

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.