Phosphate recovery from wastewater by cellulose-based adsorbent derived from agricultural waste and its reuse as a slow-release fertilizer

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 slow-release 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. • A biodegradable phosphate adsorbent (FCC) was made from rice straw. • Phosphate uptake capacity of 3 mg PO 4 3 − − P /g from contaminated water was achieved. • The adsorbent had a 40 g/g water absorption capacity and functioned as a hydrogel. • Phosphate-loaded adsorbent as a slow-release fertilizer boosted plant growth.