A straw-derived carbon-based emitter for integrated irrigation and heavy metal removal

Straw-derived CBE enables irrigation and heavy metal removal. • Optimized CBE shows high flux and sufficient mechanical strength. • CBE enables safe irrigation using heavy metal–contaminated water. Open burning of agricultural straw poses a serious threat to the sustainable development of agriculture. To address this challenge, this study developed an eco-friendly carbon-based emitter (CBE) using waste maize straw that integrates irrigation and heavy metal removal, providing a feasible pathway for straw resource utilization and the safe reuse of wastewater. The CBE was fabricated from discarded maize straw through a vacuum pyrolysis-molding-sintering process. The fabricated CBEs exhibited flexural strength ranging from 2.25 to 3.72 MPa, open porosity between 52.66% and 55.41%, and hydraulic flux from 42.09 to 206.78 L m −2 h −1 . The optimal formulation (straw: biochar: clay = 2:4:1) with a sintering temperature of 900 °C achieved the best hydraulic performance. The CBE features a hierarchical lotus-root-like porous structure and shows high removal efficiencies for heavy-metal-contaminated irrigation water, with removal rates of 99.99%, 94.87%, and 83.73% for Cu(II), Cd(II), and Pb(II), respectively. The removal mechanisms are mainly attributed to chemical adsorption by surface oxygen-containing functional groups (–OH, –COOH) combined with pore-size sieving effects. Under multi-ion coexistence conditions, the effluent quality still meets the agricultural irrigation standards. Overall, this study demonstrates a multifunctional strategy for converting waste maize straw into structured CBE which integrates low-pressure irrigation with in-process heavy metal interception. These findings provide practical implications for straw valorization, safe wastewater reuse, and sustainable agricultural production. Download: Download high-res image (441KB) Download: Download full-size image