Rare earth-derived conductive zeolite electrodes empower NH4+ recovery from mining wastewater via FCDI and their application as ammonia release fertilizer

Rare earth mining and smelting generate substantial tailings and ammonia-rich wastewater, which present significant environmental hazards and hinder sustainable industrial growth. To mitigate these challenges, an innovative approach has been developed, utilizing conductive zeolites derived from rare earth tailings (RET) as flow electrodes in Flow-Electrode Capacitive Deionization (FCDI). This method offers dual benefits: recycling tailings and efficiently removing NH 4 + from wastewater. The optimized FCDI system, operating at 1.2 V with a flow rate of 19.2 mL/min and pH 4, demonstrates exceptional performance, achieving a 97.22 % NH 4 + removal efficiency in simulated wastewater and an average adsorption capacity of 195.45 mg/g. These results outperform conventional electrode materials such as activated carbon and mesoporous carbon derived from polyaniline. Mechanistic investigations show that the distinctive porous structure of RET-derived conductive zeolite Al 0.3 enhances ion exchange and electro-adsorption, promoting effective NH 4 + migration and enrichment. Pilot tests on real mining wastewater further confirm the practical viability of this technology, achieving 90.49 % NH 4 + removal and retaining 79.52 % of the recovered ammonia within the conductive zeolite. Notably, the ammonia-loaded conductive zeolite exhibits potential as a slow-release fertilizer. Plant trials indicate that applying only 1 % of this conductive zeolite fertilizer results in nearly threefold corn plant height growth and over twice the root length compared to controls, with heavy metal content well below national fertilizer standards (GB 38,400–2019). This technology marks a paradigm shift in the “waste-to-resource” cycle, effectively reducing tailings pollution and ammonia contamination while converting waste into valuable agricultural resources. By merging environmental remediation with sustainable agriculture, it offers a scalable solution that promotes circular economy principles in the mining industry, unlocking vast opportunities for wastewater treatment, tailings utilization, and eco-friendly fertilizer production.