Phosphorus Recovery from Eutrophic Lake Water Using Al/Fe Micro-Electrolysis

Abstract

Phosphorus (P) is a critical and nonrenewable resource. P crisis threatens future global food security, while P-induced eutrophication is damaging aquatic ecosystems. In eutrophic lakes, P is often heavily concentrated in algae-accumulated zones, creating “P reserves” for reuse. In this study, P was harvested from eutrophic lake water using Al/Fe micro-electrolysis and the stability of the harvested P was tested through anoxia incubation. The results showed that, compared with Fe micro-electrolysis, Al micro-electrolysis was more effective at co-harvesting dissolved and particulate P, and the yields were stable under anoxia conditions, making them suitable as slow-release P fertilizers. At 15 V, the P harvesting efficiency of Al micro-electrolysis was 2.68 times higher than that of Fe micro-electrolysis. This could be attributed to the powerful netting–bridging of amorphous Al hydroxides, which favor floatation separation and thereby P harvesting. Under anoxia, the transformation of Fe species caused P release from Fe micro-electrolysis yields, potentially enhancing P loss through leaching if the yields are used as soil P fertilizers. This study provides a promising strategy for P resource recycling from eutrophic lakes, which may be beneficial to the restoration of lake ecosystems and mitigation of the P crisis.