Research On Recovery Of Phosphorus From Eutrophic Water By Iron-aluminum Electrocoagulatio

Phosphorus(P)is an essential element widely used in the production of fertilizers,food additives,and other chemical products.The rate of global P mining far exceeds the natural formation rate,leading to the gradual depletion of P resources,which affects global economic and social stability.To address the P crisis,P resource recycling is one effective measure.Excessive P in water bodies also causes eutrophication,affecting the health of aquatic ecosystems and leading to a series of ecological environmental problems.P recovery from eutrophic water not only achieves P resource utilization but also reduces the P level in eutrophic water.This study explores the iron(Fe)/aluminum(Al)electrocoagulation for recovering P from eutrophic water bodies,analyzes the P recovery efficiency under different voltages and algae decomposition conditions,elucidates the P recovery mechanism of Fe/Al electrocoagulation by analyzing zeta potential and molecular weight key,and evaluates the feasibility of Fe/Al electrocoagulation for recovering P from eutrophic water.The main conclusions are as follows:(1)Fe/Al electrocoagulation has excellent P recovery efficiency for both particulate and dissolved P,and the P recovery efficiency gradually increase as the voltage increases.Overall,the Al electrocoagulation is superior to Fe electrocoagulation for P recovery.At the 5V,10 V,and 15 V,the P recovery efficiency of Fe electrocoagulation is 10.0%,12.7%,and 23.5%,while that of Al electrocoagulation is 12.3%,47.7%,and 86.6%,respectively.During the electrocoagulation process,the surface zeta potential gradually increases but does not reach the isoelectric point,indicating that bridging-netting besides the electrostatic neutralization mechanism also participates in the P recovery process.Under anaerobic conditions,the Fe flocculation product undergoes changes in Fe form and is prone to release P,while the Al flocculation product has higher stability.Under strong acid or strong alkali conditions,the Fe/Al electrocoagulation product is unstable and easily releases P.(2)Algae decomposition changes the P components and organic macromolecular composition in the water,regulating the P recovery process of Fe/Al electrocoagulation.With the decomposition of algae biomass,the main P form gradually changes from particulate P and dissolved organic P to dissolved inorganic P.The proportions of particulate P and dissolved organic P decreased from 42.0% and 51.4% to 1.9% and 5.1%,respectively,while dissolved inorganic P increased from 6.4% to 91.4%.This promoted the coagulation of P with Fe/Al electrocoagulation products and accelerates the P recovery process.The P recovery rate of Al electrocoagulation increases by 2 times with prolonged algae decomposition time.Due to the small molecular weight of Fe electrocoagulation products,their P recovery is significantly regulated by the macromolecular substances produced by algae decomposition.The initial decomposition of algae biomass produces macromolecular substances(100～150k Da),which promote the P recovery of Fe electrocoagulation,but as macromolecular substances degrade into small molecular substances,the P recovery process is mainly regulated by the changes in P components.(3)The overall economic feasibility of Al electrocoagulation for algae recovery is superior to that of Fe electrocoagulation,with lower energy and material consumption,but both are regulated by voltage and algae decomposition.The Fe/Al electrocoagulation product and residual liquid both contain metal ions,which have a certain toxic effect on the environment and need to be properly treated...