Coupling phosphonate oxidation and phosphate sequestration via Cu-La dual sites in La-based layered carbonate...

Phosphonates are refractory pollutants that contribute to eutrophication through their transformation into bioavailable phosphate. Although Cu-based advanced oxidation processes (AOPs) can degrade phosphonates via high-valent Cu(III) species, the released phosphate strongly coordinates with Cu sites, causing catalyst poisoning and rapid performance decay. Herein, a Cu-containing La-based layered carbonate hydroxide (CuLa-LCH) is designed to couple phosphonate oxidation with in situ phosphate sequestration. The CuLa-LCH/peroxymonosulfate (PMS) system achieves complete degradation of aminotris(methylenephosphonic acid) within 30 min, while simultaneously enabling efficient phosphate sequestration via La sites. Mechanistic and theoretical results reveal that Cu sites activate PMS to form Cu(III) intermediates that initiate C-N bond cleavage and subsequent oxidation toward C-P bond cleavage and phosphate release, whereas spatially coupled La-containing sites preferentially sequester the liberated phosphate, preventing Cu deactivation. This dual-site functionality sustains catalytic activity by continuously removing phosphate from Cu centers. The CuLa-LCH/PMS system also shows good reusability, water-matrix tolerance and operational stability, while preliminary techno-economic analysis suggests its potential practical feasibility. This study provides a viable strategy for coupling phosphonate oxidation with phosphate sequestration for sustainable water treatment.