Semillas de carbón de hueso de doble interfaz diseñadas para la cristalización de fosfato de calcio

Conventional phosphate removal technologies for secondary effluent rely on external chemical agents, posing sustainability challenges. Crystallizing phosphate with the Ca²⁺ naturally present in wastewater offers a promising solution. However, nucleation requires the formation of new crystal-liquid interfaces, and the associated interfacial energy creates a high nucleation energy barrier (∆G*) that hinders this process. Here, we developed bone-derived char seeds, which decreased the effective interfacial energy for hydroxyapatite nucleation by 71.1 %, lowering the ∆G* by a factor of 41.5. This reduction achieved nucleation rates in near-neutral secondary effluent comparable to those requiring pH > 11 in conventional processes. Using only endogenous Ca²⁺ in wastewater, a bone char fixed-bed column treated over 20,000 bed volumes of actual secondary effluent while achieving a phosphate retention capacity exceeding 48.8 g P/kg of bone char-the highest reported for phosphate capture materials. This exceptional performance derives from bone char's unique structure: an inorganic carbonate apatite skeleton providing atomically matched templates for crystal nucleation, and an organic methyl-rich surface layer modulating hydrophobicity. These features respectively optimized the interfacial energies of the bone char-hydroxyapatite and bone char-liquid interfaces involved in hydroxyapatite nucleation. This dual-interface engineering effectively lowered the ∆G* and accelerated hydroxyapatite crystallization. Global Ca²⁺ distribution mapping shows that the technology has immense potential for application in approximately 74.3 % of global regions. This study charts a new trajectory for deep phosphate removal, promoting the formation of a more sustainable wastewater treatment framework.