Lanthanum Materials Enable Catalytic Hydrolysis of Phosphate Esters: Implications for Water Treatment and Eutrophication Control

Abstract

In the context of comprehensive phosphorus (P) management, in addition to orthophosphate, the environmental fate and regulation of potentially harmful phosphate esters are an emerging concern. However, there is still a discernible knowledge gap on the interaction between phosphate esters and Lanthanum (La) based materials, a widely applicable phosphate scavenger, under environmentally relevant conditions. In this study, we observed that La(OH)3 and La2O3 enable catalytic hydrolysis of a model phosphate ester compound, para-nitrophenyl phosphate (p-NPP) (20–70 times faster than self-hydrolysis), in environmentally relevant scenarios (wastewater and natural waters). 31P solid-state NMR reveals an initial surface adsorption via a Lewis acid–base reaction between the surface La active sites and the phosphate groups, followed by the cleavage of the ester bond and the progressive transformation of phosphate further bound into crystalline LaPO4. Density functional theory computation suggested the electron enrichment on the P atom after p-NPP adsorption, resulting in the reduction of activation energy. Also, La(OH)3 is extendable to catalytic hydrolysis of a suite of phosphate mono-, di-, and triesters. This study bridges the knowledge gap on the transformation of phosphate esters in the presence of lanthanum-based materials during water pollution control.