Lanthanum-Based Passivators for Aquatic Phosphorus Control: Bridging the Gap from Material Design to Field...

Effective control of internal phosphorus (P) loading is critical for mitigating eutrophication in aquatic ecosystems, yet it remains a persistent challenge. In situ chemical passivation using lanthanum-based passivators (LBPs) is a prominent strategy with laboratory studies demonstrating high P sequestration efficiency through inner-sphere complexation and LaPO4 precipitation. However, translating laboratory findings to reliable field-scale applications remains elusive. Moving beyond conventional summaries of P adsorption performance, this Review provides a critical, application-focused analysis of the key barriers hindering real-world LBP deployment. After outlining the multiscale P removal mechanisms by LBPs, three major, yet understudied, challenges are addressed: (1) efficacy at trace P concentrations typical of natural waters; (2) susceptibility to interference from common aquatic constituents (e.g., anions and dissolved organic matter); and (3) long-term stability and potential ecological impacts. We propose a paradigm shift in LBP development to overcome the identified barriers, including standardized testing in complex matrices, novel material engineering for enhanced selectivity and stability, and long-term monitoring. This review aims to refocus future research toward strategies that will ensure the reliable, sustainable field-scale performance of LBPs.