Synchronous sequestration of inorganic and organic phosphorus from eutrophic surface water and sediments via recoverable La-CaO2@HNTs/SA hydrogel beads

Mounting evidence indicates that eliminating phosphate (P i ) alone is not enough to lower outbreak risks of undesirable algae, and synchronously sequestrating organic phosphorus species (OPs) dissolved in overlying water and residing in sediments cannot be ignored. However, more efforts were focused on the immobilization of P i than OPs because of insufficient understanding and analytical challenges. Herein, CaO 2 -loaded halloysite nanotubes/lanthanum-crosslinked sodium alginate (La-CaO 2 @HNTs/SA) hydrogel beads were newly developed and employed as a capping material for efficiently sequestrating P i and OPs from eutrophic water and sediment. Batch sorption results showed that the La-CaO 2 @HNTs/SA has a high uptake capacity towards P i (i.e., 44.05 mg-P/g) and Myo -inositol hexakisphosphate (IHP, a representative pollutant of OPs, 36.28 mg-P/g), and good selectivity for P in the presence of NO 3 – , Cl − , and HCO 3 – , profited by synergy of electrostatic attraction, inner-sphere complexation, surface precipitation, and partial degradation. After applying La-CaO 2 @HNTs/SA, P levels in overlying water could rapidly reduce from 0.95 to 0.01 mg-P/L within 120 min. Further thin-layer capping experiments (60 days) indicated that La-CaO 2 @HNTs/SA performed very well in immobilizing P i and OPs in overlying and pore waters and enhancing reductant-soluble P transformation (BD-P; ∼19 % to 11 %) to more stable HCl-extracted P (HCl-P; ∼33 % to 43 %) in sediments under continuous P input, with minor effect on benthic microorganisms. These findings advance the use of eco-friendly La-CaO 2 @HNTs/SA in eutrophication alleviation via simultaneous sequestration of P i and OPs.