Polyphosphate Adsorption and Hydrolysis on Aluminum Oxides

Abstract

The geochemical behaviors of phosphate-containing species at mineral−water interfaces are of fundamental importance for controlling phosphorus mobility, fate, and bioavailability. This study investigates the sorption and hydrolysis of polyphosphate (a group of important long-chained phosphate molecules) on aluminum oxides in the presence of divalent metal cations (Ca 2+ , Cu 2+ , Mg 2+ , Mn 2+ , and Zn 2+ ) at pH 6−8. γ-Al 2 O 3 with three particle sizes (5, 35, and 70 nm) was used as an analogue of natural aluminum oxides to investigate the particle size effect. All metal cations enhanced polyphosphate hydrolysis at different levels, with Ca 2+ showing the most significant enhancement, and the difference in the enhancement might be due to the intrinsic affinity of metal cations to polyphosphate. In the presence of Ca 2+ , the hydrolysis rate decreased with increasing mineral particle size. Solid-state 31 P nuclear magnetic resonance spectroscopy (NMR) revealed the main surface P species to be amorphous calcium phosphate precipitates, phosphate groups in polyphosphate that formed direct bonds with the mineral surface as inner-sphere complexes, and phosphate groups in polyphosphate that were not directly bonded to the mineral surfaces. Our results reveal the critical roles of mineral−water interface processes and divalent metal cations on controlling polyphosphate speciation and transformation and phosphorus cycling.

Manganese Oxide Catalyzed Hydrolysis of Polyphosphates

“…Using pair distribution function (PDF) analysis of X-ray total scattering, the PDF spectra of phosphate adsorbed on birnessite indicated that the peaks at ∼1.54 Å can be ascribed to the P–O pairs in the PO 4 tetrahedron and the peaks at ∼3.14 Å are most likely due to P–Mn pairs, also suggesting the formation of inner-sphere complexes on birnessite. Our recent solid state 31 P NMR results showed that, upon polyphosphate adsorption at the surface of γ-Al 2 O 3 , the main surface P species are phosphate groups in polyphosphate that formed direct bonds with the mineral surface as inner-sphere complexes (likely as bidentate binuclear complexes) and phosphate groups in polyphosphate that were not directly bonded to the mineral surfaces . Due to similarity in P K-edge XANES spectra between α-MnO 2 adsorbed orthophosphate (α-MnO 2 –orthoP) (Figure a) and Fe/Al oxide-adsorbed orthophosphate samples, , surface inner-sphere phosphate complexes are possible to form upon phosphate adsorption onto Mn oxides.…”

“…20 Our recent study showed that polyP can be hydrolyzed at the surface of γ-Al 2 O 3 (an analogue of natural Al oxides), which was affected by mineral particle size and solution chemistry such as pH and the presence of metal cations. 21 Amorphous MnO 2 showed high reactivity toward P 3 hydrolysis (i.e., complete degradation into three orthoP molecules within 2 h at pH 4.0), and the hydrolysis rate in natural lake water was further promoted due to the presence of Ca 2+ and Mg 2+ . 22 Thus, mineral catalyzed hydrolysis is expected to play an important role in polyP transformation at environmental interfaces, yet related investigations are few.…”

“…A recent study showed that triphosphate (P 3 ) adsorbed on goethite can be fully hydrolyzed at pH 4.5 and slightly hydrolyzed at pH 6.5 and 8.5 within 3 months . Our recent study showed that polyP can be hydrolyzed at the surface of γ-Al 2 O 3 (an analogue of natural Al oxides), which was affected by mineral particle size and solution chemistry such as pH and the presence of metal cations . Amorphous MnO 2 showed high reactivity toward P 3 hydrolysis (i.e., complete degradation into three orthoP molecules within 2 h at pH 4.0), and the hydrolysis rate in natural lake water was further promoted due to the presence of Ca 2+ and Mg 2+ .…”

Critical Review of Polyphosphate and Polyphosphate Accumulating Organisms for Agricultural Water Quality Management

“…We also relied on results from the Web of Science metaanalysis and research article synthesis when summarizing knowledge gaps related to microbial P forms and cycling mechanisms in agricultural water quality management research. We will not synthesize research on abiotic and biotic Fe and P interactions because these subjects have been thoroughly reviewed elsewhere (Chacon et al, 2006;Gerke, 2010;Lin et al, 2018;Martins et al, 2011;River & Richardson, 2018;Safarzadeh-Amiri et al, 2017;Saia et al, 2017;Wan et al, 2019;Wilfert et al, 2015;Wu et al, 2019) All data and analysis scripts associated with this publication are available on GitHub at <will fill in upon publication> and Zenodo (DOI: <will fill in upon publication>).…”

Investigations of mechanism of Ca2+ adsorption on silica and alumina based on Ca-ISE monitoring, potentiometric titration, electrokinetic measurements and surface complexation modeling

“…The particles of both oxides remaining in water are in a continuous contact with Ca 2+ in the soil environment. Remembering that assemblages of these oxides from the industry sector are still released into the natural system (Kasprzyk-Hordern 2004;Lee et al 2010), research on their behavior towards calcium ions was carried out over the past decades (Roach and Himmelblau 1961;Huang and Stumm 1973;Meng and Letterman 1993;Brigante and Avena 2016;Ragab et al 2017;Wan et al 2019). For example, Tadros and Lyklema (1969) investigated calcium adsorption on silica using potentiometric titrations and the Eppendorf flame photometer.…”