Manganese Oxide Catalyzed Hydrolysis of Polyphosphates

Abstract

Polyphosphate (polyP) is a group of important phosphorus (P) species that plays critical roles in the marine P cycle and potentially mediates phosphorus (P) burial in sediments. Revealing the transformation of polyP is important for understanding the P cycle in aquatic environments. This study systematically investigated the hydrolysis of polyP with different chain lengths by four representative types of manganese (Mn) oxides (α-MnO 2 , β-MnO 2 , δ-MnO 2 , and birnessite) under varied solution conditions. All four Mn oxides can rapidly hydrolyze polyP, with the hydrolysis rate in the order of α-MnO 2 > δ-MnO 2 > birnessite > β-MnO 2 . The hydrolysis rates for longer chained polyP were relatively higher than those of shorter chained ones. Results from kinetic studies and time-resolved 31 P solution nuclear magnetic resonance (NMR) spectroscopy indicated that the reaction mechanism was through a terminal-only hydrolysis pathway via one-by-one cleavage of terminal P−O−P bonds. The presence of Ca 2+ obviously enhanced both the hydrolysis rate and extent. The presence of other common metal cations (Mg 2+ , Cu 2+ , Zn 2+ , and Mn 2+ ) also showed promotion on polyP hydrolysis by δ-MnO 2 . Formation of cation-polyP ternary surface complexes is likely the dominant mechanism of cation promotion on polyP hydrolysis on Mn oxides. P K-edge X-ray absorption near edge structure (XANES) analysis indicated that solid calcium polyphosphate (Ca-polyP) granules can be hydrolyzed by α-MnO 2 and transformed into amorphous calcium phosphate (ACP) phase, with increasing ACP content as pH increased. This study highlights the rapid transformation of polyP at the mineral−water interface, and has significant implications for the alteration of P bioavailability in aquatic environments and for P burial in marine sediments.

Highly enhanced oxidation of arsenite at the surface of birnessite in the presence of pyrophosphate and the underlying reaction mechanisms

“…S4), consistent with the slow disproportionation reported for Mn(III)-PP at circum-neutral pH (Qian et al, 2019). The minor decrease of Mn(III)-PP after 12 h is possibly related to Mn oxides catalyzing PP hydrolysis (Wan et al, 2019).…”

Molecular Mechanism of Linear Polyphosphate Adsorption on Iron and Aluminum Oxides

“…Previous studies show that orthophosphate and myo -inositol hexakisphosphate adsorption on Fe and Al (oxyhydr)­oxides generally occurs through the formation of bidentate binuclear surface complexes via surface ligand exchange. ,,, Polyphosphates differ from these molecules in that they have a chain of middle P groups that can also interact with mineral surfaces in addition to the terminal phosphate groups and in that polyphosphates with different chain lengths possess different molecular elasticities. Our recent research revealed that polyphosphates can be readily hydrolyzed on Al and manganese (Mn) oxide surfaces via the gradual cleavage of the terminal P groups, suggesting the tendency of polyphosphate terminal P groups to form bidentate binuclear complexes with surface Mn/Al atoms. ,, According to QCM results, the adsorption amount (surface density of P unit) is similar for polyphosphates with different chain lengths. This suggests that polyphosphate molecules may adopt a lay-down configuration on mineral surfaces.…”

“…Our recent research revealed that polyphosphates can be readily hydrolyzed on Al and manganese (Mn) oxide surfaces via the gradual cleavage of the terminal P groups, suggesting the tendency of polyphosphate terminal P groups to form bidentate binuclear complexes with surface Mn/Al atoms. 17,20,54 According to QCM results, the adsorption amount (surface density of P unit) is similar for polyphosphates with different chain lengths. This suggests that polyphosphate molecules may adopt a lay-down configuration on mineral surfaces.…”

Dissolved organic phosphorus utilization by the marine bacterium Ruegeria pomeroyi DSS‐3 reveals chain length‐dependent polyphosphate degradation

“…Future studies should consider supporting an effort to characterize the range of inorganic polyP chain lengths in marine systems. Due to the roles of polyP in geologic P sequestration (Diaz et al ., 2008 ; Huang et al ., 2018 ; Wan et al ., 2019a , 2019b , 2021 ) and microbial nutritional physiology, a greater understanding of the molecules that make up the polyP component of particulate and dissolved marine P pools may have larger implications for marine P cycling, DOM biogeochemistry and ecosystem functioning.…”