Molecular Mechanism of Linear Polyphosphate Adsorption on Iron and Aluminum Oxides

Abstract

Polyphosphate is a polymeric P species with environmental and industrial significance. Understanding their interaction with natural minerals is fundamental for predicting their transport and fate in the environment. This study investigates the molecular mechanism of interaction between linear polyphosphates with varied chain length (15P, 60P, and 130P) and Fe/Al oxides using quartz crystal microbalance with dissipation (QCM-D), 31 P solid-state nuclear magnetic resonance (NMR) spectroscopy, and attenuated total reflection−Fourier transformed infrared (ATR−FTIR) spectroscopy. QCM-D results show that all three polyphosphates irreversibly adsorb on Fe/Al oxides at pH 4−10 with similar massbased adsorption amounts despite the large difference in chain lengths. ATR−FTIR and NMR spectroscopy results suggest that terminal phosphate groups of the polyphosphate molecules may form bidentate binuclear surface complexes, and a fraction of middle phosphate groups may form monodentate mononuclear surface complexes on Fe/Al oxides. The interaction modes persist for both minerals and all tested pH conditions. A combination of these complementary techniques helps gain a mechanistic understanding of polyphosphate interaction with Fe/Al oxides, and the results fill a knowledge gap on polyphosphate cycling in natural environments.

Impacts of orthophosphate-polyphosphate blends on the dissolution and transformation of lead (II) carbonate

“…Following surface adsorption, IR bands experience either shifting or changes in intensity and are discussed below. The peak assignments for the ATR-FTIR spectra of adsorbed phosphates on lead carbonate are extrapolated based on the data of condensed phosphates adsorption on titania, serpentine, and metal (hydr)oxides [27][28][29][30][31] . A detailed description of the ATR-FTIR analysis can be found in the supplemental material (Sections S1 and S2).…”

“…This is seen via the vibration bands at 1108-1115 29 and 1205 cm -1 27 respectively (Figure 7). However, IR spectra suggest that not all phosphate groups were bound to the lead surface, as indicated by the presence of unbound P2O7 (967-975 cm -1 ) 31 possibly allowing for further lead complexation.…”

Release and mineral formation of lead corrosion products with orthophosphate-polyphosphates

“…Following surface adsorption, IR bands experience either shifting or changes in intensity and are discussed below. The peak assignments for the ATR-FTIR spectra of adsorbed phosphates on lead carbonate are extrapolated based on the data of condensed phosphates adsorption on titania, serpentine, and metal (hydr)oxides [27][28][29][30][31] . Lower lead release in the presence of cyclophosphates (Trimetap and HexametaP) compared to linear polyphosphate (TripolyP) can likely be explained by fundamental chemistry: First, TripolyP (5 oxygens) has more available reactive oxygen sites than TrimetaP (3 oxygens) 32 (Figure 10).…”

“…This is seen via the vibration bands at 1108-1115 29 and 1205 cm -1 27 respectively (Figure 7). However, not all phosphate groups were bound to the lead surface as indicated by the presence of unbound P2O7 (967-975 cm -1 ) 31 possibly allowing for further lead complexation.…”

Construction of a Self-Assembled Polyelectrolyte/Graphene Oxide Multilayer Film and Its Interaction with Metal Ions

“…QCM is a technology that can be employed to monitor surface trace mass changes in the range of nanograms per cm 2 . It is widely used to study LbL self-assembly, biomolecular interactions, polymer chain conformations, , as well as adsorption, − degradation, antifouling, − and sensing , processes. The surface of the typically gold-coated QCM sensor can be modified easily and used as a substrate to construct a multilayer film using LbL self-assembly technology.…”