Zinc Phytate Research Articles

Infusing phytate-based biomass flame retardants into the cellulose lumens of Chinese fir wood attains superior flame retardant efficacy

To be suitable for certain construction and furniture applications, wood must be treated with a flame retardant and impregnating flame retardants into the cellulose lumens of wood is an effective flame retardant method. Phytic acid, the main storage form of phosphorus in various plant tissues, is an inexpensive, and non-toxic biomaterial that shows potential applications as an environmentally friendly bio-based flame retardant. In this study, phytic acid and zinc phytate were used to impregnate delignified wood under vacuum and pressure, which greatly enhanced the flame retardancy and smoke suppression properties of Chinese fir, while still maintaining its original texture. Phytic acid and zinc phytate were hydrogen-bonded to cellulose in wood. Phytic acid and zinc phytate were hydrogen-bonded to cellulose in wood. The results showed that the total heat release (THR) of Chinese fir treated with zinc phytate decreased from 55.66 MJ/m2 to 5.90 MJ/m2, and a compact carbonized protective layer was quickly formed on the surface of Chinese fir after ignition. Thermogravimetric analysis (TGA) showed that the char yield of Chinese fir treated by the flame retardant was 177.6 % higher than that of untreated wood. This study provides an efficient, sustainable, and economical method to prepare Chinese fir with excellent flame retardancy and thermal insulation performance.

Aldehyde-free and bio-based durable coatings for cellulose fabrics with high flame retardancy, antibacteria and well wearing performance

The bio-based coatings of cellulose fabrics (cotton) had attracted increasing attention for multifunction and sustainability but suffered from poor durability and low efficiency. Here, the aldehyde-free and durable coatings for cotton fabrics (CPZ@CF) with satisfactory flame retardancy, antibacteria as well as wearing performance were prepared through the interfacial coordination effect where the well-organized zinc phytate complex were in situ grew on the pre-treated surface of cotton fabrics with chitosan (CS) and Zn2+. The CZP@CF exhibited excellent antibacterial activity for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with 99.99 % antibacterial rates benefiting from the synergistic effect between Zn2+ and CS. Meanwhile, even the CPZ coatings loading was only 1.5 wt%, the fire safety of CZP@CF remarkably enhanced owing to the excellent synergistic catalytic charring and free radical capture. More importantly, the antibacterial rates of CZP@CF for S. aureus and E. coli still reached 99.99 % and 91.67 % after 50 washing cycles. Additionally, this treatment method did not deteriorate the fabrics properties, including mechanical and breathability as well as wearing performance, which provided the approach to fabricate the flame retardant and antibacterial textiles with well durability and wearing performance.

In-situ polymerized zinc phytate chelated Si-C-P geopolymer hybrid coating constructed by incorporating chitosan oligosaccharide and DOPO for flame-retardant plywood

Zinc phytate (ZnPA) chelated geopolymer and in-situ polymerized chitosan oligosaccharide (COS)/DOPO explored a challenging and exciting flame retardant organic–inorganic hybrid coating via sol–gel method to find halogenated high-efficiency bio-flame retardants are widely used as decorative materials for flame-retardant plywood. Herein, the results show that the appropriated ZnPA (0.5 wt%) enhances the flame retardancy of the geopolymer coating, the peak of heat release rate (p-HRR) decreases from 136.09 to 99.39 kW·m−2, the fire growth index (FGI) dropped from 0.47 to 0.28 kW m−2 s−1, the fire performance index (FPI) climbs from 1.00 to 2.52 s·m2·kW−1, and the flame retardancy index (FRI) climbs from 1.00 to 2.52. Meanwhile, through the microstructural analysis of the residual layer, a strong, compact and non-flammable resilient residues is obtained after combustion; Moreover, the pyrolysis kinetics show that the Z.-L.-T. three-dimensional diffusion reaction model governs the pyrolysis of hybrid coatings. Appropriated ZnPA increases the pyrolysis Eα from 138.95 kJ·mol−1 to 160.75 kJ·mol−1 at 741 ∼ 890 ℃ and improves the thermal stability of the coating. The Si-C-P structure improves the formaldehyde adsorption rate by 46.5%. Therefore, this study, by preparing COS-pretreated ZnPA and DOPO to co-construct alkali-excited cenospheres-based Si-C-P coating, reveals the sustainable development of modified bio-based geopolymer flame-retardant coatings in the construction industry.

In-situ grown SiC whiskers enhance flame retardancy of alkali-activated gold tailings geopolymer composite coatings by incorporating expanded graphite

Herein, a gold tailings-based flame-retardant coating blended with zinc phytate (ZnPA)/β-cyclodextrin (β-CD)/expanded graphite (EG) is prepared by the sol-gel method. The coating is used in flame-retardant plywood. It explores the efficient recycling of industrial solid waste. Firstly, the microstructure analysis reveals that EG forms in-situ SiC ceramic whiskers in the solid solution of orthosilicate and pyrophosphate. Meanwhile, the synergistic flame-retardant effect is explained through morphological characterization and pyrolysis kinetics analysis. Adding 2 wt% EG significantly improves the flame retardancy of the coating, as evidenced by a decrease in the peak of heat release rate (p-HRR) and an increase in the fire performance index (FPI). The p-HRR decreases from 104.67 kW·m−2 to 75.08 kW·m−2, while the FPI increases from 2.11 s·m2·kW−1 to 3.51 s·m2·kW−1. Moreover, the pyrolysis kinetics is modeled using the Zhuralev-Lesokin-Tempelman (Z.-L.-T.) three-dimensional diffusion-reaction model, revealing an increase in Eα from 74.90 to 85.82 kJ·mol−1 in the temperature range of 674–890 °C. The coating exhibits 60% formaldehyde adsorption performance. Therefore, this study proposes a new in-situ whisker synergistic flame-retardant system and sheds light on the potential applications of new geopolymers in the sustainable development of the green flame-retardant field.

Constructing porous ZnFC-PA/PSF composite spheres for highly efficient Cs+ removal

Radioisotope leaking from nuclear waste has become an intractable problem due to its gamma radiation and strong water solubility. In this work, a novel porous ZnFC-PA/PSF composite sphere was fabricated by immobilization of ferrocyanides modified zinc phytate into polysulfone (PSF) substrate for the treatment of Cs-contaminated water. The maximum adsorption capacity of ZnFC-PA/PSF was 305.38 mg/g, and the removal efficiency of Cs+ was reached 94.27% within 2 hr. The ZnFC-PA/PSF presented favorable stability with negligible dissolution loss of Zn2+ and Fe2+ (< 2%). The ZnFC-PA/PSF achieved high-selectivity towards Cs+ (Kd = 2.24×104 mL/g) even in actual geothermal water. The adsorption mechanism was inferred to be the ion-exchange between Cs+ and K+. What's more, ZnFC-PA/PSF worked well in the fixed-bed adsorption (E = 91.92%), indicating the application potential for the hazardous Cs+ removal from wastewater.

Mechanisms of ZnO Nanoparticles Enhancing Phototransformation of Biologically Derived Organic Phosphorus in Aquatic Environments.

Zinc oxide nanoparticles (ZnO NPs), as the highly efficient photocatalysts, could enhance the transformation of biogenic organic phosphorus (OP) to orthophosphate (PO43-) by photodegradation, accelerating eutrophication. Conversely, orthophosphate can also transform ZnO NPs and thus potentially alter their catalytic and chemical properties. Here, we investigated the transformation mechanisms of three biogenic OP compounds and ZnO NPs under ultraviolet light (UV) illumination: inositol phosphates (IHPs), nucleic acids (DNA), and aminoethylphosphonic acid (AEP). The physicochemical characteristics of the resulting products were systematically characterized. Results show that ZnO NPs accelerated the transformation of IHPs, DNA, and AEP to inorganic phosphorus with the direct photolysis efficiencies of 98.14, 87.68, and 51.76%, respectively. The main component of the precipitates remained ZnO NPs, and Zn3(PO4)2 was identified. Zinc phytate was determined in the ZnO NP-IHP system. 31P NMR and FTIR further confirmed that the aquatic phase contained orthophosphate. Photoproduced hydroxyl (·OH) and superoxide (·O2-) were proved to play a dominant role in the OP photomineralization. Furthermore, ZnO NPs significantly enhanced the intensity of ·OH and ·O2- compared to the OP and Zn2+ solution alone. This work explored the light-induced mineralization processes of OP with ZnO NPs indicating that nanophotocatalysts may play a positive role in transformation of OP species in aquatic environments to further contribute to eutrophication.

Transformation of zinc oxide nanoparticles in the presence of aluminum oxide with pre-sorbed phosphorus ligands

Naturally occurring oxides could react with zinc oxide (ZnO) nanoparticles (NPs) and then change its transformation and toxicity to ecological receptors. The reaction may be affected by a variety of environmental factors, yet the relevant processes and mechanisms are limitedly investigated. Natural prevalent ligands, as an important factor, can sorb on natural oxide minerals and change its surface property, finally affecting ZnO NP transformation. This study investigated the interactions of ZnO NPs with phosphorus ligands (i.e., phytate and orthophosphate) pre-sorbed γ-alumina (γ-Al2O3) via batch experiments and multi-technique analyses. A limited amount of aqueous Zn2+ is observed when the concentration of ZnO NPs is relatively low (<64.8 mg L−1) in the presence of phytate pre-sorbed γ-Al2O3. Solid Zn(II) species includes binary/ternary surface Zn(II) complexes on γ-Al2O3 with minor amounts of zinc phytate precipitates. As the concentration of ZnO NPs increases, surface Zn(II) complexes gradually transform into zinc phytate and Zn−Al layered double hydroxide (Zn−Al LDH) precipitates. The quantitative analysis indicates that, as the concentration of ZnO NPs increases from 32.4 to 388.8 mg L−1, the proportion of Zn(II) species as binary/ternary surface complexes decreases from 81.9 to 30.2%; and the proportion as zinc phytate and Zn−Al LDH increases from 17.9 to 27.6% and 0 to 43.8%, respectively. The pre-sorption of orthophosphate can also inhibit ZnO NP transformation into Zn−Al LDH precipitates on γ-Al2O3. This study suggests that natural ligands pre-existed on natural oxide minerals could greatly influence the solubility, stability, transformation, and fate of easily dissoluble metal oxides (e.g., ZnO) in the environments.

A highly efficient metal ferrocyanide adsorbent based on zinc phytate for cesium removal

Human health and sustainable development of nuclear energy pose new challenges for cesium removal. Herein, exploiting a novel metal ferrocyanides (MFCs) adsorbent is highly desirable for efficiently eliminate Cs+ from contaminated water. Based on zinc phytate (Zn-PA), the newly synthesized hybrid material of ZnFC-PA exhibits top-class adsorption capacity (qm = 559.76 mg/g) and excellent stability in a wide range of pH. The rapid adsorption kinetics and superior selectivity in the existence of numerous competing ions confirm the outstanding performance for cesium separation. Furthermore, the adsorption performance is roughly static after several cycles, and the distribution coefficient Kd still remains at a high level (3.3 × 104 mL/g) even in practical geothermal water. The excellent adsorption performance and reusability make it a promising Cs+ adsorbent to remediate the environment.

Self-templating synthesis of porous carbon with phytate salts for supercapacitor application

Zinc phytate was synthesized as a self-sacrificing template to prepare porous carbon for supercapacitor with the starting materials of phytate acid and zinc acetate. The obtained carbon material possesses a hierarchically porous structure with pore size distributed at 1 and 10 nm, contributing to a specific surface area of 1125 m2 g−1 according to the nitrogen sorption analysis. Moreover, the porous structure can be effectively adjusted by introducing KOH during the preparation procedure of phytate salt, resulting in a significant increase of micropore content. The absence of KOH signal in the X-ray diffraction pattern of carbon precursor and uniform K, Zn distribution in carbon precursor indicate the formation dual-metal phytates and contributing to the micropore for the prepared porous carbon by in-situ K activation instead of KOH activation. With developed microporosity, the specific capacitance can be promoted up to 294 from 195 F g−1 in KOH electrolyte and 247 from 187 F g−1 in H2SO4 electrolyte. Our findings provide a guide to prepare porous carbon with tunable porosity through a facile self-templating method.

ZnPA@ZIF-8 nanoparticles: Synthesis, sustained release properties and anticorrosion performance

Zeolitic imidazolate framework-8 (ZIF-8) has attracted extensive attention in many different fields because of its advantages such as small size, ordered channels, adjustable structure, large specific surface area and simple synthesis. In this paper, zinc phytate (ZnPA) as single metal source and 2-methylimidazole (2-MI) as ligand were creatively used to synthesize ZnPA@ZIF-8 nanoparticles by a one-step process. ZnPA and 2-MI are both green and environmentally friendly corrosion inhibitors. In addition, Zn2+ in ZnPA can coordinate with 2-MI to produce ZIF-8, leading to anchor and encapsulate of ZnPA on ZIF-8. Thus, the design of ZnPA@ZIF-8 nanoparticles is of significance for anticorrosion of metal. Furthermore, the introduce of ZnPA@ZIF-8 nanoparticles into waterborne polyacrylate (WPA) was reported for the first time and an in depth study of anticorrosion performance and mechanism of WPA/ZnPA@ZIF-8 composite coating were conducted. The results showed that ZnPA@ZIF-8 nanoparticles were triumphantly fabricated. Moreover, ZnPA@ZIF-8 nanoparticles could be dissolved and successfully released the ZnPA under the stimulation of salt solution. WPA/ZnPA@ZIF-8 composite coating exhibited prominent corrosion resistance, compared with WPA coating, WPA/ZnPA composite coating and WPA/ZIF-8 composite coating. The impedance modulus at 10−2 Hz of WPA/ZnPA@ZIF-8 composite coating was 106.05 Ω∙cm2, which was increased by 2.97 orders of magnitude than pure WPA coating. The above results demonstrated the application potential of ZnPA@ZIF-8 nanoparticles in metal anticorrosion.

In-situ chemical conversion film for stabilizing zinc metal anodes

Zinc metal anodes face several challenges, including the uncontrolled formation of dendrites, hydrogen evolution, and corrosion, which seriously hinder their application in practice. To address the above problems such as dendrite formation and corrosion, we present a simple and applicable immersion method that enables in situ formation of a zinc phytate (PAZ) coating on the surface of commercial Zn flakes via a substitution reaction. This protective coating mitigates corrosion of zinc flakes by the electrolyte, reduces the interfacial impedance, and accelerates the migration kinetics of zinc ions. Besides, this method can preferentially expose the (002) crystal plane with strong atomic bonding, which not only improves the corrosion resistance of the zinc flake, but can also guide the parallel deposition of zinc ions along the (002) crystal plane and reduce the formation of dendrites. Benefiting from the above advantages, the PAZ@Zn||Cu half-cell has shown over 900 cycles with average coulombic efficiency (CE) of 99.81% at 4 mA cm−2. Besides, the PAZ@Zn||PAZ@Zn symmetric cell operate stably for >1000 h at 5 mA cm−2 and >340 h at 10 mA cm−2. Furthermore, we demonstrated that this in situ chemical treatment enables the formation of a robust, well-bound protective coating. This method provides insights for advancing the commercialization of zinc anodes and other metal anodes.

Dendrite‐Free Zinc Deposition Induced by Zinc‐Phytate Coating for Long‐Life Aqueous Zinc Batteries

AbstractRechargeable aqueous zinc batteries (AZBs) have been recognized as attractive energy storage devices because of their intrinsic superiorities, e. g., high safety, low material cost and environmental benignity. However, challenges such as dendrite formation on the surface of zinc (Zn) anode, poor reversibility of Zn plating/stripping and short circuit of the cell, having detrimental impact on cycle life and safety, hinder their further development. Herein, we design an artificial solid electrolyte interphase (SEI) layer for the Zn anode by coating it with a zinc‐phytate (ZP) layer via a facile acid‐etching approach. The symmetric cell with a modified Zn electrode exhibits excellent cycling stability and a low polarization voltage, since the ZP layer can guide uniform Zn deposition under the layer without dendrite formation and maintain a smooth interface between separator and electrode, which suggests Zn2+ transport properties of the coating layer. Moreover, comparing full cells, one employing a bare Zn anode (MnO2/carbon nanofibers (CNFs)||Zn), with the other with a modified Zn anode (MnO2/CNFs||ZP−Zn), the MnO2/CNFs||ZP−Zn cell delivers much better long‐term cycling stability (capacity retention after 1000 cycles of 130 mAh g−1 vs. 50 mAh g−1 at a specific current of 0.5 A g−1). The coating via acid etching method offers a new powerful technique for further development of practical AZBs.

Rigid polyurethane foam composites based on bivalent metal phytate: thermal stability, flame retardancy, and fire toxicity

ABSTRACT As the main form of phosphorus in plant seeds, phytic acid has potential value in flame retardant field. In this study, a series of bivalent metal phytate (PA-M) flame retardants were prepared using phytic acid and divalent metal salts as raw materials. FTIR, SEM-EDS, XRD, and TG tests confirmed that copper phytate (PA-Cu), zinc phytate (PA-Zn), cobalt phytate (PA-Co) and nickel phytate (PA-Ni) were successfully synthesized. Furthermore, flame retardant rigid polyurethane foam (RPUF/PA-M) composites were prepared by one-step water-blown technology using PA-M as flame retardant. TG test results showed that RPUF/PA-Cu30 had the highest char residue at 700 C, which was 26.2 wt%, significantly higher than 12.4 wt% of RPUF. Cone calorimetry, smoke density test, and TG-FTIR analysis confirmed that RPUF/PA-Co30 composite exhibited excellent smoke suppression and toxicity reduction performance when 30 phr PA-Co was added. Compared with RPUF, the THR, TSR, and SDR of RPUF/PA-Co30 were decreased by 13.9%, 27.3% and 43.9%, respectively, and the release of toxic gases (isocyanate compounds, aromatic compounds, CO and HCN) and combustible gases (hydrocarbons and esters) were significantly reduced. The analysis of char residues of RPUF/PA-M composites suggested that PA-M could promote the formation of dense carbon layer with high graphitization degree and improved the fire resistance of composites. This work provided a new way for fabricating fire safety RPUF composites.

Effects of Myo-inositol Hexakisphosphate on Zn(II) Sorption on γ-Alumina: A Mechanistic Study

Myo-inositol hexakisphosphate (IHP), a most common organic phosphorus in many soils, can strongly interact with aluminum (Al) oxides and influence the fate of metal ions. In this study, the effects of presorbed IHP on γ-Al2O3 (γ-alumina) surfaces on Zn(II) sorption were investigated in batch experiments using a combination of powder X-ray diffraction (XRD), in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), 31P and 27Al solid-state nuclear magnetic resonance spectroscopies (NMR), and Zn K-edge extended X-ray absorption fine structure spectroscopy (EXAFS). The results of the batch experiments show that the presorption of IHP increases the sorption density of Zn(II) on γ-Al2O3 surfaces. The XRD data indicate that the presorption of IHP hinders the formation of Zn–Al layered double hydroxide (LDH) precipitates by raising the critical concentration of Zn(II) required to precipitate the complex. Solid-state NMR spectra further suggest that the chemical environment and speciation of IHP presorbed change, i.e., from inner-sphere surface complexes to ternary surface complexes and to zinc phytate precipitates (Zn-IHP) with the increase in Zn(II) concentration or pH. Linear combination fittings (LCFs) of the EXAFS spectra indicate that the proportion of Zn(II) in binary or ternary surface complexes decreases and that in Zn–Al LDH increases with increasing concentration of Zn(II) at pH 7. Furthermore, the order at which IHP and Zn are added in the reaction can influence the cosorption mechanism. At pH 7, more binary or ternary Zn surface complexes and Zn-IHP form, and less Zn–Al LDH precipitates form if Zn is added first. These results demonstrate that both the timing and concentration of IHP and divalent metals have sweeping influences on their solubility and speciation and these intricacies need to be taken into consideration toward predicting their fates in the environment.

Application of metallic phytates to poly(vinyl chloride) as efficient biobased phosphorous flame retardants

ABSTRACTSimple, direct precipitation was used to synthesize green, renewable, biobased flame retardants. Copper phytate (Cu–Phyt), zinc phytate, aluminum phytate, and tin phytate (Sn–Phyt) were synthesized. Thermogravimetric analysis performed in N2 revealed that the metallic phytate (M–Phyt, where M is Cu, Zn, Al, or Sn) salts showed good charring. The limiting oxygen index (LOI), cone calorimetry (CONE) test data, tensile strength, and impact toughness were measured for flexible poly(vinyl chloride) (PVC) containing 15 wt % M–Phyt salts. The PVC/Sn–Phyt LOI rose from 24.9 to 30.3%, and the PVC/Sn–Phyt mechanical properties were on par with those of the pure PVC. The CONE test results indicate that PVC/Cu–Phyt showed the lowest total smoke production (TSP) and peak heat‐release rate (pHRR) among the samples. The TSP and pHRR of PVC/Cu–Phyt were 15.77 m2 and 181.77 kW/m2, respectively, 62.63 and 44.48% lower than those of the neat PVC. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46601.

In situ ATR-FTIR spectroscopic study of the co-adsorption of myo-inositol hexakisphosphate and Zn(II) on goethite

The coexistence of myo-inositol hexakisphosphate (IHP; phytate) and aqueous Zn(II) may affect the adsorbed amounts and speciation of each other on minerals, which can further influence the transport and fate of IHP and Zn(II) in soils and sediments. The objective of this study was to investigate the co-adsorption mechanism of IHP and Zn(II) on goethite (Gt). A combination of macroscopic experiments and in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to investigate the co-adsorption of IHP and Zn(II) at the Gt–water interface in the pH range of 3.0–7.0. Adsorption experiments showed that the presence of IHP promoted Zn(II) adsorption, and vice versa, on the surface of Gt. The ATR-FTIR spectra of IHP adsorbed on Gt in the presence of Zn(II) differed from the spectra of IHP adsorbed without co-adsorbed Zn(II) and of zinc phytate (Zn-IHP) precipitates, suggesting that the formation of Gt–IHP–Zn ternary surface complexes was the most likely mechanism for the co-adsorption of IHP and Zn(II) on Gt. The results show that the coexistence of IHP and Zn(II) may have altered both the extent and mechanism of IHP and metal adsorption on Gt, with respect to binary Gt–IHP and Gt–Zn(II) systems. These findings indicate that the coexistence of IHP and heavy metals significantly affects the adsorbed amounts and speciation of these compounds in the natural environment, where the aqueous concentrations of reactants are below saturation with respect to metal phytate precipitates.

Zinc Bioavailability from Phytate-Rich Foods and Zinc Supplements. Modeling the Effects of Food Components with Oxygen, Nitrogen, and Sulfur Donor Ligands.

Aqueous solubility of zinc phytate (Ksp = (2.6 ± 0.2) × 10-47 mol7/L7), essential for zinc bioavailability from plant foods, was found to decrease with increasing temperature corresponding to ΔHdis of -301 ± 22 kJ/mol and ΔSdis of -1901 ± 72 J/(mol K). Binding of zinc to phytate was found to be exothermic for the stronger binding site and endothermic for the weaker binding site. The solubility of the slightly soluble zinc citrate and insoluble zinc phytate was found to be considerably enhanced by the food components with oxygen donor, nitrogen donor, and sulfur donor ligands. The driving force for the enhanced solubility is mainly due to the complex formation between zinc and the investigated food components rather than ligand exchange and ternary complex formation as revealed by quantum mechanical calculations and isothermal titration calorimetry. Histidine and citrate are promising ligands for improving zinc absorption from phytate-rich foods.

Effects of Zinc Phytate on Flame Retardancy and Thermal Degradation Behaviors of Intumescent Flame-retardant Polypropylene

ABSTRACTIn this paper, zinc phytate was prepared and used as a synergist in intumescent flame-retarded polypropylene composites. The results showed that the polypropylene composites with 17 wt% intumescent flame retardant and 2 wt% zinc phytate have a limiting oxygen index 29.2 and achieve the UL-94 V-0 rating. Moreover, the peak heat release rate of the polypropylene composites decreases from 374 to 275 kW/m2. Real-time Fourier-transform infrared spectroscopy showed that the zinc phytate delays the emission of carbon dioxide indicating that zinc phytate slows the degradation of polypropylene which regulates the suitability of intumescent flame-retardant system in polypropylene.

Enhanced Dissolution and Transformation of ZnO Nanoparticles: The Role of Inositol Hexakisphosphate.

The toxicity, reactivity, and behavior of zinc oxide (ZnO) nanoparticles (NPs) released in the environment are highly dependent on environmental conditions. Myo-inositol hexakisphosphate (IHP), a common organic phosphate, may interact with NPs and generate new transformation products. In this study, the role of IHP in mediating the dissolution and transformation of ZnO NPs was investigated in the laboratory kinetic experiments using powder X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy, (31)P nuclear magnetic resonance spectroscopy, high-resolution transmission electronic microscopy, and synchrotron-based extended X-ray absorption fine structure spectroscopy. The results indicate that IHP shows a dissolution-precipitation effect, which is different from citrate and EDTA that only enhances Zn dissolution. The enhanced dissolution and transformation of ZnO NPs by IHP (<0.5 h) is found to be strikingly faster than that induced by inorganic phosphate (Pi, > 3.0 h) at pH 7.0, and the reaction rate increases with decreasing pH and increasing IHP concentration. Multitechnique analyses reveal that interaction of ZnO NPs with IHP induces rapid transformation of ZnO NPs into zinc phytate complexes initially and poorly crystalline zinc phytate-like (Zn-IHP) phase finally. Additionally, ZnO NPs preferentially react with IHP and transform to Zn-IHP when Pi and IHP concurrently coexist in a system. Overall, results from this study contribute to an improved understanding of the role of organic phosphates (e.g., IHP) in the speciation and structural transformation of ZnO NPs, which can be leveraged for remediation of ZnO-polluted water and soils.

Iron and zinc complexation in wild-type and ferritin-expressing wheat grain: implications for mineral transport into developing grain

We have used synchrotron-based X-ray fluorescence and absorption techniques to establish both metal distribution and complexation in mature wheat grains. In planta, extended X-ray absorption fine structure (EXAFS) spectroscopy reveals iron phytate and zinc phytate structures in aleurone cells and in modified aleurone cells in the transfer region of the grain: iron is coordinated octahedrally by six oxygen atoms and fewer than two phosphorous atoms. Zinc is coordinated tetrahedrally by four oxygen atoms and approximately 1.5 phosphorus atoms in an asymmetric coordination shell. We also present evidence of modified complexation of both metals in transgenic grain overexpressing wheat ferritin. For zinc, there is a consistent doubling of the number of complexing phosphorus atoms. Although there is some EXAFS evidence for iron phytate in ferritin-expressing grain, there is also evidence of a structure lacking phosphorus. This change may lead to an excess of phosphorus within the storage regions of grain, and in turn to the demonstrated increased association of phosphorus with zinc in ferritin-expressing grains. Derivative X-ray absorption spectra also suggest that mineral complexation in the transfer region of ferritin-expressing grains is quite different from that in wild-type grain. This may explain why the raised levels of minerals transported to the developing grain accumulate within the crease region of the transgenic grain.