Phosphate Complexes Research Articles

Genetic Algorithm Based Wavelengths Selection Coupled with Partial Least Squares for Simultaneous Spectrophotometric Determination of Phosphate and Silicate in Detergent Products

Background: Phosphate and silicate are very important in a variety of compounds such as mineral resources, underground water, detergents and cleaners. Phosphate and silicate in water positively influence the metabolism of plants and animals. They have led to an environmental problem. This problem can have serious consequences because phosphate and silicate are widely utilized in water softening, surfactants and a large number of other applications. Methods: Genetic algorithm (GA) is an appropriate method for selecting wavelengths for PLS (partial least squares) calibration of mixtures which have almost identical spectra without losing prediction capacity using spectrophotometric method. In this paper, we have described a simple, sensitive and selective spectrophotometric method for the simultaneous determination of phosphate and silicate based on the formation of phospho- and silicomolybdenum blue complexes in the presence of ascorbic acid. Results: The complexes of phosphate and silicate with a reagent in the presence of ascorbic acid have been simultaneously determined by genetic algorithm- partial least squares (GA-PLS) although they showed a spectral overlap. The calibration curve was linear over a concentration range of 0.01-2.00 and 0.01-3.80 µgmL-1 for phosphate and silicate, respectively. The root mean square error (RMSE) for phosphate and silicate was 0.372 and 0.301, respectively. Conclusion: The present study indicates that the GA can be a good method for feature selection in spectral data sets. Results show that GA-PLS is an excellent calibration method for the determination of phosphate and silicate. In the end the proposed method was successfully applied for the simultaneous determination of phosphate and silicate in synthetic detergents. Keywords: Phosphate, silicate, spectrophotometry, GA-PLS, detergent products, surfactants.

Does dentifrice provide the necessary saturation of ions in oral fluids to favour remineralisation?

Background ― Changes in the molecular composition of mixed human saliva using endogenous and exogenous methods of caries prevention were studied and the duration of these changes in relation to the initial state of the oral fluid was determined. Material and Methods ― In total, 200 European healthy, addiction-free, university-educated males and females, aged 22–30 were recruited for the study. Participants collected their mixed saliva samples after the use of a multi-mineral toothpaste (exogenous prevention) and after three days of taking a calcium glycerophosphate tablet (endogenous prevention). In the first stage of the study, samples of mixed saliva were analysed by infrared (IR) lab spectrometer and equipment of infrared microspectroscopy beamline at the Australian Synchrotron (Victoria, Australia) was used in the second stage of study. Results ― Based on the experimental data obtained by IR-spectroscopy technique, the mineral/organic and carbon/phosphate ratios were calculated. The changes in the organic mineral balance of the oral cavity induced by these two preventive methods were analysed. The statistical significance of the results for the confidence level of p is indicated. The data shows that changes in the molecular composition of mixed saliva when using an exogenous method of caries prevention only provides a short-term effect, continuing for the first 30 minutes after the preceding prevention. Moreover, calcium glycerophosphate tablets can change the organic-mineral balance in mixed saliva, increasing the content of mineral groups and complexes. The content of endogenous, biologically accessible phosphate groups and complexes in the mixed saliva exceeds by approximately 12% that of the mixed saliva before the use of the prevention agents. Conclusion ― Use of calcium glycerophosphate tablets in combination with brushing (a combination of endogenous and exogenous prevention methods) leads to the long-term presence of high concentrations of ions, mineral complexes and groups (phosphates) in the oral fluid.

Experimental constraints on the effect of phosphorous and boron on Nb and Ta ore formation

Evolved granites and pegmatites are important sources for critical metals, including niobium (Nb) and tantalum (Ta). The ore deposits that are commonly associated with these granitic rocks are commonly enriched in phosphorous (P) and boron (B), yet there are few experimental constraints on the influence of these fluxing compounds on ore forming processes. Here, the effects of phosphorous (P), boron (B), temperature and melt alkalinity on the solubility of manganocolumbite (MnNb2O6) and manganotantalite (MnTa2O6) in evolved, fluid-saturated granitic melts were studied. Solubility experiments were performed at 100 MPa and 800 to 1000 °C, using three haplogranitic melt compositions with alumina saturation indices (ASI) of 0.8 (peralkaline), 1.0 (subaluminous) and 1.2 (peraluminous). The possible effect of P and the influence of B in P-rich granitic systems were investigated by adding 4 wt% P2O5 and 4 wt% P2O5 + 4 wt% B2O3, respectively, to the starting compositions.The addition of P decreased the solubility of manganocolumbite and manganotantalite in peralkaline granitic melts. In agreement with previous studies, we suggest that P was present as network forming alkali phosphate complexes such as MXPOY in the peralkaline melt structure (M = K, Na etc.), resulting in the observed effect of P at ASI = 0.8. The presence of P had a positive effect on the solubility of manganocolumbite and manganotantalite in subaluminous granitic melts, which became less significant in peraluminous systems. This may reflect the formation of complexes such as AlXPOY and (Ta,Nb)XPOY in the melt. Empirical relationships describing the effect of P on manganocolumbite and manganotantalite solubility in the aforementioned haplogranitc melts at 100 MPa and 800 °C were determined.The addition of B to P-rich peralkaline melts had a minor effect on manganocolumbite solubility, but resulted in an increase of manganocolumbite and manganotantalite solubility in subaluminous systems. For peraluminous melts, a minor increase of the solubility of manganocolumbite and manganotantalite with the addition of B was typically observed. We propose that the addition of B to the P-enriched melts resulted in the formation of network-forming boro-phosphate complexes until the B/P molar ratio in the melts reached unity. Once the B/P molar ratio was greater than one, polymerizing MBO2 complexes were probably formed in peralkaline melts, while B acted presumably as a network modifier in subaluminous and peraluminous systems with B/P > 1.In combination with literature data, we determined similar dissolution enthalpies for manganocolumbite and manganotantalite for given a ASI (and pressure), where the dissolution enthalpy increased with ASI from ∼60 kJ/mol at ASI ≈ 0.6 to ∼150 kJ/mol at ASI ≈ 1.2. Cooling is thus likely to be of greater importance for magmatic mineralization in peraluminous compared to peralkaline systems. The primary influence of B and P in peraluminous systems is to act as fluxes, lowering the crystallization temperature of melts, which allows for the crystallization of primary magmatic tantalite.

Lanthanum Carbonate - A New Phosphate Binding Drug in Advanced Renal Failure.

Lanthanum (La) is considered to be a non-essential element. La has been used for several decades in China to improve yield in plant production and has also been shown to have significant performance enhancing effects in feeding trials on animal husbandry. The estimated dietary intake of La in humans is below 150 µg, which is lower than 10% of the estimated limit of safe and acceptable daily intake. The present review is based on literature search in available databases. Upon ingestion of La as carbonate, the lanthanum ion (La3+) is released in the stomach and traps dietary phosphate as insoluble lanthanum phosphate complexes in the gut, thereby inhibiting phosphate absorption. Lanthanum carbonate as a drug to lower serum phosphate in endstage kidney failure was approved for human use by the US FDA in 2004 and by the EU in 2006. When used to treat patients with advanced renal insufficiency, lanthanum carbonate is administered orally at a dose of maximally 3000 mg per day. The uptake of lanthanum ions from the gut to the circulation is negligible. And few systemic side effects have been recorded upon the use of lanthanum carbonate as a phosphate binding drug, although gastrointestinal discomfort with pain, vomiting and diarrhea may occur. Lanthanum carbonate has the potential to chelate to drugs with anionic groups and therapeutic co-administration with lanthanum carbonate may reduce the bioavailibility of drugs like tetracyclines, quinolones and levothyroxine. The findings in this review confirm that lanthanum carbonate is a clinically useful phosphate binding drug with few side effects in advanced renal failure.

Calcium(ii)-catalyzed enantioselective conjugate additions of amines.

The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA]2)-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed. This mild catalytic system represents a significant advance towards the general convergent asymmetric amination of α,β-unsaturated electrophiles, providing medicinally relevant chiral aminosuccinimide products in high yields and enantioselectivities. Furthermore, the catalyst can be reused directly from a previously chromatographed reaction and still maintain both high yield and selectivity.

Valorizing Rice Straw and Its Anaerobically Digested Residues for Biochar to Remove Pb(II) from Aqueous Solution

To seek a new path to valorize rice straw (RS) and its anaerobically digested residues (DRS), biochar production at different temperatures for removing Pb(II) from aqueous solution and its basic physicochemical characteristics for elucidating potentially adsorption mechanisms were investigated. Overall, pH, electrical conductivity (EC), ash, specific surface area (SA), micronutrient content, and aromaticity of RS biochars (RSBCs) and DRS biochars (DRSBCs) increased with the promoted pyrolysis temperature, and opposite trends were found on the yield, volatile matter, H, N, and O. Lower pH and K content but higher yield, carbon stability, and N and P content were achieved by DRSBCs. Consequently, DRSBCs exhibited lower Pb(II) removal, which was 0.15–0.35 of RSBCs. Maximum adsorption capacities of 276.3 and 90.5 mg·g−1 were achieved by RSBC and DRSBC, respectively, at 500°C. However, distinct mechanisms dominated Pb(II) removal, in which carbonates and carboxylates were responsible for RSBCs, and phosphate silicate precipitation and complexation with carboxylate groups controlled DRSBCs.

Electrochemical nanoarchitectonics through polyaminobenzylamine-dodecyl phosphate complexes: redox activity and mesoscopic organization in self-assembled nanofilms.

Molecular design and preparation of redox active films displaying mesoscopic levels of organization represents one of the most actively pursued research areas in nanochemistry. These mesostructured materials are not only of great interest at the fundamental level because of their unique properties but they can also be employed for a wide range of applications such as electrocatalysts, electronic devices, and electrochemical energy conversion and storage. Herein, we introduce a simple and straightforward strategy to chemically modify electrode surfaces with self-assembled electroactive polyelectrolyte-surfactant complexes. These assemblies are composed of amino-appended polyaniline and monododecyl phosphate. The complexes were deposited by spin-coating and the films were characterized by spectroscopic and X-ray-based techniques: XRR, GISAXS, WAXS, and XPS. The films presented a well-defined lamellar structure, directed by the strong interaction between the phosphate groups and the positively charged amine groups in the polyelectrolyte. These films also displayed intrinsic electroactivity in both acidic and neutral solutions, showing that the polymer remains electroactive and ionic transport is still possible through the stratified and hydrophobic coatings. The stability and enhanced electroactivity in neutral solutions make these assembled films promising building blocks for the construction of nanostructured electrochemical platforms.

Effect of fluoride dentifrice and casein phosphopeptide-amorphous calcium phosphate cream with and without fluoride in preventing enamel demineralization in a pH cyclic study.

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) complexes are anticariogenic and capable of remineralizing the early stages of enamel lesions. The use of fluoride prevents dental decay and the association of CPP-ACP with fluoride can increase remineralization.Objective:To evaluate the effect of CPP-ACP and CPP-ACPF creams associated with a fluoride dentifrice to prevent enamel demineralization in a pH cyclic model.Material and Methods:Previously selected by surface microhardness (SH) analysis, human enamel blocks (n = 56) were submitted to daily treatment with dentifrice in a pH-cycling model. The enamel blocks were divided into four groups; G1: Crest™ Cavity Protection - Procter & Gamble (1,100 ppmF of NaF); G2: Crest™ +MI Paste (MP) - Recaldent™ GC Corporation Tokyo, Japan); G3: Crest™ + MI Paste Plus (MPP) - Recaldent™ 900 ppm as NaF, GC Corporation Tokyo, Japan), and G4: control, saliva. Specimens were soaked alternatively in a demineralizing solution and in artificial saliva for 5 d. The fluoride dentifrice, with proportion of 1:3 (w/w), was applied three times for 60 s after the remineralization period. The undiluted MP and MPP creams were applied for 3 m/d. After cycling, SH was re-measured and cross section microhardness measurements were taken.Results:The SH values observed for the groups G3 (257±70), G1 (205±70), and G2 (208±84) differed from the G4 group (98±110) (one-way ANOVA and Tukey's post hoc test). There were no differences between the groups G1xG2, G2xG3, and G1xG3 for demineralization inhibition. The percentage of volume mineral showed that, when applied with fluoride dentifrice, MPP was the most effective in preventing enamel demineralization at 50 µ from the outer enamel surface (Kruskal-Wallis and Mann Whitney p<0.05).Conclusion:Fluoride dentifrice associated with CPP-ACPF inhibited subsurface enamel demineralization.

Lanthanum oxide nanorods for enhanced phosphate removal from sewage: A response surface methodology study

Lanthanum-based adsorbents are ideal candidates for phosphate removal because of their excellent affinity to phosphate. However, their application in the removal of trace-levels of phosphate from sewage is still unsatisfactory due to the limited adsorption capacity and inadequate optimization of the operational parameters. To overcome these drawbacks, we have developed a novel lanthanum hydroxide (LH), using a facile precipitation and hydrothermal process that involves a nanorod-like structure with the lengths ranging from 124 to 1700 nm, depending on the La/OH molar ratio. The phosphate adsorption capacity of the developed LH is up to 170.1 mg-P g−1 in synthetic water, while a slightly lower adsorption capacity of 111.1 mg-P g−1 is observed in a sewage sample. A polynominal model consisting of three variables (i.e. dosage, reaction time and initial phosphate concentration) for predicting efficiency of phosphate removal has been successfully developed using a face-centred central composite design (CCD)-based methodology. The results also suggest a strong interactive effect of the dosage with the phosphate concentration, and reaction time, which can significantly affect the optimization of the phosphate removal by LH. Both X-ray photoelectron spectroscopy and X-ray diffraction studies indicate that the inner sphere complexation of phosphate with LH is probably the major mechanism governing phosphate removal.

Simultaneous adsorption of uranium(VI) and phosphate on red clay

Combined sorption of U(VI) and phosphate ions on red clay was studied in their concentration range 0.1–1 mM/dm3. The sorption of uranium and phosphate ions was investigated and compared on several clay forms: NaCl, T-clay, H-clay, HDTMA-clay and R-clay. The order of constant distributions was logKd(Na) > logKd(T)∼logKd(H)∼logKd(R) > logKd(HDTMA) for ceq = 0.0001 mol/dm3, indicating that the modified Na-adsorbent form was the most effective in the removal of U (VI) from the aqueous phase. A huge, 8-fold increase in U(VI) sorption was observed upon the addition of phosphate ions to the initial aqueous phase. The de Job method has been successfully used to evaluate U (VI) surface complexes with phosphate anions (V). Adsorption and desorption isotherms were obtained and it was found that the desorption isotherms are located above the adsorption isotherms (for T and R-clay). This indicates the presence of chemisorption in addition to the ion exchange, as well as the contribution of surface complexes and insoluble basic salts of U (VI) in the adsorption process. The analysis of changes in the U(VI) sorption with the increasing molar ratio R = [U(VI)]/[PO43−] showed that U(VI) concentration in the sorbent phase was the highest for R = 0.6–1.7 and R = 3.1–3.8. This finding suggests that two kinds of surface complexes were probably formed, i.e. one with a high content of phosphate ions and the other with a high content of U(VI) ions. The XPS spectra of sorption products revealed the formation of U(VI)–phosphate complex on the surface of red clay. The FTIR spectra, in turn, showed a very interesting effect of phosphates and the U(VI)–phosphate complex on the solid state of the cations of HDTMA+ anchored on the clay surface.

The self-catalysis of ferrate (VI) by its reactive byproducts or reductive substances for the degradation of diclofenac: Kinetics, mechanism and transformation products

Abstract In this study, the effect of phosphate, Fe(III), Fe(II), and reductive substances (i.e., Mn2+ and SO32−) on diclofenac (DCF) oxidation and its degradation mechanism by Ferrate (Fe(VI)) were investigated. The removal rate of DCF in reaction solution at pH 9.0 adjusted by NaOH (67.36%) was higher than that by phosphate buffer (14.87%) because of the complexation of phosphate with Fe(III) and/or Fe(II) restraining the self-catalysis of Fe(VI). Fe(III) or Fe(II) could significantly catalyze Fe(VI) to generate more intermediates (i.e., Fe(V) and Fe(IV)), whose oxidation capacity was magnitude stronger than that of Fe(VI), leading to the improvement of DCF degradation, besides, the presence of reductive substances, e.g., Mn2+ and SO32−, could also increase the self-catalysis of Fe(VI), enhancing the removal of DCF, which will be further verified in follow-up studies. Seven oxidation products (OPs) were detected using a quadrupole-time of flight-mass spectrometer coupled with an ultra performance liquid chromatograph (LC-QTOF/MS). Based on these identified OPs, the potential degradation mechanism of DCF by Fe(VI) was proposed showing six reaction pathways, including hydroxylation, decarboxylation, C N bond cleavage, dehydrogenation, formylation, and dechlorination-hydroxylation. This study suggests that Fe(VI) can effectively oxidize and degrade DCF.

Understanding the Reduction Kinetics of Aqueous Vanadium(V) and Transformation Products Using Rotating Ring-Disk Electrodes.

Vanadium(V) is an emerging contaminant in the most recent Environmental Protection Agency's candidate contaminant list (CCL4). The redox chemistry of vanadium controls its occurrence in the aquatic environment, but the impact of vanadium(V) speciation on the redox properties remains largely unknown. This study utilized the rotating ring-disk electrode technique to examine the reduction kinetics of four pH- and concentration-dependent vanadium(V) species in the presence and the absence of phosphate. Results showed that the reduction of VO2+, HxV4O12+x(4+x)- (V4), and HVO42- proceeded via a one-electron transfer, while that of NaxHyV10O28(6-x-y)- (V10) underwent a two-electron transfer. Koutecky-Levich and Tafel analyses showed that the intrinsic reduction rate constants followed the order of V10 > VO2+ > V4 > HVO42-. Ring-electrode collection efficiency indicated that the reduction product of V10 was stable, while those of VO2+, HVO42-, and V4 had short half-lives that ranged from milliseconds to seconds. With molar ratios of phosphate to vanadium(V) varying from 0 to 1, phosphate accelerated the reduction kinetics of V10 and V4 and enhanced the stability of the reduction products of VO2+, V4, and HVO42-. This study suggests that phosphate complexation could enhance the reductive removal of vanadium(V) and inhibit the reoxidation of its reduction product in water treatment.

Influence of Linkage Stereochemistry and Protecting Groups on Glycosidic Bond Stability of Sodium Cationized Glycosyl Phosphates.

Energy-resolved collision-induced dissociation (ER-CID) experiments of sodium cationized glycosyl phosphate complexes, [GP x +Na]+, are performed to elucidate the effects of linkage stereochemistry (α versus β), the geometry of the leaving groups (1,2-cis versus 1,2-trans), and protecting groups (cyclic versus non-cyclic) on the stability of the glycosyl phosphate linkage via survival yield analyses. A four parameter logistic dynamic fitting model is used to determine CID50% values, which correspond to the level of rf excitation required to produce 50% dissociation of the precursor ion complexes. Present results suggest that dissociation of 1,2-trans [GP x +Na]+ occurs via a McLafferty-type rearrangement that is facilitated by a syn orientation of the leaving groups, whereas dissociation of 1,2-cis [GPx+Na]+ is more energetic as it involves the formation of an oxocarbenium ion intermediate. Thus, the C1-C2 configuration plays a major role in determining the stability/reactivity of glycosyl phosphate stereoisomers. For 1,2-cis anomers, the cyclic protecting groups at the C4 and C6 positions stabilize the glycosidic bond, whereas for 1,2-trans anomers, the cyclic protecting groups at the C4 and C6 positions tend to activate the glycosidic bond. The C3 O-benzyl (3 BnO) substituent is key to determining whether the sugar or phosphate moiety retains the sodium cation upon CID. For 1,2-cis anomers, the 3 BnO substituent weakens the glycosidic bond, whereas for 1,2-trans anomers, the 3 BnO substituent stabilizes the glycosidic bond. The C2 O-benzyl substituent does not significantly impact the glycosidic bond stability regardless of its orientation. Graphical abstract ᅟ.

Removal of phosphate from aqueous solution by activated siderite ore: Preparation, performance and mechanism

Abstract Activated siderite ore (ASO) was prepared by annealing siderite ore at different temperatures for different durations. The performance of ASO on the removal of phosphate from aqueous solution and the effects of particle size, contact time, pH, initial phosphate concentration, temperature, and coexisting anions on phosphate removal were investigated. X-ray diffractometer, thermogravimetric analyzer (TGA), transmission electron microscopy (TEM), surface area analyzer, Fourier transformed infrared spectra and other techniques were utilized to characterize ASO before and after adsorption. The results showed that a large amount of CO2 was released meanwhile the siderite began to transform to hematite when the annealing temperature increased to 450 °C. The specific surface area of annealed product increased from 4.17 m2/g to 57.5 m2/g as the temperature came to 470 °C. Phosphate can be removed efficiently by ASO in a relatively wide pH range between 3.0 and 11.0. The effects of coexisting anions were not significant within the experimental concentration ranges except HCO3−. The adsorption process of phosphate on ASO fitted pseudo-second order kinetics model. ASO showed a high-efficient adsorption capacity of 9.24 mg/g estimated from Langmuir isotherm at 30 °C. Results of TEM and FTIR analysis suggested that under the condition of pH = 6.5 and phosphate concentration (100 mg/L), two different monoprotonated phosphate complexes exist at ASO, with one surface complex coordinated in a monodentate binuclear (bridging) fashion, and the other as a monodentate mononuclear complex. A small amount of co-precipitation is most likely to be another mechanism for the removal of phosphate. These fundamental data indicate that siderite is a promising precursor for preparing porous material at least for adsorption of phosphate.

Colonization and Maize Growth Promotion Induced by Phosphate Solubilizing Bacterial Isolates.

Phosphorus (P) limits the production of maize, one of the major food crops in China. Phosphate-solubilizing bacteria (PSB) have the capacity to solubilize phosphate complexes into plant absorbable and utilizable forms by the process of acidification, chelation, and exchange reactions. In this study, six bacteria, including one Paenibacillus sp. B1 strain, four Pseudomonas sp. strains (B10, B14, SX1, and SX2) and one Sphingobium sp. SX14 strain, were those isolated from the maize rhizosphere and identified based on their 16S rRNA sequences. All strains could solubilize inorganic P (Ca3(PO4)2, FePO4 and AlPO4), and only B1 and B10 organic P (lecithin). All strains, except of SX1, produced IAA, and SX14 and B1 showed the highest level. B1 incited the highest increase in root length and the second increase in shoot and total dry weight, shoot length, and total P and nitrogen (N), along with increased root length. In addition, by confocal laser scanning microscopy (CLSM), we found that green fluorescent protein (GFP)-labeled B1 mainly colonized root surfaces and in epidermal and cortical tissue. Importantly, B1 can survive through forming spores under adverse conditions and prolong quality guarantee period of bio-fertilizer. Therefore, it can act as a good substitute for bio-fertilizer to promote agricultural sustainability.

Enantio- and Diastereoselective Cyclopropanation of β,γ-Unsaturated α-Ketoester by a Chiral Phosphate/Indium(III) Complex.

We report herein an enantioselective cyclopropanation of β,γ-unsaturated α-ketoesters with diazoesters by the complexes of InBr3 and chiral calcium phosphate. The reaction proceeds via a Michael addition-cyclization pathway to afford highly functionalized chiral cyclopropanes with excellent enantioselectivities (up to >99% ee) as a single diastereoisomer.

STUDY OF DISPERSE SYSTEMS OF CeO2 AND CeF3 IN STIFFENED MELTS NaNO3-KNO3 BY METHODS OF SPECTROSCOPY OF DIFFUSE REFLECTANCE AND BY THE CHEMICAL ANALYSIS

Processes of dispersion and solubility of CeO2 and CeF3 in the melts of systems NaNO3-KNO3 which are widely used as medium for synthesis of various oxide materials are investigated. The basis of the mechanism of the specified processes is made by the acid-basic and oxidationreduction reactions between initial substances and saline melt. For identification and definition of oxidation degree of Cerium in interaction products are applied spectroscopy of diffuse reflectance in an UV range of a spectrum and the substantial chemical analysis with use as a reagent of a solution of phosphoric acid. For reduction of influence of own absorption of ions NO3– as the sample of comparison it is used stiffened melt of NaNO3-KNO3. Definition of content of Ce(III) is carried out basing on decrease of intensity of coloring of KMnO4. Content of Ce(IV) is established photometrically on intensity of absorption of a phosphate complex (at high content of Ce(IV)) and on decrease of coloring of methanyl yellow (at low content). The data of spectroscopy of diffuse reflectance specifies in prevalence of Ce(IV) with small admixture of Ce(III) in case of system CeO2-(NaNO3-KNO3) and Ce(III) with admixture of Ce(IV) in case of system CeF3-(NaNO3-KNO3). Because of influence of H3PO4 on oxidation degree of cerium in last system, definition of Ce(III) and Ce(IV) by chemical analysis was not carried out. As for system with CeO2, contents of Ce(IV) by method of the chemical analysis are established at level 8-16%масс., and they are higher at system heat treatment on air in comparison with heat treatment in an inert (He) medium. Some inconsistency in the results received by a method of spectroscopy of diffuse reflectance and the chemical analysis, which reason while up to the end is not established, is observed. The role of the superficial phenomena on border solid state – saline melt - gas in processes of dispersion of CeO2 and CeF3 is shown.

Iron Phosphate Catalyzed Asymmetric Cross-Dehydrogenative Coupling of 2-Naphthols with β-Ketoesters.

Chiral iron phosphate complexes were successfully exploited for asymmetric cross-dehydrogenative coupling reactions between 2-naphthols and β-ketoester derivatives. On the basis of kinetic studies, it is suggested that iron monophosphate complexes constitute the active catalysts that induce stereoselectivity during the carbon-carbon bond-formation step.

Complex Formation of Lead(II) with Nucleotides and Their Constituents.

Lead is widely distributed in the environment; it is known to mankind for thousands of years and its toxicity is nowadays (again) well recognized, though on the molecular level only partly understood. One of the reasons for this shortcoming is that the coordination chemistry of the biologically important lead(II) is complicated due to the various coordination numbers it can adopt (CN = 4 to 10) as well as by the 6s2 electron lone pair which, with CN = 4, can shield one side of the Pb2+ coordination sphere. The chapter focuses on the properties of Pb2+ complexes formed with nucleotides and their constituents and derivatives. Covered are (among others) the complexes formed with hydroxy groups and sugar residues, the interactions with the various nucleobases occurring in nucleic acids, as well as complexes of phosphates. It is expeced that such interactions, next to those like with lipids and proteins, are responsible for the toxic properties of lead. To emphasize the special properties of Pb2+ complexes, these are compared as far as possible with the corresponding properties of the Ca2+, Fe2+, Cu2+, Zn2+, and Cd2+ species. It needs to be mentioned that the hard-soft rule fails with Pb2+. This metal ion forms complexes with ligands offering O donors of a stability comparable to that of Cu2+. In contrast, with aromatic N ligands, like imidazole or N7 sites of purines, complex stability is comparable to that of the corresponding Fe2+ complexes. The properties of Pb2+ towards S donor sites are difficult to generalize: On the one hand Pb2+ forms very stable complexes with nucleoside 5'-O-thiomonophosphates by coordinating to nearly 100% at S in the thiophosphate group; however, on the other hand, once a sulfur atom replaces one of the terminal oxygen atoms in the phosphodiester linkage, macrochelate formation of the phosphate-bound Pb2+ occurs with the O and not the S site. Quite generally, the phosphodiester linkage is a relatively weak binding site, but the affinity increases further to the mono- and then to the di- and triphosphate. The same holds for the corresponding nucleotides, though the Pb2+ affinity had to be estimated via that of the Cu2+ complexes for some of these ligands. Complex stability of the pyrimidine-nucleotides (due to their anti conformation) is solely determined by the coordinating tendency of the phosphate group(s); this also holds for the Pb2+ complex of adenosine 5'-monophosphate. For the other purinenucleotides macrochelate formation takes place by the interaction of the phosphate-coordinated Pb2+ with the N7/(C6)O site of, e.g., the guanine residue. The extents of the formation degrees of these chelates are summarized. Unfortunately, information about mixed ligand (ternary) or other higher order comlexes is missing, but still it is hoped that the present overview will help to understand the interaction of Pb2+ with nucleotides and nucleic acids, and especially that it will facilitate further research in this fascinating area.

Effect of humic acid preloading on phosphate adsorption onto zirconium-modified zeolite.

A zirconium-modified zeolite (ZrMZ) was prepared, and then, humic acid (HA) was immobilized on the ZrMZ surface to prepare HA-loaded ZrMZ (HA-ZrMZ). The obtained ZrMZ and HA-ZrMZ were characterized by energy dispersive X-ray spectroscopy, elemental analyzer, N2 adsorption/desorption isotherms, pH at the point of zero charge, and X-ray photoelectron spectroscopy. The adsorption characteristics of phosphate on ZrMZ and HA-ZrMZ were comparatively investigated in batch mode. The adsorption mechanism of phosphate on ZrMZ and HA-ZrMZ was investigated by ionic strength effect and 31P nuclear magnetic resonance. The mechanism for phosphate adsorption onto ZrMZ was the formation of inner-sphere phosphate complexes at the solid/solution interface. The preloading of HA on ZrMZ reduced the phosphate adsorption capacity, and the more the HA loading amount, the lower the phosphate adsorption capacity. However, the preloading of HA on ZrMZ did not change the phosphate adsorption mechanism; i.e., the formation of inner-sphere phosphate surface complexes was still responsible for the adsorption of phosphate on HA-ZrMZ. The decreased phosphate adsorption capacity for ZrMZ after HA coating could be attributed to the fact that the coating of HA on ZrMZ reduced the amount of binding active sites available for phosphate adsorption, changed the adsorbent surface charges, and reduced the specific surface areas and pore volumes of ZrMZ.