Decomposition Of Citrate Research Articles

Morphological and structural differences of Fe-Zn-Al oxide nanocomposites obtained from citrate decomposition and microemulsion method

Ternary Fe-Zn-Al oxide nanostructured material was either co-precipitated in water-in-oil microemulsion or prepared by citrate method. After calcination, the structural features of both samples were studied by XRD, N2 physisorption, SEM, TEM, TPR-H2 and their catalytic behavior in CO2 hydrogenation was determined. The sample obtained from the citrate method consists of Fe2O3 and a Fe-containing spinel phase. The mixed oxide synthesized by the microemulsion method consists of pure iron oxide in Fe3O4 inverse spinel structure epitaxially grown on a Fe-Zn-Al oxide parent structure. Compared to the sample obtained by the citrate method, the structural features of the composite from the microemulsion method are of potential interest for catalytic applications or for transfer to other multinary systems due to the presence of epitaxy.

Synthesis of char-based adsorbents from cotton textile waste assisted by iron salts at low pyrolysis temperature for Cr(VI) removal.

Char-based adsorbents (char-FeCl3, char-FeCl2, and char-FeCit) derived from cotton textile waste (CTW) were synthesized by one-step low-temperature pyrolysis approach with different iron salts. The properties of the samples were conducted by BET, SEM, EDS, XRD, XPS, TEM, and FTIR. The results suggested that the surface areas of char-FeCl3 and char-FeCl2 were higher than those of char-FeCit. The presence of Fe2O3 as well as pyrolysis gas (HCl (g) and H2O (g)) could catalyze the formation of porosity. Meanwhile, FeCl3 showed the strongest catalysis effect to decompose cellulose to produce char. The pyrolysis process analysis was investigated by means of thermogravimetry-DSC. FeCl3 and FeCl2 could accelerate the breakage of cellulose structure whereas FeC6H5O7 was not beneficial to form char at low temperature as the incomplete decomposition of citrate. The adsorption property of Cr(VI) for the chars was evaluated. Adsorption processes were fitted well with the Freundlich model, and char-FeCl3 presented the best adsorptive capacity (70.39mg/g). Thus, this low-temperature pyrolysis method was economical and technologically simplified as well as efficient adsorption capacity of Cr(VI) removal. Graphical abstract.

Adsorption Of Cs+ and IO3− Ions by Pseudoboehmite Before and After the Decomposition of Citrate Adsorbed on Its Surface

AbstractCitrate is distributed widely in the Earth’s surface environments as a biological product released by microbes and plants. Citrate is also often used as a chelating agent for the selective dissolution of iron coatings and free iron oxides in soils. Adsorption experiments of Cs+ and IO3− before and after the complexation of citrate with the pseudoboehmite surface were conducted to evaluate the effects of citrate on the adsorption of these ions on the surface of pseudoboehmite. Additional adsorption experiments of Cs+ and IO3− after the decomposition of citrate adsorbed on the pseudoboehmite surface were also performed to confirm the recovery of the original surface properties. Citrate decomposition was carried out by means of 10% H2O2 treatments at 75°C and pH 5, 7, and 9. The results indicated that citrate complexation decreased remarkably the adsorption of both Cs+ and IO3− in the pH range 3–10, which was due to a decrease in the number of active charged sites available for adsorption of these ions. Decomposition of citrate adsorbed on the pseudoboehmite surface was found to be complete after three rounds of treatment with 10% H2O2 at 75°C and pH > 7. After the decomposition of citrate adsorbed on the pseudoboehmite surface, the adsorption of both Cs+ and IO3− was restored completely to the initial amounts before citrate complexation, and the inhibition effect of citrate on the adsorption of these ions disappeared under all pH conditions.

Effect of calcium and copper/iron co-doping on defect-induced properties of La2NiO4-based materials

The La2-xCaxNi1-y(Fe/Cu)yO4+δ solid solutions with х = 0.2, 0.4, 0.5 and y = 0, 0.1, 0.2, 0.3 were synthesized by decomposition of citrate–nitrate precursors. The single-phase La2-xCaxNi1-y(Fe/Cu)yO4+δ materials crystallized in the K2NiF4-type structure, sp. gr. I4/mmm. The crystal structure parameters of La2-xCaxNi1-y(Fe/Cu)yO4+δ were refined by the Rietveld method. The unit cell volume of La2-xCaxNi1-y(Fe/Cu)yO4+δ decreased with x and increased with y. All studied samples exhibited oxygen excess compared to the stoichiometric composition (δ > 0) in the temperature range 30–1100 °C except for La1.6Ca0.4Ni1-yCuyO4+δ (y = 0.2 and 0.3). Calcium and copper doping decreased the total oxygen content while iron doping increased it in La2-xCaxNi1-y(Fe/Cu)yO4+δ. Thermal expansion coefficients (TECs) of La2-xCaxNi1-y(Fe/Cu)yO4+δ slightly increased with dopant concentration and varied in the range (14.5–15.1) × 10−6 K−1. The contribution of chemical expansion was shown to be negligible. The total conductivity of La2-xCaxNi1-y(Fe/Cu)yO4+δ was thermally activated within the whole studied temperature range 30–1000 °C and could be described in terms of small polaron conduction mechanism. The values of total conductivity increased with x and decreased with y in La2-xCaxNi1-y(Fe/Cu)yO4+δ. The analysis of the Seebeck coefficient vs temperature for La2-xCaxNi1-y(Fe/Cu)yO4+δ showed that the main charge carriers are electron holes localized on Ni2+ cations represented by low-spin Ni3+ cations which had a tendency to change the spin configuration gradually to high-spin when the temperature and dopant content increased.

Oxygen transport phenomena in (La,Sr)2(Ni,Fe)O4 materials

Oxygen conductivity of La1.5Sr0.5Ni1−yFeyO4+δ membranes.

Mechanisms by which citric acid increases phosphate availability

Cluster roots release carboxylic acids, especially citric acid, into the rhizosphere. We investigated how the citrate ion and the acidity interact to release phosphate. We prepared solutions with differing citrate concentrations and differing pH and mixed these solutions with a soil. We investigated the effects of: pH, duration of mixing, the presence of chloroform, solution:soil ratio, and the effects of background electrolyte. We compared the results obtained with citrate with those obtained with arsenate. In the absence of chloroform, decomposition of citrate began after one hour. In the presence of chloroform it was delayed until after 24 hours. The higher the pH, the faster the decomposition. In the presence of chloroform, the ratio between phosphate and citrate in solution was steady between one and 24 hours. We chose a duration of six hours for further observations. Desorption of phosphate by citrate was most marked near pH 4. The peak in desorption was sharp in 0.01 M CaCl2 because, at high pH, much of the citrate was complexed with calcium. These effects of pH were modelled by assuming that divalent phosphate ions were displaced by divalent citrate ions. When compared with arsenate, citrate ions were better at dissolving surface iron atoms and thus releasing phosphate, but much worse in competing with phosphate ions in solution for sorption sites. The acid component of citric acid has direct effects. It moves the pH into a region in which the HPO4− ion dominates and therefore facilitates uptake; it acts as a preservative thus slowing down citrate decomposition, and it directly increases desorption. However its most important effect occurs through interaction with citrate with greatest desorption near pH 4.

On the nature of citrate-derived surface species on Ag nanoparticles: Insights from X-ray photoelectron spectroscopy

Abstract Citrate is an important stabilizing, reducing, and complexing reagent in the wet chemical synthesis of nanoparticles of silver and other metals, however, the exact nature of adsorbates, and its mechanism of action are still uncertain. Here, we applied X-ray photoelectron spectroscopy, soft X-ray absorption near-edge spectroscopy, and other techniques in order to determine the surface composition and to specify the citrate-related species at Ag nanoparticles immobilized from the dense hydrosol prepared using room-temperature reduction of aqueous Ag+ ions with ferrous ions and citrate as stabilizer (Carey Lea method). It was found that, contrary to the common view, the species adsorbed on the Ag nanoparticles are, in large part, products of citrate decomposition comprising an alcohol group and one or two carboxylate bound to the surface Ag, and minor unbound carboxylate group; these may also be mixtures of citrate with lower molecular weight anions. No ketone groups were specified, and very minor surface Ag(I) and Fe (mainly, ferric oxyhydroxides) species were detected. Moreover, the adsorbates were different at AgNPs having various size and shape. The relation between the capping and the particle growth, colloidal stability of the high-concentration sol and properties of AgNPs is briefly considered.

Efficient removal of paracetamol using LaCu1−xMxO3 (M = Mn, Ti) perovskites as heterogeneous Fenton-like catalysts

A series of perovskite-like oxides LaCu1−xMxO3 (M=Mn, Ti; 0.0⩽x⩽0.8) was prepared by amorphous citrate decomposition and characterized by XRD, ICP-OES and XPS techniques. The catalysts were tested in the Fenton-like degradation of paracetamol with H2O2, under mild reaction conditions, 25°C and nearly neutral pH. Values of decomposition of paracetamol between 80 and 97% at 300min were achieved for most of samples. The presence of the Cu2+/Cu+ pair at the surface of the catalysts is necessary to carry out the reaction and the catalysts containing higher amount of copper at the surface, resulted to be more active. The leaching of metals was less than 1%, which discards the contribution of the homogenous Fenton-like reaction and remarks the high stability of the metals into the mixed oxide network. The catalytic activity of LaCu0.8Mn0.2O3 was maintained after three cycles of reaction, which proves the stability and reusability of the catalyst.

Homogeneity range, oxygen nonstoichiometry, thermal expansion and transport properties of La2−xSrxNi1−yFeyO4+δ

Phase boundaries of tetragonal La2−xSrxNi1−yFeyO4+δ solid solutions (sp.gr. I4/mmm) prepared via the decomposition of citrate–nitrate precursors, followed by multiple annealing treatments at 1100 °C in air and quenched to RT.

Effects of Annealing on the Photoluminescence Properties of Citrate-Capped YVO4:Bi3+,Eu3+ Nanophosphor

We investigated the effects of annealing on the photoluminescence (PL) properties of a citrate-capped YVO4:Bi3+,Eu3+ nanophosphor. The 300 °C annealed nanophosphor exhibited the highest PL intensity at 619.5 nm corresponding to an f–f transition of Eu3+ under near-UV excitation. Fourier transform infrared spectroscopy indicated a decrease in the amounts of adsorbed water and citrate on the nanophosphor surface with annealing. Dehydration and the increase in near-UV absorption contributed to the improved PL intensity, since water is a Eu3+ luminescence quencher. The thermal decomposition of citrate, which photoreduces vanadate under near-UV irradiation, caused the improved photostability. Annealing at ≥400 °C decreased the PL intensity. A color change from white to yellow may be attributed to absorption by byproducts, possibly formed by the segregation of YVO4:Bi3+,Eu3+. A shorter PL lifetime and lower activation energy of thermal quenching at higher annealing temperature were confirmed from PL decay curve...

Effect of aluminum on metabolism of organic acids and chemical forms of aluminum in root tips of Eucalyptus camaldulensis Dehnh.

Eucalyptus (Eucalyptus camaldulensis) has relatively high resistance to aluminum (Al) toxicity than the various herbaceous plants and model plant species. To investigate Al-tolerance mechanism, the metabolism of organic acids and the chemical forms of Al in the target site (root tips) in Eucalyptus was investigated. To do this, 2-year old rooted cuttings of E. camaldulensis were cultivated in half-strength Hoagland solution (pH 4.0) containing Al (0, 0.25, 0.5, 1.0, 2.5 and 5.0mM) salts for 5weeks; growth was not affected at concentrations up to 2.5mM even with Al concentration reaching 6000μgg(-1) DW. In roots, the citrate content also increased with increasing Al application. Concurrently, the activities of aconitase and NADP(+)-isocitrate dehydrogenase, which catalyze the decomposition of citrate, decreased. On the other hand, the activity of citrate synthase was not affected at concentrations up to 2.5mM Al. (27)Al-NMR spectroscopic analyses were carried out where it was found that Al-citrate complexes were a major chemical form present in cell sap of root tips. These findings suggested that E. camaldulensis detoxifies Al by forming Al-citrate complexes, and that this is achieved through Al-induced citrate accumulation in root tips via suppression of the citrate decomposition pathway.

Photochemical degradation of citrate buffers leads to covalent acetonation of recombinant protein therapeutics

Novel acetone and aldimine covalent adducts were identified on the N-termini and lysine side chains of recombinant monoclonal antibodies. Photochemical degradation of citrate buffers, in the presence of trace levels of iron, is demonstrated as the source of these modifications. The link between degradation of citrate and the observed protein modifications was conclusively established by tracking the citrate decomposition products and protein adducts resulting from photochemical degradation of isotope labeled (13)C citrate by mass spectrometry. The structure of the acetone modification was determined by nuclear magnetic resonance (NMR) spectroscopy on modified-free glycine and found to correspond to acetone linked to the N-terminus of the amino acid through a methyl carbon. Results from mass spectrometric fragmentation of glycine modified with an acetone adduct derived from (13)C labeled citrate indicated that the three central carbons of citrate are incorporated onto protein amines in the presence of iron and light. While citrate is known to stoichiometrically decompose to acetone and CO(2) through various intermediates in photochemical systems, it has never been shown to be a causative agent in protein carbonylation. Our results point to a previously unknown source for the generation of reactive carbonyl species. This work also highlights the potential deleterious impact of trace metals on recombinant protein therapeutics formulated in citrate buffers.

Steam reforming of methanol over Cu/Zn/Zr/Ga catalyst: effect of the reduction conditions on the catalytic performance

The effect of the reduction conditions on the catalytic performance of Cu based catalyst in the methanol steam reforming process was investigated. The catalyst was prepared in our laboratory using the method of thermal decomposition of citrates. The influence of catalyst reduction methods on the methanol steam reforming process was studied with hydrogen, carbon monoxide, methanol and water mixture and pure methanol used as reductants. The most selective catalysts were obtained by the reduction with methanol and water mixture and also with pure methanol.

Growth of two-dimensional KGd(WO 4) 2 nanorods by modified sol–gel Pechini method

KGd (WO 4) 2 nanocrystalline powder was obtained by modified sol–gel Pechini method. The synthesis procedure was optimized with TGA and DTA analyses. Synthesized polymeric resin was calcinated at 550 and 700 °C using resistive furnace in an open atmosphere. Crystallinity of annealed powder was confirmed using X-ray diffraction. Absorption peaks of FT-IR for gel and the annealed samples, at two different temperatures show the decomposition of citrate–ethylene glycol complex and formation of KGW particles. Raman analysis confirms that the derived particles have well constructed bridges of W–O–O–W. External morphology of the particles was analysed through SEM.

Bismuth subcarbonate nanoparticles fabricated by water-in-oil microemulsion-assisted hydrothermal process exhibit anti- Helicobacter pylori properties

Well-crystallized bismuth subcarbonate ((BiO) 2CO 3) nanoparticles were successfully synthesized by water-in-oil (w/o) microemulsion-assisted hydrothermal method. In this synthesis, bismuth citrate and urea are used as the precursors and the thermal decomposition of citrate leads to the formation of major carbonate anion. The reaction, nucleation and growth steps are confined inside the water droplets and hence uniform and well-crystallized spherical nanoparticles are formed. Importantly, these nanoparticles exert comparable anti- Helicobacter pylori activities to the clinically used drug, colloidal bismuth subcitrate (CBS), which offers a promise for development of new nanomedicines.

Electrical properties and acetone-sensing characteristics of LaNi 1− xTi xO 3 perovskite system prepared by amorphous citrate decomposition

Perovskite type oxides LaNi 1− x Ti x O 3 ( x = 0.0–1.0) were prepared by thermal decomposition of amorphous citrate precursors followed by annealing at 700–1000 °C in ambient air. These products were characterized by various analytical methods such as XRD, FT-IR, EDAX, SEM and XPS. Ti in the LaNi 1− x Ti x O 3 had significant influence on the crystal size of the nanocrystals and the activation energy ( E a) which was measured at 50–800 °C in air atmosphere. The LaNi 1− x Ti x O 3 system showed an interesting metal-insulator transition with increasing Ti concentration, which can be adjusted to enhance the response and selectivity of the materials to acetone. The LaNi 0.5Ti 0.5O 3-based sensor exhibited a quick change in the resistance to 1–5 ppm acetone within 40 s and took less than 70 s for recovery at 350 °C, which could hardly be influenced by the environmental humidity. The XPS analysis results showed that the adsorbed oxygen on the surface of sensing material and its concentration are the important factors for the acetone detection. The origin of the gas response is attributed to the thermal reaction, which occurs between acetone and adsorbed oxygen species, forming an acetone–oxygen complex, and then the final product CH 3COOH is desorbed as a gas at 350 °C.

Thermal characterization of the intermediary products of the synthesis of Zn-substituted barium hexaferrite

The focus of this work is the use of thermal analyses and Fourier Transform Infrared Spectroscopy (FTIR) for characterization of the gel decomposition, resulting from the formation of Y-barium hexaferrite substituted by Zn ions (Zn-Y-barium hexaferrite). Samples with Ba2Zn2Fe12O22 composition were synthesized by the citrate auto-combustion method. During the TG experiments the highest mass loss was attributed to citrate decomposition owing to the self-combustion reaction, confirmed by the disappearance of –OH band, and the drastic decrease of –CO2 −and –NO3 − bands. Zn substitution resulted in an X-band microwave absorber material.

Interactive effects of organic acids in the rhizosphere

Organic acids released into the rhizosphere may perform many beneficial functions to the plant including metal detoxification and enhancement of nutrient acquisition. Typically, these organic acids are studied in isolation; however, roots simultaneously exude a cocktail of organic acids and other substances, and their combined impact on rhizosphere processes may be quite different. It has been hypothesized that some exudates may play secondary roles (e.g. inhibitors of microbial activity, blockage of sorption sites), which might enhance the longevity and nutrient-mobilization capacity of others. Here we investigated how the decomposition, sorption and P-solubilizing effects of citrate, malate and oxalate are affected by the presence of malonate and shikimate. We found that in a range of agricultural soils the decomposition of citrate, malate and oxalate was rapid, but not influenced by the presence of large quantities of shikimate or malonate. This suggests that the individual organic acids are taken up by different transport mechanisms or components of the microbial community. At large concentrations, malonate decreased sorption of citrate, malate and oxalate on the soil, whilst shikimate had little effect. The capacity of citrate, malate and oxalate to desorb P was significantly greater in cocktails containing malonate compared with the single organic acid; no effect was seen with shikimate. We conclude that neither malonate nor shikimate at realistic concentrations will significantly affect the biodegradation of citrate, malate or oxalate in the rhizosphere, and while malonate did enhance P desorption, this effect is additive rather than synergistic. Overall, we found little evidence that malonate and shikimate act as secondary regulators of citrate, malate and oxalate behavior in soil.

In situ structural changes during toluene complete oxidation on supported EuCoO 3 monitored with 151Eu Mössbauer spectroscopy

Ceria–zirconia supported (10 and 20 wt.% EuCoO 3) versus bulk EuCoO 3 perovskite were prepared via citrate decomposition at 700 °C and tested for toluene complete oxidation. S BET, XRD, XPS, H 2-TPD and in situ 151Eu Mössbauer investigations were performed. Electron delocalization processes around the Eu cations are induced by the reaction, as proved via the evolution of the Mössbauer parameters. All characterization data indicate the formation of a well-dispersed EuCoO 3 at the surface of Ce 0.9Zr 0.1O 2 for the 10 wt.% loading and larger crystallite formation for 20 wt.% loading. In terms of intrinsic activity for toluene combustion, supported catalysts were more active than bulk EuCoO 3. All structural changes during operation time are reversible.

Synthesis of needle-like BaTiO3particles from the thermal decomposition of a citrate precursor under sample controlled reaction temperature conditions

Needle-like BaTiO3 particles with controlled microstructure have been prepared from the thermal decomposition of a metal-organic precursor under sample controlled reaction temperature (SCRT) conditions. In a first step, a mixed barium and titanium citrate precursor consisting of a single phase compound with controlled morphology and stoichiometry have been prepared. The precursor has been converted isomorphologically into BaTiO3 by thermal treatment under SCRT conditions. The so-obtained needle-like particles are constituted of self-assembled nanoparticles. The size of the assembled subunits has been tailored by controlling the reaction rate and the partial pressure of the gases generated during the thermal decomposition of the barium titanium citrate. This microstructural control accomplished by the SCRT method can not be achieved by conventional thermal decomposition of the citrate precursor. Finally, the set of samples obtained with different microstructures has been investigated in terms of stabilization of the cubic phase at room temperature.