Ratio Of Citric Acid Research Articles

Ce-doped YAG phosphors prepared via sol–gel method: Effect of some modular parameters

Cerium doped yttrium aluminum garnet (YAG:Ce3+) nanopowders have been synthesized using sol–gel method. Different synthesized parameters such as molar ratio of citric acid and ethylene glycol to the total metallic ions, complexing molar ratio and pH of the solution have been changed and their influence on structural and luminescence properties have been investigated. Thermal gravimetry and differential scanning calorimetry (TG/DSC), X-ray diffraction technique (XRD), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence (PL) have been used to characterize the samples. Single cubic phase YAG was formed with pH⩽4 and for pH⩾6 additional impurities crystalline phase namely Y4Al2O9 (YAM) and YAlO3 (YAP) have been detected. All samples exhibit intense broad green–yellow emission band in the range of 460–700nm with a maximum intensity at around 530nm assigned to the 5d→4f (2F5/2, 2F7/2) interconfigurationnelles transitions of Ce3+ ion in YAG nanomaterial. The origin of the highest emission intensity obtained for pH=4, citric acid to the total metallic ions of 1:1 (CA:M3+, of 1:1) and a molar ratio of ethylene glycol:citric acid corresponding to 2:1 (EG:CA=2:1) parameters are discussed.

Low temperature synthesis of Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanopowders by solution based auto combustion method

Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT–BCT) nanopowders were synthesized by citrate–nitrate auto combustion method using TiO2 as a source of titanium. The formation mechanism, phase evolution and particle size were investigated using thermal analysis, Fourier transform infra-red spectroscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscope. The molar ratio of metal, citric acid and ethylene diamine tetraacetic acid was kept at 1:1.5:0.1 and pH ~ 9, to get a uniform and complete combustion. Perovskite BZT–BCT was formed in the as-burnt state (280 °C), though calcination at 700 °C is required to remove a small amount of impurities, which is significantly lower than the solid state reaction method. The particle size of BZT–BCT powder was in the range of 40–70 nm.

Influence of the Citric Acid and Metal Cation Ratio on the Structural and Morphological Characteristics of Aluminum Oxide Synthesized by Pechini Method

Given the opportunities that aluminas present in relation to the broad field of applications to which they refer, the literature has reported great diversity in methodology to obtain these materials in the search of generating the best properties. In this way, the aim of this work is to evaluate the use of different citric acid and metallic cation ratio on the structural and morphological characteristics of the alumina synthesized by Pechini method and calcined at 1100°C. The samples were characterized by X-ray diffraction, thermal analysis, particle size and scanning electron microscopy. The results showed a large amount of loss of mass after pyrolysis. The α-alumina phase was achieved for the two studied ratio reaching values for crystallite size of 41.4 and 52.5 nm, crystallinity of 88 and 91.2%, agglomerates size of 12.3 and 14μm, for the synthesized samples 2:1 and 3:1, respectively. According to the SEM images, the changes in the citric acid: metallic cation ratio did not significantly modify the morphology of the alumina.

Development of green/biodegradable polymers for water scaling applications

The usage of green polymers are widely increased from day-to-day as detergent builders, paper-sizing agents, flocculants, thickeners, emulsifiers, and scale inhibitors due to their friendly nature with the water systems. Minimizing the formation of inorganic scale deposits in processing industrial waters presents a challenge for water treatment systems. In the present investigation, we have developed water soluble green polymers based on malic acid (MA) and citric acid (CA) through a bulk-melt condensation process and applied as water scaling inhibitors. The copolymer of poly(malic acid-citric acid) (PMC) was synthesized by varying the ratio of MA and CA monomers with 1:3, 1:1, and 3:1, and studied their descaling property with carbonate, sulfate and phosphate ions. The scale inhibition property of the homopolymers was also investigated and compared with the copolymers. As the ratio of CA was increased in the copolymer formation, there was a greater influence on the scale inhibition. Interestingly, copolymers showed the highest phosphate inhibition (98%) and have no significant change with its homopolymers. The results indicate that the synthesized green copolymers PMC were water soluble, biodegradable, non-toxic and hence, have a good water descaling property without disturbing the taste, quality and purity of water. Characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR) analysis and Thermal Gravimetric Analysis (TGA) were performed in order to understand its thermal properties and copolymer confirmation.

Ruthenium promoted cobalt catalysts prepared by an autocombustion method directly used for Fischer–Tropsch synthesis without further reduction

Ru promoted Co/SiO2 Fischer–Tropsch synthesis (FTS) catalysts with high reduction levels were synthesized through an autocombustion method using citric acid (CA) as a reductant and nitrate ions as oxidants. The as-synthesized catalysts were used directly in FTS reaction without further reduction. The effects of the ruthenium promoter, citric acid contents and reductant types on the catalyst structures and FTS performance were systematically studied. Results indicated that the introduction of a small amount of Ru (1 wt%) improved the reduction and dispersion of cobalt during the autocombustion process, and significantly enhanced the FTS activity. The CO conversion of the catalyst increased rapidly from 0.8 to 41.4% after Ru promotion. The citric acid contents (molar ratio of citric acid to nitrates: CA/N) in the precursor also played an important role in controlling the structures and FTS performance of the catalysts. With the increase of CA/N, the metal reduction level increased and the Co crystalline size decreased but the activity of the catalyst first increased and then decreased with gradually increasing CA/N. An excessive amount of the reductant could result in more residual carbon species and decrease the activity of the catalyst. For different types of reductants (at the same molar ratio of reductants to nitrates), the catalyst prepared by citric acid exhibited the highest activity whereas the catalyst synthesized by oxalic acid showed the lowest methane selectivity. The Ru promoted cobalt catalysts prepared by the autocombustion method, which omits the complex and high energy consumption reduction process, can be used directly for highly efficient FTS and thus will be more promising in the future.

Influence of citric acid molar ratio on the sintering behavior of nanocrystalline BaCe0.8Sm0.2O(3-delta).

The samarium-doped barium cerate (BaCe0.8Sm0.2O(3-delta), BCS) nano crystalline powders were synthesized via citric-nitrate method. The BCS nanopowders were prepared with various molar ratio of citric acid to metal nitrate. The pure perovskite structure was obtained from the BCS calcinated at 1200 degrees C and its crystalline size was increased with increase of the molar ratio citric acid to metal nitrate, while the aggregated particle size was significantly decreased as increasing the molar ratio. Also, excellent densification behavior was observed when high molar ratio of citric acid to metal nitrate was used. It was clarified that the molar ratio of citric acid determines the aggregated particle size and, in turn, finial microstructure after sintering.

한라봉 감귤 과립의 물리화학적 특성

Three different granule powders of Citrus Hallabong were prepared with different ratios of fresh juice and citric acid (J10C3=10.0:3.08, J08C4=8.75:4.33, J07C5=7.5:5.58) at fixed quantities of juice powder (70%), pressed cake powder (10%), and additives (6.92%), and their physicochemical properties were measured and compared with targeted commercial product (CP). The moisture content of Hallabong granules (HG) was 5.08∼5.44% (w/w), which was two times higher than that of CP. Titratable acidities increased with higher citric acid content and were 1.7∼2.3 times lower in HG compared to that of CP. Soluble solids of HG increased with higher citrus juice content (90∼98°Brix) and were slightly lower than that of CP. Vitamin C contents of HG increased with higher citrus juice content and were 5.8∼7.6 times lower than that of CP. In terms of color difference, L and b values of HG were higher while a value was lower than those of CP. Bulk and compaction densities of HG were 0.541∼0.660 g/mL and 0.561∼0.689 g/mL, respectively and were similar to those of CP. Water solubility and swelling capacity were 66.6∼72.0% and 3.84∼6.40 g/g, respectively, and were similar to those of CP. Hygroscopicity of HG after an hour of elapsed time was 1.6∼1.8 times higher than that of CP. Sensory evaluation test showed that color, sweetness, and overall acceptance of HG were not significantly different from those of CP, whereas flavor and bitterness of HG were lower than those of CP. In conclusion, convenient food granules could be made with Citrus Hallabong juice and pressed cake, which is similar to the commercial product.

Solution combustion synthesis of cobalt oxides (Co3O4 and Co3O4/CoO) nanoparticles as supercapacitor electrode materials

Co3O4 and Co3O4/CoO nanoparticles have been synthesized by a one-step solution combustion process by adjusting the molar ratio of citric acid (fuel) and Co(NO3)2·6H2O (oxidizer). The effects of citric acid/Co(NO3)2·6H2O molar ratios on phase composition and morphology of products were investigated by XRD and SEM. With the increase of the fuel dosage, the products transformed from granular aggregates of cubic Co3O4 into a mixture of cubic Co3O4 and tetragonal CoO with fluffy sheet morphologies. Electrochemical measurements indicated that the products (Co3O4) showed a capacitance up to 179.7 F·g−1 (at 0.2 A·g−1) when the citric acid/Co(NO3)2·6H2O molar ratio was 7/27. Significantly, the capacitance could be further improved by 102% (362.8 F·g−1 at 0.2 A·g−1) after annealing at 350°C for 3h under nitrogen atmosphere. This annealed sample also demonstrated decent rate performance (285.7 F·g−1 at 4 A·g−1) and cycling stability (73.5% retention after 1000 cycles). The current study suggests that this process has promise in large-scale production of electrode materials for supercapacitors.

High methoxyl pectin from dragon fruit (Hylocereus polyrhizus) peel

Pectin from different fractions of dragon fruit (Hylocereus polyrhizus) peel was extracted using 1% citric acid and the physico-chemical characteristics of the pectin were studied. The highest pectin yield (26.38% on dry weight basis) was obtained from fresh inner layer of the peel when extraction was carried out at temperature: 73 °C, time: 67 min, pH: 2.03, and sample to citric acid ratio: 1:4 (w/v). The pectin also demonstrated the highest degree of esterification (63.74%) when compared with pectin from other fractions of the dragon fruit peel investigated in this study. The calculated degree of esterification confirmed that the extracted pectin is a high methoxyl pectin. The molecular weight of the pectin determined using size exclusion chromatography was 0.88 × 105 Da. Monosaccharide composition determined using high performance liquid chromatography revealed that the pectin was predominantly constituted of galacturonic acid (39.11%), followed by moderate concentrations of mannose, rhamnose, galactose, glucose and minor amounts of xylose and arabinose. The pectin exhibited Newtonian behaviour at concentrations of 0.5% and 1.0%, and pseudoplastic behaviour at concentrations of 2.0% and 3.0%. Although the viscosity of the dragon fruit peel pectin was lower than that of commercial apple and citrus pectins, it can be used as a functional and health ingredient in low viscous foods and beverages.

Synthesis of manganese–zinc ferrite nanopowders prepared by a microwave-assisted auto-combustion method: Influence of sol–gel chemistry on microstructure

Based on the quantitative analysis and optimization of the complexing conditions for the sol–gel process, single phase Mn–Zn ferrite (Mn0.745Zn0.173Fe2.082O4) nanopowders with high saturation magnetization (MS=75.42emu/g) were one-step synthesized via a microwave-assisted sol–gel auto-combustion approach. The microstructures and magnetic property of the resulting powders were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy and magnetic measurement of M×H curves. The XRD patterns indicated that the low value of CA/M⁎ (the reduced molar ratio of citric acid to metal ions) and inadequate microwave irradiation are easy to result in the formation of impurity phases. Furthermore, the poor chelating of metal ions can be effectively improved by adding the ethylene glycol, which also acts as fuel to increase the reaction temperatures during the auto-combustions when oxidation degree Q (the relative amount of the oxidant) is high enough. The influences of the gel׳s chemistry, defined by the gel-parameters: CA/M⁎, oxidation degree Q and gross calorific value H (the total heat potentially produced by the complete oxidation of hydrocarbons), on the formation of single phase Mn–Zn ferrite nanopowders and their microstructures were investigated with the help of the orthogonal testing method. The microstructure of single phase Mn–Zn ferrite nanopowders is closely associated with the gel׳s chemistry. Moreover, the average grain size is more sensitively impacted by the gel-parameters than the residual microstrain and, relatively, the influences on the cell parameter are the smallest, with the impacting sequences of the gel-parameters: oxidation degree Q>gross calorific value H>CA/M⁎ for the grain size, oxidation degree Q>CA/M⁎>gross calorific value H for the microstrain and gross calorific value H>CA/M⁎ >oxidation degree Q for the crystal lattice parameter.

Study on Synthesis of Ester of Citric Acid and Palmityl Alcohol

Esters of Citric acid and palmityl alcohol were synthesized by esterification reaction under catalysis of cation exchange resin and P-toluene sulfonic acid respectively. The effects of amount of catalyst, ratio of raw materials, reaction time and temperature on the synthesis reaction were investigated . The experimental results showed that optimum of process conditions were 1:1~1:1.5 molar ratio of citric acid and palmityl alcohol, reaction temperature of 130~140°C, reaction time of 2 h. Conversion of palmityl alcohol were all more than 90% under 0.3% dosage using p-toluene sulfonic acid as the catalyst, or 0.5% dosage using 721 cation exchange resin with sulfonic acid type as catalyst. The synthesized product had good surface activity.

Synthesis and optical properties of pure monoclinic zirconia nanosheets by a new precursor

Pure monoclinic zirconia nanosheets were successfully prepared by the polymeric complex method. In this approach, zirconium acetylacetonato, Zr(acac)4, citric acid (CA) and ethylene glycol (EG) were used as the source of Zr4+ and the chelating and polymerization agent, respectively. The effects of heat treatment and EG:CA ratios on the structure, morphology and zirconia particle size were investigated. UV–vis spectra illustrated that ZrO2 nanosheets did not show any extrinsic states aroused from surface trap states, defect states, or impurities.

Fully Supramolecular Polyrotaxanes as Biphase Drug Delivery Systems

Pseudopolyrotaxanes (PPR) consisting ofα-cyclodextrin rings and polyethylene glycol axes with end thymine groups have been synthesized and characterized successfully. Fluorescein (Fl) as a model drug was conjugated to the hydroxyl functional groups of cyclodextrin rings of PPR via ester bonds and PPR-Fl as the primary drug delivery system was obtained. Finally PPR-Fl was capped by hydrogen bonds between end thymine groups and a suitable complementary molecule such as polycitric acid, citric acid, or adenine. The aim of this work was to control the release of the fluorescein-cyclodextrin (Fl-CD) conjugates, as the secondary drug delivery systems, from PPR-Fl by controlling the noncovalent interactions between stoppers and thymine end groups. It was found that the rate of release of the Fl-CD from PPR-Fl could be controlled by pH and the ratio of citric acid or adenine to the PPR-Fl.

The development of highly crystalline single-phase Bi20TiO32 nanoparticles for light driven oxygen evolution

The oxygen-producing photocatalysts play a critical role in the development of the artificial Z-scheme photocatalysis. Bismuth titanates have various complex forms, among which Bi20TiO32 could be an ideal oxygen evolution photocatalyst, but one has been suffering from its metastable structure and the complicate preparation. Herein, pure phase Bi20TiO32 samples were successfully synthesized by a simple sol–gel method followed by calcination of precursors. The effects of chelating agent, source of Bi and Ti precursor's composition have been studied. By combining bismuth nitrate, titanium isopropoxide, and citric acid, highly crystalline Bi20TiO32 was obtained after calcination since citric acid helps the formation of a stable complex in the sol–gel preparation with slow hydrolysis reactions due to highly steric hindrance in titanium isopropoxide. The effect of citric acid to metal ion ratio in this synthesis has been studied and optimized. It was found that only calcinations at 375°C produced a pure phase while others did not. Here we first reported that pure Bi20TiO32 with high crystallinity was obtained with 1:1 ratio of citric acid to metal ions and it showed the highest photocatalytic activity of oxygen evolution under the illumination. The effects of grain size and co-catalyst on Bi20TiO32 photocatalytic activity of the as-prepared samples have been studied. More generally, it suggests the incorporation of bismuth into a simple oxide of wide band gap via the simple sol–gel method as a strategy to design photocatalysts with excellent properties.

Fast Hydrolysis of Antler Residue by PEF Assisted Pepsin

Under optimized pulsed electric field (PEF) treatment for production of antlers calcium citrate malate and antlers collagen polypeptideby one-factor test were studied. The yield of dissoluble calcium (YDC) and protein degree of hydrolysis (DH) were used as characteristic indexes, the tests were carried out using different factors, which is as follows: the molar ratio of citric acid to malic acid (2:1-1:2), mixed acid content (0.1-1.0 mol/L), E/S (1-6 %), electric field intensity (5-30 kV/cm) and pulse number (2-12) were studied. The results indicated that the optimum conditions were E/S 4.0%, acid concentration 0.5 mol/L, electric field intensity 20 kV/cm, pulse number 8, the DH of 19.3±0.34 % and the YDC of 26±0.45 % were obtained.

The effects of citric acid on the synthesis and performance of silver–tin oxide electrical contact materials

A sol–gel auto-combustion method was developed to synthesize the Ag–SnO2 composite powders, which were then used as the starting material to prepare Ag–SnO2 electrical contact materials by hot pressing. It was found that citric acid strongly influences the thermal behaviors, phase evolution, morphology and composition distribution of the Ag–SnO2 composite powders. During the synthesis of Ag–SnO2 composite powders, citric acid can facilitate the formation of sol solution, lower the energy required for the decomposition of dry gel, and reduce the agglomeration of particles. Besides, a comparatively high molar ratio of citric acid to metal ions prevents effectively the occurrence of composition segregation in the Ag–SnO2 electrical contact materials. Therefore, the prepared Ag–SnO2 electrical contact materials have good performances in density, hardness and electric conductivity.

Preparation of Coherent La<sub>0.85</sub>Sr<sub>0.15</sub>MnO<sub>3</sub> Thin Films on La<sub>0.6</sub>Sr<sub>0.4</sub>Co<sub>0.2</sub>Fe<sub>0.8</sub>O<sub>3</sub> Substrates

A sol-gel method combined with spin-coating process has been developed for deposition of nanostructured thin films of La0.85Sr0.15MnO3(LSM) on La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF) pellets. The quality of the LSM films depends sensitively on the solution chemistry and other processing parameters. It was found that the optimal molar ratio of citric acid to ethylene glycol and to metal ions is 4:16:1 for the LSM sol. An amount of ethylene glycol was added into initial LSM sol to adjust the viscosity and the best value tested was 1.62×10-2Pas. A more uniform LSM film can be obtained with a suitable heating rate during firing. Modification of LSCF with a thin film coating of LSM has potential to enhance both stability and electrocatalytic activity for oxygen reduction.

Effect of citric acid, PVOH, and starch ratio on the properties of cross-linked poly(vinyl alcohol)/starch adhesives

The properties of tapioca starch adhesives were improved by cross-linking and the cross-linked adhesive compared with pure tapioca starch and poly(vinyl alcohol) adhesives. The effect of starch ratio, type of PVOH, and adding citric acid were important factors on the cross-linked adhesives. Wood adhesives made from cross-linked PVOH/starch were prepared by PVOH and tapioca starch, using hexamethoxymethyl melamine (HMMM) and citric acid (CA) as a cross-linking agent and catalyst, respectively. The effect of CA, PVOH/starch ratio, and type of PVOH such as medium (M PVOH) and high molecular weight (H PVOH) were investigated. The condition of the cross-linking reaction was 175 °C for 15 min. The structural properties of cross-linked adhesive were investigated by FT-IR spectroscopy. The results were confirmed in terms of thermal properties with a differential scanning calorimeter (DSC) and the shear strength of the adhesive. The cross-linked adhesive resulted in the increase of T g and showed good blend compatibility with all of the cross-linked adhesives. The adhesive strength significantly increased when using CA as a catalyst in the cross-linking reaction. The optimum contents of the cross-linked PVOH/starch adhesives were 1:1.8 for M PVOH and 1:0.5 for H PVOH.

Influence of citric acid on thermoplastic wheat flour/poly(lactic acid) blends. II. Barrier properties and water vapor sorption isotherms

The effects of citric acid on wheat flour/glycerol/poly(lactic) acid (PLA) blends prepared by one-step twin-screw extrusion have been studied to improve barrier properties of starch based materials. A series of injected samples were produced from prepared compounds with varying ratio (0–20 part) of citric acid. The effects of citric acid on the water vapor permeability, oxygen permeability and water solubility in the film were then investigated. The barrier properties results proved that citric acid behaves as compatibilizing agent between starch and PLA phases for ratios between 0 and 10 parts. When the added amount exceeds 10 parts, CA acted as a plasticizer and/or promoted the hydrolysis of the starch glycosidic bonds.

Catalytic Pyrolysis/Gasification of Refuse Derived Fuel for Hydrogen Production and Tar Reduction: Influence of Nickel to Citric Acid Ratio Using Ni/SiO2 Catalysts

Gasification technology is an attractive alternative for the thermal treatment of solid wastes, producing a high energy value hydrogen rich syngas. The presence of tar in the produced gas diminishes its quality and potential use in further processes; for this reason the reduction of tar in waste gasification is a major challenge. In this work the pyrolysis/gasification of refuse derived fuel (RDF) from municipal solid wastes, was investigated using a two-stage reaction system with Ni/SiO2 catalysts prepared by a sol–gel method varying the citric acid concentration (CA). The fresh and reacted catalysts were characterised for surface area and pore size distribution, temperature programmed oxidation, and high resolution scanning electron microscopy. The effect of the nickel to citric acid ratio (Ni:CA) was evaluated in terms of the characteristics and performance of the Ni/SiO2 catalysts. The results showed that the prepared Ni/SiO2 catalysts exhibited a relatively high surface area and an increase in pore size distribution as the Ni:CA ratio was increased. The efficiency of the prepared catalysts on tar reduction and hydrogen production was examined during the pyrolysis/gasification of RDF; the results were compared with a blank experiment using a bed of sand. The tar fraction was quantified using gas chromatography/mass spectrometry. A low tar concentration of ~0.2 mgtar/gRDF was attained using the catalysts with Ni:CA ratios of 1:1 and 1:3; additionally a high hydrogen concentration (58 vol%), and low CH4 (2.2 vol%) and C2–C4 concentrations (0.8 vol%), were attained using the catalyst with a Ni:CA ratio of 1:3. A higher tar concentration of ~1.7 mgtar/gRDF was attained using the bed of sand, while the hydrogen production was remarkably decreased. The major tar compounds identified in the tar samples using the Ni/SiO2 catalysts were phenol, cresols, naphthalene, fluorene, and phenanthrene.