Oxalate Salts Research Articles

Homogeneous Precipitation of Lanthanide Oxalates.

Oxalic acid is an important separation agent in the technology of lanthanides, actinides, and transition metals. Thanks to the low solubility of the oxalate salts, the metal ions can be easily precipitated into crystalline material, which is a convenient precursor for oxide preparation. However, it is difficult to obtain oxalate monocrystals due to the fast precipitation. We have developed a synthetic route for homogeneous precipitation of oxalates based on the thermal decomposition of oxamic acid. This work primarily concerns lanthanide oxalates; however, since no information was found about oxamic acid, a brief characterization was included. The precipitation method was tested on selected elements (Ce, Pr, Gd, Er, and Yb), for which the kinetics was determined at 100 °C. Several scoping tests at 90 °C or using different starting concentrations were performed on Ce and Gd. The reaction products were studied by means of solid-state analysis with focus on the structure and morphology. Well-developed microcrystals were successfully synthesized with the largest size for gadolinium oxalate.

Antimicrobial activity of supramolecular salts of gallium(III) and proflavine and the intriguing case of a trioxalate complex

The use of the gallium oxalate complex [Ga(ox)3]3− as a building block in the formation of a drug-drug salt with the antimicrobial agent proflavine (PF) as its proflavinium cation (HPF+), namely [HPF]3[Ga(ox)3]·4H2O, is reported together with the preparation of the potassium salt K3[Ga(ox)3] and the novel dimeric gallium(III) salt K4[Ga2(ox)4(μ-OH)2]·2H2O. All compounds have been characterized by solid state methods, and their performance as antimicrobial agents has been evaluated by disk diffusion assay against the bacteria strains Pseudomonas aeruginosa ATCC27853, Staphylococcus aureus ATCC25923, and Escherichia coli ATCC25922. While the [HPF]3[Ga(ox)3]·4H2O drug-drug salt is effective against all three strains, the gallium oxalate salt K3[Ga(ox)3] showed impressive selectivity towards P. aeruginosa, with little to no antimicrobial activity against the other two organisms. This work presents novel breakthroughs towards Ga based antimicrobial agents.

Highly active small Pd nanocatalysts obtained by visible-light-induced photoreduction with citrate and oxalate salts under batch and flow approaches

With a suitable combination of citrate and oxalate salts as photoinitiators, a visible-light induced Pd NP synthesis was conducted. Depending on the reaction conditions of the catalysis, the ligands may have a great impact on the catalytic activity.

New solvates and a salt of the anti-HIV compound etravirine.

Four new solvates of the anti-HIV compound etravirine [systematic name: 4-({6-amino-5-bromo-2-[(4-cyanophenyl)amino]pyrimidin-4-yl}oxy)-3,5-dimethylbenzonitrile, C20H15BrN6O] with dimethyl sulfoxide (C2H6OS, two distinct monosolvates), 1,4-dioxane (C4H8O2, the 0.75-solvate) and N,N-dimethylacetamide (C4H9NO, the monosolvate), which exhibit conversion to the same anhydrous etravirine phase upon desolvation, and a stable etravirinium oxalate salt {6-amino-5-bromo-4-(4-cyano-2,6-dimethylphenoxy)-2-[(4-cyanophenyl)amino]pyrimidin-1-ium hemioxalate, C20H16BrN6O+·0.5C2O42-} were obtained. The crystal structures were solved by single-crystal X-ray diffraction and analyzed by powder X-ray diffraction, and the intermolecular interactions were explored by Hirshfeld surface analysis. Lattice energies were evaluated using the atom-atom force field Coulomb-London-Pauli (AA CLP) approximation, which distributes the total energy as four separate contributions: Coulombic, polarization, dispersion and repulsion. The formation of the solvates and the oxalate salt was further characterized by thermal analysis and IR spectroscopy.

Two photon absorption induced optical limiting action of oxalate salt of pyridine for laser-assisted optoelectronic techniques

Two photon absorption induced optical limiting action of oxalate salt of pyridine for laser-assisted optoelectronic techniques

Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions**

AbstractEthynylbenziodoxolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report that aryl‐substituted EBX reagents can be directly activated by visible light irradiation. They act as both oxidants and radical traps, alleviating the need for a photocatalyst in several reported EBX‐mediated processes, including decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides and the C−H alkynylation of THF. Furthermore, the method could be applied to the synthesis of alkynylated quaternary centers from tertiary alcohols via stable oxalate salts and from tertiary amines via aryl imines. A photocatalytic process using 4CzIPN as an organic dye was also developed for the deoxyalkynylation of oxalates.

Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions*.

Ethynylbenziodoxolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report that aryl‐substituted EBX reagents can be directly activated by visible light irradiation. They act as both oxidants and radical traps, alleviating the need for a photocatalyst in several reported EBX‐mediated processes, including decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides and the C−H alkynylation of THF. Furthermore, the method could be applied to the synthesis of alkynylated quaternary centers from tertiary alcohols via stable oxalate salts and from tertiary amines via aryl imines. A photocatalytic process using 4CzIPN as an organic dye was also developed for the deoxyalkynylation of oxalates.

Methylene blue and metformin photocatalytic activity of CeO2-Nb2O5 coatings is dependent on the treatment time of plasma electrolytic oxidation on titanium

Despite UV photolysis is common industrial water treatment, existent approaches are still not fully effective nor practical due to the growing amount of discharged effluents. Titanium dioxide (TiO2) has been used as a semiconductor for photocatalytic degradation of pollutants, but its efficiency is limited due to its rapid reverse reaction. Thus, novel approaches are needed to improve the quality and cost benefits of photocatalysts. In this study, the processing time effect of CeO2-Nb2O5 coatings on titanium synthesized via a one-step method of Plasma Electrolytic Oxidation (PEO) in an electrolytic solution containing ammonium niobium oxalate salt [NH4NbO(C2O4)2] and cerium oxide (CeO2) powder at 300, 450, and 600 s. The structural and optical properties, morphology, wettability, coating thickness, and elemental chemical composition were investigated. The performance of CeO2-Nb2O5 coatings regarding the photocatalytic activity was evaluated under UV irradiation, using methylene blue (MB) and metformin as model pollutants. Energy Dispersive Spectroscopy confirmed the incorporation of Ce and Nb into the oxide film. The Scanning Electron Microscopy demonstrated that the PEO process produced CeO2-Nb2O5 coatings with a thickness from 9.6 to 55.8 µm and irregular and porous structures that changed in proportion and size according to treatment time. X-ray diffraction (XRD) analysis revealed that the coatings demonstrated crystallization corresponding to CeO2 and Nb2O5 phases. All the experimental groups presented an estimated band gap of 3.3 eV, suggesting that the obtained coatings could be active in the UV light range. Also, such coatings showed an increased surface area that varied from 3.93 to 5.62 cm2 as high it was the treatment time, which could facilitate the degradation of pollutants. These results were consistent with the photocatalytic activity assay, where samples treated for 600 s showed the most significant degradation of MB under UV irradiation, especially at 15 and 30 min of irradiation when compared to untreated titanium and photolysis process (p < 0.05). Regarding metformin, after 120 min of UV exposure, 27% was degraded due to photolysis. Whereas after 210 min, 67% of the pharmaceutical degradation was observed on the 600 s-treated CeO2-Nb2O5 coating. A crystalline CeO2-Nb2O5 coating with improved surface characteristics and photocatalytic activity was synthesized by tailoring the treatment time process. This study makes advantageous for degrading pollutants and medicines, since sewage treatment systems are sometimes slow or not fully effective.

Preparation and characterization of nanocrystalline NiO by the thermal decomposition of oxalate salts for the dehydrogenation of 2-butanol to methyl ethyl ketone

In the present study, highly active nanocrystalline nickel oxide samples were prepared by using a simple, solvent-free, and cost-effective preparation method. Commercial nickel oxalate dihydrate powder was mixed with deionized water to form a soft paste which was sonicated till dryness and then, calcined in static air. The prepared nickel oxide samples were characterized by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 adsorption-desorption techniques. The surface basicity of the prepared oxide samples was measured by adsorption of CO2 molecules followed by desorption measurements using the thermogravimetry (TG) technique. The catalytic activity of the prepared nickel oxide samples towards the dehydrogenation of 2-butanol to methyl ethyl ketone (MEK) was studied at a temperature range of 225-325°C. The effects of calcination temperature, reaction temperature, and weight hourly space velocity WHSV on the catalytic activity were studied to determine the best calcination temperature and the optimum operating conditions. The sample calcined at 400°C showed the highest activity and the optimum operating conditions were found to be at the reaction temperature of 300°C and WHSV of 15 L h-1 g-1. The selectivity to MEK was higher than 85% for all the conducted experiments.

Experimental, and theoretical investigations on the structure and vibrational spectral analysis of oxalate complex of nicotinamide and computational scrutiny against prostate cancer

This investigation involved oxalate salt of B vitamin experimental and theoretical spectra analysis. Docking studies and molecular dynamic simulation analysis were also carried out against the target protein involved in prostate cancer. At room temperature, the infra-red and Raman spectra results were chronicled in at range 4000–400 cm–1. In the crystalline environment along with the shifting of some spectral bands, the effect of hydrogen bonding force is detected. HF and DFT/B3LYP were employed to estimate the optimized geometry with the basis set of 6-311++G (d,p). Hypothetical wavenumbers presented a respectable agreement with the investigational values. The various genuine modes are observed and some of them are perceived in the experimentally observed spectra. Hyperconjugative interaction and intramolecular charge transfer (ICT) values were calculated with the help of the natural bond orbital (NBO) study. HOMO-LUMO plot technique was employed to examine the compound's hardness of chemical, chemical potential, and electro-negativity. The molecules' bioactivity and therapeutic efficacy were estimated through the lower band gap value of the frontier orbitals. In silico analysis was performed, to analyse the therapeutic efficacy of oxalate complex of Nicotinamide against Prostate cancer through Molecular docking and dynamics study. ADME/T analysis revealed the pharmaceutical efficacy of the oxalate complex of Nicotinamide by satisfying Lipinski’s Rule of Five, BBB, HOA, etc. Highlights of the work Comparative studies of theoretical and experimental vibrational spectra of the B vitamin Theoretical wavenumber numbers were showed good agreement with the experimental values Theoretical bond lengths and bond angles were slightly deviated from the experimental values Theoretical calculations shows that B vitamin exists in a Cocrystal Number of modes calculated from the factor group method is match with the theoretical method

Luminescence in Li3ScBr6: Ce

Synthesis and photoluminescence properties of Li3ScBr6:Ce phosphor are described. The phosphor was synthesized by a simple wet-chemical method. Lithium carbonate and Scandium oxide in stoichiometric proportions were dissolved in HBr. Activator was added in form of oxalate salt. After evaporating the solution to dryness the phosphor powder was obtained. Strong ultraviolet emission was observed for this phosphor. The UV emission is typical of Ce3+. It consists of a 359 nm band having a component at about 340 nm. The excitation spectrum has the most intense band at 314 nm besides smaller bands/shoulders around 255, 280 and 335 nm.

The Effect of NaCl Concentration and Incubation Time on Oxalate and Total Acid in Fermented Cabbage using Various Microorganisms

As the highest agrocultural product, cabbage (Brassica oleracea var. capitata) remain consider as perishable vegetable and also known to contain an antinutritional compound, called oxalate. The oxalate salts is non-soluble compound in water, and thus settle on human kidney. The preservation and improvement of the nutritional aspect of cabbage can be achieved by fermentation through the enzyme production. Therefore, we study the effect of salt addition and incubation time, as the two important factor in commonly cabbage-based fermentation, combined with someoxalate-degrading bacteria, which wasL. plantarum, L. plantarum – S. cerevisiae, and A. aceti – S. cerevisiae on the oxalate and total acid level in cabbage fermentation. The fermentation was conducted in submerged system at room temperature (25 – 27 °C) with the NaCl concentration addition ranging from 0 – 5% until 10 days. Those condition was carried out for the three types of the tested cultures. The oxalate and total acid level was measured using the permanganometric and acid base titration, respectively. The results indicated that L. plantarum-induced fermentation combined with 3% NaCl during 10 days gave the lowest oxalate level in the fermented cabbage biomass,which was 0.005 mg/100 g FW. Moreover, these single-cultured fermentation was able to produce the highest total acid level in the brine solution, 1.270% at the 8 days of fermentation. This fermentation serves as an alternative method to improve cabbage consumption.

STUDY OF THERMAL CO-DECOMPOSITION OF MANGANESE AND CERIUM OXALATES IN AIR AND IN INERT MEDIA

Controlled thermal decomposition of oxalate salts is a promising method for the preparation of highly dispersed materials. In this work, co-decomposition of Mn and Ce salts is studied upon variations of the cation ratio and the gas atmosphere of the process (air and inert gas). To this aim, a series of Mn and Ce oxalates is prepared by co-precipitation from aqueous solutions of nitrates with Mn:Ce ratios varying from 0:1 to 1:0. It is shown by X-ray powder diffraction and by scanning electron microscopy that cerium Ce(C2O4)3·10H2O and manganese MnC2O4·2H2O oxalates are formed. Also, increasing manganese content increases the amount of the corresponding salts and affects the morphology of the particles. It was shown by a number of physicochemical methods such as thermal analysis, in situ X-ray diffraction, and mass spectrometry shows that the oxalate decomposition proceeds in two stages and depends on the cation ratio and the decomposition atmosphere. The first stage is a weight loss accompanied by removal of structural water; this process is accelerated in a flow of an inert gas. The second stage is the formation of oxides from the anhydrous salt accompanied by CO2 or CO/CO2 release. Due to exothermic oxidation reaction, the decomposition occurs at lower temperatures in air than in an inert gas. The introduction of manganese does not significantly affect the temperature ranges of the first and second stages of salt decomposition. However, the addition of the second cation affects the decomposition product: as the manganese content increases, the size of CeO2 particles decreases and simple manganese oxides Mn3O4 and MnO are formed in air and in the inert atmosphere, respectively. The catalytic properties in the oxidation of CO, Mn and Ce oxides obtained by the decomposition of oxalates in an inert gas and in air are studied. It is shown that the catalysts formed in the oxidizing environment are more active.

Synthesis, characterization and evaluation of iron oxides and niobium in the removal of dyes in Fenton type reactions and photocatalysis

In this work, catalysts based on niobium oxide modified with iron oxide were developed for the photocatalytic treatment of effluents contaminated with dyes. The catalysts were prepared, in different proportions of niobium and iron, using niobium ammonium oxalate salts, iron nitrate and ammonium acetate and calcination at 400 °C. The solids were characterized by X-ray diffraction, infrared spectroscopy with Fourier transform, measured at zero point charge and evaluated in adsorption, Fenton reaction type advanced oxidation and methylene blue heterogeneous photocatalysis. It was observed that the increase in niobium concentration increased the values of point of zero charge and decreased the reaction system final pH. The solid with Fe/Nb2 ratio showed the best performance as an adsorbent and in oxidation reaction, followed by the one with Fe / Nb1.5 ratio. The solids showed practically the same result (1.8 eV), in addition, the presence of iron niobite (Fe/Nb1) favored the photocatalytic system.

Assessment of Paronychia Argentea Extraction on Kidney Stone by Using Calcium Oxalate Method

Urinary calculi are stones (urolithiasis) that can form anywhere in urinary tract outside of the kidneys and mostly composed of calcium oxalate and phosphate, additionally with elevated throughout the last two decades in the world. Chemical composition plays a major part in nephrolithiasis. Therefore, the high concentrations of lithogenic substances in urine enhance the crystallization method in urine tract system. The most kidney stones form from calcium oxalate, the present study was inspected the effect of the crude aqueous extract as well as the fractionated methanol extract (ethyl acetate, isopropanol, acetone and methanol residue) of paronychia argentea on the crystallization of calcium oxalate salts. The effect of aqueous extract and fractionated methanol extract on the size, number, type of calcium oxalate crystals. Paronychia argentea both the crude aqueous and the fractionated extract, especially ethyl acetate fraction have antiurolithic activity via reducing crystal size as well as activate the formation of calcium oxalate dihydrate (COD) crystals out from calcium oxalate monohydrate (COM) with increasing concentration of extract. The shifting of crystallization process to producing calcium oxalate dihydrate (COD) rather than oxalate monohydrate (COM) and the reducing the crystal size and calcium ion concentration, in addition to the diuretic action of extract plays an important role in controlling urolithiasis.

Synthesis and In Vitro Studies of O-Alkylaminoethylated Derivatives of 3E-Hydroximinocholestene as Potent and Selective Antileukemic Agents

New O-alkylaminoethylated derivatives of 3-hydroximinocholestene were synthesised and studied for in vitro cytotoxic effects. The obtained oily oxime ethers were solidified by preparing their oxalate salts. The steroidal compounds were screened against 60 human cancer cell lines at 10 μM. The study indicated that the compounds display selective cytotoxicity against leukemia cell lines. Dimethylamine (7a) and pyrrolidine (7d) derived O-alkylated steroidal oxalates displayed percent growth inhibition of 73.36%and 69.97 %, respectively, against CCRF-CEM leukemia cancer cell line. Partition coefficient values of the new steroids were also estimated to study the correlation of lipophilicity with the biological activity. The overall percentage growth inhibition of leukemia cell lines was 42% and 41% when treated with compounds 7a and 7d, respectively. Results obtained in the present study would help developing potent cytotoxic compounds with specificity toward leukemia cancer.

Combined filtration and oxalic acid leaching for recovering phosphorus from hydrothermally carbonized sewage sludge

Hydrothermal carbonization is a promising pretreatment for the energetic utilization of municipal sewage sludge. However, the carbonized slurry must be dewatered and the valuable compound phosphate recovered. This article reveals a new approach of combined slurry filtration and subsequent phosphate leaching using oxalic acid (18–72 g l−1) in a single apparatus for the first time. A slurry of hydrothermally carbonized sludge was filtered, washed, leached twice with oxalic acid and washed again. A thorough characterization of the filtration performance and the process products was conducted. The suspension is difficult to filter, but the permeability of the filter cake increases during acidic leaching. The specific filter cake resistance of (4.5 ± 2.2) · 1015 m−2 indicates poor filterability of the hydrochar slurry. 41–83% of phosphate and sodium are leached from the hydrochar, while all other investigated inorganics are leached to a lower extent. 12–31% of iron, calcium and manganese are removed from the hydrochar. The relative contents of carbon, hydrogen and oxygen increase in the residual hydrochar after leaching. After leaching, oxalic acid accounts 10.5–16.9% of the dry hydrochar due to adsorption and poor cake washing. Co-leached calcium, bivalent iron and magnesium precipitate from the leachate as oxalate salts. In conclusion, combined filtration and phosphate leaching enables efficient phosphate removal and generates an ash-reduced hydrochar for energetic utilization. However, to enable its technical application, the filtration performance and system integration need to undergo further development.

Utilization of coffee pulp waste for rapid recovery of pectin and polyphenols for sustainable material recycle

Coffee pulp is one of the major underutilized byproduct of coffee processing in farm level. Disposal of this agro-industrial waste has become one of the most challenging tasks for coffee planters. However, most of the efforts are towards the management of coffee pulp as an effluent, and not-on re-use. The problem is compounded due to the large volumes produced in diluted forms, which makes it expensive to reuse. The preliminary proximate analysis of coffee pulp indicated it to be rich in pectin and polyphenols. The efficacy of various chemicals like ethanol, sulfuric acid, hydrochloric acid, nitric acid, ammonium oxalate and metal salts for effective precipitation of pectin from coffee pulp was evaluated. HPLC characterization of the extracted and concentrated polyphenols fractions was analyzed. The maximum extraction of pectin was achieved by using metal salts and ethanol with 6.0% and 6.7% on wet weight basis respectively. The equivalent weight of extracted pectin (1180.5 mg/g) was found to be higher than that of commercial pectin (724.8 mg/g). The methoxyl content of the commercial pectin and crude pectin were 9.3 and 5.6% respectively. Gallic, vanillin, catechin, ethyl catechol, coumaric, Caffeic, and ferulic acid were the major polyphenols as quantified by the HPLC. The polyphenol fraction showed a good antioxidant activity with phosphomolybdate, FRAP, DPPH, and ABTS radicals respectively. The sustainable utilization of coffee pulp as a source of pectin and polyphenols with good antioxidant activities could help to solve the problem of waste generated in coffee processing in farm level.

(Invited) Highly Selective and Efficient Conversion of CO2 to Fomate and Oxalate

We succeeded in fabricating a dental amalgam composition on a copper foam electrode and could convert CO2 selectively to formate. The formate could be produced at a current efficiency of 80~100% in a wide range of the potential of 0.6 V. The remaining electricity was used only for producing H2. The concentration of the produced formate is over 1.2 M in the batch electrolysis of 30-hours operation. The CO2-to-formate conversion system, built based on the electrode in the dimension of 9 cm x 9, is shown to be stable in continuous operation at 100 mA/cm2 for more than a month. In the case of the conversion to oxalate, the electrolysis of CO2 in an organic solvent with a sacrificial anode, the current efficiency of 95%, and the production of 80 g of the oxalate salt could be obtained for 18-hour electrolysis using the three- stack-cell electrolysis unit. Figure 1

Organic molecular salts of allopurinol with improved solubility

Abstract Allopurinol is considered to be one of the most effective medications, which is regularly prescribed to reduce urate level and treat chronic gout. The drug belongs to biopharmaceutics Classification System (BCS) class IV category with poor aqueous solubility and permeability. High-throughput solid-form screening of the active pharmaceutical ingredient for new binary solid forms was carried out in order to improve drug properties. Multicomponent solids with oxalic acid and maleic acid were obtained during liquid assisted grinding of equivalent stoichiometry. The novel binary systems were characterized by PXRD, FT-IR, DSC, TGA and SEM images. Vibrational spectroscopy was exploited to confirm the ionization states of the multicomponent systems. Thermal analysis indicates the new solid phases with the possibility of hydrates in the oxalate and maleate salts, which degraded to allopurinol after melting. Powder dissolution experiment was carried out on the drug and the salts in pH-1.2 (acidic) and pH-7 (phosphate buffer, neutral) medium, which suggests that salts improved dissolution up to 4 fold compared to the native drug. In both the aqueous medium, maleate salt exhibited higher dissolution rate compared to the oxalate salt, which is correlated with its (former) lower melting point and higher crystal surface area.