Amount Of Oxalic Acid Research Articles

Modification of surface properties and photocatalytic performance of pure and oxygen-doped graphitic carbon nitride via DBD plasma treatment

Graphitic carbon nitride (CN) is a non-metallic semiconductor with applications in photocatalysis, including the photocatalytic reduction of Cr(VI) under visible irradiation. To improve its intrinsic properties, two modification strategies were applied: i) oxygen doping by co-calcination of urea with two different amounts of oxalic acid, and ii) dielectric barrier discharge (DBD) plasma treatment. The plasma treatment was applied to pristine and previously oxygen-doped CNs. The properties of the photocatalysts were studied by XRD, FTIR, FESEM, EDS, PL and DRS analysis, as well as by determination of the number of acidic surface functional groups. Both modification methods increased the oxygen content: during oxygen doping, nitrogen was replaced by oxygen in the lattice, while during plasma treatment, oxygen-containing functional groups were introduced at the surface. Plasma treatment of oxygen-doped CNs facilitated surface functionalisation due to the open heptazine ring structure. Oxygen doping narrowed the band gap, which was further slightly reduced by subsequent plasma treatment, thereby lowering the oxidation and reduction potentials. Although the absorption of visible light was improved, the reduction of the band gap resulted in a reduced activity for the photocatalytic reduction of Cr(VI). The best results were obtained with plasma-treated pure CN, due to the increased content of oxygen-containing surface groups, which led to a slightly reduced recombination rate of charge carriers.

PH and Pectinase Dual-Responsive Zinc Oxide Core-Shell Nanopesticide: Efficient Control of Sclerotinia Disease and Reduction of Environmental Risks.

Sclerotinia sclerotiorum is one of the fungi that cause plant diseases. It damages plants by secreting large amounts of oxalic acid and cell wall-degrading enzymes. To meet this challenge, we designed a new pH/enzyme dual-responsive nanopesticide Pro@ZnO@Pectin (PZP). This nanopesticide uses zinc oxide (ZnO) as a carrier of prochloraz (Pro) and is encapsulated with pectin. When encountering oxalic acid released by Sclerotinia sclerotiorum, the acidic environment promotes the decomposition of ZnO; at the same time, the pectinase produced by Sclerotinia sclerotiorum can also decompose the outer pectin layer of PZP, thereby promoting the effective release of the active ingredient. Experimental data showed that PZP was able to achieve an efficient release rate of 57.25% and 68.46% when pectinase was added or under acidic conditions, respectively. In addition, in vitro tests showed that the antifungal effect of PZP was comparable to that of the commercial Pro (Pro SC) on the market, and its efficacy was 1.40 times and 1.32 times that of the Pro original drug (Pro TC), respectively. Crucially, the application of PZP significantly alleviated the detrimental impacts of Pro on wheat development. Soil wetting experiments have proved that PZP primarily remained in the soil, thereby decreasing its likelihood of contaminating water sources and reducing potential risks to non-target organisms. Moreover, PZP improved the foliar wettability of Pro, lowering the contact angle to 75.06°. Residue analyses indicated that PZP did not elevate prochloraz residue levels in tomato fruits compared to conventional applications, indicating that the nanopesticide formulation does not lead to excessive pesticide buildup. In summary, the nanopesticide PZP shows great promise for effectively managing Sclerotinia sclerotiorum while minimizing environmental impact.

New modifications of PBAT by a small amount of oxalic acid: Fast crystallization and enhanced degradation in all natural environments

Biodegradable plastics are often mistakenly thought to be capable of degrading in any environment, but their slow degradation rate in the natural environment is still unsatisfactory. We synthetized a novel series of poly(butylene oxalate-co-adipate-co-terephthalate) (PBOAT) with unchanged melting point (135 °C), high elastic modulus (140 - 219 MPa) and elongation at break (478 - 769%). Fast isothermal crystallization with a semi-crystallization time < 20 s was demonstrated by the PBOAT. In N2 and air atmospheres, the PBOAT maintained the Td,5% higher than 329 °C. They also had good thermal stability at melt processing temperature for more than 20 min. PBOAT exhibited faster hydrolysis and seawater degradation, even under natural soil burial without light, but still kept stable under low humidity conditions during the storage and the shelf-life. Moreover, the hydrolysis mechanisms were clarified based on Fukui function analysis and DFT calculation, indicating that the hydrolysis of PBOAT would be more straightforward. The mechanism of soil burial is also elucidated through detailed characterization of the structure changes. The PBOAT offered a fresh approach to the development of high-performing, naturally degradable materials.

Modification of the Intensity of Compounds Biosynthesis in the Petioles of Rhubarb (Rheum rhaponticum L.) Induced by the Ozonation Process

Abstract Rhubarb (Rheum rhaponticum L.) is a vegetable that, despite many health-promoting properties, contains large amounts of oxalic acid, which has a negative impact on human health. Treatment of rhubarb petioles with gaseous ozone is one way to improve their quality by changing their chemical properties. As part of the research, an analysis of the mechanical and chemical properties of rhubarb petioles was performed. The analyzes showed that the applied doses of ozone of 10 ppm during 1, 3 and 5 minutes lowered the concentration of oxalic acid during 5 days of tests performed after the ozonation treatment. The most favorable effect on the reduction of oxalic acid, amounting to 36%, was caused by gaseous ozone at a concentration of 10 ppm during 5 minutes compared to the control. In addition, it was noted that on the 1st and 3rd day after using ozone gas, the antioxidant activity of the tested raw material increased significantly. Also on the same days of testing, the total amount of polyphenols increased as a result of the use of ozone fumigation. The largest increase in the total amount of polyphenols, amounting to 12%, was observed for a dose of 10 ppm 5 minutes on the 1st day after the ozonation treatment compared to the control variant. In turn, no positive effect of the ozonation process on the content of vitamin C and the value of destructive force during three-point bending of rhubarb leaf petioles was noted.

A New Fe2O3-Graphene-Hydrazine Sulphate Nanocomposite as Anode Material with Enhanced Electrocatalytic Activity in an H2O2 Fuel Cell

In the present study, synthesis of various phases of iron oxide was carried out by simple combustion method. The synthesized iron oxides and their composites with graphene and hydrazine sulphate are investigated as electrocatalytic materials for hydrogen peroxide (H2O2) fuel cells. The activity was seen to be dependent on the phase composition, surface features and electrical properties which was altered due to the use of the different amount of oxalic acid as one of the precursors during the synthesis. The catalysts which are more active for decomposition of hydrogen peroxide, showed lower electrocatalytic activity. A significantly improved electrocatalytic performance is obtained when a nanocomposite electrocatalyst is prepared using iron oxide, graphene and hydrazine sulphate.

Elemental concentrations in green vegetables from the perspective of urolithiasis risk

Although green vegetables are valuable sources of essential elements, and are safe in that they lack harmful elements, they are high in oxalic acid, increasing the risk of urolithiasis. We performed elemental analyses on spinach (Spinacia oleracea L), Malabar nightshade (Basella alba), and water Morning Glory (Ipomoea aquatica), which contain large amounts of oxalic acid, and compared the data to those of Japanese mustard spinach (Brassica rapa var. perviridis), which is the second most commonly consumed green vegetable (after spinach) in Japan. We focused on concentrations of Ca, Mg, and Sr that suppress the formation of ureteral stones (calculi). The calcium concentration in spinach was [Formula: see text]g/g in leaves and [Formula: see text]g/g in stalks, and the level in Japanese mustard spinach were [Formula: see text]g/g in leaves and [Formula: see text]g/g in stalks. The overall Sr concentration in Japanese mustard spinach was thus 10-fold higher than in spinach, but the Mg concentration was lower than that in spinach. The concentrations of Ca and Sr in Malabar nightshade and water Morning Glory were 3- to 5-fold higher than in spinach. As the former vegetables are consumed much less often than spinach, the risk of urolithiasis is low. We explored how the concentrations of these elements changed after boiling.

Microbially-driven alkaline regulation: Organic acid secretion behavior of Penicillium oxalicum and charge neutralization in bauxite residue

Microbially-driven alkaline neutralization in bauxite residue by functional microorganisms is a promising approach for the ecological rehabilitation on alkaline disposal areas. However, the alkali resistance and acid secretion mechanism of functional microorganisms are still unknown, which limits their application. Here, saline-alkaline resistance, acid production performance, and differentially expressed genes of Penicillium oxalicum (P. oxalicum, a functional fungus screened from a typical disposal area) were investigated and its bio-neutralization efficiency was evaluated. This fungus exhibited high tolerance to alkalinity (pH 12), and salinity (NaCl 2.0 M), and produced a large amount of oxalic acid to reduce the medium pH to 2.0. Transcriptome showed that alkali stress induced the overexpression of genes related to antioxidant and stress-resistant enzymes (GST, KatE) and glycolytic pathway rate-limiting enzymes (HK). The rate of glycolysis and other organic acid metabolism processes was increased with higher stress resistance of P. oxalicum. The integrated application of P. oxalicum and maize straw accelerated the dissolved organic carbon content and stabilized the leachate pH of bauxite residue at about 7.4. 3DEEM and BIOSEM analysis indicated that P. oxalicum maintained high activity in the residue leachate and continuously decomposed the maize straw for their metabolism. P. oxalicum showed strong alkaline resistance, biomass degradation capacity, and alkaline regulation potential, which should be beneficial for microbial-driven alkaline regulation in bauxite residue.

Semicontinuous Process of Rare Earths Recovery from End-of-Life NdFeB Magnets on a Large Laboratory Scale

Hydrometallurgical methods for NdFeB recycling typically consist of several unit operations and require the extensive use of energy, water and chemicals which may negatively affect the applicability of these methods on an industrial scale. Based on the data from our previous studies, a simplified process of rare earth elements (REE) recovery from spent NdFeB magnets was developed further. The possibility of regenerating the leaching agent, as well as water recovery, in the process was investigated. This study also investigates a possibility of scaling up the recycling process developed on a laboratory scale. The leaching and precipitation stages were tested on a larger scale, where about 1 kg of end-of-life magnets was used as feed to the leaching step. In this study, end-of-life magnets were obtained from the manual disassembly of computer hard disc drives. After disassembly, the magnets were demagnetized, broken into pieces and fed to the leaching process. In the following step, rare earths were precipitated in the form of oxalates. The rare earths’ precipitation efficiency reached a maximum of 95.6%. The results showed that the co-precipitation of Fe highly depends on the amount of oxalic acid used as the precipitant. Smaller losses of Fe were achieved while using a stoichiometric amount of oxalic acid in relation to the REE present in the solution. At the end of the investigated process, rare earth oxalates were calcinated to oxides and their purity was investigated. The recirculation of a solution after oxalate precipitation and acid regeneration was tested with hydrochloric and sulfuric acids used as leaching agents. Solution recirculation was found to be possible only in the case of hydrochloric acid.

Recovery of Rare Earth Elements from the Leaching Solutions of Spent NdFeB Permanent Magnets by Selective Precipitation of Rare Earth Oxalates

After mechanical pre-treatment, the typical hydrometallurgical route of NdFeB magnet recycling starts with leaching in acidic solutions. However, due to the high concentration of iron ions in the leaching solution, the selective recovery of rare earths from the solution is challenging. In our work, the selective precipitation of rare earth oxalates as a potential separation method was proposed. The precipitation of neodymium oxalate was first tested on model solutions, which was then followed by experimental tests carried out on real solutions after the leaching of NdFeB magnets. The recovery of rare earths in the form of oxalates was investigated with the use of different amounts of oxalic acid in relation to its stoichiometric amount. The most efficient separation of rare earths was observed in the case where sulfuric acid was used for leaching. The use of oxalic acid in stoichiometric amounts resulted in the precipitation of about 93% of all rare earths present in the solution, whereas the concentration of Fe and other elements (Ni, Co, and B) practically did not change. An increase in oxalic acid of 20% and 40% more than the stoichiometric amount (100%) led to the increase in the precipitation efficiency of rare earths to 96.7% and 98.1%, respectively. However, the use of oxalic acid in a 1.4 ratio caused a 7% decrease in Fe concentration, which suggests Fe co-precipitation. In order to investigate a possibility of further increasing the separation of rare earths from iron, an additional method was tested, in which iron was first oxidized from Fe2+ to Fe3+ before the precipitation of rare earth oxalates.

The quantity of OA and activity of cellulase and polygalacturonase are involved in variation of virulence in Sclerotium rolfsii

In order to understand the pathogenic mechanisms of Sclerotium rolfsii on peanut and to analyze the variation of virulence in S. rolfsii strains, the highly virulent strain (ZY2) and weakly virulent strain (GP3-1) were investigated under both in vivo and in vitro conditions. The results indicated that S. rolfsii directly infected peanut by producing infection cushions. ZY2 formed infection cushions earlier than GP3-1, and ZY2 produced a greater number of infection cushions compare to GP3-1. Both strains could utilize cellulose, xylose, or polygalacturonic acid in the Czapek medium. The activities of cellulase (CL) and polygalacturonase (PG) in the inoculated peanut stems increased significantly at 9 ​h after inoculation. The activities of CL and PG produced by ZY2 in the inoculated stems were significantly higher than that produced by GP3-1. Both strains could produce oxalic acid (OA), and the content of OA produced by ZY2 in the inoculated stems was higher than that produced by GP3-1. In summary, it suggested that S. rolfsii destroyed peanut cells through physical and biochemical factors by secreting a large amount of OA, CL and PG during the formation of infection cushions. The difference in OA content, activity of CL and PG produced by highly and weakly virulent strains played important roles in variation of virulence.

Facile synthesis of anatase TiO2 nanoparticles using titanium metal and its enhanced photocatalytic activity under visible light

A green sol-gel method was employed to synthesize TiO2 nanoparticles (NPs) using titanium metal. The syn-thesized TiO2 NPs underwent comprehensive characterization using techniques including X-ray diffraction (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), and UV–Vis diffuse reflectance spectroscopy (UV-Vis DRS) to evaluate their structure, morphology, and spectral properties. By adjusting the amount of oxalic acid, tailored physico-chemical properties of anatase TiO2 catalysts were achieved. The obtained TiO2 catalysts demonstrated a high surface area, excellent absorption, and remarkable photocatalytic degradation of methylene blue under visible light irradiation. This enhancement is primarily contributed by the large surface area and oxygen vacancies.

A Comparative Study on Heavy Metal Removal from CCA-Treated Wood Waste by Yarrowia lipolytica: Effects of Metal Stress.

Bioremediation is an effective way to remove heavy metals from pollutants. This study investigated the effects of Yarrowia lipolytica (Y. lipolytica) on the bioremediation of chromated copper arsenate (CCA)-treated wood wastes. Copper ions stressed the yeast strains to improve their bioremediation efficiency. A comparison of changes in morphology, chemical composition, and metal content of CCA wood before and after bioremediation was conducted. The amount of arsenic (As), chromium (Cr), and copper (Cu) was quantified by microwave plasma atomic emission spectrometer. The results showed that yeast strains remained on the surface of CCA-treated wood after bioremediation. The morphologies of the strains changed from net to spherical because of the Cu2+ stress. Fourier-transform infrared spectroscopy showed that carboxylic acid groups of wood were released after removing heavy metals. A large amount of oxalic acid was observed when the optical density (OD600nm) was 0.05 on the 21st day. Meanwhile, the highest removal rate of Cu, As, and Cr was 82.8%, 68.3%, and 43.1%, respectively. Furthermore, the Cu removal from CCA-treated wood increased by about 20% after Cu2+ stress. This study showed that it is feasible to remove heavy metals from CCA-treated wood by Y. lipolytica without destroying the wood structure, especially by copper-induced Y. lipolytica.

Predicting the catalytic performance of Nb-doped nickel oxide catalysts for the oxidative dehydrogenation of ethane by knowing their electrochemical properties

In the present article, a relationship between the catalytic performance in the oxidative dehydrogenation of ethane (ODHE) for Nb-doped NiO catalysts and their electrochemical properties has been proposed. To do so, highly stable and selective Nb-doped NiO catalysts for the ODHE to ethylene have been synthesized by optimizing synthesis parameters such as the amount of oxalic acid in the synthesis gel and the calcination temperature. These catalysts have been characterized by means of XRD, HRTEM, Raman and UV–vis diffuse reflectance spectroscopies, TPR and XPS. Moreover, Electrochemical Impedance Spectroscopy (EIS), capacitance measurements (Mott-Schottky analysis) and cyclic voltammetries studies were also carried out. Electrochemical characterization indicates changes in the type of semiconductivity: p-type for samples calcined at 350 °C and the sample prepared in the absence of oxalic acid and calcined at 500 °C, to n-type for samples prepared in the presence of oxalic acid in the synthesis gel and calcined at 500 °C. According to the obtained results, the most selective catalysts present a low Nb-incorporation on the NiO lattice with a large amount of tiny Nb2O5 nanoparticles covering NiO crystallites. This work presents, for the first time, a complete electrochemical characterization of Nb-doped NiO catalysts showing a correlation between electrochemical properties and catalytic performance.

Role of Oxalic Acid in Expression of Resistance against the Pod Borer Helicoverpa armigera (Lepidoptera: Noctuidae) in Chickpea Varieties

Background: Pod borer is most serious problem to cultivation of chickpea across the world. In India, Madhya Pradesh rank first in both area and production of chickpea. This region is considered most affected yield of chickpea due to H. armigera. Host plant resistance is an important component for managing this pest. To develop cultivars with resistance to insects, it is important to understand the role of oxalic acid associated with resistance to this pest. The current study aimed to study the role of oxalic acid in expression of resistance against the pod borer Helicoverpa armigera (Lepidoptera: Noctuidae) in chickpea varieties under climate change. Methods: This investigation was carried out at Research Farm of Soybean Seed Production-Unit, College of Agriculture, JNKVV (MP) during Rabi season 2019-20 and 2020-21. The field experiment was laid out in split split plot design with 24 treatments and three replications. The treatments included three date of sowing i.e. 15th November, 30th November and 15th December as a main plots, two irrigation levels i.e. I0-no irrigation and I1- irrigation at 35 DAS as a sub plots and four chickpea varieties i.e. JG 12, JG 36, JG 14 and JG 24 as sub sub plots. The observation on number of eggs and larval population of H. armigera were recorded from one-meter row length (mrl). At five randomly selected places were averaged separately for each plot and made in to number of eggs and larval population per meter row length (mrl). The amount of oxalic acid in chickpea leaves was determined by UFLC method. The correlation was worked out with population of pod borer and amount of oxalic acid in chickpea varieties. Result: In this investigation, the ultra-fast liquid chromatography (UFLC) profiles of the leaf exudates of chickpea varieties exhibited amounts of oxalic acid significantly negative correlation with egg count and larvae incidence of H. armigera.

Physiological response of ectomycorrhizal fungi (Lactarius delicious) to microplastics stress

&lt;p&gt;The pollution and toxicological effects of microplastics in soil have gradually attracted widespread attention, but studies on the ecological effects of microplastics on soil microorganisms and their mechanisms are still very scarce. To explore the physiological response of ectomycorrhizal fungi (Lactarius delicious, Ld) to microplastic stress, Ld was used as the test strain, and 80 nm and 4 μm monodisperse polystyrene microspheres (PS-MPs) were selected. The solid plate method and the liquid culture method were used to study the effect of PS-MPs with two particle sizes on the growth, nutrient content, reactive oxygen species (ROS) production, organic acid secretion and other indicators of the strain Ld. The results showed that with increasing PS-MPs concentration, the biomass of strain Ld decreased gradually. When the strain Ld was exposed to high concentrations of PS-MPs (200-300 mg L-1), PS-MPs with particle size of 4 μm showed stronger inhibition of biomass than PS-MPs with particle size of 80 nm. After exposure to the PS-MPs environment of two sizes, the concentration of PS-MPs increased (0-300 mg L-1), and the contents of phosphorus (P), potassium (K), H2O2 and superoxide anion radical (O2·-) in Ld mycelia increased significantly (p &amp;lt; 0.05). This showed that the antioxidant substances in Ld could not remove excess ROS, but could reduce the stress of microplastics by increasing the absorption of P and K from the environment, which was beneficial to its own metabolic activities. In addition, the strain Ld could secrete oxalic acid, acetic acid and succinic acid into the culture medium, which the amount of oxalic acid secreted was the highest. We speculated that strain Ld responded to the stress of microplastics by secreting a large amount of organic acids. Therefore, the mechanism of the influence of microplastics on ectomycorrhizal fungi may involve oxidative stress, and the mycelia responded to the toxicity of microplastics by secreting more organic acids and increasing the absorption of P and K. The results of this study will provide a scientific basis for the study of the acute toxicity of microplastics to ectomycorrhizal fungi.&lt;/p&gt;&#x0D;

Chemical Composition and Antioxidant Properties of Common and Lemon Verbena.

The nutritional profiles of common and lemon verbena leaves were analyzed (proximate constituents, free sugars, organic acids, tocopherols, and fatty acids) and the leaves were prepared in hydromethanolic and aqueous (decoctions and infusions) extracts. The phenolic compound composition and antioxidant activity (2,2-Diphenyl-1-picrylhydrazyl (DPPH); 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric-reducing antioxidant power (FRAP); and cupric-reducing antioxidant capacity (CUPRAC) assays) of the extracts were characterized. The nutritional composition varied between the studied species, with lemon verbena showing higher amounts of protein, ash, and fat than common verbena, whereas the opposite trend was recorded for the dietary fiber content. The main free sugars detected in both species were fructose, glucose, and sucrose, which were present in higher amounts in the common verbena samples. Succinic acid was the most abundant organic acid in both species while high amounts of oxalic acid were detected in lemon verbena. The main fatty acids in both species were α-linolenic, palmitic, and linoleic acid. Regarding the phenolic compound content, the extracts of lemon verbena presented higher amounts of total phenolic compounds (TPCs), total flavonoids (TFs) and total phenolic acids (TPAs) than the common verbena extracts while the aqueous extracts (infusions and decoctions) were richer in TPCs, TFs, and TPAs than the hydromethanolic ones in both species. Nine phenolic compounds were identified and quantified, including seven phenolic acids and two flavonoids. The lemon verbena samples were characterized by higher antioxidant activity compared to the common verbena samples while the aqueous extracts showed higher antioxidant efficacy than the hydromethanolic ones. In conclusion, both species showed promising results in terms of the nutritional value, chemical composition, and antioxidant activities, which were positively correlated with the phenolic compound contents. Moreover, the extraction protocol may affect the chemical composition and bioactive properties of both species, with aqueous extracts showing better results than hydromethanolic ones.

Extraction and quantification of oxalic acid in leaves of plant species used in the treatment of chronic non-communicable diseases

Introduction: Chronic non-communicable diseases (CNCDs) are a group of diseases characterized by having the highest mortality and morbidity rates in the world. Despite the increase in new drug technologies, the use of medicinal plants as an aid in therapy for these diseases is a widespread reality. However, most plant species contain inorganic crystals of calcium oxalate, a product of plant metabolism, which has several functions in plant tissues. For the human species, its ingestion is associated with the arising of kidney problems such as urinary lithiasis, especially in people who have a predisposition to these conditions. Aim: To determine the amount of oxalic acid in plant species, which are used in the treatment of CNCDs. Methodology: After collection and characterization the plant species, aqueous and acidic extracts were obtained from 0.5 g of the plant drug of each species and, subsequently, were titrated with a standardized 0.02 mol.L-1 potassium permanganate solution and the concentrations of oxalic acid were expressed in g/100 g of dry vegetable drug. Result: The data obtained from the concentration of oxalic acid ranged from 4.58 ± 0.09 g/100 g to 17.21 ± 0.07 g/100 g and demonstrated that the concentrations from acid extraction are higher compared to the aqueous extraction, for all vegetables species analyzed. Methodological optimization was performed for the species that showed the highest results, Psidium guajava and Artocarpus heterophyllus. Conclusion: The data obtained can serve as input for medical decisions and for professionals who prescribe medicinal plants.

Dissolution of Magnetite and Hematite in Mixtures of Oxalic and Nitric Acid: Mechanisms and Kinetics

Dissolution mechanisms and kinetics have a key role in better understanding of processes. In this work, magnetite and hematite powder were dissolved in oxalic and nitric acid mixtures at different temperatures. Higher temperature and higher amounts of oxalic acid in the system accelerated the dissolution kinetics but did not result in higher solubility levels. Oxalic acid had also drawbacks in the process since higher amounts in the system promoted formation of a solid product, humboldtine (Fe(II)C2O4∙2H2O), which, in turn, inhibited the dissolution. This problem may be overcome by adding even a small amount of nitric acid to the system. Kinetic analysis showed, in the variable-rate-controlling step, that two linear fits of the Kabai model described the dissolution better in an oxalic acid and acid mixture of 70/30. Thermodynamic data and special cubic models showed that the nitric acid concentration had a significant role in the solubility, whereas the concentration of oxalic acid had only minor effects on solubility. The results also showed that measuring the oxalate and nitrate concentrations did not provide additional information about the dissolution mechanism itself. The pH, however, might be a tool for following the extent of dissolution, even though it is not a direct indicator of the dissolution mechanism.

The effect of NaOH concentration and stem size in the making of Oxalic Acid from Banana Stem

The main purpose of this research is to determine the effect of NaOH concentration and size of banana stem pieces on the concentration of oxalic acid produced. The experiment procedure is add 20 grams of banana stems that have been dried into 200 ml NaOH then heated and stirred at temperature of 100°C for 1 hour. Then the molten mixture was added with hot 500 ml of water, then cooled and filtered. Filtrate was taken and added to 100 ml CaCl2. Solution is filtered and the sediment is taken. Sediment is inserted into the Erlenmeyer and 200 ml dilute H2SO4 added and then filtered. 10 g active carbon is added into filtrate of the solution, then filtered. Taking 10 ml of the filtrate above to be titrated. From the research has been done, it can be concluded that the greater the concentration of NaOH, the greater the amount of oxalic acid obtained. The longer the size of the banana midrib, the greater the amount of oxalic acid obtained. And, the maximum amount of oxalic acid obtained is 2.99 g that reach at a concentration of 50% NaOH with a length of the banana leaf 2.5 cm.

Optimization of the performance of bulk NiO catalyst in the oxidative dehydrogenation of ethane by tuning the synthesis parameters

Highly stable and selective bulk NiO catalysts have been synthesized for the oxidative dehydrogenation (ODH) of ethane to ethylene. Interestingly, by optimizing synthesis parameters such as the amount of oxalic acid in the synthesis gel and the calcination temperature, undoped NiO catalysts have shown a consistent selectivity to ethylene of ca. 75%. The optimal catalyst requires the presence of a certain amount of oxalic acid in the synthesis gel and a final calcination at low temperatures (i.e. 350 °C). These catalysts have been deeply characterized by means of XRD, TPR, HRTEM, Raman and UV–vis diffuse reflectance spectroscopies, XPS and Electrochemical Impedance Spectroscopy measurements and tested in the ethane ODH. A novel electrochemical study has been undertaken, showing the p-character of all the NiO catalysts synthesized but differing in their capacitance values and density of cationic vacancies. The catalytic performance of NiO catalysts has been explained in terms of the different physicochemical properties (including changes in the number of vacancies) of the samples and the isolation of electrophilic oxygen species.