Dilute Nitric Acid Research Articles

Determination of Lutetium In Radiopharmaceutical Samples Using High Resolution ICP-AES Technique

An analytical method was developed for the determination of Lutetium in dilute nitric acid medium using high resolution ICP-AES analytical technique. These studies were required for the determination of Lutetium contents in radiopharmaceutical samples. For the patients suffering from cancers, 177Lu DOTA-TATE peptide receptor radionuclide therapy is used. This necessitates the use of 177Lu and obviously the quantification of Lutetium for its efficient application during medical therapy which is used for the preparation of the patients suffering from cancers. Due to short half life of 177Lu of 6.67 days, it is most likely to get added up with Hf, as it is build up on storage, the undesired impurity element. Hence the effect of Hf on the determination of Lu was studied. Subsequently seven actual samples of 177Lu were analysed for Lu contents after taking into account Hf contribution if any

Efficient process for xylitol production from nitric acid pretreated rice straw derived pentosans by Candida tropicalis GS18

Valorization of agricultural residues has garnered worldwide interests due to their inexpensive, renewable and environment friendly nature. Among various lignocellulosic wastes, rice straw is the third-most abundantly available biomass rich in hemicelluloses and an easily accessible biomass for biological production of xylitol. In the present study, dilute nitric acid was employed for fractionation of hemicellulosic component of rice straw. Screening of various parameters such as solid to liquid ratio, acid concentration, residence temperature and time was carried out for maximal liberation of fermentable sugars. Xylose conversion was attained to the extent of 71.32% from the xylan of rice straw upon treating with 1% (v/v) dilute HNO3 at 121 °C for 30 min. In the process, complete removal of furfurals and HMF as well as partial removal of acetic acid was achieved by using 2% (w/v) activated carbon. Maximum xylitol titre of 25.15 g/L and 34.21 g/L was obtained during fermentation of non-detoxified and detoxified hydrolysate of rice straw biomass respectively by the newly isolated strain of Candida tropicalis GS18 at 30 °C, 150 rpm and pH 5.5 after 96 h of fermentation. This study suggested the use of dilute nitric acid as an effective and environment friendly catalyst for efficient recovery of xylose from rice straw and its subsequent use for xylitol production.

Surface modified perovskite SrCo0.8Fe0.1Nb0.1O3-δ oxide for enhanced electrocatalytic activity of oxygen evolution reaction

• Simple acid etching modification treatment of SCFN surface. • The resulting A-site defects and oxygen vacancies increase OER activity. • The overpotential of SCFN-60 was decreased by 70 mV after acid treatment. It is of great significance to develop efficient and inexpensive electrocatalysts for reducing the overpotential of oxygen evolution reaction (OER). The surface of catalysts always plays an important role in catalytic reactions. Herein, we report the improvement of catalytic performance of a perovskite SrCo 0.8 Fe 0.1 Nb 0.1 O 3-δ (SCFN) by simple surface treatment with dilute nitric acid. It was found that the acid treatment could partially dissolve the A-site cation of Sr, increase the oxygen vacancy concentration and change the oxidation state of the B-site transition metal. Moreover, the modification method also increased the hydroxide adsorption capacity and concentrations of active oxide species. The OER activity and stability of HNO 3 treated sample of SCFN-60 were remarkably improved, and the overpotential was significantly reduced to 360 mV (0.1 M KOH). This work provides a simple strategy for increasing the OER activity of perovskite oxides in an alkaline solution at room temperature.

Gas-Liquid Interfacial Plasma engineering under dilute nitric acid to improve hydrophilicity and OER performance of nickel foam

The world has been moving rapidly to find new eco-friendly energy sources. Water electrolysis consists of two reactions of Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER), whereas the OER is considered the rate-limiting step. The most commercialized electrode for OER in the alkaline electrolyte is Ni foam, but its original surface is hydrophobic. It is possible to accelerate the adsorption and desorption process of reactants and products during OER by adding hydrophilic functional groups such as –OH on the surface of Ni foam. In this study, a novel Gas-Liquid Interfacial Plasma (GLIP) engineering at room temperature was successfully applied to modify the Ni foam surface dilute (1 ​M) HNO3 solution. At a current density of 400 ​mA ​cm−2, GLIP-treated Ni foam electrodes at 1 ​M HNO3 concentrations showed OER overpotentials of 458 ​mV. Among all, GLIP with 1 ​M HNO3 treatment of 30 ​min showed 129 ​mV less overpotential than the nickel foam before treatment. In summary, GLIP can be justified as an environmentally friendly and efficient surface treatment to improve the wettability and OER performance of Ni-based electrodes in water electrolysis.

Nitration of Aromatic Compounds: A study of different nitrating systems with Bronsted acid-surfactant-catalyst (BASC) in water

A simple, mild and region-selective method for the nitration of aromatic compounds using sodium nitrate/ sodium nitrite/ dilute nitric acid (6 wt.%) in the presence of bronsted acid-surfactant-catalyst (BASC) in water at room temperature was explored. An exclusive ortho-selectivity was observed with excellent yields in case of phenolic compounds. Here dodecyl benzene sulfonic acid (DBSA) performs dual role as catalyst and surfactant. This catalyst possesses some characteristic features like nonvolatility, imflamibility, low cost, good performance and is easily biodegradable. Mild reaction conditions and good to excellent yields of the products are the noteworthy advantages of this method.

Comparison of Ultrasound-assisted Methods for Copper Determination in Bovine and Ovine Liver as Strategies for Food Surveillance and Animal Status Monitoring

Four methods for the efficient extraction of copper from bovine and ovine liver were optimized. Sample preparation consisted of extractions with dilute nitric acid or dilute tetramethyl ammonium hydroxide, assisted by an ultrasonic bath or an ultrasonic probe. Copper was determined by flame atomic absorption spectrometry. The experimental conditions were optimized using multivariate experiments. All methods were considered adequate for copper extraction, however, the two methods involving the probe turned out to be more efficient and faster, so they were selected for subsequent validation. Trueness was verified after the analysis of a certified reference material and the performance of a microwave-assisted extraction. Results were statistically equivalent, at the 95% significance level, to the values declared on the certificate. Precision (expressed as relative standard deviation) was better than 5% for all methods. Samples obtained from Uruguayan animals were analyzed. Obtained results agreed with previous results from sheep and cattle abroad. The proposed methods are simple alternatives for food surveillance and animal status monitoring, being straightforward and aligned with Green Chemistry principles, as it was demonstrated by performing the analytical Eco-Scale comprehensive approach. A discussion related to the particle size distribution obtained during the multivariate experiments was also included, to give some deeper insight into ultrasound effect on the biological tissue in different media. In addition, ultrasound-assisted extraction was compared to magnetic stirring to prove the effect of ultrasound.

Kinetics Investigation of Phosphorus Leaching from Steelmaking Slag

ABSTRACT The removal of phosphorus is essential to recycling steelmaking slag in metallurgical processes. In this study, dilute nitric acid was selected as the leaching agent for dissolving steelmaking slag. The effects of the variables on leaching percentage of phosphorus were investigated. Experimental results showed that, the leaching percentages of phosphorus increase as the concentration of nitric acid increases. Increasing the liquid/solid ratio and decreasing the slag particle size increased the leaching percentages of the phosphorus. However, the temperature and stirring speed had minor effects on the dissolution of phosphorus. Diffusion through the product layer was the rate-limiting step of the leaching process, and the corresponding apparent activation energy was determined to be 1.61 kJ/mol. Based on experimental results, a semi-empirical kinetic equation was established.

Greenness of procedures using NADES in the preparation of vegetal samples: Comparison of five green metrics

The principles of green analytical chemistry have led to the development of analytical procedures that are increasingly sustainable. Different metrics have been created for the evaluation of greenness, although determination of the green nature of new analytical methods remains challenging, including for extraction methods that involve the use of natural deep eutectic solvents (NADES). In this study, the following five chemical metrics for the evaluation of greenness were considered: National Environmental Methods Index (NEMI), Green Analytical Procedure Index (GAPI), Analytical Eco-Scale, Analytical GREEnness (AGREE), and White Analytical Chemistry (WAC). These methods were applied in evaluation of the environmental and sustainability characteristics of three different methods for the preparation of plant material samples: microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and microwave-assisted acid digestion (MW-AD). These methods employed different NADES as extraction solvents, as well as dilute nitric acid as an oxidizing agent, for the determination of As, Cd, Pb, and V by inductively coupled plasma mass spectrometry (ICP-MS). The NEMI metric found no differences between the MAE-NADES and UAE-NADES methods. The GAPI metric found differences between the MAE-NADES and UAE-NADES methods and identify the disadvantageous aspects of each step of the methods. The Analytical Eco-Scale and AGREE identified the MAE-NADES method as the greenest, while WAC-12 RGB indicated the UAE-NADES method as the greenest procedure. A detailed discussion is provided of the application of each metric, together with their differences and advantages.

Development of a simple and fast ultrasound-assisted extraction method for iodine determination in phosphate rock and phosphogypsum by-product using titrimetric method

ABSTRACT Phosphate rocks, as well as their derivatives and by-products, are complex minerals that make elemental analysis very complicated. Iodine is commonly found in these matrices, and its concentration must be controlled. The present work describes the development of a novel rapid digestion protocol based on ultrasonic-assisted acid digestion for the determination of iodine in phosphate rock and phosphogybsum samples by Iodometric titration. The developed method occurs at low digestion temperature and uses a dilute nitric acid 5% (v/v) solution instead of concentrated acid. The investigated parameters influencing UAD, were completely optimised using experiments design methodology (DOE). Iodine recoveries from dilute nitric acid digestion without sonication were generally lower overall when compared to UAD results, illustrating the effect of ultrasound on iodine dissolution. This technique effectively addresses iodine volatilisation and sample losses problem encountered while using classical digestions. Method validation included: defining the detection and quantification limit of iodine using this method were about 2.2 and 8 mg.kg−1, respectively, and it's suitable for the proposed application. Moreover, the repeatability and reproducibility, expressed as RSD for phosphogybsum sample was 7%, 8.3% respectively, while for phosphate samples is tacked as the mean of relative standard deviation 3.4%, 3.8%. Additionally, accuracy of the method was assessed by analysing a certified reference material and the iodine concentration was found to be in good agreement with the indicative values for this CRM. Thus, the mean recoveries in fortified sample were between 96% and 107%.The developed method is fast, accurate, and it is applicable to the monitoring of iodine in the phosphate industries.

Electrodialytic Enrichment and Matrix Conversion for the Determination of Trace Metals in Ultra-Pure Water.

The presence of trace contaminants in ultra-pure water (UPW) used in fabrication process can greatly affect the yield and quality of industrial products. In the present study, the electrodialytic enrichment of metal cations as a means of continuously monitoring the UPW quality was studied. A newly designed electrodialytic enrichment device (EED) was used to quantitatively transfer metal ions from samples to dilute nitric acid, which was then directly introduced into an inductively coupled plasma—mass spectrometry (ICP–MS) instrument. This process could be performed without contamination of the sample, and the enrichment factor was solely dependent on the flow rate ratio of the sample and acceptor solutions. The transference of analytes into the acidic solution improved the responsivity of the ICP–MS analysis, especially at low concentrations of less than 1 μg/L. Blank solutions to support the analysis of UPW could be produced using the EED effluent, from which metal ions were quantitatively removed. In addition, calibration curves with concentration ranges of several nanograms per liter were obtained by preparing standards using a dynamic gravimetric method while employing a single bottle and continuous mass monitoring to avoid any contamination from the volumetric flasks. The sensitivities associated with the ICP–MS analysis of a number of trace metal ions were improved by one or two orders of magnitude. The data show that the present EED is able to continuously produce enriched analyte solutions to allow the ongoing monitoring of UPW quality.

Improving Fast Pyrolysis Bio-Oil Yield and Quality by Alkali Removal from Feedstock.

Alkali removal from forest residues, eucalyptus residues, and wheat straw was studied by water and dilute nitric acid leaching. Leaching parameters were optimized for each feedstock in laboratory-scale experiments. After the optimization of leaching on the laboratory scale, nitric acid-leached and untreated feedstocks were pyrolyzed in a bench-scale bubbling fluidized bed unit. In the case of eucalyptus residues and wheat straw, nitric acid leaching was found to increase the organic liquid yield compared to untreated feedstock. In addition, the sugar content of the fast pyrolysis bio-oils was increased, and the alkali content reduced. On the other hand, the pyrolysis experiments with acid-leached forest residues were unsuccessful due to the bed agglomeration. These problems are expected to be a result of the lack of catalytically active elements in biomass which enhance especially the cracking reactions of lignin. Finally, the results were demonstrated in the pilot-scale unit where nitric acid-leached oat straw was pyrolyzed with high organic liquid yield.

Effect of Preparation Method on the Catalytic Performance of HZSM-5 Zeolite Catalysts in the MTH Reaction.

A kind of nano-ZSM-5 zeolite crystal was synthesized by the hydrothermal method, and HZSM-5 zeolite powder was obtained via acid exchange. By using pseudoboehmite as a binder, a series of HZSM-5 zeolite catalysts for methanol-to-hydrocarbons (MTH) were prepared through adjusting the binder content between 20 and 50% in addition to the molding method of wet extrusion and mechanical mixing. XRD, 27Al NMR, SEM-EDS, ICP, low-temperature N2 adsorption and desorption, NH3-TPD, Py-FTIR, FT-IR, TG and elemental analyses were used to characterize the properties of fresh catalysts and coke-deposited catalysts. Then, MTH catalytic performance was evaluated in a continuous-flow fixed-bed reactor. The characterization and evaluation results showed that the addition of dilute nitric acid during the molding process increased the amount of moderate-strength acid and formed a hierarchical pore distribution, which helped to reduce the reaction ability of cracking, aromatization and hydrogen transfer, improve the diffusion properties of the catalyst and slow down the coke deposition rate. The catalyst with a binder content of 30% made by wet extrusion with dilute nitric acid had the best performance, whose activity stability of MTH increased by 96 h, higher than other catalysts, and the coke deposition rate was slower, which was due to the most suitable distribution of acid strength and B/L ratio as well as the most obvious hierarchical pore structure.

Surface functionalization of polyaniline and excellent electrocatalytic performance for oxygen reduction to produce hydrogen peroxide

We have developed the CNT@PANI-NO electrocatalyst that is significantly different from the conventional electrocatalyst previously reported. • Polyaniline (PANI) can be changed into PANI-NO with the functional group of –NO. • Introducing PANI-NO on the surface of CNT obtains the CNT@PANI-NO. • PANI-NO has promoted selectivity of H 2 O 2 than PANI. • CNT@PANI-NO exhibits excellent electrochemical performance for H 2 O 2 production. Electrochemical two-electron oxygen reduction is an environmental-friendly and promising method to generate H 2 O 2 . However, a great challenge remains to develop more economic and effective electrocatalysts for practical application. Here, we have developed a CNT@PANI-NO electrocatalyst that is significantly different from the conventional electrocatalyst previously reported (such as metal, alloy, carbon materials doped with heteroatoms, metal single-atom catalysts). We firstly find that the polyaniline (PANI) treated by dilute nitric acid can be changed into the PANI-NO product with the functional group of –NO. Then we introduce the PANI-NO on the surface of carboxylated carbon nanotubes to obtain the CNT@PANI-NO nanocomposites, which exhibit excellent electrochemical performance to H 2 O 2 production. The H 2 O 2 selectivity of the typical CNT@PANI-NO is between 87% and 94% at the potential of 0.2–0.68 V (vs. RHE), the faradaic efficiency is close to 95% and the current density is up to 2.9 mA/cm 2 (at 0.3 V) in alkaline condition. The DFT results give the origin of the catalytic activity. This study provides a new idea for the application of polymer in electrocatalysis and a new way to develop the high-performance 2e-ORR electrocatalyst.

A sensitive vesicle mediated dispersive liquid-liquid microextraction of parts per quadrillion levels of beryllium from seawater samples prior to graphite furnace atomic absorption spectrometry determination

A rapid and highly sensitive vesicle mediated dispersive liquid–liquid microextraction procedure is developed for the determination of parts per quadrillion level of beryllium in seawater and air filter samples for providing its natural background and contamination levels. In this procedure, dioctylsulfosuccinate, an anionic vesicular surfactant and acetylacetone are used as dispersing and chelating agents, respectively. At pH > 9.5, beryllium forms hydrophobic beryllium-acetylacetonate complex spontaneously at room temperature. This complex is selectively filled into the vesicular cavities of dioctylsulfosuccinate and is extracted into small chloroform phase from bulk aqueous phase. The beryllium present in the chloroform phase is back extracted with dilute nitric acid and is analyzed by graphite furnace atomic absorption spectrometry. This method is applied to groundwater, seawater, coal fly ash, air filter and sea sludge samples. Under the optimized conditions, the limit of detection, limit of quantification and linear dynamic range are 10 fg mL−1, 33 fg mL−1 and 40–500 fg mL−1 for seawater; 0.15 ng g−1, 0.5 ng g−1 and 0.4–4 ng g−1 for air filter and 1.5 ng g−1, 0.39 ng g−1 and 0.4–4 ng g−1 for coal fly ash, respectively. For 1 L seawater sample an enrichment factor of 954 is achieved. Coefficient of determination (R2) is found to be 0.997. The recoveries are in the range of 94–105% at 200–500 fg mL−1. The relative standard deviations are 20%, 11%, 8% for ppq, ppt and ppb levels of Be, respectively. The accuracy of the procedure is verified by analyzing NIST SRMs 1640 and 1640a trace elements in natural water.

Investigation on the catalytic combustion of CO over LaMn1‐xCuxO3 promoted by acid treatment

AbstractThere are large amounts of CO pollutants in the off‐gas of the iron and steel industry, which cause serious harm to the environment and human health. To control the emission of CO more effectively, in this paper, LaMn1‐xCuxO3 (x = 0, 0.25) perovskite catalysts were prepared and then modified by dilute nitric acid. And the physicochemical properties and the catalytic activity of perovskite were investigated and analyzed. The activity results indicate that the Cu2+ substitution and acid treatment could obviously promote the catalytic activity of catalysts for CO oxidation. Among the prepared samples, LaMn0.75Cu0.25O3‐H exhibits the highest activity with 90% CO conversion at 176.5°C, and the self‐sustained combustion of CO is successfully achieved. And the long‐time stability test shows that LaMn0.75Cu0.25O3‐H can keep 100% CO conversion, and the activity remains almost unchanged. Combined with the x‐ray photoelectron spectroscopy (XPS) and H2 temperature‐programmed reduction (H2‐TPR) results, the increased activity of LaMn0.75Cu0.25O3‐H catalyst is mainly ascribed to the high concentration of Mn4+ and abundant oxygen vacancies. On the other hand, the morphology of perovskite catalysts was remolded by acid etching, and the formation of the porous structure significantly increases the specific surface area. The above results show that the substitution of Cu and acid treatment for perovskite catalysts is a feasible strategy to improve CO catalytic combustion activity.

Pure Gold Dissolution and Stainless-Steel Corrosion in Dilute Nitric or Nitrous Acid Containing Halide Salts

Pure Gold Dissolution and Stainless-Steel Corrosion in Dilute Nitric or Nitrous Acid Containing Halide Salts

Separation and catalytic depolymerization of empty palm fruit bunch lignin

Lignin is a heterogeneous and complex polymer and a potential renewable source of aromatic compounds as precursors to many industrially useful products. Microbial biotransformations for lignin valorization are reported but require not only its separation from biomass matrix but also breakdown into its monomeric components. Abundantly available empty palm fruit bunch was used as the lignin-rich biomass to process it to obtain a mixture of lignin-derived monomeric aliphatic and aromatic compounds. A two-step acid-alkali treatment was deployed to extract lignin and its breakdown into smaller fragments. Dilute nitric acid treatment could extract 80% of the lignin and the hydrolysate was fractionated through a series of nanofiltration membranes. The residual polymeric lignin obtained after monomer separation was catalytically depolymerized using Cu/Al2O3 under optimized conditions i.e., 180 °C, 7 MPa, 60 min, methanol: water ratio as 1:1 to give 80% conversion. Lignin mixture at every step was analyzed by GC-MS and gel permeation chromatography (GPC). The scheme resulted in 37% of the overall lignin being obtained as monomers.

Recent advances on polaprezinc for medical use (Review).

The present study described the chemical and biological properties of zinc complex of L-carnosine (L-CAZ; generic name, polaprezinc; chemical name, catena-(S)-[µ-[N(α)-(3-aminopropionyl) histidinato (2-) N1, N2, O: N(τ)]-zinc], molecular formula, C9H14N4O3Zn; molecular weight, 291.6404; CAS registry number, 107667-60-7). Characterized as a white or yellowish white crystalline powder, this drug is insoluble in glacial acetic acid and almost insoluble in water, methanol, ethanol and ether. It is soluble in dilute hydrochloric acid, dilute nitric acid and sodium hydroxide solution, and its melting point is 260-270˚C. Polaprezinc is an anti-ulcer drug that was jointly studied and developed by Hamari Chemicals Co., Ltd. and Zeria Pharmaceutical Co., Ltd., and was first approved in Japan in 1994. This review article summarizes the research advances of polaprezinc, including the patents, preparations, synthetic routes, pharmacokinetics, pharmacological effects and application in clinical research.

Improving the performance of Pd based catalysts for the direct synthesis of hydrogen peroxide via acid incorporation during catalyst synthesis

The direct synthesis of hydrogen peroxide from molecular H2 and O2 offers an attractive alternative to the current means of production of this powerful oxidant, on an industrial scale. Herein we investigate the role of nitric acid addition, during catalyst preparation as a means of improving catalytic performance, under reaction conditions that have previously been found to be optimal for H2O2 production. The addition of dilute nitric acid during catalyst preparation is found to lead to a significant improvement in H2O2 synthesis activity, through the modification of particle size and control of Pd oxidation state.

Recovery of uranium from carbonaceous radioactive waste of the UF6 production line in a uranium conversion plant: Laboratory and pilot plant studies

Carbonaceous radioactive waste is produced by adsorption of effluent gases of UF6 production line, on a bed of charcoal. Current research was aimed at developing a process for recovery of uranium from this waste in a laboratory and at pilot scale. As a first step, leaching of uranium from carbonaceous radioactive waste was undertaken by successive steps using Al(NO3)3 and nitric acid, the former used to eliminate corrosivity of the F− ions. The stoichiometry of reaction between F− and Al3+ ions form complexes ranging from AlF2+, AlF2+ to AlF3 depending upon their molar ratio. The results showed that the increase of NO3−/U ratio increased the uranium leaching efficiency. Presence of some impurities especially silica in leach liquor caused formation of crud during solvent extraction. In order to remove such impurities, first uranium was precipitated as ammonium diuranate, and then it was dissolved in nitric acid to produce uranyl nitrate solution. This solution was purified by extraction with TBP (30 vol%) /Kerosene, followed by stripping with dilute nitric acid. The pilot scale data confirmed the results of the lab scale with minor variations. The purity of the obtained uranyl nitrate solution was acceptable for returning it as a feed to UF6 production plants.