Increase In Concentration Of Nitric Acid Research Articles

Understanding the fast formation mechanism of hard nanoporous alumina films on aluminum in acidic solutions containing nitric acid

Nanoporous alumina films formed on aluminum via anodization are widely used for scientific and technical purposes owing to their various advantageous properties, including excellent corrosion and wear resistance, good thermal and electrical insulation, and facile producibility at low cost. Herein, we report a novel approach to fabricate hard porous anodic alumina (PAA) films by adding an appropriate amount of nitric acid to sulfuric-, oxalic-, and phosphoric-acid solutions at critical high current densities. The effects of the nitric additives on the anodizing behavior, film growth mechanism, microstructure, chemical composition, film thickness, microhardness, and appearance of the PAA films formed from various solutions were systematically investigated. The addition of nitric acid enhanced the formation of alumina and resulted in fast growth rates of 196 μm/h and 166 μm/h for sulfuric- and oxalic-based solutions, respectively, while maintaining high hardness of approximately 380 and 430 HV0.1, respectively. The surface hardness of the films decreased to some extent with the increase in nitric acid concentration and/or film thickness owing to the strong corrosive nature of nitric acid during prolonged anodization, although nitrogen inclusion in anodic alumina films was not detected through X-ray photo-electron spectroscopy, which differs from the other acidic anions. In particular, the barrier layer thickness and pore intervals of PAA films increased with the nitric concentration in the aforementioned solutions, leading to a fast growth rate and high hardness inside the films.

Studies on the adsorption of Pb(II) from aqueous solutions using sugarcane bagasse-based modified activated carbon with nitric acid: Kinetic, isotherm and desorption

Activated carbon (AC) made from sugarcane bagasse (SB) was modified by nitric acid (HNO3) oxidation, to investigate whether this enhanced its capacity for lead (Pb) removal. The modified ACs were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and Fourier transform infrared (FTIR) spectroscopy. The micrographs showed the modified AC samples looked clean, but the surface had eroded, resulting in pore blockage in the micropores. However, the results showed that an increase in nitric acid concentration resulted in a significant decrease in specific surface area after modification. The experimental results indicated that nitric acid modification increased the oxygen-containing functional groups (i.e., hydroxyl, carboxyl, carbonyl, and ester) on the adsorbent surfaces. The presence of surface functional groups influenced the samples' adsorption capacity for heavy metal ion (Pb(II) removal from an aqueous solution. The maximum Pb(II) adsorption capacity, according to the Langmuir model, was around 212.31 mg g−1. Kinetic studies were evaluated by pseudo-first-order and pseudo-second-order models to describe the possible Pb(II) adsorption mechanism, that demonstrated a faster adsorption rate on the adsorbent, and the pseudo-second-order model fitted well for all of the samples. A possible adsorption mechanism could be the ion exchange of functional groups in surface complexation with the heavy metal ions. In summary, modified AC from SB is a novel, useful, and potentially economical adsorbent, with the capacity to efficiently remove metal ions from aqueous solutions, thus offering a potential solution to the growing problem of agricultural waste disposal.

Kinetic study on arsenopyrite dissolution in nitric acid media by the rotating disk method

The kinetics of arsenopyrite compact samples dissolution in nitric acid media was investigated using the full factorial experiment model (FFEM). The effects of nitric acid concentration (2–5 M), temperature (303–348 K), disk rotation frequency (3.33–10 rps) on the arsenopyrite dissolution rate were studied. Nitric acid concentration and temperature have a significant effect, and disk rotation frequency does not. With an increase in nitric acid concentration from 4 M to 5 M and temperature from 318 K to 333 K, the dissolution rates of iron and arsenic increase by 30.1–30.4 times, from 0.26–0.27 × 10–6 mol dm−2 s−1 to 7.83–8.21 × 10–6 mol dm−2 s−1. Increasing temperature to 348 K does not lead to a significant increase in the dissolution rate. The data obtained were processed using the FFEM to obtain kinetic equations (R2 = 0.95): WFe=0.04CHNO31.8e-4419Tω0.1, WAs=0.04CHNO31.8e-4420Tω0.1. Using SEM–EDS and XPS analyses, the mechanism of arsenopyrite passivation was determined. Under mild conditions (nitric acid concentration of 3 M and temperature of 303 K), local conglomerates containing iron polysulphides (Fe2Sx) are formed on the arsenopyrite surface. They do not create diffusion difficulties when dissolving arsenopyrite. Under harsh conditions (nitric acid concentration of 5 M and temperature of 333 K), polysulphides begin to aggregate. It leads to the formation of the passivating film containing elemental sulphur. The film is thin (20–30 μm) and porous. While the arsenopyrite dissolution rate is high. Further increase of parameters leads to thickening and compaction of the passivating film and decrease in the arsenopyrite dissolution rate.

Effect of acid corrosion on properties of composite insulator core rod

In recent years, there have been a number of composite insulator decay-like fracture faults characterized by resin degradation and irregular fracture morphology, which seriously threaten the safety and stability of power system. At present, the research of composite insulator’s decay-like fracture is still in the initial stage at home and abroad, and there is no clear conclusion on the causes of its fracture, influencing factors and other important scientific and technical issues, and there is no unified understanding of the mechanism of decay-like fracture. In view of the above problems, this paper carries out acid corrosion test on core rod samples to explore the corrosion law of nitric acid on core rod and its influence on properties. The results show that acid corrosion is one of the factors causing the degradation of epoxy resin. With the increase of nitric acid concentration and soaking time, the degradation rate of epoxy resin accelerates, and the core rod sample gradually changes from emerald green to yellowish brown, then to light yellow, and finally to white hair like glass fibre. The effect of the sample under the long-time action of low concentration nitric acid is the same as that under the short-time action of high concentration nitric acid. Nitric acid will continuously erode into the core rod, resulting in the decrease of hardness and performance on the core rod surface.

Kinetics of solid acids catalysed nitration of toluene: Change in selectivity by triphase (liquid–liquid–solid) catalysis

AbstractNitrotoluenes are precursors to a variety of commercially important products such as dyes, pharmaceuticals, and plastics. The protonated form of Y, ZSM‐5, and mordenite zeolites as well as strongly acidic cation exchange resin (Amberlite IR‐120) were examined as triphase catalyst (liquid–liquid–solid) for the nitration of toluene to produce mainly mononitrotoluenes. Among the solid acid catalysts tested, zeolites were found to be more active than cation exchange resin with highest activity for H‐mordenite followed by HZSM‐5 and HY zeolites. The reaction was found to be free from external diffusional resistance. The effects of other parameters (temperature, catalyst loading, and nitric acid concentration) on the rate of toluene nitration over H‐mordenite catalyst were also investigated. The selectivity for p‐nitrotoluene increases with temperature but decreases with increase in nitric acid concentration. The acidity level of the catalyst determines the product distribution; the stronger the acidity, the lower the ortho/para ratio is in the product mixture. The triphasic nitration reaction is kinetically controlled with an activation energy of 24.24 kJ/mol. The catalyst could be reused for several cycles with negligible loss in activity.

Room temperature ionic liquid system for the mutual separation of Pu(IV) from other actinides using 2-hydroxy acetamide extractant

Abstract N , N -dioctyl-2-hydroxyacetamide (DOHyA) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C 4 mim][NTf 2 ]) was employed for the extraction of actinides from nitric acid medium. The extraction of Pu(IV) was studied as a function of various parameters such as concentration of nitric acid, extractant concentration, temperature, alkyl chain length attached to amidic nitrogen of the extractant etc. The distribution ratio of plutonium(IV) (D Pu(IV) ) obtained in DOHyA/[C 4 mim][NTf 2 ] was compared with that obtained in DOHyA/ n -dodecane ( n -DD). Extraordinary extraction of Pu(IV) was achieved when ionic liquid was employed as a diluent. D Pu(IV) in DOHyA/[C 4 mim][NTf 2 ] decreased marginally with increase in nitric acid concentration up to 3 M nitric acid, and there after the D Pu(IV) remained constant. A significant separation was achieved for Pu(IV) over U(VI) and Am(III) from the employed mixture of actinides at various nitric acid concentrations using DOHyA/[C 4 mim][NTf 2 ]. Stripping of metal ion (Pu(IV)) from the loaded ionic liquid phase was carried out using aqueous soluble complexing agents such as oxalic acid and acetohydroxamic acid.

BenzoDODA grafted polymeric resin—Plutonium selective solid sorbent

A new ligand grafted polymeric resin (BenzoDODA SDVB) was synthesized by covalently attaching plutonium selective ligand (BenzoDODA) on to styrene divinyl benzene (SDVB) polymer matrix. BenzoDODA SDVB resin was evaluated for separation and recovery of plutonium(IV) from nitric acid medium. Sorption of Pu(IV) was found to decrease with the increase in nitric acid concentration, with very small sorption above 7.0M HNO3. Sorption kinetics was fast enough to achieve the equilibrium within 60min of contact where the kinetic data fitted well to pseudo-second-order model. Sorption isotherm data fitted well to Langmuir model suggesting chemical interaction between the BenzoDODA moiety and plutonium(IV) ions. Sorption studies with some of representative radionuclides of high level waste showed that BenzoDODA SDVB is selective and therefore could be a promising solid sorbent for separation and recovery of plutonium. Further, the theoretical calculations done on BenzoDODA SDVB resin suggested Pu(NO3)4·BenzoDODA (1:1) sorbed complex conformed to generally observed square antiprism geometry of the plutonium complexes, with contributions from oxygen atoms of four nitrate ions as well as from four oxygen atoms present in BenzoDODA (two phenolic ether oxygen atoms and two carbonyl oxygen atoms of amidic moiety).

PGM market report: outlook for platinum: supply & demand in 2016

A new ligand grafted polymeric resin (BenzoDODA SDVB) was synthesized by covalently attaching plutonium selective ligand (BenzoDODA) on to styrene divinyl benzene (SDVB) polymer matrix. BenzoDODA SDVB resin was evaluated for separation and recovery of plutonium(IV) from nitric acid medium. Sorption of Pu(IV) was found to decrease with the increase in nitric acid concentration, with very small sorption above 7.0 M HNO3. Sorption kinetics was fast enough to achieve the equilibrium within 60 min of contact where the kinetic data fitted well to pseudo-second-order model. Sorption isotherm data fitted well to Langmuir model suggesting chemical interaction between the BenzoDODA moiety and plutonium(IV) ions. Sorption studies with some of representative radionuclides of high level waste showed that BenzoDODA SDVB is selective and therefore could be a promising solid sorbent for separation and recovery of plutonium. Further, the theoretical calculations done on BenzoDODA SDVB resin suggested Pu(NO3)4·BenzoDODA (1:1) sorbed complex conformed to generally observed square antiprism geometry of the plutonium complexes, with contributions from oxygen atoms of four nitrate ions as well as from four oxygen atoms present in BenzoDODA (two phenolic ether oxygen atoms and two carbonyl oxygen atoms of amidic moiety).

N,N-dialkyl-2-hydroxyacetamides for modifier-free separation of trivalent actinides from nitric acid medium

Abstract The alkyl derivatives of N,N,-dialkyl-2-hydroxyacetamide (DAHyA), namely, N,N,-dihexyl-2-hydroxyacetamide (DHHyA), N,N,-dioctyl-2-hydroxyacetamide (DOHyA), N,N,-didecyl-2-hydroxyacetamide (DDHyA), were synthesized and characterized by FT-IR, and NMR spectroscopy. The extraction behaviour of Am(III) in a solution of DAHyA in n-dodecane was studied as a function of various parameters to evaluate the feasibility of using DAHyA for partitioning of trivalent actinides from high-level liquid waste (HLLW). The distribution ratio of Am(III) (D Am(III)) in 0.1 M DAHyA/n-DD increased from 10−4 to > 200 with increase in nitric acid concentration from 1 M to 6 M. A D Am(III) value 10–70 was obtained in a nitric acid concentration range from 3–4 M. The extraction of Am(III) in 0.1 M DAHyA/n-dodecane decreased in the order DHHyA > DOHyA > DDHyA. The third-phase formation behaviour of nitric acid and neodymium (III) in 0.2 M DAHyA/n-dodecane was studied. Near stoichiometric amount of neodymium (III) can be loaded in octyl and decyl derivatives without any third-phase formation from 3–4 M nitric acid medium. Unlike other extractants, the loaded trivalent metal ion in DAHyA can be recovered even with 1 M nitric acid. Therefore, the study revealed that N,N,-dialkyl-2-hydroxyacetamides are promising candidates for partitioning the trivalent actinides from HLLW.

폐솔더 박리액으로부터 확산투석법에 의한 질산의 회수

A basic study was conducted to effectively recover nitric acid from a waste solder stripper by diffusion dialysis using anion exchange membranes. The effects of flow rate, flux ratio, nitrate concentration, and metallic ion types and concentration on the recovery percentage of nitric acid were investigated. The recovery percentage of nitric acid was decreased with the increase of flow velocity. But the recovery percentage of nitric acid was increased as the increase of flux ratio(W/F) and showing a recovery percentage of nitric acid of about 99% at a flux ratio of 1.5 or more. As the increase of nitric acid concentration in feed solution, the recovery percentage of nitric acid was increased up to 3.0M, but in case of greater than 3.0M, the recovery percentage gradually was decreased. Leakage percentage of metallic ions through the membrane were in the order of Pb, Na and Cu but Fe and Sn did not leakaged. As a result of diffusion dialysis using real waste solder stripper at a flow rate of , W/F = 1.3, a recovery percentage of nitric acid of approximately 94% was gained.

Synergistic extraction and separation studies of Ce(III) from acidic nitrate medium using binary mixture of Cyanex 921 and Cyanex 923 in kerosene

ABSTRACTThe effect of parameters like shaking time, nitric acid, nitrate ion, extractant concentration, temperature, diluents, and phase volume ratio on the extraction of Ce(III) from acidic nitrate medium using binary mixture of Cyanex 921 and Cyanex 923 in kerosene has been investigated. Synergism was observed in the range 0.001-1.0 mol/L HNO3. With increase in extractant concentration and O/A phase volume ratio, extraction increases while with increase in nitric acid concentration and temperature, extraction decreases. Sulphuric acid and hydrochloric acid are found to be effective in stripping. Separation factors for Nd/Ce are higher as compared to those for Ce/La and Pr/Ce.

Studies on the Separation and Recovery of Plutonium from Nitric Acid Medium using Di-nonyl Phenyl Phosphoric Acid (DNPPA) / n-Dodecane as Extractant System

This paper deals with the studies on the separation and recovery of plutonium from nitric acid medium using Di-nonyl phenyl phosphoric acid (DNPPA) in n-paraffin as an extractant system. The different extraction parameters were investigated. The percentage extraction of plutonium decreased with increase in nitric acid concentration. The optimum solvent concentration for quantitative separation of plutonium from aqueous feed solution was 0.15 M of DNPPA whereas n-paraffin/n-dodecane was the most suitable of diluents with an organic to aqueous phase ratio of 1:1. Among the various strippants used, 0.5 M solution of (NH4)2CO3 was found to be the most suitable for back extraction of plutonium from the loaded organic phase. The developed method was used to separate and recover plutonium from actual wash solution of ion exchange column used for plutonium purification. More than 73% of plutonium was separated from 7 M HNO3 wash solution using 0.15M of DNPPA in n-dodecane.

Extraction of trivalent americium and europium from nitric acid solution with a calixarene-based diglycolamide

A ligand derived from calix[4]arene functionalized at the lower rim with four diglycolamide (DGA) binding units containing n-butyl groups, which is denoted as calix[4]arene-BDGA, was synthesized and characterized by MS, 1H NMR and 13C NMR. The extraction behaviors of Am(III) and Eu(III) from nitric acid solution were investigated with calix[4]arene-BDGA in 95% kerosene/5% n-octanol (v/v). Effects of acidity, concentration of extractant and temperature on the distribution ratio of Am(III) and Eu(III) were evaluated. The results indicated the distribution ratio values of Am(III) and Eu(III) increase with the increase of nitric acid concentration in the examination of acidity range from 0.5 to 5.0mol/L. The ligand has a higher selectivity for Eu(III) than for Am(III) with the separation factor SFEu(III)/Am(III) values of 4.5–7.3. Slope analysis from nitric acid medium indicated that Am(III) and Eu(III) were extracted as di-solvated species by calix[4]arene-BDGA. The extraction mechanism was described and the thermodynamic parameters (ΔH, ΔS and ΔG) were also presented.

Electrochemical noise resistance evaluation of 304L SS in nitric acid and simulated nuclear high level waste

The paper focuses on corrosion monitoring of 304L stainless steel (SS) (solution annealed, sensitised) in nitric acid (4, 8 and 12M) at 298 and 323 K electrolyte temperatures, and simulated high level waste (HLW, 323 K), using electrochemical noise (EN) measurements. Double loop electrochemical potentiokinetic reactivation test was conducted to assess the degree of sensitisation. Electrochemical noise records revealed passivation process during the monitoring period, under all conditions studied, except for the sensitised specimen in 4M nitric acid (323 K), which showed localised attack. The results showed an inverse relation between EN resistance and corrosion activity. An increase in nitric acid concentration resulted in an increase in corrosion activity, while increasing the electrolyte temperature increased the corrosion activity marginally. A profound increase in corrosion activity occurred for the sensitised specimen in nitric acid when compared to the solution annealed specimen, but the increase was marginal in simulated HLW. The results are detailed in the paper.

Aggregation behavior of dinonyl phenyl phosphoric acid (DNPPA): Dynamic Light Scattering and spectrophotometric investigations

Dynamic Light Scattering (DLS) and spectrophotometric studies were carried out to investigate the aggregation behavior of dinonyl phenyl phosphoric acid (DNPPA) under varying experimental conditions such as aqueous phase acidity, nature of diluents, and ligand concentration. The aggregation of 0.05M DNPPA/n-dodecane and the extraction of U(VI) and rare earth elements (REE) decreased with increase in nitric acid concentration. This observation was further supported by changes in absorption spectra of DNPPA pre-equilibrated with increasing concentrations of nitric acid.

Studies on the Separation and Recovery of Palladium from Simulated High Level Liquid Waste (SHLW) Solution with Novel Extractant N,N,N′,N′-tetra (2-ethylhexyl) Dithiodiglycolamide DTDGA

The extraction properties of N,N,N',N'-tetra-(2-ethylhexyl) dithiodiglycolamide (DTDGA) have been evaluated for separation and recovery of palladium from simulated high-level liquid waste (SHLW) solution. Extraction of Pd was found to increase with increase in nitric acid concentration up to 4.0 M, above which the extraction remains almost constant. Acid uptake studies show 1:1 stoichiometry between DTDGA and HNO3 at nitric acid concentration above 3.0 M. The acid uptake constant (KH) was found to be 0.60 which could be due to the presence of two carbonyl groups of amidic moiety. DTDGA has shown very high extractability and selectivity for Pd over other metal ions present in SHLW. The separation factor (SF) for Pd over other metal ions was found to be more than 104. Almost complete back extraction of palladium from organic phase was achieved with 0.01 M thiourea in 0.1 M nitric acid. Reusability studies of the extractant indicate that DPd remains almost constant even after five successive cycles of extraction and stripping. Two extraction stages will be required for complete extraction of 100 mg/L Palladium in 3.0 M nitric acid solution using 0.0025 M DTDGA/n-dodecane solvent system.

Studies on the Separation and Recovery of Thorium from Nitric Acid Medium using (2-ethyl hexyl) Phosphonic Acid, Mono (2-ethyl hexyl) Ester (PC88A)/N-Dodecane as Extractant System

This paper deals with the studies on the separation and recovery of thorium and 233-uranium from nitric acid medium using (2-ethyl hexyl) phosphonic acid, mono (2-ethyl hexyl) ester/n-dodecane as an extractant system. The different extraction parameters were investigated. The distribution ratio of thorium decreased with increase in nitric acid concentration. The optimum solvent concentration for quantitative separation of thorium from aqueous feed solution was 0.75 M of PC88A whereas dodecane was the most suitable of diluents with an organic to aqueous phase ratio of 1:1. Among the various strippants used, 2 M solution of (NH4)2CO3 was found to be the most suitable for back extraction of thorium. The developed method was used to recover thorium and 233U from radioanalytical waste generated during thorium analysis by ethylene diamine tetraacetic acid (EDTA) titremtric method and recoveries for both Th and U were more than 85%.

Hydrodesulphurization and hydrodenitrogenation of light gas oil using NiMo catalyst supported on functionalized mesoporous carbon

The effect of functionalization on the hydrotreating activity of NiMo catalysts supported on mesoporous carbon supports (mC) was studied. mC support was prepared by volume templating of alkali modified SBA-15 using sucrose as carbon source. The mC supports were functionalized using nitric acid of various concentrations (upto 8 M HNO 3). The supports and catalysts were characterized by N 2 physisorption, SAXS, XRD, FTIR, TGA, Raman spectroscopy, SEM, TEM, and HRTEM. SAXS results showed the changes in structural orderliness of virgin and functionalized mC supports. Physisorption analysis indicated progressive reduction in surface area (SA) and pore volume with the increase in nitric acid concentration. Enhancement of surface functional groups after functionalization was observed through FTIR. SEM images showed that the carbon supports retain needle like morphology even after nitric acid etching. As seen by HRTEM, qualitatively Type-II like NiMoS phase (lower support metal interaction (SMI)) is generated on functionalized mC supported catalysts, which is active for hydrotreating. Hydrotreating activity study of these NiMo catalysts were carried out under industrial operating conditions in a laboratory trickle bed reactor using coker light gas oil feed and it was found that NiMo supported on 6 M acid treated mC showed the highest activity. Based on equal catalyst mass, the hydrodesulphurization and hydrodenitrogenation activities of NiMo/mC catalyst were higher than that of NiMo/γ-Al 2O 3 owing to lower SMI and higher SA. This study reveals that the functionalized mCs can become potential alternative catalyst support to conventional γ-Al 2O 3, for the hydrotreating of gas oil feedstocks.

Extraction Behavior of Some Actinides and Fission Products from Nitric Acid Medium by a New Unsymmetrical Diglycolamide

A new unsymmetrical diglycolamide, N,N-di-2-ethylhexyl-N',N'-di-octyl-3-oxapentane-1,5-diamide, trivially known as di-ethylhexyl-di-octyl-diglycolamide (DEHDODGA) has been synthesized, and characterized by 1H, and 13C nmr, mass, and IR spectroscopy. Extraction behavior of 241Am(III), (152+154)Eu(III), 239Pu(III), 239Pu(IV), 233U(VI), 137Cs(I), and (85+89)Sr(II) from nitric acid medium by a solution of DEHDODGA in n-dodecane was studied, at 298–333 K. The effect of concentrations of HNO3 and DEHDODGA and of temperature on the distribution ratio (D M) was studied. Extraction of Eu(III), Am(III), Pu(III), and Pu(IV) increased with increase in nitric acid concentration, and the distribution ratio of Cs(I) was insignificant. However, the distribution ratios of U(VI) and Sr(II), though not insignificant, but was quite less compared to trivalents, and Pu(IV). The D Sr(II) increased with increase in the concentration of nitric acid, reaching a maximum at 4 M followed by decrease. The stoichiometry of Am(III) – DEHDODGA was determined by slope analysis of extraction data, and the enthalpy change accompanied by the extraction of Eu(III), Pu(III), and Am(III) was determined and reported in this article.

Electrolytic extraction of palladium from nitric acid and simulated high-level liquid waste

Electrochemical behavior of palladium (II) nitrate in nitric acid medium and simulated high-level liquid waste has been investigated to explore the feasibility of recovering this potentially useful fission product from high-level liquid waste. The cyclic voltammogram of palladium (II) in nitric acid medium at stainless steel electrode consists of a cathodic wave occurring at an onset of -0.4 V (vs. Pd) due to the irreversible reduction of palladium (II) to metallic palladium at 298 K. The recovery of palladium was quantitative at nitric acid concentrations ranging from 1 to 4 M, however, the recovery from simulated high-level liquid waste (SHLLW) solution was only 30% due to the interferences of various ions present in SHLLW. The faradic efficiency of electrolysis lowered with increase in nitric acid concentration and only silver was found to get co-deposited to the extent of 5% along with palladium from SHLLW solution.