Ratio Of Nitric Acid Research Articles

Chemical recycling of high-density polyethylene (HDPE) wastes by oxidative degradation to dicarboxylic acids and their use as value-added curing agents for acrylate-based materials

Plastic waste has become a serious pollution problem due to the material's high consumption volume and durability. Therefore, effective waste treatment and conversion technology are urgently required. In this work, a chemical recycling process has been developed to convert high-density polyethylene (HDPE) from post-consumer milk bottles to value-added chemicals, especially mixed diacids with high succinic acid content, via hydrothermal nitric acid oxidation. The results reveal that HDPE can be completely recycled into water-soluble compounds with a yield ranging from 15 to 70% (∼8–36% carbon recovery) at 180–200 °C for 2–4 h. The oxidized products examined by 1H NMR spectroscopy are a mixture of succinic acid (C4), glutaric acid (C5), and adipic acid (C6), whose compositions are strongly governed by the reaction temperature, reaction time, filling capacity, nitric acid concentration and the HDPE/nitric acid ratio. With 20 ml of 0.18 g/ml nitric acid solution (1/7.2 HDPE/nitric acid ratio), a maximum product yield (%carbon recovery) of 69% (35%) with C4:C5:C6+ ratio of 55:30:15 (mol%) is achieved at 180 °C for 3 h. When the filling capacity was increased from 40 to 60% by adding extra water at the same HDPE: nitric acid ratio, prolonging the reaction time for 1 h resulted in the products with a high succinic acid composition (>94%) and 75% yield (36% carbon recovery). The benefits of employing dilute nitric acid solutions with the same HDPE: nitric acid ratio on the selectivity of succinic acid is also confirmed by a reaction at 200 °C for 2 h. As oxidation typically occurs at a higher rate at a higher temperature, the maximum product yield (∼53–56%) is received at 200 °C for 2 h. This lower optimum yield obtained at higher reaction temperature and higher nitric acid concentration implies heterogeneous degradation due to limited diffusion of reactive molecules. By adjusting the HDPE: nitric acid ratio (1:3.6 to 1:10.8), the optimum content of nitric acid is in a range of 3.6x–5.4x. The as-received products are successfully developed as UV-curable acrylate precursors by esterifying their carboxylic groups with hydroxyethyl acrylate, using 5 mol% p-toluene sulfonic acid as a catalyst. UV-cured sheets obtained after irradiating under a UV lamp for 10 min have a gel fraction of 80–90% tested in toluene, chloroform, and ethanol.

The Preparation of Graphite Oxide Controlled by Optimum Oxidation Potential with any Rejected Nitro-Oxidizer

Nitro-oxidizers (nitric acid-27S, nitrogen tetroxide and mixed nitrogen oxide) are common liquid oxidants widely used in liquid rockets and missile weapons. How to deal with large quantities of scrapped nitro-oxidizers is a complex, costly and dangerous project. We pretreated it with hydrogen peroxide (H2O[Formula: see text] and converted the active oxidant component of nitro-oxidizers into nitric acid, which can be used as oxidant source to prepare graphite oxide from natural graphite. The comprehensive oxidation ability of the reaction system can be effectively controlled by adding different volumes of H2O2, and the oxidation ability can be expressed by the redox potential of the system. Combined with FT-IR, Raman and XRD characterization analysis, the optimal redox potential interval, [1700, 1800][Formula: see text]mV, has been determined for the synthesis of graphite oxide. With the help of data interpolation and function nonlinear fitting and the initial potential of rejected nitro-oxidants obtained, the composition ratio of nitric acid and nitrogen tetroxide (N2O[Formula: see text] has been preliminarily determined with the optimum amount of H2O2. Furthermore, the optimum oxidizing atmosphere for the synthesis of graphite oxide can be formed in spite of a wide range of concentrations of oxidant components, and the resulting graphite oxide has been proven to be a qualified and effective product.

Effect of various ratios of nitric acid – chloride on electronic properties of passive films on AISI 304L stainless steel

AbstractIn this study, the electrochemical behavior of 304L SS stainless steel in various nitric acid/chloride ratios was investigated. The characteristics of the passive film, formed at the open circuit potential (OCP) and at the passive potential (0.65 V vs SCE) were also compared. OCP results show that a stable passive film formed over the surface with higher nitric acid/chloride ratios. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements showed that with higher nitric acid/chloride ratios, the film resistance increases (R1) for OCP, passive potential, and the critical current density (icrit) and corrosion rate (icorr) decreases. Mott–Schottky analysis revealed that the film formed at OCP shows n-type behavior for 0.01 N and 1 N concentration and shows p-type behavior for 0.1 N nitric acid concentration. At 0.65 V (vs. SCE) of film formation potential, the film formed in 1 N concentration shows n – type behavior. In 0.01 N and 0.1 N acid concentration, p-type behavior has been observed. Also, according to Mott–Schottky analysis, it was found that a lower defect density was found in 0.1 N nitric acid, for both the potentials. X-ray photoelectron spectroscopy spectra show evidence that the surface contains Fe and Cr as major elements. However, at OCP, Fe2O3was the main constituent of the passive film, whereas the passive potential film was rich in Cr2O3. In addition, nitrogen and chloride were adsorbed in the passive film at passive potential.

PEMANFAATAN ADSORBEN DARI BIJI ASAM JAWA UNTUK MENURUNKAN BILANGAN PEROKSIDA PADA CPO (CRUDE PALM OIL)

This study was aimed to discover the effectiveness of tamarind seeds as adsorbent for the reduction of PV (Peroxide Value) in CPO (Crude Palm Oil) at the best adsorbent dose and contact time. Materials used were CPO, tamarind seeds, nitric acid, and distilled water. Variables observed were adsorbent : nitric acid ratio and oven temperature in adsorbent activation process, and contact time and adsorbent dose in adsorption process. This study was began with adsorbent modification, where the cleaced and crushed tamarind seeds to pass through 140 mesh were activated with 4 N nitric acid at 1:1, 1:2, 1:3 and 1:4 of adsorbent : nitric acid ratio while heated at 80 oC for 2 hours. Adsorbent was then dried in oven at 110 oC, 120 oC, 130 oC and 140 oC. Adsorbent with the higher iodine number was used in adsorption process that was carried out by heating 100 grams of CPO on hot plate at 90 oC with 1000 rpm of stirring speed, and followed by adsorbent addition of 0.5 %, 1,0 %, and 1,5 % (of CPO used) and 25, 35, and 45 minutes of contact time, and after that oil was filtered using vacuum pump. The study results showed that the best ratio of adsorbent : nitric acid 4 N was 1:2 at 130 oC of oven temperature with 511.773 mg/g of iodine number. The best adsorbent dose was 1.0 % at 35 minutes of contact time that gave higher reduction of PV with peroxide value of 0,00868 meq/kg with the reduction percentage was 39,72 %. This study showed that nitcic acid-activated adsorbent from tamarind seeds was effective to reduce PV in CPO.

Preparation and Microstructure of Two Kinds of Exfoliated Graphite

Two kinds of exfoliated graphite have been prepared from graphite flake and graphite powder, and their preparation conditions were respectively optimized by orthogonal experiments and parallel experiments. The effect of graphite size on the characteristics of exfoliated graphite was researched. The microstructure of two kinds of exfoliated graphite was measured by SEM. The results show that the optimal preparation conditions for exfoliated graphite flake are as following: the mass-volume ratio of graphite to mixed acid is 1: 4, the volume ratio of nitric acid to phosphoric acid is 1: 2, the mass ratio of graphite to potassium permanganate is 1: 0.1, and the reaction temperature is 25°C. For exfoliated graphite powder, the optimal mass ratio of graphite powder to potassium permanganate is 1: 0.22, and the consumption of oxidant for exfoliated graphite powder is more than that for exfoliated graphite flake. The longitudinal expansion of graphite flake is more apparent than that of graphite powder and leads to a worm-like fluffy rope.

Preparation of apatite-type La9.33(SiO4)6O2 electrolyte by urea-nitrates combustion

Apatite-type La9.33(SiO4)6O2 powders have been prepared by urea-nitrates combustion at low temperature. Process parameters of combustion and characteristics of electrolyte were studied and optimized. Gelation time of precursor has been shortened distinctly by introducing an appropriate solvent system. Molar ratio of nitric acid to lanthanum oxide dependence of the nature of the phases has first been characterized. Well-crystallized La9.33(SiO4)6O2 powders with an average size of 30.5 nm were obtained at a calcining temperature as low as 800°C for 12h. Dense ceramic with a relative density of 96% was prepared by sintering the green compact of these nanopowders at 1400°C for 3 h. The sintering body exhibited a high ionic conductivity of 4.38 × 10−3 S/cm at 700°C.

Novel Graphene-Like Electrodes for Capacitive Deionization

Capacitive deionization (CDI) is a novel technology that has been developed for removal of charged ionic species from salty water, such as salt ions. The basic concept of CDI, as well as electrosorption, is to force charged ions toward oppositely polarized electrodes through imposing a direct electric field to form a strong electrical double layer and hold the ions. Once the electric field disappears, the ions are instantly released back to the bulk solution. CDI is an alternative low-energy consumption desalination technology. Graphene-like nanoflakes (GNFs) with relatively high specific surface area have been prepared and used as electrodes for capacitive deionization. The GNFs were synthesized by a modified Hummers' method using hydrazine for reduction. They were characterized by atomic force microscopy, N2 adsorption at 77 K and electrochemical workstation. It was found that the ratio of nitric acid and sulfuric acid plays a vital role in determining the specific surface area of GNFs. Its electrosorption performance was much better than commercial activated carbon (AC), suggesting a great potential in capacitive deionisation application. Further, the electrosorptive performance of GNFs electrodes with different bias potentials, flow rates and ionic strengths were measured and the electrosorption isotherm and kinetics were investigated. The results showed that GNFs prepared by this process had the specific surface area of 222.01 m²/g. The specific electrosorptive capacity of the GNFs was 23.18 µmol/g for sodium ions (Na+) when the initial concentration was at 25 mg/L, which was higher than that of previously reported data using graphene and AC under the same experimental condition. In addition, the equilibrium electrosorption capacity was determined as 73.47 µmol/g at 2.0 V by fitting data through the Langmuir isotherm, and the rate constant was found to be 1.01 min⁻¹ by fitting data through pseudo first-order adsorption. The results suggested that the chemically synthesized GNFs can be used as effective electrode materials in CDI process for brackish water desalination.

Synthesis of RDX Catalyzed by Brønsted Acidic Ionic Liquids

The experimental study was carried out on the direct nitrolysis of hexamethylenetetramine (HA) to synthesize hexahydro-1,3,5-trinitro 1,3,5-triazine (RDX) with nitric acid (95%) catalyzed by Brønsted acidic ionic liquids. Various ionic liquids, such as [HMim]X, [(CH2)4SO3HMim]X, and [(CH2)4SO3HPy]X (X− = pTSO−, , CF3COO−), and various parameters, such as equivalents of ionic liquid, mass ratio of nitric acid (95%) to the starting material, and reaction time, were investigated. Ionic liquid [(CH2)4SO3HPyr]NO3 showed good catalytic activity. In the presence of 3.0% mol ratio [(CH2)4SO3HPyr]NO3 ionic liquid to HA, the yield of RDX was improved by 10.5% compared to the system without ionic liquid.

Lidar temperature measurements during the SOLVE campaign and the absence of polar stratospheric clouds from regions of very cold air

NASA Goddard Space Flight Center's Airborne Raman Ozone, Temperature, and Aerosol Lidar (AROTEL) measured extremely cold temperatures during all three deployments (1–16 December 1999, 14–29 January 2000, and 27 February to 15 March 2000) of the SAGE III Ozone Loss and Validation Experiment (SOLVE). Temperatures were significantly below values observed in previous years with large regions regularly below 191 K and frequent temperature retrievals yielding values at or below 187 K. Temperatures well below the saturation point of type I polar stratospheric clouds (PSCs) were regularly encountered, but their presence was not well correlated with PSC observations made by NASA Langley Research Center's aerosol lidar colocated with AROTEL. Temperature measurements by meteorological sondes launched within areas traversed by the DC‐8 showed minimum temperatures consistent in time and vertical extent with those derived from AROTEL data. Calculations to establish whether PSCs could exist at measured AROTEL temperatures and observed mixing ratios of nitric acid and water vapor showed large areas favorable to PSC formation but that were lacking PSCs. The flight on 12 December 1999 encountered large regions having temperatures up to 10 K below the NAT saturation temperature but only small, localized regions that might be identified as PSCs.

Numerical Investigation of the Influence of Mineral Dust on the Tropospheric Chemistry of East Asia

An investigation of the influence of mineral dust ontrace gas cycles in the troposphere is carried out inthis study. A 3D regional scale atmospheric chemistrymodel (STEM-III) which includes aerosol processes isused for the numerical simulations for May 1987.Heterogeneous interactions between gaseous species(SO2, N2O5, HNO3, HO2andH2O2) and the dust particles are considered.Emissions of dust behind convective cold fronts aremodeled. The transport and distribution of mineraldust predicted from the model is compared withsatellite measurements (aerosol index from TOMS). Themodel is shown to capture the synoptic variability inthe observed aerosol index. Calculations show twomajor dust events in May 1987, during which thedust levels close to the source reach more than500 μg/m3. The transport of dust is mostlyrestricted towards the north, with the net continentaloutflow of ∼6 Tg for the entire month. Results showthat the presence of mineral aerosol can greatlyimpact sulfate and nitrate distributions. Averagedover the month of May, the presence of dust isestimated to increase particulate sulfate and nitratelevels in east Asia by ∼40%. Furthermore, the sulfateand nitrate on the dust particles are predicted to beassociated with the coarse mode (3–5 μm particlediameter), consistent with observations over Japan.The influence of mineral dust on the photochemicaloxidant cycle is also investigated. For the entiremonth, a5–10% decrease in boundary layer ozone ispredicted by the model closer to regions of higherdust levels. The ratio of nitric acid to NOx overmarine regions is reduced by a factor between 1 and 2in the boundary layer to more than 2 in the freetroposphere as a result of aerosol processes.

STUDIES ON RDX AND RELATED COMPOUNDS: I. THE DIRECT NITROLYSIS OF HEXAMINE TO RDX

Maximum yields, of about 40%, of RDX were obtained with nitric acid of all concentrations down to 88%, providing the molar ratio of nitric acid to hexamine was sufficiently high. The rate of nitrolysis increased rapidly as the molar ratio of nitric acid to hexamine was increased and continued to do so after the molar ratio was raised above that required for maximum yields. The initial rate was shown to have an upper limit, however, at very high molar ratios. An intermediate in the nitrolysis reaction was isolated and identified as 3,5-dinitrocyclotrimethylenetriamine-1-nitrate (I). (I) was formed rapidly in sufficient quantities of 85 to 91% nitric acid at 0 °C., but had a high rate of decomposition which was independent of both acid concentration and ratio of nitric acid to (I) with 80 to 90% nitric acid. Under nitrolysis conditions some of the hexamine was converted to products not capable of giving RDX, owing apparently to hydrolysis of precursors to (I). The activation energy for the conversion of (I) to RDX was found to be identical with that for the rate controlling step of the conversion of hexamine to RDX. This fact, together with the general kinetic behavior of (I), provided evidence that (I) was a true intermediate and that its reaction to RDX was the rate controlling step in the direct nitrolysis of hexamine. The mechanism of the over-all reaction is discussed in relation to published information concerning the constitution of concentrated nitric acid. Nitracidium ion is believed to be the active nitrolyzing agent.