Mixture Of Nitric Acid Research Articles

Health impact of toxic metals in facial cosmetics used in Calabar, Nigeria

The present study highlights the health risk factor of heavy metals in cosmetics considering their habitual use in the society today. This safety assessment has become inevitable because of the high demand for these products which has resulted to flooding the markets with low quality cosmetics. Digestion was by 20 mL mixture of nitric acid (HNO3) and hydrogen peroxide (H2O2) in the ratio of 3:1 and was heated in a hot plate for 2-3 hours at 90 °C. The choice of this mixture was informed by literature to yield the highest amounts in metal digestion. The mean metal concentrations of these products are; 1.2758, 0.9599, 0.1262, 0.0504 and 0.0068 mg/kg while the ranges are: 0.140-5.823, 0.054-3.908, 0.021-0.820, 0.028-0.071 and 0.001-0.236 mg/kg respectively for Mn, Ni, Cr, Cd and Pb. From the analysis, 40 %, 74.28 %, and 17.14 % of the products has Cd, Ni and Mn respectively exceeded the standard. Pb was not detected in majority of the products. Though cosmetic safety cannot be ascertained only by their heavy metal content, the present paper focuses solely on the contribution of heavy metals as a risk factor to the consumption of these products.  Â

Nghiên cứu thời gian và nhiệt độ hoạt hóa ống nano carbon ứng dụng chế tạo vật liệu xúc tác điện cực pin nhiên liệu methanol

Carbon nanotubes were activated by a mixture of nitric acid and sulfuric acid (volume ratio 1:1) with different time and temperatures. The platinum-ruthenium electrocatalyst material (PtRu) based on activated carbon nanotubes (CNTs) was synthesized by chemical reduction method. The precursors H2PtCl6 and RuCl3 were used with the efficient reduction of NaBH4 agent in ethylene glycol. Analytical methods such as X-ray diffraction, transmission electron microscopy, and cyclic voltammetry were used for analysis and evaluation. The results showed that PtRu nanoparticles on activated CNTs were successfully synthesized. The PtRu/CNTs sample using activated carbon nanotubes for five hours at 50oC was the highest methanol oxidation ability.

Selective nitration of phenol to o-nitrophenol in the presence of metal-free reduced graphene oxide at room temperature

Reduced graphene oxide catalyzed selective synthesis of o-nitrophenol from an equimolar mixture of phenol and nitric acid in dichloroethane at room temperature.

Kinetics of Formation of Gaseous Products in γ-Radiolysis of Mixtures Modeling Liquid Radioactive Waste

The kinetics of the formation of gaseous products and variation in the parameters of acidity (pH) and chemical oxygen consumption (COC) are studied in relation to the γ-radiolysis of aqueous solutions of mixtures of formic, oxalic, and nitric acid as the model system of radiolytic transformations of acid components of liquid radioactive waste. It is found that with an increase in the absorbed dose of γ-radiation, the acidity and the COC value both decrease because of the decrease in the concentration of organic acids in the mixture. The gaseous products CO2 and H2 were identified. Their concentrations increase nonlinearly with the absorbed dose. Radiation-chemical yields of H2 and CO2 are calculated. Using data from experiment and the literature on composition of liquid products of radiolysis of aqueous solutions of acids, kinetics of formation of gaseous products are studied using soft KINET (version 4.2.5).

Nitrogen oxide reduction through absorbent solutions containing nitric acid and hydrogen peroxide in hollow fiber membrane modules

Emissions of nitrogen oxides such as NO and NO2, which are commonly known as NOx, are threats to human existence and cause environmental problems. Mainly, two techniques have been developed to drastically reduce these emissions, which are dry and wet processes. The wet process has several advantages, major identifiable advantages are the adaptability to the flue gas, low operating temperatures and no poisoning and inactivation catalyst. Also, a mixture of hydrogen peroxide and nitric acid are used as absorbents solution for NOx reduction in the wet process. The advantages of using this mixture include the ability to reduce the negative effect of NOx and does not contaminate the scrubbing solution. In addition, nitric acid has an economical advantage in the process considering the fact that it is produced in the process. Finally, it can be conducted at ambient temperature. This study furthermore used a mixture of hydrogen peroxide and nitric acid solutions as an absorbent to reduce NOx in hollow fiber membrane modules. The hydrogen peroxide oxidized HNO2 to nitric acid, while enhances the oxidation through an autocatalytic reaction. The effects of the feed gas flow rate, hydrogen peroxide concentrations and number of fibers on the NOx reduction, absorbed NOx and flux were varied to study. The experimental results showed that the increase in the feed gas flow rate from 100 to 200 mL/min decreased NOx reduction from about 98 to 94% but increased the absorbed NOx and flux from about 0.13 to 0.255 mmol/h and 0.85–1.63 mmol/m2.h, respectively The increase in proportion of NOx in the feed gas effect was dominant than the increase in absorbed NOx. An increase in hydrogen peroxide concentration from 0.5 to 10 wt.% in the absorbent solutions increased NOx reduction, absorbed NOx and flux from about 94 to 98%, 0.257–0.267 mmol/h and 1.09–1.13 mmol/m2.h, respectively. Additionally, the H2O2 plays an important role in enhancing HNO2 oxidation to HNO3. Furthermore, an increase in the number of fibers from 50 to 150 in the membrane module increased NOx reduction and absorbed NOx from 86 to 97% and 0.23–0.27 mmol/h. Flux decreased from 2.98 to 1.13 mmol/m2.h due to increment in the gas-liquid contact surface area.

Solubilization of Rhodium in Hydrochloric Acid Using an Alkali Metal Salt Method

Acids such as aqua regia, a 3:1 mixture of hydrochloric acid (HCl) and nitric acid, that contain strong oxidizing agents are used in the dissolution-based recovery of platinum group metals (PGMs). However, nitrate-nitrogen emission has become subject to increasingly strict environmental regulations in recent years. Accordingly, we herein propose a dissolution process for PGMs via the formation of complex oxides using HCl alone. We prepared complex oxides of alkali metals and rhodium (Rh), which is particularly hard to dissolve, and investigated their dissolution behaviors in HCl. Rh-containing complex oxides were prepared by calcining Rh powder and alkali metal salts in air, and dissolution tests using HCl were conducted on the complex oxides obtained. It was found that Rh-containing complex oxides were completely dissolved under appropriate calcination and dissolution conditions.

Pyridine-Imidazlolium Salts: Oxidatively Cleavage of N-C Bond via Nitration

Azaheterocycles derivatives with pyridine-imidazole skeleton are compounds of great value for medicinal chemistry. We report herein the nitration of 1,1′-(pyridine-2,6-diylbis(methylene))bis{3-[2-(4-nitrophenyl)-2-oxoethyl]-1H-imidazol-3-ium} bromide using a typical mixture of nitric and sulphuric acid. The nitration occur with the oxidative cleavage of N–C bond between imidazolium ring and methylene group.

Development of a Sulfamic Acid-Based Chemical Formulation for Effective Cleaning of Modified 9Cr–1Mo Steel Steam Generator Tubes

A new sulfamic acid-based formulation is developed for the effective chemical cleaning of modified 9Cr–1Mo steel as a replacement for the conventional corrosive nitric acid (HNO3) and hydrofluoric acid (HF) mixture. The effect of sulfamic acid concentrations and inhibitor (2-mercaptobenzimidazole, MBI) on the metal loss during cleaning of modified 9Cr–1Mo steel was studied using weight loss and electrochemical impedance spectroscopic methods. The metal loss was found to increase with increase in acid concentration, but it was significantly lower with increasing inhibitor concentration, with an efficiency of > 90%. The corrosion rates of modified 9Cr–1Mo steel with 10% sulfamic acid + 2 mM MBI, 10% sulfamic acid without inhibitor and HNO3 + HF mixture were 1290, 6426, and 303,515 μm year−1 respectively. The optimal composition for efficient cleaning, with least base metal loss, was found to be 10% sulfamic acid + 2 mM MBI. Laser Raman spectroscopic (LRS) analysis of the corrosion products obtained during chemical cleaning process revealed that a protective chromium oxide film was formed during the cleaning with sulfamic acid + inhibitor as compared to iron oxide-based films with HNO3 + HF mixture and 10% sulfamic acid solutions.

Risk assessment of heavy metals content in different hair dyes and their users’ urine samples

ABSTRACT Human toxicity of heavy metals is the result of long-term exposure to pollutants found in hair dyes. In this study, levels of lead (Pb), cadmium (Cd), mercury (Hg) and urine were evaluated in various hair dyes products sold in local stores in Riyadh using inductive coupled plasma optical emission spectrometry (ICP-OES) after digestion with a mixture of nitric acid (HNO3), hydrofluoric acid (HF) and hydrogen peroxide (H2O2) for hair dyes, while a mixture of HNO3 and H2O2 was used for urine. The mean concentrations of the selected heavy metals in hair dye ranged (0.0015–0.0035 ppm) from Cd, (0.003–0.014 ppm) from Pb, which were within the permissible international limits, while for Hg (1.1–4.3 ppm) from Hg was higher than the permissible international limits. The mean concentrations of the selected heavy metals in urine ranged (0. 002, 0.011 and 1.3 ppm) from Cd, Pb, and Hg respectively in the urine. However, in the case of urine samples, the average concentration of Pb was higher than the permitted international limits. The current study showed that the use of hair dyes exposes users to low concentrations of toxic heavy metals that can cause potential health damage to users.

Acid modified multiwalled carbon nanotubes condition by reflux

Nanomaterials, especially carbon nanotubes (CNTs), show excellent combinations of thermal, mechanical and electrical properties. However, as-produced CNTs are entangled and form agglomerates, due to their several micron lengths. Therefore, the dispersion efficiency of CNTs is limited. We decreased the length and improved dispersion with acid modified multiwall-CNTs (A-MWCNTs) formed by a reflux method. MWCNTs were modified with an acid mixture of sulfuric acid and nitric acid at the ratio of 3:1 by volume. The reflux temperature and time were varied between 80 to 120 °C and 10 to 30 min. FTIR found an increase in carboxylic acid groups on the surfaces with increasing reflux temperature and time. Therefore, A-MWCNTs showed good dispersion in polar solvents; i.e. water, DMF and DMAc. Furthermore, A-MWNCT lengths were shortened with increased reflux temperature and time. Carboxylic acid groups on A-MWCNT surfaces decreased the electrical conductivity by two orders of magnitude. However, epoxy resin in which the A-MWCNTs, modified at 120 °C and 30 min were encapsulated, showed better conductivity, since the shortest MWCNT lengths and the carboxylic groups on the A-MWCNT surfaces allowed good dispersion in epoxy resin.

1-methyl-2,4,5-trinitroimidazole (MTNI), a melt-cast explosive: synthesis and studies on thermal behavior in presence of explosive ingredients

ABSTRACTTraditionally, TNT based melt-castable explosives have been used till date. Recently, energetics communities are looking for an alternate to TNT in melt-cast formulation because of its toxicity and environmental concerns. 1-Methyl-2,4,5-trinitroimidazole (MTNI) is an insensitive high energy material and potential for use as a melt-cast high explosive formulations in place of TNT. MTNI has superior explosive performance as compared to that of TNT. Typically MTNI is synthesized starting from imidazole by step-wise nitration using strong nitric acid mixture followed by N-methylation offers poor yield. The key step involves during synthesis of MTNI is substitution of third nitro group at fifth position of 2,4-dinitroimidaziole which is limiting for its large-scale preparation. We report herein, an improved method for synthesis of MTNI from 1-methyl-2,4-Dinitroimidazole (MDNI) under different nitration conditions in good yield. Heteropoly acid (HPA) is an efficient, mild and green catalysts used as nitric acid activator. The synthesized MTNI by this method was characterized by FT-IR, NMR & elemental analysis. Thermal behavior of MTNI was determined by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA) and ignition temperature tester. Further, the effects of thermal energy on decomposition of formulations containing MTNI with solid high explosives such as RDX & CL-20 or polymeric binders like HTPB & GAP were investigated. Thermal decomposition mechanisms of MTNI and its precursor, MDNI based on Pyrolysis-GC/MS analysis were also described.

Solvent‐deficient method lowers grain‐boundary resistivity of doped ceria

AbstractNanoparticles of gadolinium‐doped cerium oxide (GDC) were synthesized using solvent‐deficient method and their sinterability and electrical properties were investigated using the powder and cold sintering process. The GDC powder was uniaxially pressed into cylindrically‐shaped pellets with a mixture of nitric acid and hydrogen peroxide at 200°C to encourage particle arrangement during forming process. These bulk samples were annealed using two different temperature profiles: at 800°C for 5 hours and at 1300°C for 1 minute—800°C for 5 hours. The samples produced using HNO3/H2O2 mixture showed higher relative density than ones without it. Ionic conductivity of the sample sintered through the two‐step profile was obtained from electrochemical impedance spectroscopy. Although the grain conductivity for the samples (8.0 × 10−3 S cm−1 at 500°C, and 3.3 × 10−2 S cm−1 at 700°C) is on par with a conventionally sintered sample, the measured total conductivity (3.9 × 10−3 S cm−1 at 500°C, and 2.5 × 10−2 S cm−1 at 700°C) is about 10 times higher than the conventionally sintered one and is comparable to the values seen in the previous studies for GDC which employed higher sintering temperature, pointing to the effectively lower grain‐boundary impedance. This result could be attributed to no significant phase segregation along grain boundaries due to the low‐temperature processing.

Microwave and open vessel digestion methods for biochar

Digestion of biomass derived carbonaceous materials such as biochar (BC) can be challenging due to their high chemical recalcitrance and vast variations in composition. Reports on the development of specific sample digestion methods for such materials remain inadequate and thus require considerable attention. Nine different carbonaceous materials; slow-pyrolyzed tea-waste and king coconut BC produced at 300 °C, 500 °C and 700 °C, sludge waste BC produced at 700 °C, wet fast-pyrolyzed Douglas-Fir BC and steam activated coconut shell BC have been tested to evaluate a relatively fast and convenient open-vessel digestion method using seven digestion reagents including nitric acid (NA), fuming nitric acid (FNA), sulfuric acid (SA), NA/SA, FNA/SA, NA/H2O2 and SA/H2O2 mixtures. From the tested digestion reagents, SA/H2O2 mixture dissolved low temperature produced BC (LTBC) within 2 h with occasional shaking and no external heating. Except peroxide mixtures, the other reagents were used to evaluate microwave digestion (MWD) efficiency. Nitric acid mixture was capable of only completely digesting LTBC in the MWD procedure whereas FNA, NA/SA and FNA/SA mixtures resulted in the successful dissolution of all tested carbonaceous materials. Amongst them, FNA provided the least matrix effect in the quantification of the four metals tested using flame atomic absorption spectrophotometry. Tested recoveries for FNA were satisfactory as well. It was concluded that FNA is a preferable reagent for microwave digestion of BC.

Accurate Determination of Harmful and Doping Elements in Soft Magnetic Ferrite Powders Using Inductively Coupled Plasma Tandem Mass Spectrometry

Abstract A novel strategy was proposed and developed for eliminating spectral interference in the analysis of soft magnetic ferrite powders by inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) in the MS/MS mode using mixed reaction gases. The samples were digested in a microwave-based digestion system using a mixture of nitric acid and hydrochloric acid. The contents of harmful elements (Na and Mg) and doping elements (Al, K, Ti and Co) in the digestion solution were determined by ICP-MS/MS. For spectral interferences in the complex matrix composition of different soft magnetic ferrite powders, in the MS/MS mode, the interferences were eliminated using mixed reaction gases of NH3/He/H2 through mass shift and on-mass methods. The limits of detection for Na, Mg, Al, K, Ti and Co were 16.6, 3.08, 5.40, 11.3, 0.64 and 0.53 ng L–1, respectively. The developed method was evaluated by sector field ICP-MS (SF-ICP-MS), and no significant difference was observed between the two analytical methods at a 95% confidence level, indicating that the developed method was accurate and reliable. This method was demonstrated as simple and quick and could be used for interference-free determination of Na, Mg, Al, K, Ti and Co in soft magnetic ferrite powders, providing a new technical means for the quality control of harmful and doping elements in soft magnetic ferrite powders.

Oxygen-containing functional groups on bioelectrode surface enhance expression of c-type cytochromes in biofilm and boost extracellular electron transfer

Introducing oxygen-containing functional groups is a common and convenient method to increase the hydrophilicity of bioelectrodes. In this study, the effect of oxygen-containing functional groups on biofilm was systematically studied to understand how the electron transfer between electrochemically active bacteria (EAB) and bioelectrode was boosted. After electrolysis pretreatment in sulfuric and nitric acid mixture, the oxygen content of the carbon fiber brushes increased from 4.6% to 30.9%. Comparing with the control, the maximum power density increased by 27.7%, while the anode resistance decreased by 21.8%, because charge transfer resistance significantly reduced. The analysis results showed that the content of c-type cytochromes (c-Cyts) in the EAB biofilm was four times higher than that in the control, while the biomass just slightly increased and the bacteria community was similar with that of the control. These findings suggested that the fundamental reason for the enhanced extracellular electron transfer between EAB and electrode was the increased c-Cyts.

Exposure of children to heavy metals from artisanal gold mining in Nigeria: evidences from bio-monitoring of hairs and nails

In recent times, there had been reported cases of Pb poisoning in Anka gold mining area, Northwest Nigeria. Therefore, this study was carried out to determine the extent of bioaccumulation of heavy metals in the hairs and nails of children in the area. Forty samples (twenty nails and twenty hairs) samples were collected from ten boys and ten girls of ages 5–9 residing in the area. To ascertain the sources of heavy metals in children, 15 soils samples, 15 groundwater samples, 5 samples of mine tailings, and 5 plants samples were collected. Hair and nails of the subjects were collected using internationally acceptable techniques. All samples were kept in uncontaminated ziplock bags prior to laboratory preparation and analysis. The samples were cleaned using nonionic detergent (triton X-100) and deionized water. The hairs and nails were digested with 10 mL of 6:1 mixture of nitric acid and perchloric acid. The soils, mine tailings, and plants were air-dried at room temperature, sieved, and chemically digested using the aqua regia method. The concentrations of metals in all the samples were determined using high-performance liquid chromatography–inductively coupled plasma–mass spectrometry. Statistical analysis was employed to unravel potential sources of metals in the media. Results showed that heavy metals in children of the area are above results from similar studies and pathological ranges for heavy metals in hairs and nails. Also, heavy metals in environmental media are above the recommended standards. Multivariate analysis showed that the metals are mainly from mining and other anthropogenic sources. Results of correlation between heavy metals in hairs and nails with those in geological samples revealed that heavy metal that bioaccumulates in the children of this area are mostly from contaminated environmental media. It is recommended that complete remediation and effective health education be carried out in the area.

Etchant for Normal and Abnormal Grain Growth Microstructure in RAFM Steel at Different Annealed Temperatures

Abstract To reveal the prior austenite grain (PAG) boundaries in Ferritic Martensitic steels with reduced activation by a peculiar etchant mixture of hydrochloric acid, nitric acid, and water has been developed. Etching with this system successfully delineates both, inside the grain and grain boundaries in RAFM steels at annealing temperatures 950–1250 °C and observed the abnormal grain growth at 1250 °C. Other two etchants Vilella's and Waterless Kalling's agents are uneffective at 1250 °C and do not reveal the abnormal grain growth. The specimens were austenitized at temperatures in the range 950–1250 °C. The suitable etching agent is successful to observe the micro structural features of RAFM steels.

Synthesis and characterization of hydrophilic gilsonite fine particles for improving water-based drilling mud properties

In this study, hydrophilic gilsonite fine particles were produced by reaction of natural gilsonite with a mixture of sulfuric acid and nitric acid followed by a planetary ball mill process. The hydrophilic gilsonite was characterized using FTIR, XRD, FE-SEM, DLS, elemental analysis, and mass spectroscopy. All experiments showed that the characteristics of the hydrophilic gilsonite, due to its surface modification, were different from those of natural gilsonite. Moreover, hydrophilic gilsonite molecules were dispersed in water as fine particles with an average diameter of 300 nm without adding any dispersant. The effects of hydrophilic gilsonite on the rheological properties as well as the fluid loss of the water-based drilling mud were investigated before and after the hot-roll process. The results showed that simultaneous adding of 10 g of hydrophilic gilsonite fine particles to the base fluid and reducing the starch concentration to half of its initial value resulted into the best composition for efficient water-based drilling mud. In this case, the rheological properties of the mud were stabilized with a minimum change in the decrease of the yield point, foam formation was prevented after the hot-roll process, and the pH of the system was stabilized in a suitable range at high temperatures. Moreover, this composition could reduce the fluid loss by 50.8% and the filter cake thickness by 66.7% in low-temperature, low-pressure conditions, while the fluid loss reduction was 75% in high-temperature high-pressure conditions. Moreover, the results revealed that hydrophilic gilsonite was an effective additive during the 16 h hot-roll process.

Heavy Metals Levels in Plastics Housing of Televisions: Is there a changing trend across three decades (1980-2000)?

Background: This study investigated the concentration of some heavy metals in plastic housing of televisions produced over three decade (1980-2000) with the aim of providing information and comparing the trend in the concentration of these metals. Methods: The heavy metal concentrations were determined by atomic absorption spectroscopy after acid digestion using a 1:1 mixture of sulphuric and nitric acid. Results: The mean concentration of the heavy metals (mg/kg) in the television sets for 1980s, 1990s and 2000s, respectively, were as follows: 12.75 (Nd); 1.32 (Pb); 1.84, 1.47 & 2.79 (Ni); 1.53, 16.19 & 40.42 (Ag); 82.24, 159.69 & 113.29 (Zn); 7.12, 4.23 & 5.26 (Cr); 3.26, 2.76 & 2.39 (Cu); 4.84, 24.05 & 26.67 (V); 9.30, 8.40 & 12.63 (Co); 2.59, 4.05 & 4.28 (Cd). Conclusion: Although the mean concentrations for Zn, Cu and Ag in the television samples were relatively high, compared to the total threshold limit concentration (TTLC), they were below the threshold limit. These results suggest that there may not be any immediate environmental hazard posed from the TV plastic housings. The correlations analysis showed that most of the metals declined in TV housings over the subsequent decades.

XPS and structural studies of high quality graphene oxide and reduced graphene oxide prepared by different chemical oxidation methods

Abstract High quality graphene oxide (GO) and reduced graphene oxide (rGO) have been synthesized by chemical oxidation of graphite flakes via three modified Hummers methods using a mixture of sulfuric acid (H2SO4), phosphoric acid (H3PO4) and nitric acid (HNO3) as intercalating agents and potassium permanganate (KMnO4) and hydrogen peroxide (H2O2) as oxidizing agents. In this study the production of dangerously explosive gases was avoided. The temperature was carefully controlled using ice baths, ensuring the temperature was kept at the minimum during the reaction. The prepared samples were extensively characterized using various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicated greater presence of oxygen containing groups and an increase in the (C/O) ratio, both of which served as reliable indicators of high quality graphene oxide. Atomic ratio of carbon to oxygen (C/O) quantified by XPS was calculated to be 25.67, 1.81, 1.63, and 2.77 of graphite, GO-I, GO-II, and GO-III, respectively. As revealed by FTIR analysis, the GO-I had more hydrophilic oxygen functional groups compared to GO-II and GO-III.