Mixture Of Nitric Acid Research Articles

Altın Geri Dönüşüm Prosesindeki Azot Oksit Emisyonunun Düşürülmesi

In jewelry workshops, during the production, the gold is accumulated as dust in the working environment. The recovery of these golden micro particles is provided by gold recycle workers. Nitric oxide is formed in a method called “polishing waste” which is the leaching process of gold within aqua regia (mixture of hydrochloric acid and nitric acid) for gold recovery. Nitric oxide is not only found in the working environment but also released into the atmosphere. Wet scrubbing with sodium hydroxide is used in order to eliminate NO gas, formed in the process. Since the water solubility of NO gas is very low, the wet scrubbing filtration system made with alkali materials is not sufficient alone. In this study, nitrous oxide gas (N2O), which is harmless to environment and human health, is given off to the atmosphere by reducing NO formation with addition of solid sulfamic acid to aqua regia. It was observed that NO parameter was zero and nitric oxide was not present at all during the process.

A New Family of Fused Azolo[1,5-a]pteridines and Azolo[5,1-b]purines.

The nitration of azolo[1,5-a]pyrimidin-7-amines with several nitration agents (such as acetic nitric anhydride, nitronium tetrafluoroborate, and a mixture of concentrated nitric acid and sulfuric acid) has been investigated. It has been shown that, depending on the conditions, the nitration of pyrazolopyrimidin-7-amines bearing electron-withdrawing groups in the pyrazole ring leads to nitration products in the pyrimidine and/or pyrazole ring. The nitration of triazolo[1,5-a]pyrimidin-7-amines with “nitrating mixture” has been optimized, thus allowing us to obtain a series of 6-nitro[1,2,4]triazolo[1,5-a]pyrimidin-7-amines, followed by their reduction into the corresponding [1,2,4]triazolo[1,5-a]pyrimidin-6,7-diamines (yields 86–89%). The latter have been subjected to heterocyclization by a variety of electrophilic compounds (such as CS2, glyoxal, triethyl orthoformate) with the formation of five- or six-membered annulated cycles.

Functionalization of multiwalled carbon nanotubes with active pharmaceutical ingredient via carboxylation

We experimented the functionalization of multiwalled carbon nanotubes by simple and laboratory friendly reaction path. The exercise performed by hypothesizing the enhancement in the activation of Multiwalled Carbon nanotubes (MWCNTs) walls which subsequently were used for the functionalization of active pharmaceutical ingredient (API). The tailoring of MWCNTs was achieved by suspending the MWCNTs in acidic mixture of nitric acid and sulphuric acid (HNO3/H2SO4) in volume proportionate. The reaction mixture was stirred manually followed by ultra-sonication and magnetic stirring for specific time interval to achieve the desired end product. After achieving promising analytical data, the functionalised MWCNTs (f-MWCNTs) were doped with API in alkaline medium. The obtained solids were further characterised by key analytical techniques like FTIR and Powder XRD (p-XRD).

Studies on leaching characteristics of electronic waste for metal recovery using inorganic and organic acids and base.

In this paper, we report leaching of precious and scattered metals such as gold (Au), copper (Cu), nickel (Ni), zinc (Zn), iron (Fe), and lead (Pb) from printed circuit boards of scrap mobile phones by hydrometallurgical process using inorganic acid, organic acid and base. The amount of metals leached by different leachants are quantified using atomic absorption spectroscopy. Among various inorganic acids, aqua regia (mixture of nitric acid (HNO3) and hydrochloric acid) is found to be the strongest leachant for most of the metals such as Zn (2.04 wt %), Fe (17.90 wt %), Ni (0.66 wt %), Pb (5.86 wt %) and Au (0.04 wt %). The basic leachant, ammonium thiosulphate is found to be very effective in leaching of Au (0.03125 wt %). The dissolution of Cu in HNO3 gives the highest amount of Cu in the solvent, that is, ∼ 7.52 wt %. The metallic phases present in the electronic waste before and after leaching are identified by X-ray diffraction analysis. The microscopic structure has been studied using a scanning electron microscope which depicts erosion of the structure after leaching.

Oxidation time effects of multiwalled carbon nanotubes on thermal, mechanical, and cure kinetics of epoxy‐based nanocomposites

AbstractIn this work, multiwalled carbon nanotubes (MWCNT) were oxidized in a mixture of sulfuric and nitric acid (3:1 v/v) using two distinct times (9 and 18 hours). The effects of different oxidation levels and concentrations of MWCNT on curing kinetics, thermal, and mechanical properties of bisphenol A diglycidyl ether nanocomposites were studied. The nanocomposites were produced using in situ polymerization technique at two different volume fractions (0.15% and 0.50% v/v) without using solvents. X‐ray photoelectron spectroscopy results indicated that MWCNT were in fact oxidized and just 9 hours of acid treatment showed a greater amount of oxygen on the MWCNT surfaces. Results of differential scanning calorimetry and dynamic mechanical analysis showed small variations in the glass transition temperatures of the nanocomposites, indicating alterations in the quality of the interphase matrix/carbon nanotubes. Concerning the thermogravimetric analysis results, the most thermally stable samples were those containing 0.15% v/v of pristine and 18 hours of oxidized MWCNT, which also had the highest stiffness of all nanocomposites. Finally, the cure kinetics of nanocomposites is fairly represented by Kamal and Sourour's semiempirical model with an autocatalytic behavior at 100°C and 120°C, but decelerated at 140°C.

EFFECT OF WASHING ON HEAVY METALS CONTENTS ON DATE FRUITS

The quantities of aluminum (Al, Cadmium (Cd), nickel (Ni) and tin (Sn) were estimated in twenty samples of packaged dates imported from the Middle East and North Africa countries collected from the Malaysian markets in Selangor - West Malaysia. The varieties include, Ajwa, Deglet Nour, Lulu, Mariami, Zahdi (two samples from different suppliers), Medjool, Mabroom, Khudri, Lamri, two unidentified species under trade marks ( nomades standard, palm dates), Safawi ( two samples from different suppliers), Khasouei, Khalas-Ihsa, fard, Roshdi, Mashrook and Rabbi .20 g of each sample was washed with 15 mL of deionized distilled water for 90 second. Washing residues and washed date tissues were dried and digested by mixture of nitric acid and hydrogen peroxide (15:20). The effectiveness of water washing on the removal of residues of heavy elements accumulated on dates was measured by comparing the contents in both washing residues and date tissue after washing. where the effectiveness ranged from 9.35 to 34% of the total content according to type of element. The study concluded that washing dates before direct consumption or manufacturing can play an important role in the removing some of the contents of heavy elements and reduces the health risk that can be caused to the consumer.

Influence of the surface etching on the corrosion behaviour of a three‐dimensional printed Ti–6Al–4V alloy

AbstractRecently, there has been an extension of three‐dimensional (3D) printing technology of metal materials in the medical field. Additive technology has made it possible to manufacture customized implants. However, 3D printing products often require surface treatment. The possible treatments include acid etching. This study investigated the effect of surface etching on the corrosion resistance of Ti–6Al–4V alloy concerning biological applications. The samples were etched in a mixture of hydrofluoric acid and nitric acid. The corrosion behaviour was described by measuring the time dependence of polarization resistance in a saline solution and surface analysis. The results showed that etching creates a fluoride‐rich layer on the surface, which negatively affects the corrosion behaviour of the material for up to 24 hr. Cytocompatibility tests showed that the resulting layer does not affect the biocompatibility of the material.

Highly accurate determination of Zn and Cu in human hair by ultrasound-assisted alkali dissolution combined with laser-induced breakdown spectroscopy

Hair is an ideal biomarker for monitoring human health and environmental risks through the determination of trace elements in the hair. However, accurately quantifying trace elements in hair using laser-induced breakdown spectroscopy (LIBS) is a big challenge. A simple and low-cost method, ultrasound-assisted alkali dissolution (UAAD), was proposed for quantifying trace elements in human hair. In this work, three different solvents (deionized water, nitric acid mixture, and sodium hydroxide) were used to dissolve the hair assisted by ultrasound; and then the hair solution was dripped onto filter paper. The effect of alkali dissolution on enhancing the spectral intensity of zinc (Zn) and copper (Cu) was then analyzed. Using ultrasound-assisted alkali dissolution combined with laser-induced breakdown spectroscopy (UAAD-LIBS), the limits of detection (LoDs) for determining Zn and Cu elements can reach to 0.3517 μg/g and 0.0146 μg/g, respectively. Based on this simple method with low LoDs, the quantitative analysis results of LIBS for three actual samples were compared with inductively coupled plasma optical emission spectrometry (ICP-OES). The relative errors of Zn and Cu between UAAD-LIBS and ICP-OES were less than 7.6% and 4.9%. These results show that using UAAD as a sample pretreatment process is an effective method of LIBS analysis.

Evaluación de diferentes reactivos aplicados en la precipitación del oro

En el presente trabajo de investigación se evalúa 4 diferentes reactivos utilizados en la precipitación del oro desde soluciones, dos de ellos utilizados de forma clásica como son el bisulfito de sodio y el sulfato ferroso, frente a dos especies poco comunes como el azúcar y el almidón. En la parte experimental se mezcló oro de aluvión con material arenoso de río para valorar la eficiencia de los reactivos, la lixiviación del oro se llevó a cabo con agua regia siendo este un agente oxidante particularmente fuerte formado por la mezcla de ácido nítrico y ácido clorhídrico en una proporción de volumen 3:1 respectivamente, en el análisis de datos se aplicó un software de programación estadístico, siendo el azúcar el mayor agente precipitante.

Preliminary Study for the Determination of Rare Earth Elements Using the ICP-MS Technique

This paper proposes an optimized method for the determination of rare earth elements (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) from soils using ICP-MS technique. First, the soil samples were thermal treated at three different temperatures 550ºC, 700ºC and 8500C in order to eliminate organic matter interferences. Then, the residual samples remaining from the calcination process were extracted in acidic medium with two different digestion methods (method I - a mixture of nitric acid and hydrogen peroxide; method II - aqua regia mixture) in order to quantify rare earth elements content. The highest recovery percentages for the major rare earth elements analyzed (Sc, Y, La, Ce, Pr, Nd. Sm) were situated in the range 86.13% to 99.90%, in sample residues thermally treated at 700�C and extracted with nitric acid and hydrogen peroxide.

Stress and Deformation of Optimally Shaped Silicon Microneedles for Transdermal Drug Delivery

In this study, we demonstrated the fabrication of the concave conic shape microneedle with the aid of COMSOL Multiphysics simulation. The stress and buckling of the microneedle structure were simulated by applying various loads ranging from 50 to 800 g perpendiculars to the tip in order to predict the occurrence of microneedles structure deformation. The simulation study indicated that the surface buckling deformation does not occur to the microneedle structure with the increment of the load. The microneedles with dimensions of height and diameter tip ranging from 60 to 100 μm and 1 to 4 μm, respectively had been fabricated via an etching process in a mixture of hydrofluoric acid, nitric acid, and acetic acid. Three optimized microneedles but different in the structures were fabricated via the acidic etching process. The reproducibility of 3 different microneedle structures was 15, 20, and 60%, respectively. Stress and buckling analyses of the fabricated microneedles were further carried out on the rat skin. The obtained experimental results show promising applications for the deep dermis, stratum corneum to epidermis layer penetration.

Distribution Spread and Environmental Risk Status of Pb, Cd And Cr in Soils of an Open-Air Waste Dumpsite along Tombia/Amassoma Road in Yenagoa Metropolis

In spite of the popularity of open-air waste dumping in Nigeria, it remains a relatively less effective waste management option across the globe because of its associated environmental impacts which includes the release of green house gases (GHGs), persistent organic pollutants (POPs), and metal micro-pollutants amongst others. This study aims to assess the potential environmental risks associated to metals released and vertically delineated across the soil profile within surroundings of dumpsite. Heavy metals in soil samples were acid-digested using the aqua-regia mixture of hydrochloric and nitric acid, followed by instrumentation analysis using the GBC 908 PBMT model atomic absorption spectrophotometer. Contaminated sites showed metal concentrations ranging from 1.493 to 109.460 mg/kg, 0.133 to 4.237 mg/kg, and 5.200 to 25.367 mg/kg for lead, cadmium and chromium respectively, with location 1 land area showing the most contamination. Only soil chromium was observed within regulatory stipulations in all cases. There was significant variation (p < 0.05) between the different sample locations, thereby indicating variations in composition of dumped wastes. Lead and cadmium showed the strongest positive correlation (r = 0.855, p < 0.01) and the application of some heavy metal pollution indicators revealed relatively higher metal loads and degree of contamination, as well as depicting potential ecological risk for soils of location 1. The significant heavy metal contamination of soils in the Tombia-Amassoma waste dumpsite requires that the local environmental sanitation and regulatory authorities take necessary remedial action to forestall the escalation of public health concerns that may emanate from this open-air dump.

Investigation of heavy metals in agricultural soils and vegetables irrigated with river water exposed to industrial effluent in Mojo, Ethiopia

The objective of this study was to examine the level of heavy metals and alkali metals in soil, cabbage and water samples collected from Qoka Negewo, where Mojo River is used for irrigation. Mixture of nitric acid, perchloric acid, and hydrogen peroxide was used for optimizing the wet digestion method for soil and cabbage samples. One way anova test result revealed that there were significant difference (p < 0.05) at 95 percent confidence level in concentration of metals among soil, cabbage and water in all samples. The heavy metal concentration of soil samples was found to be relatively a little higher than the corresponding concentration in cabbage samples. The concentration of the metals was compared with internationally recommended permissible limits, and most of them were found below the permissible limits, indicating insignificant health risk by consuming the cabbage, and using the water for irrigation purpose. The hazard risk index calculated for cabbage was found to be <1, which also indicates the predicted exposure is unlikely to pose potential health risks.

Functionalisation of multi-walled carbon nanotubes by esterification method for poly(ethylene)glycol attachment and their characterization

In this study, we have successfully functionalised multi-walled carbon nanotubes (MWCNT) surfaces with poly(ethylene)glycol (PEG) via an esterification method in which the oxygenated functional groups are created by chemical oxidations with a mixture of nitric acid and sulfuric acid solutions (ratio of 1:3, v/v), and then it is reacted with functional groups of PEG. Different techniques including FE-SEM, TEM, EDS, FT-IR spectrometry, Raman spectroscopy and TGA are applied to identify the characteristics of MWCNTs. The effects of catalyst and different mass ratios of PEG:MWCNTs on the characteristics of MWCNTs are investigated for the first time. The TGA analysis indicates that when the mass ratio of PEG:MWCNTs is 140:1, the highest weight loss of 30.86 wt% is obtained. Additionally, an increase in the amounts of catalysts decreases the content of PEG attached on the nanotubes. The catalyst of 0.3 ml H2SO4 and the mass ratio of PEG:MWCNTs = 140:1 demonstrates to be the most effective for PEG functionalised MWCNTs. It can be chosen as the best experimental conditions to perform PEG functionalised MWCNTs.

DSC/TG and SEM Studies of Synthesized Potassium Sulphamate (PS) and Potassium Dinitramide (KDN) Crystals

In the present paper, thermal decomposition and crystal researches of synthesized potassium sulphamate (PS) and potassium dinitramide (KDN) crystals were studied using differential scanning calorimetry/ thermal gravimetry (DSC/TG) and scanning electron microscope (SEM) techniques, respectively. Initially, PS crystals were synthesized using sulphamic acid and potassium hydroxide pellets. Afterwards, PS crystals were used for synthesizing potassium dinitramide (KDN) crystals by the nitration of PS in sulfuric and nitric acid mixture. One sample of PS was used for studying DSC/TG curves, while three samples of KDN crystals were used for the studying DSC/TG curves. The three samples of KDN crystals which were used in the present studies are, a) stored KDN (1 month), b) stored KDN (2 months), and c) washed KDN. All the obtained DSC/TG curves of three KDN crystals are dissimilar to each other, and the probable reasons for this dissimilarity are discussed in the manuscript. For further clarifications, TG curve of KN was compared with the TG curves of three samples of KDN used in the present study. It was observed that, while storage, KDN slowly converts into KN with some rate which gradually changes the physical and chemical properties of KDN.

Functionalization, characterization, and antibacterial activity of single wall and multi wall carbon nanotubes

The raw-SWNTs and raw-MWNTs were chemically oxidized with a mixture of sulfuric acid and nitric acid under ultrasonic vibration. The functionalized-SWNTs (F-SWNTs) and functionalized-MWNTs (F-MWNTs) were characterized by using ultra violet-visible spectrophotometer, X-ray diffraction, and field emission scanning electron microscopy (FESEM). The antibacterial efficiency of SWNTs and MWNTs towards Escherichia coli (E. coli) as gram-negative bacteria was evaluated via viable count method and fluorescence microscopy. The results of viable count method showed that the SWNTs and MWNTs have higher inhibitory effect after being treated with H2SO4/HNO3.The E. coli images under fluorescence microscopy exhibited that almost red color for dead cells, which confirms the efficient lethal ability of F-SWNTs and F-MWNTs.

Crystal structure and Hirshfeld surface analysis of 4-allyl-2-meth-oxy-6-nitro-phenol.

The asymmetric unit of the title compound, C10H11NO4, which was synthesized via nitration reaction of eugenol (4-allyl-2-meth-oxy-phenol) with a mixture of nitric acid and sulfuric acid, consists of three independent mol-ecules of similar geometry. Each mol-ecule displays an intra-molecular hydrogen bond involving the hydroxide and the nitro group forming an S(6) motif. The crystal cohesion is ensured by inter-molecular C-H⋯O hydrogen bonds in addition to π-π stacking inter-actions between the aromatic rings [centroid-centroid distances = 3.6583 (17)-4.0624 (16) Å]. The Hirshfeld surface analysis and the two-dimensional fingerprint plots show that H⋯H (39.6%), O⋯H/H⋯O (37.7%), C⋯H/H⋯C (12.5%) and C⋯C (4%) are the most important contributors towards the crystal packing.

Nitric Acid Functionalization of Petroleum Coke to Access Inherent Sulfur

Sulfonated carbon-based catalysts have been identified as promising solid acid catalysts, and petroleum coke (petcoke), a byproduct of the oil industry, is a potential feedstock for these catalysts. In this study, sulfur-containing (6.5 wt%) petcoke was used as a precursor for these catalysts through direct functionalization (i.e., without an activation step) with nitric acid to access the inherent sulfur. Catalysts were also prepared using sulfuric acid and a mixture of nitric and sulfuric acid (1:3 vol ratio). Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and titration were used to identify and quantify the acid sites. The activities of the prepared catalysts were determined for the esterification of octanoic acid with methanol. Petcoke had few −SO3H groups, and correspondingly no catalytic activity for the reaction. All acid treatments increased the number of −SO3H groups and promoted esterification. Treatment with nitric acid alone resulted in the oxidation of the inherent sulfur in petcoke to produce ~0.7 mmol/g of strong acid sites and a total acidity of 5.3 mmol/g. The acidity (strong acid and total) was lower with sulfuric acid treatment but this sample was more active for the esterification reaction (TOF of 31 h−1 compared to 7 h−1 with nitric acid treatment).

Tailoring surface properties of carbon nanofibers via oxidation and its influence on dental pulp stem cell viability of PCL/CNF composites

The effect of oxidation time on the surface chemical and morphological properties of carbon nanofibers (CNFs) and their suitability for use as a reinforcement agent in the development of bone scaffolds was assessed. The CNFs were modified using a 3:1 v/v mixture of concentrated sulfuric (H2SO4) and nitric acid (HNO3) for different periods of time. Several analytical techniques were used to characterize the oxidized CNF surface properties. Photoacoustic Fourier transform infrared spectroscopy (PAS-FTIR) showed the creation of carboxylic groups due to the acid treatments. Scanning electron microscopy images revealed differences in the nanofibers before and after acid treatment. The relationship between the CNF crystals and their defects when varying the oxidation time were determined by Raman spectroscopy. The CNF FTIR results, contact angle measurements, and dispersion tests showed the formation of carboxylic groups due to the oxidative treatment. The results confirmed the presence of microstructures with defects, as well as chemically active functional surface groups, such as carboxyls and hydroxyls. Furthermore, a composite was prepared using polycaprolactone (PCL) as a matrix and the CNF as the reinforcement. The storage module of the oxidized CNFs was improved with respect to the nonoxidized CNFs. Furthermore, the scaffolds of PCL with oxidized CNFs enhanced the cell proliferation.

Determination of Methylene blue Number to Characterize the Lapsi Based Activated carbon Prepared by Chemical Carbonization

Determination of Methylene blue Number of the activated carbons prepared by Chemical Carbonization from waste material, seed stone of Lapsi has been studied. Methylene blue Number has been determined by single point method using batch adsorption method. Acids like concentrated sulphuric acid and a mixture of concentrated sulphuric acid and concentrated nitric acid have been used to prepare activated carbon. The activated carbon prepared by using a mixture of concentrated sulphuric acid and concentrated nitric acid has been found to have higher methylene blue number than the activated carbon prepared by using concentrated sulphuric acid. The activated carbons thus prepared can be used as effective adsorbents for the remediation of pollutants from water.