Mixture Of Concentrated Sulfuric Acid Research Articles

Nutritional diagnosis of nitrogen and phosphorus in Ocimum basilicum L. plants grown under macronutrient applications

The objective of this work was to assess the nutritional status of basil (Ocimum basilicum L.) plants grown under application of macronutrients, in a Typic Hapludult. The experiment was conducted in Cruz das Almas, BA, Brazil, in a greenhouse. The treatments were based on a Baconian matrix statistical arrangement, in which one of the nutrients is supplied in different quantities, whereas the other nutrients are maintained at the reference rates. Six nutrients, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) were evaluated at three different rates. Two additional treatments were used (reference rates; and without nutrient applications), totaling 20 treatments. A completely randomized experimental design with five replications was used, totaling 100 experimental units. Plant material was collected 50 days after treatment applications and dried in an oven for 72 hours. Approximately 0.1 g of dry weight of leaves, stems, and roots were subjected to acid digestion in a mixture of concentrated sulfuric acid and hydrogen peroxide. The digested material was diluted in 100 mL of distilled water to obtain the extract for nutritional diagnosis. The optimal maximum N and P accumulations in basil leaves for high plant performances were 51 and 3.0 g kg-1, respectively. The estimated rates for each nutrient to provide the optimal total N accumulation in basil plants were: N = 235.61, P =91.27, K = 175, S = 41.98 (mg dm-3), Ca = 0.97, and Mg = 0.36 (cmolc dm-3).

Block copoly(phenylquinoxaline)s as potential ionomers for proton exchange membranes

Poly(phenylquinoxaline)s are a family of aromatic condensation polymers known for their outstanding thermal and chemical stability. Based on this polymer class new sulfonated block copoly(phenylquinoxaline)s with different hydrophobic segments have been developed. The block copolymers were synthesized via polycondensation reactions between 3,3′,4,4′-tetraaminodiphenylether and two different tetraketones: tetrafluorphenylbis-phenylethandion and phenylbisphenylethandion. Block copoly(phenylquinoxaline)s up to a molecular weight Mn of 29.3 kg mol−1 were obtained. The sulfonations of these block copolymers were carried out in a mixture of concentrated sulfuric acid and oleum (4:1) leading to ion exchange capacities of 1.77–2.36 mmol g−1. Flexible films of sulfonated block copoly(phenylquinoxaline)s were realized by doctor blading of solutions in N’N-dimethylacetamide (DMAC) or N-ethyl-2-pyrrolidone (NEP). The resulting membranes achieved proton conductivities in the range of 48–110 mS cm−1. Additionally, water uptake and dimensional stability were determined and presented.

Adsorption of volatile benzene series compounds by surface-modified glass fibers: kinetics, thermodynamic adsorption efficiencies, and mechanisms.

The presence of volatile benzene series compounds (VBSCs) in the environment is continually increasing, with the potential for negative effects on human health. It is therefore important to develop new materials for the adsorption of these compounds using various modification techniques. Glass fibers are a promising adsorbent for VBSCs and offer a number of advantages. In the present work, the surfaces of glass fibers were modified using hydrogen peroxide, a sodium hydroxide solution, or Piranha solution (a mixture of concentrated sulfuric acid and hydrogen peroxide). The adsorption characteristics of the resulting specimens were investigated, employing 10 volatile benzene-based compounds, and the activated glass fibers showed significantly improved adsorption efficiencies. The fibers activated with the Piranha solution were further modified with a triethoxysilyl benzene compound to obtain an aryl-modified material that demonstrated enhanced adsorption of aniline, salicylaldehyde, benzyl alcohol, and xylene relative to that obtained from a combination of polyurethane foam and XAD-2 resin. The adsorption efficiency of benzyl alcohol by these aryl glass fibers was found to be as high as 93% and the adsorption mechanism is believed to be associated with hydrogen bonding and π-π conjugation. This study provides a reliable technique for the quantification of VBSCs and a basis for the evaluation of various adsorption materials.

Ultrahigh “Relative Energy Density” and Mass Loading of Carbon Cloth Anodes for K-Ion Batteries

Mass loading and potential plateau are the two most important issues of potassium (K)-ion batteries (KIBs), but they have long been ignored in previous studies. Herein, we report a simple and scala...

Thermally-treated and acid-etched carbon fiber cloth based on pre-oxidized polyacrylonitrile as self-standing and high area-capacitance electrodes for flexible supercapacitors

The fast development of portable devices has greatly stimulated the demand for flexible supercapacitors (FSCs). The key to assembling FSCs lies in the development of electrodes with high-performance and good flexibility. In this work, oxygeneous groups modified nitrogen-doped carbon fibers cloth (ONCC) was obtained through annealing the pre-oxidized polyacrylonitrile cloth (PPC), followed by a facile oxidation process using a mixture of concentrated sulfuric acid and concentrated nitric acid. By changing annealing temperature, the nitrogen content can be controlled in the obtained ONCC. It was found that the PPC annealed at 950 °C followed by acid etching for 60 min could deliver the excellent areal and gravimetric specific capacitance of 1385 mF cm−2 and 294.7 F g−1 at the current density of 1 mA cm−2, outstanding rate performance and superb cycling stability. Furthermore, the assembled FSC delivered a high energy density of 19.8 μWh cm−2 (4.03 Wh kg−1) at a power density of 50.1 μW cm−2 (10.2 W kg−1) and good flexibility under different bending conditions. This work provides a facile and efficient route to prepare high-performance carbon fiber based electrode materials in large scale for flexible all-solid-state energy storage devices.

Proton-Conductive Block Copolyphenylchinoxalines Ionomers for Fuel Cells and Electrolysis

The proton exchange membrane fuel cell (PEMFC) is considered to be the most promising power source for portable and automotive applications. Currently, perfluorinated polymers such as Nafion are the state of the art materials. However, high operation temperatures, cause weakening of their properties. In addition, their shortcomings such as high cost and high methanol permeation property, limit their application. To remedy these problems, aromatic hydrocarbon polymers have been extensively studied as alternative materials for proton exchange membranes (PEMs). Recently, introduction of block copolymer structures to PEMs has been considered as a strategy to overcome the weak points of a random copolymer system. Block copolymers composed of hydrophilic and hydrophobic segments are expected to form ion transport channels due to hydrophilic/hydrophobic phase separated structures and show improved proton conductivity. Poly(phenlyquinoxalines) are a family of aromatic condensation polymers known their outstanding thermal and chemical stability. Based on this polymer class new sulfonated block copolyphenylchinoxalines with hydrophilic and hydrophobic segments have been developed. The block copolymers were synthesized via polycondensation reactions between 3,3`-4,4`tetraaminodiphenylether and two different tetracetones (tetrafluorphenylbis-phenylethandion and phenylbisphenylethandion. High molecular Blockcopolyphenylchinoxalines with 20 000 in number average molecular weight were obtained. The sulfonation of these blockcopolymers was carried out in a mixture of concentrated sulfuric acid and oleum (4:1). In dependence of the reaction time blockcopolyphenyl-chinoxalines with ion exchange capacities of 0,6 - 2,35 mmol/g could be prepared. All sulfonated blockcopoly-phenylchinoxalines show good solubility in dimethylacetamide (DMAC). For the preparation of the membranes a phase inversion process via immersion precipitation was developed. The membranes achieved proton conductivities comparable to Nafion. Additionally the water uptake, oxidation and dimensional stability were investigated and presented.

Nitrobenzene. Determination in workplace air

Nitrobenzene is a pale yellow oil with an almond-like odor. On an industrial scale it is obtained by nitration of benzene with a mixture of concentrated sulfuric acid, water and nitric acid. The compound is used in the production of aniline. Nitrobenzene is possibly carcinogenic to humans. The aim of this study was to develop a method for determining concentrations of nitrobenzene in workplace air in the range from 1/10 to 2 of MAC values. The developed method is based on the adsorption of nitrobenzene on a silica gel, extraction with methanol and chromatographic analysis of the resulting solution. The tests were performed using a liquid chromatograph (HPLC) 1200 series of Agilent Technologies with a diode array detector (DAD). Determinations were performed using an Ultra C18 column (25 cm × 4.6 mm, dp = 5 µm). The procedure was validated according to Standard No. EN 482. On the basis of obtained results, the concentration range was established as 1.8–36 µg/ml, which corresponds to 0.1–2 mg/m3 for 18-L air sample. In the following range, the obtained calibration curve was linear, as evidenced by the regression coefficient at the level of 1. The overall accuracy of the method was 5.38% and its relative total uncertainty was 23.42%. This method enables selective determination of nitrobenzene in workplace air at concentrations of 0.1–2 mg/m3 in the presence of other compounds, such as methanol, benzene and aniline. The method for determining nitrobenzene is presented in the form of analytical procedure in the Annex.

Sulfonated Block Copolyphenylchinoxalines As Proton Exchange Membranes

The proton exchange membrane fuel cell (PEMFC) is considered to be the most promising power source for portable and automotive applications. Currently, perfluorinated polymers such as Nafion are the state of the art materials because of their good physical and chemical stability along with high proton conductivity under a wide range of relative humidity at moderate operation temperatures. However, high operation temperatures, cause weakening of their properties. In addition, their shortcomings such as high cost and high methanol permeation property, limit their application. To remedy these problems, aromatic hydrocarbon polymers have been extensively studied as alternative materials for proton exchange membranes (PEMs)and many sulfonated aromatic polymers such as poly(phenylene)poly(ether ether ketone)s, poly(ether ether sulfone) poly(arylene ether) and polyimides have been developed as alternate candidates. Generally, membranes based on these polymers can achieve high proton conductivity by increasing their ion exchange capacities (IECs), resulting in huge water uptake and a dramatic loss of mechanical properties. Recently, introduction of block copolymer structures to PEMs has been considered as a strategy to overcome the weak points of a random copolymer system. Block copolymers composed of hydrophilic and hydrophobic segments are expected to form ion transport channels due to hydrophilic/hydrophobic phase separated structures and show improved proton conductivity. Poly(phenlyquinoxalines) are a family of aromatic condensation polymers known their outstanding thermal and chemical stability. Based on this polymer class new sulfonated block copolyphenylchinoxalines with hydrophilic and hydrophobic segments have been developed. The block copolymers were synthesized via polycondensation reactions between 3,3`-4,4`tetraaminodiphenylether and two different tetracetones, followed by sulfonation using a mixture of concentrated sulfuric acid. and oleum (4:1).High molecular-weight polymers over 20 000 in number average molecular weight were easily obtained and gave tough and flexible membranes by solvent casting. The properties of their membranes, such as proton conductivity, water uptake, oxidation and dimensional stability were investigated und presented.

Cheap non-toxic non-corrosive method of glass cleaning evaluated by contact angle, AFM, and SEM-EDX measurements.

Glass surface cleaning is the very first step in advanced coating deposition and it also finds use in conserving museum objects. However, most of the wet chemical methods of glass cleaning use toxic and corrosive chemicals like concentrated sulfuric acid (H2SO4), piranha (a mixture of concentrated sulfuric acid and 30% hydrogen peroxide), and hydrogen fluoride (HF). On the other hand, most of the dry cleaning techniques like UV-ozone, plasma, and laser treatment require costly instruments. In this report, five eco-friendly wet chemical methods of glass cleaning were evaluated in terms of contact angle (measured by optical tensiometer), nano-scale surface roughness (measured by atomic force microscopy or AFM), and elemental composition (measured by energy dispersive x-ray spectroscopy or SEM-EDX). These glass cleaning methods are devoid of harsh chemicals and costly equipment, hence can be applied in situ in close proximity with plantation such as greenhouse or upon subtle objects such as museum artifacts. Out of these five methods, three methods are based on the chemical principle of chelation. It was found that the citric acid cleaning method gave the greatest change in contact angle within the hydrophilic regime (14.25° for new glass) indicating effective cleansing and the least surface roughness (0.178nm for new glass) indicating no corrosive effect. One of the glass sample showed unique features which were traced backed to the history of the glass usage.

Fully Converting Graphite into Graphene Oxide Hydrogels by Preoxidation with Impure Manganese Dioxide.

Potassium permanganate (KMnO4) has been proved to be an efficient oxidant for converting graphite into graphite oxide, but its slow diffusion in the interlayer of graphite seriously restricts the production of graphene oxide (GO). Here, we demonstrate that the preoxidation of graphite by impure manganese dioxide (MnO2) in a mixture of concentrated sulfuric acid (H2SO4) and phosphorus pentoxide (P2O5) can efficiently improve the synthesis of GO when KMnO4 is employed as the oxidant. The prepared honey-like GO hydrogels possess a high yield of single-layer sheets, large sizes (average lateral size up to 20 μm), wide ranges of stable dispersion concentrations (from dilute solutions, viscous hydrogels, to dry films), and good conductivity after reduction (~2.9 × 10(4) S/m). The mechanism for the improved synthesis of GO by impure MnO2 was explored. The enhanced exfoliation and oxidation of graphite by oxidative Mn ions (mainly Mn(3+)), which are synergistically produced by the reaction of impure MnO2 with H2SO4 and P2O5, are found to be responsible for the improved synthesis of such GO hydrogels. Particularly, preoxidized graphite (POG) can be partially dispersed in water with sonication, which allows the facile construction of flexible and highly conductive graphene nanosheet film electrodes with excellent electrochemical sensing properties.

Surface Treatment And Modification Of Graphene Using Organosilane And Its Thermal Stability

Abstract In this study, graphene was functionalized via acid oxidation in the presence of a mixture of concentrated sulfuric acid and nitric acid. The oxidized graphene was silanized using the coupling agent, 3-aminopropyltriethoxsilane, resulting in functionalized graphene. The oxidized graphene and functionalized graphene were characterized by X-Ray diffraction, Fourier transform infrared spectroscopy, High-resolution micro Raman spectroscopy, thermogravimetric analysis, and atomic force microscopy to confirm the presence of functional moieties on the graphene surface. Thermal studies also demonstrate that the functionalized material is thermally stable up to higher temperatures.

Area‐selective microwrinkle formation on poly(dimethylsiloxane) by treatment with strong acid

ABSTRACTMicrowrinkles were formed by treating poly(dimethylsiloxane) (PDMS) surfaces with a mixture of concentrated sulfuric acid and nitric acid at 80 °C followed by a water rinsing step. The acid treatment oxidized the treated area, which also swelled owing to absorption of water during the rinsing step. This absorption of water induced a compressive stress on the PDMS surface that caused the formation of wrinkles. The appearance of wrinkles was controlled by the time interval between the end of the acid treatment and the beginning of the water rinsing step. Wrinkles were formed when the time interval was shorter than 5 s, as water was absorbed by the hygroscopic acid molecules within the treated surface. For longer time intervals of 300 s, this phenomenon was not observed. Based on these findings, a procedure for forming wrinkles in specific areas was developed by hydrating the chosen areas with wet filter paper cut into specific shapes after the acid treatment. The formation of wrinkles was confined to the area under the piece of paper. The orientation and alignment of the wrinkles at the boundaries were also characterized. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 167–174

Modification of conductive polyaniline with carbon nanomaterials

The synthesis of polyaniline/single-wall nanotube, polyaniline/multi-wall nanotube and polyaniline/single-wall nanotube/graphen nanosheets nanocomposites by in situ polymerization are reported in this study. The substrates were treated with a mixture of concentrated sulfuric acid and concentrated nitric acid before usage to functionalize with carboxylic and hydroxyl groups. Aniline monomers are adsorbed and polymerized on the surface of these fillers. Structural analysis using scanning electron microscopy showed that nanomaterials dispersed into polymer matrix and made tubular structures with diameters several tens to hundreds nanometers depending on the polyaniline content. These nanocomposites can be used for production of excellent electrode materials applications in high-performance supercapacitors.

Preparation and Characterization of Chemically Modified Silk Cotton Hull Activated Carbon and Its Effects on Cd(II) Removal from Aqueous Solutions

ABSTRACTThe novel biosorbent silk cotton hull, an agrowaste material, has been successfully utilized for the removal of cadmium(II) from aqueous solutions. The adsorption of cadmium onto three kinds of activated biosorbent has been studied: modified by concentrated sulfuric acid alone (AC), a mixture of concentrated sulfuric acid and hydrogen peroxide (AC1), and a mixture of concentrated sulfuric acid and ammonium persulfate (AC2). The adsorption studies were carried out to optimize the process parameters such as pH, adsorbent dosage, contact time, and initial metal ion concentration. Maximum metal removal was observed at pH 7.0 with a contact time of 90 min at stirring speed of 200 rpm with an adsorbent dosage of 4.0 g L−1. The sorption isotherms were studied using the Langmuir, Freundlich, and Tempkin isotherm models. The maximum adsorption capacities were 100.00, 142.86, and 142.87 mg g−1 for AC, AC1, and AC2, respectively. Accordingly, the surface modification of the activated carbons AC1 and AC2 enhanced cadmium removal greatly. The experiments demonstrated that the removal of metal ions followed the pseudo-second-order kinetic model. The sorption mechanism is discussed in terms of the activated surface properties. A relationship between the oxygen content and sorption was found in this novel material. Desorption experiments were carried out using hydrochloric acid with a view to generate the spent adsorbent and to recover the adsorbed metal ions.

Polymer composites with graphene nanofillers: electrical properties and applications.

Graphene with extraordinary high elastic modulus and excellent electrical conductivity has good prospects for use as the filler material for fabricating novel polymer composites designed for electrostatic discharge and EMI shielding protection, field emission, gas sensor, and fuel cell applications. Large amounts of graphene oxide (GO) can be obtained by wet chemical oxidation of graphite into a mixture of concentrated sulfuric acid, sodium nitrate and potassium permanganate. Accordingly, carbon atoms in the basal plane and edges of GO are decorated with oxygenated functional groups, forming an electrical insulator. To restore electrical conductivity, chemical reduction or thermal annealing is needed to eliminate oxygenated groups of GO. However, such treatments induce internal defects and remove oxygenated atoms of GO partially. The remnant-oxygenated groups affect electrical conductivity of graphene greatly. Nevertheless, reduced graphene oxide and thermally reduced graphene oxide are sufficiently conductive to form polymer nanocomposites at very low percolation threshold. This review provides the fundamentals and state-of-the-art developments in the fabrication methods and electrical property characterizations as well as the applications of novel graphene/polymer nanocomposites. Particular attention is paid to their processing-structural-electrical property relationships.

Synthesis and optical property of P3HT/carbon microsphere composite film

Abstract

Preparation and magnetic properties of Fe/C composite powders

Fe/C composite magnetic powders were prepared by a sol-gel method from aqueous-mesophase pitch (AMP) and ferric chloride. The AMP was prepared by the oxidation of coal tar pitch with a mixture of concentrated sulfuric acid and nitric acid (7:3v/v), to which ferric chloride and ammonia were added to form aqueous Fe/C based gels. The gels were displaced by ethanol, dried at ambient temperature and pressure, and carbonized at 900℃ to obtain the Fe/C magnetic powders. The powders were characterized by FT-IR, XRD, TG and TEM. Results show that primary particles in the powders have an ellipsoidal shape with a uniform particle size about 5nm, which are aggregated into secondary particles with a size about 20-30nm. The carbon has a turbostratic structure and the Fe exists in the form of α-Fe、Fe2O3 and Fe3C. The powders are soft magnetic materials with a saturation magnetization increasing with Fe content.

Nitraminoazoles Based on ANTA – A Comprehensive Study of Structural and Energetic Properties

AbstractSince 5‐Amino‐3‐nitro‐1H‐1,2,4‐triazole (ANTA) is known to be a thermally very stable secondary explosive, our goal in this contribution was the synthesis of thermally stable but more powerful energetic compounds based on ANTA. Hence, we utilized ANTA to synthesize 5‐nitramino‐3‐nitro‐1H‐1,2,4‐triazole (1) by nitration with a mixture of concentrated sulfuric acid and 100 % nitric acid. ANTA was also methylated with dimethyl sulfate to yield 5‐amino‐1‐methyl‐3‐nitro‐1,2,4‐triazole (2), which was then subsequently nitrated by using the method mentioned above to yield 1‐methyl‐5‐nitramino‐3‐nitro‐1,2,4‐triazole (3). All three compounds were characterized by IR and Raman as well as multinuclear NMR spectroscopy. Additionally, X‐ray crystallographic measurements of 1 and 3 were performed. The decomposition points of the compounds were found to be low for 1 (135 °C) and 3 (108 °C), despite the high thermal stability of ANTA (>220 °C) and 2 (294 °C). In order to increase the thermal stability of the compounds, nitrogen‐rich salts of 1 and 3 with the ammonium, hydrazinium, guanidinium, aminoguanidinium, and triaminoguanidinium cations were prepared and fully characterized by means of vibrational and NMR spectroscopy, DSC measurements, and X‐ray diffraction measurements. Additionally, the impact as well as friction sensitivities and the sensitivity against electrostatic discharge were determined by using standard BAM techniques. The standard heats of formation were calculated for selected compounds at the CBS‐4M level of theory, which reveals high positive heats of formation for all compounds.

Cellulose supramolecular structure changes during chemical activation and sulfation 2nd ICC 2007, Tokyo, Japan, October 25–29, 2007

Abstract Cotton cellulose has been sulfated in the presence of organic solvents (methanol, ethanol, iso-propanol and via chlorosulfonic acid-pyridine complex, and a mixture of concentrated sulfuric acid and ethanol) and the effects were studied by polarized light microscopy, electron microscopy, IR spectroscopy, and X-ray diffraction. Sorption-desorption behavior of the sulfonated cellulose was also observed. These processes enhance interfibrillar swelling, weaken intermolecular hydrogen bonds, and loosen the packing density of microfibrils. As a result, the accessibility of esterification reagents was improved depending on the activation method. Microscopic studies showed that the surface of the initial cotton cellulose is wrinkled. The fibrillar structure of the primary fiber wall was not observed. In the case of cotton cellulose, sulfation changed its crimped fibers with different thicknesses, length and defects which were visible in a polarized light as bright luminescence. Fibers become short, thick, and straightened. Moreover, degree of anisotropy and crystallinity of the modified fibers decreased. Their size and degree of crimping are dependent on condition of modification. All pre-activation processes were successful. Thickness of fibers was increased up to 20% and the length was decreased to one-third or one-fourth. The sorption capability of cellulose was increased 2.1–3.4-fold in pre-activated samples, which is due to the increasing specific surface area (45.0–109.1 m2 g-1). Volume and radius of the pores increased up to 0.1164–0.410 m3 g-1 and 36.2–133.3 Å, respectively.

Surface modification of multi-walled carbon nanotubes using 3-aminopropyltriethoxysilane

Multi-walled carbon nanotubes (MWCNTs) were functionalized via oxidation with a mixture of concentrated sulfuric acid and nitric acid. Thus functionalized nanotubes (f-MWCNTs) were silanized using a coupling agent, 3-Aminopropyltriethoxysilane (3-APTES). The f-MWCNTs and the reaction product of f-MWCNTs and 3-APTES (APTES–MWCNTs) were characterized by Fourier Transform Infrared Spectroscopy, Energy Dispersion Spectroscopy, Scanning Electron Microscopy, and Transmission Electron Microscopy. The results indicate the attachment of silane molecules on the surface of the functionalized MWCNTs. This silanization method allows for the improvement of the chemical compatibility of MWCNTs with specific polymers for application in nanotube-based polymer matrix composites.