Amounts Of Phosphoric Acid Research Articles

Functionalization of graphene oxide coatings with phosphorus atoms and their corrosion resistance in sodium chloride environment

In this work, we compared corrosion resistance of graphene oxide, and phosphorus functionalized reduced graphene oxide coatings obtained as a result of electrophoretic deposition on the copper substrate. Doping graphene oxide with phosphorus atoms was performed by a hydrothermal method in the presence of different amounts of phosphoric acid. Structural studies confirmed the insertion of phosphorus atoms into the graphene oxide structure. FTIR spectra showed peaks at 1020 cm−1 and 1131–1450 cm−1 which can be assigned to phosphorus groups. XPS analysis indicated that phosphorus atoms were inserted in an amount of around 5%. The stable and uniform suspension of functionalized graphene precursors of coatings allowed electrodeposition. These coatings show good protective properties due to hydrophobic and intact surfaces without significant damages.

Preparation of modified porous steel slag/rubber composite materials and its properties

High value-added utilization of solid wastes, such as the development of an inexpensive inorganic rubber filler, is one of the important approaches of sustainable development. Phosphoric acid, silane KH550, and steel slag were innovatively used to prepare modified porous steel slag, which partially replaced carbon black in this study. Modified porous steel slag was combined with carbon black, rubber, accelerator, sulfur, stearic acid, and zinc oxide to prepare a series of modified porous steel slag/rubber composite materials. This study investigated the mass ratios of phosphoric acid/steel slag, silane KH550/porous steel slag, accelerator/sulfur, and stearic acid/zinc oxide and the effect of the mass ratio of modified porous steel slag/carbon black on the mechanical properties of the prepared modified porous steel slag/rubber composite materials. At the same time, the influence mechanism was analyzed. The results indicate that the modified porous steel slag/rubber composites (the amounts of phosphoric acid, steel slag, silane KH550, carbon black, accelerator, sulfur, stearic acid, zinc oxide, and rubber are 1.2, 30, 0.3, 20, 0.8, 1.2, 0.8, 2.2, and 100 g, respectively) have good mechanical properties, with the tensile strength of 18.4 MPa, Shore A hardness of 68.8, and tearing strength of 44.6 kN·m-1. Phosphoric acid and silane KH550 can improve the pore and surface structures of steel slag. Appropriate ratios of accelerator/sulfur and stearic acid/zinc oxide can destroy the internal sulfur ring, which stabilizes the cross bond of rubber. Thus, a desirable package structure can be obtained by physically combining modified porous steel slag with rubber.

Effect of Phosphoric Acid on HZSM-5 Catalysts for Prins Condensation to Isoprene from Isobutylene and Formaldehyde

A series of HZSM-5 zeolites modified with different amounts of phosphoric acid(P/HZSM-5) was pre-pared. The physicochemical features of the P/HZSM-5 catalysts were characterized via X-ray diffraction(XRD), N2 adsorption-desorption, NH3-temperature programmed desorption(NH3-TPD) and Fourier tranform infrared(FTIR) spectra of the adsorbed pyridine, and the performances of the catalysts for Prins condensation to isoprene from iso-butylene and formaldehyde were investigated. The maximum isobutene conversion and isoprene selectivity were 10.3% and 94.6% on the HZSM-5 catalyst with a Si/Al molar ratio of 600 using 5%(mass fraction) phosphoric acid. The phosphoric acid modification not only modulated the amount of acidic sites but also regulated the acid type. An appropriate amount of weak Lewis and Bronsted acid sites served as the active sites for the condensation of isobutene with formaldehyde, and the strong acid sites could cause side reactions and coke deposition.

Nanostructure of HT-PEFC Electrodes Investigated with Scattering Methods

Small angle scattering with X-rays (SAXS) and neutrons (SANS) is used as a powerful tool to investigate different components of fuel cells or even groups such as membrane electrode assemblies (MEAs) (1,2). In particular, the structure of electrode layers and membrane electrode assemblies of High Temperature Polymer Electrolyte Fuel Cells (HT-PEFCs) is studied in this contribution with neutron and x-ray scattering (1). Electrode layers in different stages of preparation, pure and doped with different amounts of phosphoric acid have been studied with SAXS. Structural changes have been observed with the addition of phosphoric acid, which is used in this type of HT-PEFC as proton conducting electrolyte. Details of the phosphoric acid distribution and possible void distribution in electrode layers have been obtained with contrast variation experiments in small angle neutron scattering, where the different parts of the sample can be highlighted by exchanging hydrogen with deuterium, here in the phosphoric acid. An outlook will point at the strength of quasielastic neutron scattering experiments to shed light on the proton diffusion on different length scales in the range of 0.1-10 nm, as a microscopic equivalent to the macroscopic conductivity, and it will address the question of what can be retrieved from a multicomponent system such as the different parts of a fuel cell. M. Khaneft, O. Holderer, O. Ivanova, W. Lüke, E. Kentzinger, M.S. Appavou, R. Zorn, W. Lehnert, Fuel Cells 16 (2016), 406 – 413O. Holderer, O. Ivanova, B. Hopfenmüller, M. Zamponi, W. Maier, A. Majerus, W. Lehnert, M. Monkenbusch, R. Zorn, Int. J. Hydrogen Energy 39 (2014) 21657 – 21662

Interaction of metakaolin-phosphoric acid and their structural evolution at high temperature

In the present study metakaolin (MK), prepared by calcination of a natural tunisian kaolin at 750°C, was mixed with different amounts of phosphoric acid (11–48wt% P2O5) and heated at various temperatures (250, 500, 750 and 1000°C) for 4h. The structure of materials was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (MEB), thermal analysis (DTA/TGA). The XRD results showed the formation of an AlPO4 phase for the MK-H3PO4 mixtures containing 11, 17 and 27wt% P2O5 independently of the heating temperature. While with 48wt% of P2O5 two major phases have been formed Al(PO3)3 at 500°C and AlSi2(PO4)3 at 1000°C. These results were confirmed by 27Al, 31P and 29Si MAS-NMR techniques.

Synthesis of Thermally Stable Nanocrystalline Phosphorus-modified Titanium(IV) Dioxides with Rutile Structure

Thermally stable nanocrystalline rutile TiO2 particles modified with small amounts of P were prepared via hydrothermal treatment from mixtures containing Ti-containing precursors, which were obtained by aging diluted HCl solutions of amorphous TiO2 at a low temperature, and small amounts of phosphoric acid. XRD results of the products and UV–vis spectra of the samples nitrified at a high temperature suggest the incorporation of P atoms in the TiO2 structure, which contributes to the enhanced thermal stability of the P-modified TiO2 samples.

The environmental sustainability of calcined calcium phosphates production from the milling of eggshell wastes and phosphoric acid

Industrial waste shells of egg cause environmental and health issues. Diversion of eggshells from landfill to a useful product or used in a better way towards the fabrication of marketable/valuable products is of high economic and ecologic interest. Different structures of calcium phosphates were prepared by milling eggshells with different amounts of phosphoric acid (H3PO4) in the presence of gelatin. The amounts of H3PO4 were varied over wide ranges (2.90 ml–8.73 ml), and the impact of such variations on calcined samples was investigated through the characterization of their morphologies by field emission scanning electron microscopy (FESEM). Long milling time is associated with size reduction of the eggshell powders. It was demonstrated that addition of 8.73 ml H3PO4 reduced the d50 eggshell particles from ∼ 1 μm to 0.96 μm after being milled for 8 h. X-ray diffraction (XRD) has been used to identify the crystalline phases present after milling and also after heat treatment for various times of up to 5 h at temperatures in the range 700–1200 °C. Monetite (CaHPO4) is the characteristic phase of ball-milled samples over the whole ranges of phosphoric acid. The thermal treatment applied to the ball-milled samples led to the interaction between the constituents, causing a modification in the proportion of calcium phosphate structures. At 2.90 and 3.88 ml of H3PO4, both tri-calcium phosphate Ca3(PO4)2 and hydroxyapatite Ca5(PO4)3OH phases are the major crystalline structures developed at 1000 and 1200 °C, while Ca2P2O7 and Ca3(PO4)2 were mainly the observed phases at lower sintering temperatures. The present work is establishing a treatment strategy to produce tailor-made calcium phosphate structures for bio-applications.

Effect of phosphoric acid as a catalyst on the hydrothermal pretreatment and acidogenic fermentation of food waste

The hydrothermal method was applied to food waste (FW) pretreatment with phosphoric acid as a catalyst. The content of soluble substances such as protein and carbohydrate in the FW increased after the hydrothermal pretreatment with phosphoric acid addition (⩽5%). The SCOD approached approximately 29.0g/L in 5% phosphoric acid group, which is almost 65% more than the original FW. The hydrothermal condition was 160°C for 10min, which means that at least 40% of energy and 60% of reaction time were saved to achieve the expected pretreatment effect. Subsequent fermentation tests showed that the optimal dosage of phosphoric acid was 3% with a VFA yield of 0.763g/gVSremoval, but the increase in salinity caused by phosphoric acid could adversely affect the acidogenesis. With an increase in the quantity of phosphoric acid, among the VFAs, the percentage of propionic acid decreased and that of butyric acid increased. The PCR-DGGE analysis indicated that the microbial diversity could decrease with excessive phosphoric acid, which resulted in a low VFA yield.

Investigation of Phosphoric Acid Distribution in PBI Based HT-PEM Fuel Cells

High temperature Polymer Electrolyte Membrane (HT-PEM) fuel cells provide a good alternative to low temperature PEMFCs. Operation at higher temperatures shows better CO tolerances and a simpler water management. Nevertheless, the phosphoric acid (PA) doped PBI HT-PEMFC as the most successful HT-PEM fuel cell type shows long-term degradation effects resulting in lower performance and limited durability. The phosphoric acid loss of the membrane-electrode-assembly (MEA) during operation, which provides high proton conductivity within the membrane, may be identified as being one of the major degradation aspects (1-3). Due to that fact, it is important to understand the degradation mechanism and to get a more detailed insight view into the process of phosphoric acid loss of the MEA during fuel cell operation. In this work acid distribution within the fuel cell test system and balancing is investigated within different test procedures. An accelerated stress test (AST) with load cycling between high current densities of 0.6 A/cm² (4 minutes) and 1.0 A/cm² (16 minutes) can provoke degradation processes in a shorter time period and increase the effect of acid loss due to higher water production in comparison to standard AST (0.3-0.6 A/cm2). Additionally long term tests at constant load conditions (0.3 A/cm2) will be performed. During the tests the MEAs will be characterized with electrochemical measurements like polarization curves, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and linear sweep voltammetry (LSV). For a defined balancing of acid distribution a precise detection of acid content in product water is necessary. Therefore a test system with cold water traps positioned directly after gas outlets is established. In addition, investigation of acid uptake of bipolar plates will be done with ex-situ storage in hot phosphoric acid as well as pristine bipolar plates that are installed for each new test. For the overall balance of acid distribution the values of phosphoric acid are determined in MEA, bipolar plates and product water. The amounts of phosphoric acid in MEA and bipolar plates are identified by two methods, titration with sodium hydroxide after acid leaching in water or a solution of water and acetone. Ion chromatography (IC) and inductive coupled plasma method (ICP-MS) allows determining the content of PA in product water. To give a better indication of acid distribution the tests will be optimized to higher operation time of more than 500 hours. Further explanation about the variation of acid content will be given. Figure 1: Distribution of phosphoric acid after 330 and 500 hours of load cycling between 0.6 and 1 A/cm2, H2/Air, 160°C. In addition, the surface structures of the bipolar plates will be analyzed by atomic force microscopy (AFM), confocal and scanning electron microscope (SEM) in conjunction with energy dispersive X-ray spectroscopy (EDX) to get an impression into the morphological and structural changes in surface area and roughness changes, as well as the distribution of elementary Phosphor. The combination of determination of phosphoric acid in MEA, bipolar plates and product water together with the imaging methods can provide a better understanding of the effects of acid distribution during different test procedures and give an overall review on various degradation steps in HT-PEMFC technology. Figure 1

Activated carbon fibers with a high content of surface functional groups by phosphoric acid activation of PPTA

Activated carbon fibers (ACFs) were prepared by chemical activation of poly(p-phenylene terephthalamide (PPTA) with phosphoric acid, with a particular focus on the effects of impregnation ratio and carbonization temperature on both surface chemistry and porous texture. Thermogravimetric studies of the pyrolysis of PPTA impregnated with different amounts of phosphoric acid indicated that this reagent has a strong influence on the thermal degradation of the polymer, lowering the decomposition temperature and increasing the carbon yield. As concerns surface chemistry, TPD and chemical analysis results indicated that the addition of phosphoric acid increases the concentration of oxygenated surface groups, with a maximum at an impregnation ratio of 100wt.%. The resulting materials present uncommon properties, namely a large amount of oxygen- and phosphorus-containing surface groups and a high nitrogen content. Porosity development following H3PO4 activation was very significant, with values close to 1700m2/g and 0.80cm3/g being reached for the BET surface area and total pore volume, respectively. The pore size distributions remained confined to the micropore and narrow mesopore (<10nm) range.

Synthesis and properties of a new fluorine‐containing polybenzimidazole for high‐temperature fuel‐cell applications

AbstractAn amorphous, organosoluble, fluorine‐containing polybenzimidazole (PBI) was synthesized from 3,3′‐diaminobenzidine and 2,2‐bis(4‐carboxyphenyl)hexafluoropropane. The polymer was soluble in N‐methylpyrrolidinone and dimethylacetamide and had an inherent viscosity of 2.5 dL/g measured in dimethylacetamide at a concentration of 0.5 g/dL. The 5% weight loss temperature of the polymer was 520 °C. Proton‐conducting PBI membranes were prepared via solution casting and doped with different amounts of phosphoric acid. In the methanol permeability measurement, the PBI membranes showed much better methanol barrier ability than a Nafion membrane. The proton conductivity of the acid‐doped PBI membranes increased with increasing temperatures and concentrations of phosphoric acid in the polymer. The PBI membranes showed higher proton conductivity than a Nafion 117 membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4508–4513, 2006

Activated Carbon from Peach Stones Using Phosphoric Acid Activation at Medium Temperatures

In the present study, the activation features of phosphoric acid have been investigated using waste peach stones as the raw material in the production of granular activated carbon. Thermogravimetry/differential thermal analysis was conducted to characterize the thermal behavior of peach stone and titration method was used to evaluate the adsorption capacity of the produced activated carbon. It was observed that the iodine value of the activated carbon increased with activation temperature. However, temperatures higher than 500°C caused a thermal destruction, which resulted in the decrease of the adsorption capacity. Activation longer than 1.5 h at 500°C resulted in thermal degradation of the porous structure of the activated carbon. The adsorption capacity was enhanced with increasing of amounts of phosphoric acid, however, excessive phosphoric acid caused a decrease in the iodine value. In addition, it was found that the carbon yields generally decreased with activation temperature and activation time. Scanning electron microscopy analysis was conducted to observe the changes in the poros structure of the activated carbon produced in different temperatures. Activation of carbon by phosphoric acid was found to be superior to that by CaCl2 and gas activation. The activated carbon produced from peach stone was applied as an adsorbent in the treatment of synthesized wastewater containing cadmium ion and its adsorption capacity was found to be as good as that of the commercial one.

Activated carbon fibers from Nomex by chemical activation with phosphoric acid

The preparation of activated carbon fibers (ACFs) by phosphoric acid activation of Nomex [ poly( m-phenylene isophthalamide)] polyaramid fibers was studied. Nomex pyrolysis in the presence of phosphoric acid was followed by thermogravimetry and infrared spectroscopy in order to establish the nature of transformations involved. Then, ACFs were obtained by impregnating Nomex with different amounts of phosphoric acid, followed by pyrolysis and washing with water. The porous texture of the resulting ACFs was characterized by N 2 and CO 2 adsorption. Phosphoric acid has a strong effect on Nomex degradation, reducing the number of decomposition steps and lowering the temperature range at which the decomposition takes place. The resulting ACFs bear P-containing functionalities like acid phosphates and polyphosphates. The impregnation ratio strongly influences the porous texture of the ACFs, but they remain microporous even at high impregnation ratios, when, as shown by SEM, the fibrous morphology is lost due to agglomeration. The results obtained suggest the practical feasibility of the process of phosphoric acid activation of Nomex polyaramid fibers. ACFs are obtained with high yields and they exhibit a well-developed porosity restricted to the micropore range and with P incorporated in form of functional groups. A major drawback identified (fiber fragmentation and agglomeration) can be avoided by using low or intermediate impregnation ratios.

Deposition of (90)YPO(4) and (144)CePO(4) radioisotopes on polymer surfaces for radiation delivery devices.

Intravascular irradiation with beta emitters inhibits restenosis in arteries after balloon angioplasty or stent implantation. Yttrium-90 ((90)Y, T(1/2)=64 h) and cerium-144 ((144)Ce, T(1/2)=286 d) emit beta particles (E(max)=2.28--3.50 MeV) having an ideal energy range for brachytherapy delivery system. In this article, a previously reported method for depositing (32)P on poly(ethylene terephtalate) (PET) surfaces is generalized and modifications that allow deposition of other beta-emitting radioisotopes, such as (90)Y and (144)Ce, are demonstrated. PET films were first coated with chitosan hydrogel and then adsorbed different amounts of phosphoric acid (PA) in aqueous solutions. Yttrium was deposited onto the surface as YPO(4) after the films were immersed in YCl(3) solutions. 1 muCi (90)YCl(3) (2 x 10(-9) g) was used in each sample as a tracer for measuring the deposition efficiency, which is defined as the percentage of YCl(3) deposited on the surface compared to the amount of YCl(3) in solutions before the deposition. In order to improve the safety of brachytherapy treatments, polyurethanes were used to seal the deposited radioisotopes on the surface to minimize the leakage of the isotopes into the patients. The generality of this method presented here for a wide variety of particular radioisotopic components allows design of a broad range of versatile radioisotope sources.

Low-temperature Fracture in Reactive-ethylene-terpolymer-modified Asphalt Binders

This paper reports on the low-temperature fracture and yield properties of a number of Strategic Highway Research Program asphalt binders that were modified with 5% by weight of a reactive terpolymer of ethylene, butyl acrylate and glycidyl methacrylate. Selected binders were also tested with the addition of small amounts of phosphoric acid. Fracture toughness and energy were determined at temperatures close to where the stiffness reached 300 MPa while the 2% offset yield stress was determined at somewhat lower strain rates in compression. Significant differences were found in the fracture properties ( K Ic and G Ic ) of these binders depending on the compatibility of the polymer with the base asphalt. It is suggested that the fracture energy and yield stress at low temperatures may be able to more accurately grade binders for their performance with respect to thermal stress cracking in the pavement compared to the currently used SHRP specification properties.

Volatile products of catalytic flash pyrolysis of celluloses

Analytical pyrolysis combined with gas chromatography (Py-GC) has been used to study the composition of volatile products of different commercial celluloses impregnated with various amounts of phosphoric acid. The influence on the yields of levoglucosan and levoglucosenone was studied taking into account the supramolecular structure, degree of polymerization, hydrophilic properties and pretreatment conditions of the celluloses. It was found that levoglucosenone predominates in the volatiles of acid catalyzed pyrolysis. However, the relative total amount of both 1,6-anhydrosaccharides varied only in a narrow range of 75–85% regardless of the impregnation and pretreatment conditions of the celluloses. The maximum progress in cellulose dehydration reactions resulting in the highest levoglucosenone content of 78% is reached with Munktell microcrystalline cellulose owing to its low accessibility and high ordered supramolecular structure. For pulps with a less ordered cellulosic supramolecular structure, breaking of glycosidic bonds with the formation of levoglucosan besides levoglucosenone occurred and the relative amount of non-dehydrated anhydrosaccharides increased.

An Improved Method for the Purification of Polyether−Polyols Using Phosphoric Acid as Neutralization Agent

The aim of this study was to develop a crystallization process for the removal of the alkaline catalyst (potassium hydroxide) from crude polyether−polyols. The process involves a first step of neutralization with an aqueous solution of phosphoric acid and subsequently the removal of water to reach supersaturation and crystal growth. Finally, the crystals formed are removed by filtration. Different amounts of phosphoric acid and water were investigated in order to establish a suitable recipe for this process. Different depressurization vs time profiles for the water evaporation were used to produce an uniform and narrow crystal size distribution with a large mean crystal size in this kind of experimental device.

Separation of ADAM derivatives of carnitine and acyl-carnitines by capillary electrophoresis

The separation of carnitine, acetylcarnitine and palmitoylcarnitine as ADAM (9-anthryldiazo-methane) derivatives was performed using capillary electrophoresis. A buffer system with 90% methanol and various amounts of phosphoric acid and micelle forming SDS was optimized with respect to the best resolution of the carnitine derivatives. A detection limit of 10 μmol/l or 32 ng carnitine was determined by laser induced fluorescence detection. Under optimized conditions low carnitine contents in acylcarnitine standards have been determined.

Adsorption Characteristics of Coal-based Activated Carbons. II. Adsorption of Water Vapour, Pyridine and Benzene

Chemically-activated carbons were prepared by carbonizing Maghara coal with different amounts of phosphoric acid at 873 K. Steam-activated carbons of different burn-off were prepared by gasifying non-activated carbon prepared by carbonization at 873 K with steam at 1173 K. Samples of steam-activated carbons were also treated with concentrated nitric acid or with potassium dichromate. The adsorption of water vapour and benzene was determined at 308 K. The adsorption of pyridine was followed on the chemically-activated carbons at 343 K. The adsorption of water vapour was found to be related to the surface area and the amount of carbon–oxygen groups. Some of the adsorbed water was found to be specifically held to the surface and could be used to determine the number of carbon–oxygen groups on the surface. Two mechanisms are involved in the adsorption of pyridine on the carbons investigated. These are physisorption on the oxygen-free surface and chemisorption on carbon–oxygen groups of an acidic nature. Benzene may be vertically oriented in micropores, horizontally oriented in wider pores and may be even inaccessible to the fraction of the surface located in ultramicropores. Benzene adsorption is also retarded by the existence of a high concentration of carbon–oxygen groups oh the surface.

96/01441 Adsorption of some substituted phenols on activated carbons from a bituminous coal

The preparation of activated carbon fibers (ACFs) by phosphoric acid activation of Nomex [poly(m-phenylene isophthalamide)] polyaramid fibers was studied. Nomex pyrolysis in the presence of phosphoric acid was followed by thermogravimetry and infrared spectroscopy in order to establish the nature of transformations involved. Then, ACFs were obtained by impregnating Nomex with different amounts of phosphoric acid, followed by pyrolysis and washing with water. The porous texture of the resulting ACFs was characterized by N2 and CO2 adsorption. Phosphoric acid has a strong effect on Nomex degradation, reducing the number of decomposition steps and lowering the temperature range at which the decomposition takes place. The resulting ACFs bear P-containing functionalities like acid phosphates and polyphosphates. The impregnation ratio strongly influences the porous texture of the ACFs, but they remain microporous even at high impregnation ratios, when, as shown by SEM, the fibrous morphology is lost due to agglomeration. The results obtained suggest the practical feasibility of the process of phosphoric acid activation of Nomex polyaramid fibers. ACFs are obtained with high yields and they exhibit a well-developed porosity restricted to the micropore range and with P incorporated in form of functional groups. A major drawback identified (fiber fragmentation and agglomeration) can be avoided by using low or intermediate impregnation ratios.