Low Phosphoric Acid Research Articles

Direct conversion of cellobiose into sorbitol and catalyst deactivation mechanism

Abstract Ru/C catalyst and extremely low phosphoric acid were used for direct conversion of cellobiose into sorbitol under hydrogen atmosphere. Effects of various parameters and catalyst reuse on the reaction performance were investigated in detail. An optimized sorbitol yield of 87.1% was attained at 458 K and 3 MPa H 2 for 1 h with catalyst usage of 15% in 0.05 wt.% phosphoric acid. The physicochemical properties of used Ru/C catalysts were characterized with various techniques to explore the specific causes for deactivation.

A composite membrane of caesium salt of heteropolyacids/quaternary Diazabicyclo-octane polysulfone with poly (tetrafluoroethylene) for intermediate temperature fuel cells.

Inorganic-organic composite electrolyte membranes were fabricated from CsXH3−XPMo12O40 (CsPOMo) and quaternary diazabicyclo-octane polysulfone (QDPSU) using a polytetrafluoroethylene (PTFE) porous matrix for the application of intermediate temperature fuel cells. The CsPOMo/QDPSU/PTFE composite membrane was made proton conducting by using a relatively low phosphoric acid loading, which benefits the stability of the membrane conductivity and the mechanical strength. The casting method was used in order to build a thin and robust composite membrane. The resulting composite membrane films were characterised in terms of the elemental composition, membrane structure and morphology by EDX, FTIR and SEM. The proton conductivity of the membrane was 0.04 S cm−1 with a H3PO4 loading level of 1.8 PRU (amount of H3PO4 per repeat unit of polymer QDPSU). The fuel cell performance with the membrane gave a peak power density of 240 mW cm−2 at 150 °C and atmospheric pressure.

Poly(2,5-bibenzimidazole) Membranes: Physico-Chemical Characterization Focused on Fuel Cell Applications

Membranes of Poly(2,5-benzimidazole) (ABPBI), prepared by polycondensation in polyphosphoric acid, were characterized from the fuel cell application point of view: mechanical properties of the membranes for different acid doping levels, thermal stability, permeability for the different gases/vapors susceptible of use in the cell (hydrogen, oxygen, methanol and ethanol), electro-osmotic water drag coefficient, oxidation stability to hydroxyl radicals, phosphoric acid leaching rate and, finally, in-plane membrane conductivity. ABPBI membranes presented an excellent thermal stability, above 500°C in oxygen, suitable mechanical properties for high phosphoric acid doping levels, a low methanol and ethanol limiting permeation currents, and oxygen permeability compared to Nafion membranes, and a low phosphoric acid leaching rate when exposed to water vapor. On the contrary, hydrogen permeation current was higher than that of Nafion, and the chemical stability was very limited. Membrane conductivity achieved 0.07 S cm−1 after equilibration with a humid environment. Fuel cell tests showed reasonable good performances, with a maximum power peak of 170 mW cm−2 for H2/air at 170°C operating under a humidified hydrogen stream, 39.9 mW cm−2 for CH3OH/O2 at 200°C for a methanol/water weight ratio of 1:2, and 31.5 mW cm−2 for CH3CH2OH/O2 at the same conditions than for methanol.

Effects of acid etchants used for bonding orthodontic brackets on the remineralization of enamel white-spot lesions

The objective of the present study was to examine the effects of phosphoric acid and polyacrylic acid used as pretreatment for orthodontic direct bonding procedures on changes in the overall mineral levels of the subsurface white-spot lesions, and to examine the effects on the surface structure using contact microradiography (CMR) and an Atomic Force Microscope (AFM). Enamel specimens with in vitro production of artificial subsurface white-spot lesions were used for these studies. The enamel acid conditions were as follows: non-etched (Group I), 10% polyacrylic acid (Group II), 2% phosphoric acid (group III), 10% phosphoric acid (Group IV). After each acid treatment, the four groups were exposed to a remineralization solution at pH 7.0 at 37 °C for 2 weeks. An AFM was used to observe the surface after the acid treatment and remineralization. After 2 weeks of remineralization, the mineral profiles were assessed using CMR. AFM observation revealed different acid etching patterns on the enamel surface of subsurface white-spot lesions after the different acid treatments. From the AFM observation after remineralization, Group I and Group II demonstrated deposits of mineral-like substances on the surface. From the CMR observation, the amount of minerals present increased in Groups I and II, while, in Group IV, the surface layer was removed and the amount of minerals present decreased. It was found that polyacrylic acid produced a less roughness than low concentration phosphoric acid. Moreover, the minerals were recovered during remineralization after treatment with polyacrylic acid. The minerals were not recovered after phosphoric acid treatment.

High performance polymer electrolytes based on main and side chain pyridine aromatic polyethers for high and medium temperature proton exchange membrane fuel cells

Novel aromatic polyether type copolymers bearing side chain polar pyridine rings as well as combination of main and side chain pyridine units have been evaluated as potential polymer electrolytes for proton exchange membrane fuel cells (PEMFCs). The advanced chemical and physicochemical properties of these new polymers with their high oxidative stability, mechanical integrity and high glass transition temperatures ( T g 's up to 270 °C) and decomposition temperatures ( T d 's up to 480 °C) make them promising candidates for high and medium temperature proton exchange membranes in fuel cells. These copolymers exhibit adequate proton conductivities up to 0.08 S cm −1 even at moderate phosphoric acid doping levels. An optimized terpolymer chemical structure has been developed, which has been effectively tested as high temperature phosphoric acid imbibed polymer electrolyte. MEA prepared out of the novel terpolymer chemical structure is approaching state of the art fuel cell operating performance (135 mW cm −2 with electrical efficiency 45%) at high temperatures (150–180 °C) despite the low phosphoric acid content (<200 wt%) and the low platinum loading (ca. 0.7 mg cm −2). Durability tests were performed affording stable performance for more than 1000 h.

Studies on the recovery of uranium from phosphoric acid medium using synergistic mixture of (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and Tri- n-butyl phosphate (TBP)

This paper describes the extraction of uranium from aqueous phosphoric acid medium using (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and tri- n-butyl phosphate (TBP) individually as well as their synergistic mixture in different diluents. The various experimental parameters are investigated to optimize optimise the suitable extraction conditions. Results indicate that a synergistic mixture of 0.90 M PC88A + 0.15 M TBP in xylene, can be used for the extraction of uranium from low phosphoric acid medium. Back extraction studies reveals that among all the common strippants used, 0.50 M solution of (NH 4) 2CO 3 was most suitable. The synergistic mixture of 0.90 M PC88A + 0.15 M TBP as extractant system and 0.5 M (NH 4) 2CO 3 as strippant is used to recover uranium from a conditioned wet process phosphoric acid and from actual radioanalytical waste generated during uranium analysis by modified Davies–Gray method. The recovery is found to be around 80% from conditioned WPA whereas better than 90% from modified Davies–Gray waste.

Proton-conducting polymer electrolytes based on phosphoric acid

The synthesis, thermal, mechanical and conduction properties of blends of a cationic polyelectrolyte, poly(diallyldimethylammonium-dihydrogenphosphate), ‘PAMA+H2PO4−’, and phosphoric acid are reported. Blends of ‘PAMA+H2PO4−xH3PO4’ with 0.5≤x≤2.0 can be cast into amorphous films, which are stable up to 150°C. DSC results show that the softening temperatures of the blends decrease from 126°C for x=0.5 to −23°C for x=2.0. The dc conductivity increases with x and reaches 10−4 S/cm at ambient temperature and 10−2 S/cm at 100°C for PAMA+H2PO4−2H3PO4. The 1H- and 31P-self-diffusion coefficients of PAMA+H2PO4−xH3PO4 for x=1,2 were determined by PFG-NMR. D(H) is always at least one order of magnitude larger than D(P), which means that inter-phosphate H+ transfer plays an important role in the samples. D(H) coincides quite well with the conductivity diffusion coefficient Dσ which is obtained from the conductivity data via the Nernst–Einstein relationship, assuming that the charge carrier concentration is equal to the repeat unit concentration. Since with the same assumption the charge carrier concentration is only (3x+2)−1 times the concentration of all the phosphate protons, the result Dσ/D(H)≈1 is rather surprising and indicative of cooperative proton transfer which does not contribute to the conductivity. D(H)/D(P) in the blends is much larger than D(H)/D(P) in pure phosphoric acid. This means that the phosphate moieties are considerably more immobilized in the blends as compared to H3PO4. This immobilization effect is more pronounced in blends with low phosphoric acid content and decreases with increasing temperature.

Polybenzimidazoles/Phosphoric Acid Solid Polymer Electrolytes: Mechanical and Electrical Properties

ABSTRACTPoly (2,2'-(m-phenylene) 5,5'-bibenzimidazole), PBI and poly (2,5-benzimidazole), ABPBI, were cast into films and doped with phosphoric acid. Their mechanical properties were studied as a function of inherent viscosity and phosphoric acid content. The commercial PBI with an I. V. of 0.8 to 0.9 had relatively low elongation at break. It was fractionated; the higher the inherent viscosity the higher the modulus and elongation. At low phosphoric acid doping the modulus rose because a crystalline phase developed, and then dropped as more phosphoric acid was added. A second doping method produced films with high crystallinity and higher conductivity (0.02-.03 vs. 0.06-.08 S/cm) but poorer elongation than those made by doping a cast film in phosphoric acid. In order to get higher molecular weight films that could have better mechanical properties, we decided to polymerize 3,4-diaminobenzoic acid to ABPBI, an AB polymer for which I. V.'s of∼16 have been reported. After learning how to purify and polymerize the monomer, I. V.'s of 6–8 were easily obtained. Conductivities of the doped ABPBI films were as high as those of the best PBI films. With their high viscosities, the ABPBI films were much tougher and had better elongation than the doped PBI films.

Relation between Shoot Phosphorus Content and Tillering Rate in Wheat Varieties Varied in Adapta bility to Low Available Phosphoric-acid Soil.

低リン酸濃度適応性の異なるコムギ品種を用いて, 圃場における分げつの出現率と地上部及び根部のリン, 窒素, カリウム含有率との関係を検討した. リン酸の不足する黒ボク土に対照区とリン酸増肥区を設けて栽培し, 主稈の第1葉の葉腋から出現する分げつ (T1) の出現率を調べた. その結果, 供試した3品種ともリン酸の不足する対照区で, 地上部及び根部のリン含有率が低かったが, 低リン酸濃度適応性が低いアサカゼコムギと農林61号では地上部のリン含有率が0.5%以下になるとT1の出現率が低下するのに対し, 低リン酸濃度適応性が高い農林64号はリン含有率が0.3%以下になってもT1の出現率はほとんど低下しなかった. なお, 地上部の窒素, カリウム含有率もリン酸増肥に伴って増加したが, 偏相関係数を検討した結果, 分げつ出現にはリン含有率が最も影響が大きいと考えられた. これらのことから, リン酸欠乏土壌で農林64号のT1の出現率が高いのは, リン吸収能が高いことによるのではなく, リン含有率が低くても分げつ能力が高いことによると考えられた.

Recovery of uranium, vanadium, yttrium and rare earths from phosphoric acid by a precipitation method

Commercial procedures for recovery of uranium from phosphoric acid are all based on solvent extraction techniques. Recovery of uranium from phosphoric acid in combination with direct production of concentrated acid is not possible on a commercial scale using solvent extraction. When a dispersion agent such as acetone, and a precipitation reagent - NH 4F - are added, uranium can be precipitated from high concentration (52% P 2O 5), as well as low concentration phosphoric acid (∼30% P 2O 5) with 0.6 kg acetone/kg P 2O 5 and 60 g NH 4F/kg P 2O 5. Variation of all parameters, such as uranium valence, phosphoric acid concentration, type and quantity of the dispersion and precipitation agents, has made it possible to develop on a laboratory scale a preferential mode of operation which appears to make uranium recovery from high concentration acid even simpler than recovery from acid of low concentration. This method also enables recovery of ⩾90% of the yttrium and ⩾80% of the rare earths contained in the phosphoric acid. To precipitate vanadium much more acetone must be used. The economic calculations presented here show that uranium recovery by the precipitation method is considerably less expensive than recovery by extraction or by other proposed routes: $60/lb at phosphoric acid capacity of 300 kt/a P 2O 5 with solvent extraction and $41/lb yellow cake with the new precipitation route and the same capacity. At present uranium prices ($28/lb yellow cake), the precipitation method does not make uranium recovery by precipitation an economic proposition in the case of plants of moderate phosphoric acid capacities (about 300 kt/a P 2O 5); however, in combination with recovery of yttrium and/or rare earths it appears to become economic - $28/lb yellow cake - at this moderate capacity.

Redox determination of uranium in presence of plutonium in low phosphoric acid medium and the recovery of plutonium

Quantitative determination of uranium in (U, Pu)O2 fuels is usually done by the DAVIES-GRAY method. High concentrations of phosphoric acid in the analytical waste generated by this method make the revocery of plutonium rather complex. Studies on the recovery of plutonium from nitric acid medium containing different concentrations of H3PO4 by conventional anion-exchange procedure reveal that more than 90% of the plutonium can be easily recovered when the phosphoric acid concentration is less than 0.5 M in the solution. A method was developed for the determination of uranium in the presence of plutonium, which involves the reduction of U(VI) to U(IV) by Fe(II) in a medium of 3.5M H3PO4 +4.5M H2SO4 instead of 10–11M H3PO4 so as to have the H3PO4 concentration ∼0.6M in the waste. A number of determinations of uranium in UO2(NO3)2 working standard solutions and (U, Pu) synthetic solutions with uranium at the 3–7 mg level were carried out by this method. The precision obtained was better than ±0.2% and the accuracy was also within the precision limits. The resulting analytical waste generated was directly subjected to anion exchange separation for the recovery of plutonium which was found to be more than 90%.

Phosphorus deficiency in cattle on two farms in Canterbury.

Abstract Extract Phosphorus deficiency in cattle has been reported from a number of countries, but there has been little reported in the veterinary literature on this condition in New Zealand. Webster (1932) Webster, W. M. 1932. Bovine sterility in New Zealand. Aust. vet. J., 8: 199–222. [Google Scholar] de-scribed infertility in cattle in the Waihi area which was associated with pica and low phosphoric acid in the soil.