Low Hydrogen Ion Concentration Research Articles

Archaea: An Agro-Ecological Perspective.

Microorganisms inhabiting bulk soil and rhizosphere play an important role in soil biogeochemical cycles leading to enhanced plant growth and productivity. In this context, the role of bacteria is well established, however, not much reports are available about the role archaea plays in this regard. Literature suggests that archaea also play a greater role in nutrient cycling of carbon, nitrogen, sulfur, and other minerals, possess various plant growth promoting attributes, and can impart tolerance to various abiotic stresses (especially osmotic and oxidative) in areas of high salinity, low and high temperatures and hydrogen ion concentrations. Thermoacidophilic archaea have been found to potentially involve in bioleaching of mineral ores and bioremediation of chemical pollutants and aromatic compounds. Looking at immense potential of archaea in promoting plant growth, alleviating abiotic stresses, and remediating contaminated sites, detailed studies are required to establish their role in different ecological processes, and their interactions in rhizosphere with plant and other microflora (bacteria and fungi) in different ecosystems. In this review, a brief discussion on archaea from the agro-ecological point of view is presented.

Predictors of the therapeutic effect of sivelestat in patients with acute lung injury associated with systemic inflammatory response syndrome.

BackgroundSivelestat, a neutrophil elastase inhibitor, was previously approved in Japan for the treatment of acute lung injury associated with systemic inflammatory response syndrome. However, sivelestat produced inconsistent therapeutic benefits. This study aimed to identify factors predicting the therapeutic effects of sivelestat.MethodsWe enrolled 53 mechanically ventilated patients who received sivelestat. The patients were classified as effective (n = 28) if they were weaned from the ventilator within 28 days, or as ineffective groups (n = 25). Patient characteristics were compared between these groups and multivariate logistic regression analysis was used to identify predictive factors. A validation study was then conducted in sivelestat-free patients.ResultsA high red blood cell count and low hydrogen ion concentration were significantly associated with a higher ventilator weaning rate in patients receiving sivelestat. The validation study revealed that the hydrogen ion concentration value also significantly associated with ventilator weaning in patients who did not receive sivelestat.ConclusionsAlthough hydrogen ion concentration was inversely associated with the ventilator weaning rate, it did not predict sivelestat efficacy. This study indicated that acute lung injury patients with a high red blood cell count would derive the most benefit from sivelestat administration.

As(V) and PO4 Removal by an Iron-Impregnated Activated Carbon in a Single and Binary Adsorbate System: Experimental and Surface Complexation Modeling Results

AbstractThe objective of this study was to predict As(V) removal by an iron-oxide impregnated carbon (L-Act, 9% Fe(III) amorphous iron-oxide) over a range of environmental conditions using the surface complexation modeling (SCM) approach. The L-Act surface sites and electric double layer were modeled using the two monoprotic site-diffuse layer model (2MDLM). As(V) and PO4 surface complexes were modeled as bidentate complexes at low hydrogen ion concentration (pH) and monodentate complexes at high pH. L-Act-As/PO4 surface complexation constants were determined from a single pH-adsorbent edge, and these were used to effectively predict pH-dependent removal of As(V) and PO4 across a range of adsorbent/adsorbate ratios in single and binary adsorbate systems and from a National Sanitation Foundation challenge water. The 2MDLM also successfully predicted As(V) removal by three literature-based iron-based adsorbents: two iron-impregnated ion exchange resins (PWX5, 16% Fe; PWX3, 10% Fe) and a hydrous ferric oxide...

철제유물 Weeping에 따른 부식화합물의 재부식 특성 연구

Excavated iron objects are preserved in stable condition through processes of conservation treatment because they are found in the form of various corrosion products. However, the conservation treatment leads to re-corrosion over time and accordingly, iron objects can be severely damaged, and therefore fundamental measures need to be prepared to control it. In this study, the types and characteristics of corrosion products were scientifically analyzed according to the re-corrosion of iron artifacts. In addition, the stability of the corrosion products was evaluated by exposing the standard samples under the re-corrosion environment. Re-corrosion proceeded with weeping in reddish brown on the cracks of iron artifacts. Weeping was detected akaganite had a low hydrogen ion concentration and high chloride ion. The selection of standard sample goethite, lepidocrocite, hematite, and magnetite, were evaluated corrosive by weeping. After the samples were immersed in HCl(pH 1), (pH 1), (pH 6) solution, they had been maintained for 180 days in relative humidity of 20%, 50%, 80% to investiage the changes of chemical components. As a result of analysis, the changes of chemical components were not showed in goethite, lepidocrocite, and hematite. But magnetite was changed to lepidocrocite in solution including chloride ion() and to goethite and lepidocrocite solution including sulfuric acid(). Results of the study, in the case of magnetite known as s stable corrosion compound, it was identified the corrosion of magnetite occurs by corrosive ions, which means weeping generated in the iron artifacts can corrode magnetite as well as base metal.

Intrinsic Potential-Dependent Performances of a Sol–Gel-Prepared Electrocatalytic IrO2–TiO2 Coating of Dimensionally Stable Anodes

The electrochemical properties of a sol–gel-prepared IrO2–TiO2 coating on Ti were investigated from the standpoint of the charging/discharging behavior in 1.0°mol dm−3 H2SO4 and in 0.50°mol dm−3 NaCl, pH 2. The potential-dependent changes from low oxidation states of Ir, with low activity, to those of higher activity (enhanced pseudocapacitive performances) were analyzed at different charging/discharging rates by cyclic voltammetry and electrochemical impedance spectroscopy. The results showed the distribution of Ir oxidation states through the coating, with lower ones being placed largely in the internal, hardly accessible, parts of the coating. The transition to higher oxidation states appears as crucial for the full development of pseudocapacitive performances. This transition occurs much easier in the NaCl than in the H2SO4 solution, since the potentials of redox transitions of Ir are much closer due to lower hydrogen ion concentration in NaCl solution. As a consequence, a unique overall coating capacitance was registered in both solutions.

Comparison of Formic and Sulfuric Acids as a Glucose Decomposition Catalyst

Dilute sulfuric acid hydrolysis of cellulose is the oldest and a well-studied technology for converting biomass to ethanol. Despite continuous technology improvements, the process still gives only a moderate selectivity due to glucose decomposition in the cellulose hydrolysis conditions. According to the recent literature, carboxylic acids have been recognized as more selective acid hydrolysis catalysts than sulfuric acid in low hydrogen ion concentrations. In this paper, formic acid was compared to sulfuric acid as a glucose decomposition catalyst at values below pH 2.2 at 180−220 °C. It was found that glucose decomposition depends only on the hydrogen ion concentration in the prevailing reaction conditions and is independent of the hydrogen ion source. Earlier contradictory findings can be the consequence of ignoring the temperature function of the dissociation constants of the acids and setting hydrogen ion concentrations at room temperature.

Novel separation of thallium-201 using p-tert-butylcalix[4]arene derivative

p-tert-Butylcalix[4]arene tetradiisopropylacetamide was synthesized in 62% yield. Extraction experiments in the water:butan-1-ol solvent system at 298 K in the presence of p-tert-butylcalix[4]arene tetradiisopropylacetamide were performed. The selective extraction of Pb2+ relative to Tl+ and Tl3+ from the aqueous solution to the organic phase in the presence of the ligand at low hydrogen-ion concentration was demonstrated. The extraction of radioactive Pb2+, Tl+ and Tl3+ by the same ligand was investigated as a function of the pH of the aqueous phase and the ligand concentration in the organic phase. The method appears to be very promising for use in the production of 201Tl of pharmaceutical quality.

PH-sensitivity of fast responsive superporous hydrogels

Stimuli-sensitive hydrogels (or smart hydrogels) are hydrogels that swell or shrink in response to small changes in environmental conditions in which they are placed. While the extent of swelling or shrinking may be large, the kinetics of such changes is slow, since the diffusion of water into and out of the hydrogel is a slow process. To obtain fast responses, we have prepared superporous hydrogels (SPHs) that can swell or shrink extremely fast regardless of their dimensions. The swelling and shrinking are orders of magnitude faster than expected for a nonporous hydrogel of the same dimensions. Water molecules are taken up into the SPHs by capillary forces, and this makes water uptake much faster than diffusion. The swelling ratio of the poly(acrylamide- co -acrylic acid) (p(AM-co-AA)) SPHs was dependent on the pH and ionic strength of the medium. The effect of pH was most pronounced and the effect of ionic strength was observed at all pH values. SPHs made at pH around 5 showed transient maximum swelling when exposed to pH 1.2 medium due to the transient low hydrogen ion concentration inside the swelling SPHs. The p(AM-co-AA) SPHs showed repeated swelling and shrinking by alternating the medium pH between 1.2 and 7.5, and the changes in swelling ratio was quite fast occurring in a matter of a minute. This fast sensitivity may make the stimuli sensitive hydrogels useful in many applications not previously possible. These materials can be used for applications where a single-piece hydrogel is more advantageous than hydrogel microparticulates.

Bioleaching and bioprecipitation of nickel and iron from laterites

Leaching of silicate ores, particularly nickel laterites, with the aid of heterotrophic organisms has been briefly reviewed. Samples of laterite ores from Greece were characterised mineralogically and a number of microorganisms isolated from them. One of these organisms (code FI) was successfully acclimatized to 6400 ppm nickel. Samples of the high-grade Greek Kastoria nickel laterite were leached with sulphuric acid and a number of organic acids. Sulphuric and citric acids extracted over 60 and 40% of the contained nickel, respectively, but the other acids employed were less efficient leachants. Oxalic acid precipitated nickel oxalate. Roughly the same extraction of iron was observed. The main leaching parameter was confirmed to be hydrogen ion concentration, although complexation with organic anions was a contributor. Organism FI (a strain of Penicillium) was used in comparison with organisms from various culture collections to bioleach nickel from samples of the low-grade Greek Litharakia nickel laterite. The organisms were cultivated in a mixture of a sugar-based nutrient mineral medium and finely ground ore. Several penicillia and aspergilli leached 55–60% of the contained nickel and cobalt, and 25–35% of the iron when sucrose was the carbon source, but FI was not efficient. However, in molasses medium, Fl extracted nearly 40% of the nickel. Biosorption and bioprecipitation reactions were observed. The mechanism of bioleaching or in situ leaching is discussed in terms of close physical and chemical association between the fungal hyphae and mineral phases in the ore. This accounted for the low overall hydrogen ion concentration observed during bioleaching.

Bioleaching and bioprecipitation of nickel and iron from laterites

Leaching of silicate ores, particularly nickel laterites, with the aid of heterotrophic organisms has been briefly reviewed. Samples of laterite ores from Greece were characterised mineralogically and a number of microorganisms isolated from them. One of these organisms (code FI) was successfully acclimatized to 6400 ppm nickel. Samples of the high-grade Greek Kastoria nickel laterite were leached with sulphuric acid and a number of organic acids. Sulphuric and citric acids extracted over 60 and 40% of the contained nickel, respectively, but the other acids employed were less efficient leachants. Oxalic acid precipitated nickel oxalate. Roughly the same extraction of iron was observed. The main leaching parameter was confirmed to be hydrogen ion concentration, although complexation with organic anions was a contributor. Organism FI (a strain of Penicillium) was used in comparison with organisms from various culture collections to bioleach nickel from samples of the low-grade Greek Litharakia nickel laterite. The organisms were cultivated in a mixture of a sugar-based nutrient mineral medium and finely ground ore. Several penicillia and aspergilli leached 55–60% of the contained nickel and cobalt, and 25–35% of the iron when sucrose was the carbon source, but FI was not efficient. However, in molasses medium, Fl extracted nearly 40% of the nickel. Biosorption and bioprecipitation reactions were observed. The mechanism of bioleaching or in situ leaching is discussed in terms of close physical and chemical association between the fungal hyphae and mineral phases in the ore. This accounted for the low overall hydrogen ion concentration observed during bioleaching.

Prediction of future short-term stream chemistry — a modelling approach

The problem of predicting future short-term chemical behaviour in acidic and acid-sensitive streams is addressed. A relatively simple method is presented which combines a chemical technique for splitting the hydrograph into ground water and soil water components, based on the conservative component acid neutralization capacity, with the long-term hydrochemical model (MAGIC) in a ‘two-box’ mode. This method, coupled with a chemical speciation program (ALCHEMI), is used to assess short-term variations in stream chemistry with change in atmospheric deposition chemistry. The method is applied for a semi-natural moorland catchment in mid-Wales (Afon Gwy). For both hydrogen ion and inorganic aluminium, the modelled stream mixing relationships are non-linear, particularly at low hydrogen ion concentrations. The results also show that the relationship between hydrogen ion and inorganic aluminium concentrations varies with time in the stream. This result has important implications as it implies that aluminium concentrations will not recover, with reduced anthropogenic sulphur deposition, as rapidly as has previously been thought. Two methods, for use with critical load evaluation of ecological stress, are presented for describing the changes occurring: the hydrogen ion and inorganic aluminium concentration duration curve; the hydrogen ion and inorganic aluminium incident frequenty diagram.

Kinetics and mechanism of the reduction of dodecatungstocobaltate(III) by oxalate. The catalytic role of alkali metal ions through outer-sphere bridging

The kinetics of reduction of dodecatungstocobaltate(III) by oxalate follow the rate laws kobs.= 2k1[HC2O4–] and kobs.= 2k2[C2O42–] at high and low hydrogen ion concentrations respectively. Both these apparent second-order rate constants (k1 and k2) depend on the concentration and type of cation present; k1 and k2 decrease in the order K+ > Na+∼ Li+ and K+ > Na+ > Li+ respectively. The K+ and Na+ assisted paths have been studied in detail. The rate constants for these catalysed paths along with those for uncatalysed ones have been evaluated. Thermodynamic parameters (ΔH‡ and ΔS‡) associated with k1 and k2 have been determined. A cation-bridged outer sphere electron transfer mechanism is most likely to take place, with simultaneous generation of free radicals (C2O4˙–).

The misbehaviour of mercury(I) ions in cold-vapour atomic absorption spectrometry

The behaviour of mercury(I) ion in the cold-vapour atomic absorption spectrometry under nonreducing conditions is discussed. The signal obtained corresponds to about 35% of total mercury present. Under the same conditions, the same quantity of Hg 2+ is found by dithizone spectrophotometry. Thus the cold-vapour signal is due entirely to disproportionation of mercury(I), which is not inhibited by chloride at mercury concentrations less than 120 μg l −1. The cold-vapour signal si pH-dependent and at low hydrogen ion concentration, approaches the value expected from complete disproportionation.

Studies on fish liver carbohydrate metabolism during acclimation to sub-lethal acidic and alkaline media

Freshwater fish, Tilapia mossambica (Peters) were acclimated to low and high hydrogen ion concentrations and their liver carbohydrate metabolism was investigated. Differential patterns of metabolism were witnessed in the liver in response to acidic and basic media. Liver exhibited suppressed glycolysis and elevated glycogen content in acidic media, but in basic media the glycolysis was elevated. In general, the hepatic tissue was oriented towards lesser production of organic acids with increased carbohydrate reserves in acidic medium, but in alkaline medium there was increased organic acid production, as a possible adaptive mechanism of the fish, enabling it to counteract the imposed pH stress.

Influence of pH of phenol-formaldehyde resin and thermal treatment on the properties of hardboard

Hydrogen ion concentration greatly affects the properties of finished hardboard products, since it serves the dual purpose of imporoving both strength and hydrophobic properties of the board. Improvement in the physical and mechanical properties was greater with increasing hydrogen ion concentration up to a certain pH (which is about 3.3 and 5 for boards pressed with resin and with pH adjusted by means of acid and alum respectively). However, higher hydrogen ion concentrations caused damage of cellulose fibers, thereby deteriorating the strength properties. In most cases the rate of improvement was much higher with alum adjustment of pH, especially when the boards were subsequently subjected to thermal treatment. With thermal treatment a greater improvement is attained at lower hydrogen ion concentrations than without it.

Mono-complex Formation Kinetics of 2-Thenoyltrifluoroacetone with Nickel(II) and Copper(II) Ions in Aqueous Solution

Abstract The mono-complex formation of 2-thenoyltrifluoroacetone (HTTA) with nickel(II) and copper(II) ions was studied in aqueous solution at 25.0 °C and an ionic strength of 0.20 mol dm−3 by means of a stopped-flow method. The rate-[H+] profiles for the formation of these mono-complexes revealed that the rate-determining step of the complex formation interchanges depending upon hydrogen-ion concentration, as in the case of the Ni(II)–bpy complex. The rate constants of the mono-complex formation with TTA−, kf, and that with HTTA, kfh, were determined from the rate-[H+] profile in the region of the high hydrogen-ion concentration, where the pseudo-equilibrium of acid dissociation of the ligand was maintained during the complex formation; kf=(9.2±3.0)×102, kfh=(1.3±0.3)×10−1 mol−1 dm3 s−1 for the Ni(II)–TTA complex and kf=(2.0±1.2)×103, kfh=(5.0±0.9)×10−1 mol−1 dm3 s−1 for the Cu(II)–TTA complex. The deprotonation-rate constants of HTTA could be evaluated from the apparent rate constants of the complex formation in low hydrogen-ion concentration. The values thus obtained agreed well with that determined independently by a pH jump method.

In-vitro Clot Forming Properties of Polyelectrolyte Complexes of [2-(Diethylamino)ethyl]dextran Hydrochloride with Poly(sodium-l-glutamate) and of Sodium Carboxymethyldextran with Chitosan

Abstract Polyelectrolyte complexes prepared at higher hydrogen ion concentrations may form clots in higher quantities than those prepared at lower hydrogen ion concentrations, irrespective of the content of anticoagulant reagents. This difference is attributable to the difference in molecular structure of polyelectrolyte complexes, especially to the presence of carboxyl groups.

Teh pH-dependence of the inhibitory effects of several divalent cations on the ovine intestine adenosine deaminase activity

1. 1. In the reaction performed in an alkaline region, the inhibitory effects of Ba 2+, Ca 2+, Mg 2+, Mn 2+ and Sr 2+ on the bovine intestine adenosine deaminase were observed. 2. 2. Mn 2+ completely inhibited its activity at pH 8.0, and Ca 2+ and Mg 2+ at pH 9.0. The inhibition of the latter two metals was reversible, and low hydrogen ion concentration was required when binding. The addition of EDTA reduced the inhibitory effects but a difference was found between Ca 2+ and Mg 2+ in the recovery process.

The Location of Cathodic Reaction during Localized Corrosion

A theoretical model for predicting the current and potential distribution within a prototypic pit was used to estimate conditions under which cathodic reaction occurs in the occluded region. The model is developed for a long, narrow occluded cell where the anode is localized in the tip region. Cathodic reaction (hydrogen reduction) on the side walls and external surface is predicted by assuming metal‐ion hydrolysis, diffusion of hydrogen ions, Ohm's law, cathodic reduction via Tafel kinetics, and constriction of current lines entering the occluded region. Results indicate that cathodic reaction within occluded regions is favored for deep narrow regions in solutions of low hydrogen ion concentration. Dimensionless groupings of system parameters are used to scan behavior over wide ranges of parameter space and to compile conditions under which appreciable cathodic reaction can be anticipated within occluded cells.

Beneficial effects of alkalotic reperfusion following ischemic cardiac arrest

The results of the present study indicate that exposure of ischemic myocardium to a solution with a low hydrogen ion concentration (pH 7.70) during the immediate post-ischemic period provides for better myocardial functional recovery and less myocardial water accumulation than does exposure to solutions with a normal hydrogen ion concentration (pH 7.40). Furthermore, exposure of the postischemic myocardium to a solution with a high hydrogen ion concentration (pH 7.10) results in poor recovery of ventricular function and significant myocardial water accumulation following reperfusion. Neither the beneficial effect of alkalotic reperfusion nor the harmful effect of acidotic reperfusion is associated with alterations in intramyocardial pCO 2 concentrations.