Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation？reduction reactions in the bioleaching system.

Oxidative coupling of methane over LaAlO3 perovskite catalysts prepared by a co-precipitation method: Effect of co-precipitation pH value

Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.

Microstructure of nano precursors of La-Mg hydrogen storage alloy synthesized by sol-gel technology at different pH values

Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.

Effects of temperatures and pH values on rheological properties of cemented paste backfill

In this study,different influence mechanisms associated with temperatures and pH values were investigated through cemented paste backfill(CPB)systems.CPB samples were prepared with temperatures ranging from 10 to 50℃ in 10℃ increments and pH values of 3,7,and 13.Then,the CPB mixture were subjected to rheological tests,thermogravimetric analysis(TG),derivative thermogravimetry analysis(DTG),Fourier-transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).Results demonstrated that the temperatures had significant effects on the rheological properties of CPB,whereas the effects of pH values were relatively unapparent.Higher temperatures(over 20℃)were prone to bring higher shear stress,yield stress,and apparent viscosity with the same pH value condition.However,an overly high temperature(50℃)cannot raise the apparent viscosity.Non-neutral conditions,for pH values of 3 and 13,could strengthen the shear stress and apparent viscosity at the same temperature.Two different yield stress curves could be discovered by uprising pH values,which also led to apparent viscosity of two various curves under the same temperatures(under 50℃).Microscopically,rheological properties of CPB were affected by temperatures and pH values which enhanced or reduced the cement hydration procedures,rates,products and space structures.

Relationship Between pH Value and Physical and Chemical Properties of Tobacco-growing Soil

[Objectives]This study was conducted to understand the relationship between soil pH and soil physical and chemical properties during tobacco planting.[Methods]Through a field experiment,the pH value of tobacco-growing soil,the contents of mineral nutrients(ammonium nitrogen,alkali-hydrolyzable nitrogen,available potassium,available phosphorus),soil bulk density and porosity were investigated.[Results]The pH value of the soil after tobacco planting increased,and the contents of ammonium nitrogen,alkali-hydrolyzable nitrogen,and available potassium were closely related to the change of pH value.The bulk density of the tobacco-planting soil decreased and the porosity increased.Planting flue-cured tobacco had certain impacts on soil pH,soil bulk density and other physical and chemical properties.[Conclusions]This study provides a theoretical basis for the investigation of the fertilization laws in the process of tobacco planting and the selection of subsequent crops.

Effects of Straw and Biochar Returned to the Soil on Soil Physical Properties and pH Value in Cold Rice Region

[Objectives]In order to explore the feasibility of using straw and biochar returned to the soil to improve soil physical properties and pH value in cold rice regions of China.[Methods]the effects of straw directly returned to the soil and charred straw(biochar)returned to the soil on soil bulk density,porosity,temperature and pH value of cold paddy soil were studied in this paper.[Results]The results showed that compared with conventional production,straw(6 t/ha),a small amount of biochar(2 t/ha)and a large amount of biochar(40 t/ha)returned to the soil reduced paddy soil bulk density at different growth stages by 6.02%-11.86%,2.69%-6.67%and 8.58%-11.32%,respectively,increased total porosity by 7.41%-14.93%,3.19%-8.38%and 9.81%-14.27%,respectively,and increased aeration porosity by 22.28%-192.11%,17.80%-92.11%and 52.44%-157.11%,respectively.Straw and a small amount of biochar returned to the soil had no significant effect on soil temperature and pH value of paddy field,but a large amount of biochar returned to the soil could significantly increase soil temperature by 5.13%-8.79%and pH value by 3.15%-5.96%in the later stage of rice growth.[Conclusions]The straw and biochar returned to the soil could reduce soil bulk density,increase total porosity and aeration porosity,and only a large amount of biochar returned to the soil could significantly increase soil temperature and pH value.

Effect of pH Value on the Micro-structures and Optical Properties of Nano-crystalline CuInS_2 by Solvothermal Method

Copper indium disulfide（CuInS2） nano-particles were synthesized by solvothermal method at 150 ℃ using copper（？） chloride,indium（Ш） chloride,thiourea and ethanol as raw materials,and characterized by X-ray diffraction（XRD）,field-emission scanning electron microscope（FESEM）,and UV-Vis spectra.The effects of pH value on its micro-structures and optical properties were investigated.The results show that,with the pH value increasing,the particle size of the nano-crystalline CuInS2 increases,and its band gap becomes narrower under alkaline condition.The band gaps of CuInS2 nano-particles are from 1.52 eV to 1.93 eV,which makes them promising candidates as absorber materials for photovoltaic applications.

Electrochemical performance of nano-scale β-Ni(OH)_2 prepared at different transformations of pH value

The influence of transforming pH values on the electrochemical performance of nano-scale Ni （OH）2 was analyzed. The measurement results of XRD indicate that the nano-scale Ni （OH） 2 prepared at different transformations of pH value is β （ Ⅱ ）-phase with different crystal lattice parameters. Cyclic voltammograms （CV） and electrochemical impedance spectroscopy（EIS） measurement results show that transformations of pH value affect the proton diffusion coefficient （D） and charge-transfer resistance （Re,） of the material. The simulation of.cell experiment shows that the sample prepared at a pH of 10. 1 exhibits the maximum specific capacity （327.8 mAh/g） and higher discharge platform, the discharge performance of electrodes depends on both D and Rct, so the kinetics characteristics that electrodes reaction is controlled by both mass-transfer step and charge- transfer step are put forward.

Dynamics of pH value and metal elements of rainfall within mixed forests in Japanese pine and cypress

The dynamics of forest ecology was studied. The pH values, electrical conductivities and concentrations of metal and nonmetal elements in rainfall, stream, through fall and stream flow were investigated based on the data collected from a small mixed forest watershed of Pinus densifora sieb et Zucc, Pinus thunbergii Parh and Chamaecypari sobtusa sieb et Zucc ex Endl at Kiryu nature reserve and a small barren watershed at Jakujo nature reserve, Ootsu, Shiga, Japan. The results show that both the mixed forest ecosystems of pine and cypress and the soil draw from granite affect the pH values and metal elements of rainfall. And the contribution of the mixed forest is greater than that of the barren. Moreover, the amount of input of most elements is larger than that of output in the ecosystem, which shows the elemental accumulation in the related forest ecosystem.

Influence of pH value and chelating reagent on performance of Li_3V_2(PO_4)3/C cathode material

The Li3V2（PO4）3/C composite cathode material was synthesized via sol-gel method using three different chelating agents （citric acid, salicylic acid and polyacrylic acid） at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, cyclic voltammetry （CV）, electrochemical impedance spectroscopy （EIS） and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.

Influence of pH Value on Photocatalytic Activity of Bi4Ti3O12 Crystals Obtained by Hydrothermal Method

Bi4Ti3O12 （BIT） crystals were controllably synthesized via a facile hydrothermal process without adding any surfactant or template. The morphologies of BIT with nanosphere, nanoplate, nanobelt, and nanosheet can be selectively obtained by adjusting the pH value of the reactant. The formation mechanisms of these distinctive morphologies were then discussed based on the structural analysis of samples obtained at different pH values. BIT sample prepared at pH=1 showed the highest photocatalytic activity under visible light irradiation. The photocatalytic activities difference for the BIT samples synthesized at different pH values was studied based on their shape, size, and the variation of local structure.

Adsorption Kinetics of NH_4^+ by Purple Soils with Different pH Values

Ammonium adsorption and desorption properties by purple soils with dif- ferent pH were studied. The results showed that the adsorption and desorption amounts of NH4＋ by purple soils increased with the increase of NH4＋ concentration, regardless of soil pH values; the largest adsorption and desorption amounts of NH4＋ by purple soil at pH 6.0 were 10.3 and 7.96 mg/g, respectively; the largest adsorp- tion and desorption amounts of NH4＋ by purple soil at pH 7.2 were 12.8 and 4.62 mg/g, respectively; the largest adsorption and desorption amounts of NH4＋ by purple soil at pH 8.0 were 13.5 and 2.23 mg/g, respectively. The isothermal adsorption ki- netics of NH4＋ by purple soils fits the Freundlich equation best （R〉0.95）. This study shows that the adsorption of NH4＋ by purple soils with different pH values is multi- molecular layer uneven surface adsorption.

Corrosion behaviour of die-cast AZ91D magnesium alloys in sodium sulphate solutions with different pH values

The corrosion behaviours of die-cast AZ91D magnesium alloys were investigated in 0.1 mol/L sodium sulphate （Na 2 SO 4 ） solutions with different pH values. The corrosion rates, morphologies, and compositions of the corrosion products were studied by means of scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR）, and X-ray diffractometry （XRD）. The results indicate that the order of corrosion rates in Na 2 SO 4 solutions with various pH values is pH 2pH 4pH 7pH 9pH 12. The corrosion rates in acidic solutions are higher than those in alkaline solutions, and the corrosion products are mainly magnesium hydroxide （Mg（OH） 2 ） and hydrated sulphate pickeringite （MgAl 2 （SO 4 ） 4 ·22H 2 O）. The results also indicate that the solution pH can influence the corrosion rate and morphology of corrosion products. Chloride ions and sulphate ions have different pitting initiation time.

The Distribution Characteristics of Soil pH Values of Tobacco-growing Areas in Dali City and Its Correlation with Soil Nutrients

[Objective] The aim was to study the distribution characteristics of soil pH values and its correlation with soil nutrients in tobacco-growing areas. [Method] Soil nutrients of 43 samples from tobacco-growing areas in Dali City were analyzed.[Results] The results showed that average pH value of tobacco-planting soil in Dali City was 6.52, soil samples which suited for flue-cured tobacco cultivation accounted for 72.09% of total soil samples. In four soil types of tobacco-growing areas, the pH values in a descending order were as follows： alluvial soil〉 paddy soil 〉purple soil〉 red soil. At the altitude range of 1 780-2 200 m, soil pH values showed a gradual decreasing trend. The average contents of soil organic matters were relatively abundant and generally suited for high-quality tobacco cultivation; the average contents of soil alkali-hydrolyzable nitrogen, available phosphorus, exchangeable calcium and exchangeable magnesium were generally at medium and abundant level, however,their rations under the medium level in some tobacco-growing areas were 6.98%,11.63%, 2.33% and 4.65%, respectively; moreover, soil with lower available potassium contents occupied a large proportion, namely 58.14%. [Conclusion] Soil pH values had significant correlation with exchangeable magnesium and exchangeable magnesium, however, they had no significant correlation with other soil nutrients.

Correspondence between Susceptibility to SCC of 7050 Aluminum Alloy and Passive Film-induced Stress at Various pH Values

The passive film-induced stress and the susceptibility to SCC of 7050 aluminum alloy in 3.5%sodium chloride solution at various pH values were investigated by slow strain rate testing（SSRT） and flowing stress differential method.The results showed that the passive film-induced stress and the susceptibility to SCC decreased with increasing pH values when pH≤7,while they increased with increasing pH values when pH7.However,the corrosion type was interpreted as exfoliation corrosion when pH=l and 14,and there was no film formed on the surface of the specimens.The whole variation plots of film-induced stress and the SCC susceptibility with pH values were both presented as a valley shape.The symbol and amount of the film-induced stress were related to the compositions of the passive film,which were analyzed using X-ray photoelectron spectroscopy（XPS）.

Comparison of pH Value, TBA Value, Glycogen and Lactic Acid Content in Muscle of Landrace and Yorkshire under Different Storage Time and Conditions

In order to assess the meat quality under different storage time and conditions, the pH value, TBA value, glycogen and lactic acid content in muscle of Landrace and Yorkshire were measured. The results showed that within 10 h post slaughtering, post slaughtering time had extremely significant influence on pH value and lactic acid content of Landrace, but had no significant influence on glycogen content and TBA value. On the other hand, post slaughtering time had extremely significant influence on pH value of Yorkshire, but had no significant influence on glycogen, lactic acid content and TBA value. The pH values of Yorkshire at 3, 5 and 10 h post slaughtering were 5.21% （ P 〈 0.01 ）, 5.64% （ P 〈 0.05 ） and 5.59% （ P 〈 0.05 ） higher than those of Landrace, respectively ; the lactic acid content in muscle of Landrace at 10 h post slaughtering was 56.04% （P 〈0.05） higher than that of Yorkshire; the TBA value in muscle of Yorkshire at 10 h post slaughtering was 89. 19% （P 〈 0.01 ） higher than that of Landrace; there was no significant difference in glycogen content between Yorkshire and Landrace. When pork stored at 4℃, storage time had no significant influence on pH value and glycogen content in muscle of Landrace, but had significant influence on drip loss, lactic acid content and TBA value ; storage time had no significant influence on pH value, glycogen content and TBA value in muscle of Yorkshire, but extremely significant influence on drip loss and significant influence on lactic acid content. The pH value in muscle of Yorkshire at 24 h post storage at 4℃ was 6.56% （P 〈0.05） higher than that of Landrace; the glycogen contents in muscle of Landrace at 24, 48, 72, 96, 120 and 144 h post storage at 4℃ were 84.90% （P〈0.05）,78.40% （P〈0.01）, 101.87% （P〈0.05）, 83.80% （P〈0.05）, 83.59% （P〈 0.05）and67.25% （P〈0.01）higher than those of York-shire, respectively; the drip loss of Landrace at 72 h post storage and TBA value at 144 h post storage were 55.70% （ P 〈 0.05 ） and 141.33 % （ P 〈 0.01 ） higher than those of Yorkshire, respectively; there was no significant difference in glycogen content between Yorkshire and Landrace. When pork stored at -20℃, storage time had significant influence on TBA value in muscle of Landrace, but had no significant influence on pH value, thawing water loss rate, glycogen and lactic acid content; storage time had no significant impact on pH value, thawing water loss rate, glycogen content and TBA value in muscle of Yorkshire, and had significant influence on lactic acid content. The pH value in muscle of Yorkshire at 24 h post storage at - 20℃ was 5.43 % （ P 〈 0.05 ） higher than that of I.andrace ; the glycogen contents in muscle of Landrace at 24, 48, 72, 96, 120 h post storage at - 20℃ were 85.08% （ P 〈0. 05 ）, 108.66% （ P 〈 0.01 ）, 72.69% （ P 〈 0.05 ）, 90.31% （ P 〈 0.01 ）, 70.38% （ P 〉 0.05 ） higher than those of Yorkshire, respectively ; the thawing water loss rates of Landrace at 24 and 72 h were 160.14% （ P 〈 0.05 ） and 74.32% （ P 〈 0.05 ） higher than those of Yorkshire, respectively ; there was no significant difference in lactic acid content and TBA value at the same time point between Yorkshire and Landrace.

Electrochemical Behavior of Steel Bar in Electrolytes:Influence of pH Value and Cations

Steel bar corrosion on electrolytes and the influence of cation were investigated. Three electrolytes of Ca（OH）2, NaOH and KOH with pH levels of 12.5, 11.5, 10.5, 9.5, 8.5 were prepared, meanwhile, the methods of free corrosion potential and electrochemical impedance spectra （EIS） were used to evaluate the influence of cations on the depassivation of the steel bar in electrolytes. The experimental results indicate that the initial corrosion pH value of the steel bar is influenced by the cation in electrolyte and the influence of K＋ in electrolyte is the most remarkable, followed by Na＋ and Ca2＋. The initial corrosion pH values are 10.5 in KOH electrolyte, 9.5 in NaOH electrolyte and lower than 8.5 in Ca（OH）2 electrolyte.

Effect of Cu and Ni on Growth, Mineral Uptake,Photosynthesis and Enzyme Activities of Chlorella vulgaris at Different pH Values

A pH dependent reduction in growth, Pigment, ATP content, O,' evolution, carbonfixation, Photosynthetic electron transport system, nutrient uptake (NO,' and NH4+),nitrate reductase, and ATPase activities and increase in K+ emux of Chlorella vulgaris wasnoticed following supplementation of Cu and Ni to the culture medium. PS II was foundto be more sensitive to both pH and metals than PS I. Though, nitrate reductase (NR) wasmore sensitive to both PH and metals, the ATPase was however, more sensitive t0 metalsbut less sensitive to acidic pH. Acid PH was found to dst the nutrient (NO,' and NH4+)uptake and nitrate reductase in a non-competitive manner. The inhibition Pnduced by thetest metals alone was of noncompetitive type for NO3' uptake, nitrate reductase andATPase and competitive for NH'+ uptake. Acidity not only inhibited the metabolicvariables directly but also through facilitated uptake of metals and increased membranepermeability. A very low sensitivity of ATPase to acidic pH seems to be resgnsible forthe survival of algae in acid environment.

pH Value Effects in Shear Rheology of Concentrated Alumina Suspensions

The influence of pH on the rheological properties of concentrated alumina suspensions was investigated. At various pH values, the alumina exhibited pseudoplastic, near Bingham flow behaviors. The fully-deflocculated suspensions exhibited Newtonian flow behaviors, while the fully-flocculated suspensions demonstrated very high viscosity and shear yield stress.

Capacitance Characterization of the Effect of pH Value on the Self-assembled Monolayers of Octadecanethiol

In this paper, the membrane capacitance (Cm), which was obtained from the electro- chemical impedance spectroscopy (EIS) method, was used to characterize the effect of pH value on the self-assembled monolayers (SAMs) of octadecanethiol(18SH) for the first time. The results not only strongly proved that inorganic ions could penetrate the SAMs of 18SH, but also ascertained that SAMs of 18SH were not an absolute of free of ion-penetration. Verifying the existence of pin-holes in the octadecanethiol SAMs was the main contribution of this paper, which coincided with the former conjecture very well.