Papers by Keyword: pH

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Authors: B.J.M. Leite Ferreira, M.C.F. Magalhães, Rui N. Correia
Abstract: We investigated the in vitro formation of apatites and other biologically relevant calcium phosphates, in particular the influence of temperature and pH in the nature of the mineral phases. With this purpose several calcium phosphates were synthesized under controlled conditions, in presence of atmospheric CO2. The results obtained suggest that both factors under study, temperature and pH, have major influence in the nature of the mineral phases obtained.
Authors: Xue Hao Li, Wei Wang, Zhen Yuan Tian, Wei Ya Xu
Abstract: In this paper, we present a numerical modeling of chemo-mechanical behaviour of sandstone. An internal variable is introduced in this model for the purpose of describing pH effect on elasto-plastic properties. A new chemo-elasto-plastic model is proposed for sandstone. The proposed model is applied to predict material responses in triaxial compression tests of sandstone after soaking in different pH acidic solutions. We concluded with good agreement between numerical simulations and experimental data.
Authors: Peng Yuan, Peng Fei Shan, Yu Hong Liu, Quan Liu, Jian Jun Chen
Abstract: In this article, a facile method to measure pH and calcium content of different kinds of eggs by Ion-selective electrodes was presented successfully. First of all, we used pH electrode to measure the pH value of egg yolk and protein respectively. For the native egg, yolk’s pH was 6.20 and protein’s pH was around 9.45. But the fresh egg yolk was different from the native hen egg, yolk’s pH was 6.20 and protein’s pH was approximately 9.20. Then, we chose calcium ion selective electrode to measure calcium content in the eggs. When it came to calcium content, there was an obvious difference between the native hen egg and the fresh egg. Calcium contents in egg yolk of the former ones are higher than that of the latter. Ion-selective electrode with these advantages makes it possible to measure composition content rapidly of eggs. This paper may be a guide to expand its application scope, further research must be continued in order to achieve big success.
Authors: Ling Liang Long, Yan Jun Wu, Lin Wang
Abstract: A new fluorescent probe 1, bearing a pyridine group as receptor for H+ and a coumarin dye as fluorophore, was synthesized and characterized by 1H NMR, 13C NMR, ESI-Ms and single crystal X-ray diffraction analysis. The probe exhibited fluorescence ratiometric response to acidic pH. With decreasing of the pH from 8.32 to 2.49, the fluorescence emission spectra exhibited large red shift from 541 to 631 nm, with the emission ratios (I541 /I631) changed dramatically from 25.9 to 0.08, and the pKa value was calculated to be 5.45. Probe 1 exhibited high selectivity to pH, other interference species including metal ions and amino acid exerted no visible effect on probe 1 detecting pH. The intracellular pH imaging applications proved that the probe is suitable for monitoring acidic pH fluctuations in living cells.
Authors: Christian Rogge, Steffen Zinn, Sylvio Schneider, Roberto Francini, Paolo Prosposito, Andreas H. Foitzik
Abstract: The objective of the present work was the development of a micro-pH meter for the determination of the pH value within bioreactors with a volume of up to 200 μl in total. Two different prototypes of optodes were designed and tested. In a first approach spectroscopic analysis of bromothymol blue in a micro-sized-channel structure was carried out utilizing glass fibers, enabling measurements in sample volumes down to the range of picoliters. In a second approach a different illumination system consisting of a RGB-sensor and a LED light source was used. Phenol red was successfully applied as the pH indicator for this setup.
Authors: So Young Kang, Jong Un Lee, Kyoung Woong Kim
Abstract: Pseudomonas aeruginosa biomass was used to investigate the biosorption properties of heavy metals in wastewater. The biosorption isotherm of Co2+ was best described by the Langmuir model when washed cells were employed, and results obtained utilizing heat-treated P. aeruginosa were also adequately represented by a Langmuir sorption isotherm. In contrast, the sorption isotherm involving unwashed P. aeruginosa showed a different isotherm profile and did not attain equilibrium in the range of metal concentrations investigated; the amount of Co2+ uptake increased with increasing initial metal concentration but never reached adsorption equilibrium, most likely due to bacterial production of extracellular polymeric substances (EPS). The biosorption results utilizing unwashed P. aeruginosa were best described by a Freundlich isotherm. The level of metal adsorption in low pH was significantly small due to competition between the cation and H+ ions for binding sites distributed on cell surfaces, while the increase in pH favored metal sorption because of the elevated quantities of negatively charged surface functional groups. The sorption of Co2+ was strongly influenced by the presence of competing cations in the solution. Trivalent Cr3+ added to the solution was preferentially adsorbed onto the cells relative to Co2+ and Ni2+. The results may be attributed to the higher adsorption affinity of Cr3+ in comparison to either Co2+ or Ni2+. The affinity order (Cr3+ > Co2+ » Ni2+) was maintained over a pH range up to 5.3 in a mixture solution.
Authors: Babar Shahzad, Yang Qi
Abstract: Pure ZnO thin films were spin coated on glass substrates using 0.5M Zinc acetate dihydrate precursor solution and then annealed at 500°C for 2h in air to get good quality thin films. The effect of sol-aging time, from as-synthesized to 4week aged, on microstructure and morphology of ZnO thin films was investigated. X-ray diffraction spectra revealed the polycrystalline wurtzite structure preferentially oriented along the (002) polar plane with variable peak intensity. AFM analysis exposed an asymmetrical cyclic morphology transition with sol-aging time from comparatively smooth surfaces with small spherical particles to a rigid wrinkle network of a high rms surface roughness value of at~42.4nm which finally untied and evolved as homogeneous surface of uniform grain distribution after 4 weeks of aging time. The minimum surface roughness of 1.6nm was obtained for the film prepared from 24h aged solution.
Authors: Kai Zhang, David C. Bell, Lorraine F. Francis
Abstract: A/W bioactive glass (BG) particles (600-1000 microns) were soaked in 0.1 M 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) solutions (0.01 g BG per 1 mL solution) at three pH ranges (acidic: 4.45-6.31, neutral: 7.45-7.64 and basic: 10.31-10.42). Crystalline calcium phosphates developed on BG surfaces after soaking in either acidic or neutral solutions. Electron diffraction (ED) results showed that whitlockite and octa-calcium phosphate (OCP) were the newly developed materials on BG in the acidic HEPES solution after soaking for 7 d and 14 d, respectively. Whitlockite also developed on the BG particles in the neutral solution of 0.5Na-HEPES after soaking for 14 d. No crystalline materials developed on BG surfaces after soaking in the basic Na-HEPES solution up to 14 d. The results of this study demonstrated that the pH of a soaking solution strongly affect both the ions release of the A/W BG particles, and the development of crystalline calcium phosphates on BG particles.
Authors: Dong Sheng Wang, Yu Chao, Ting Zhang
Abstract: Oxytetracycline (OTC) is one of the extensive use antibiotics in livestock. Untreated waste of livestock and poultry breeding discharged into the soil or applied to the soil, directly, lead to pollution of soil in antibiotics. Current antibiotics pollutes caused problem to cause social attention more and more. As soil is the main destination of antibiotics like other pollutants, the antibiotics would eventually be accumulated in the soil when they entered the environment, researching antibiotics in soil migration and diffusion in water environment is important. To analyze environmental risks in antibiotics, and to provide reference basis for antibiotic pollution control, OTC in soil adsorption process and mechanism are conducted. Research showed that first-order kinetic equation model, double constant equation model, and parabolic equation can describe the adsorption process of OTC in soil. Under PH=7 condition, the strongest adsorption and the maximum adsorption capacity are appeared. Adsorption of OTC in soil has a certain mobility, and there are certain security threats in surface water and groundwater environment.
Authors: Hai Yi Huang, Liu Dan Luo, Hua Zhang, Yan Qin Lu, Di Zhang
Abstract: Grapefruit Peel, which is the main waste from a southern fruit-Grapefruit in Guangxi, China. It has been used as a raw material for activated carbons by chemical activation with NaOH for the removal of Congo red (Direct Red 28) from aqueous solution in this study. The adsorption of CR by Grapefruit peel carbon (GPC) was carried out by many parameters such as pH, dye initial concentration, agitation time and temperature. It is favorable for the adsorption of Congo red in acid condition. The adsorption experimental results were analyzed by using the Langmuir and Freundlich isotherms models. Adsorption kinetic data were followed pseudo-second-order model.
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