Effects of Some Multivalent Ions on Coagulation and Electrokinetic Behaviours of Colemanite Particles

2013 ◽  
Vol 66 (1) ◽  
pp. 3
Author(s):  
Havvanur Ucbeyiay ◽  
Alper Ozkan
Keyword(s):  
Zeta Potential ◽  
Zero Point ◽  
The Other ◽  
Ferric Ions ◽  
Ph Values ◽  
Zero Point Of Charge ◽  
Maximum Value ◽  
Multivalent Ions ◽  
Ph Range ◽  
Good Agreement

The effects of magnesium, barium, aluminium, and ferric cations as multivalent ions on the coagulation and electrokinetic behaviours of colemanite have been investigated in relation to pH and cation concentration. The zero point of charge for colemanite was determined to be at pH 10.2. The positive surface charge of colemanite increased in the presence of multivalent ions at pH values below the zero point of charge. Also, these ions changed the zeta potential of colemanite from negative to positive within the pH range 10.2 to 12. In the experiments, the coagulation of colemanite with ferric ions was more efficient than with the other ions and the effect of ferric ions varied considerably depending on the concentration and pH. The coagulation recovery values of colemanite suspension increased quickly up to 2.5 × 10–3 M concentration of ferric ions and the maximum value (~93 %) was obtained at a pH of 11.5. It was also found that the coagulation behaviour of the colemanite suspension in the presence of multivalent cations was in good agreement with the electrokinetic characteristics.

Long-term in vitro transformation of 2-line ferrihydrite to goethite/hematite at 4, 10, 15 and 25°C

Clay Minerals ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 433-438 ◽  
Author(s):  
U. Schwertmann ◽  
H. Stanjek ◽  
H.-H. Becher
Keyword(s):  
Zero Point ◽  
Transformation Rate ◽  
Ambient Temperatures ◽  
Ph Values ◽  
In Vitro Transformation ◽  
Zero Point Of Charge ◽  
Ph Range ◽  
Increasing Temperature

Abstract2-line ferrihydrite stored in water at ambient temperatures from 4 to 25°C and at ten different pH values between 2.5 and 12 for up to 10–12 y transformed to both goethite and hematite at all temperatures and pH values except at pH 12 where only goethite was formed. The rate and degree of transformation (20–100%) increased with increasing pH and temperature. The hematite/ (hematite+goethite) ratio varied between 0 and ~0.8, increased with increasing temperature and showed a strong maximum at pH 7–8 which increased from 0.1–0.2 at 4°C to 0.7–0.8 at 25°C. The maximum coincides with the zero point of charge of ferrihydrite where its solubility and, thus, its via-solution transformation rate to goethite are minimal. We assume, therefore, that in this pH-range the (slower) via-solution transformation to hematite can more efficiently compete with that to goethite.

Über die Wechselwirkung des Vanadyl(IV)-Kations mit Nucleobasen / Interaction of the Vanadyl(IV) Cation with Nucleic Bases

1993 ◽  
Vol 48 (12) ◽  
pp. 1845-1847 ◽  
Author(s):  
P. A. M. Williams ◽  
S. B. Etcheverry ◽  
E. J. Baran
Keyword(s):  
The Other ◽  
Ph Values ◽  
Nucleic Bases ◽  
Wide Ph Range ◽  
Ph Range ◽  
Oxygen Donors

The interaction of VO2+ with the nucleic bases adenine, guanine, cytosine, thymine and uracil has been investigated spectrophotometrically in a wide pH-range and with metal to base ratios 1:1 and 1:10. Adenine, guanine and uracil interact with the cation at pH-values >5, but whereas adenine apparently coordinates through Natoms, the other two bases seem to be coordinated through oxygen donors.

scholarly journals Cytochrome P450 102A2 Catalyzes Efficient Oxidation of Sodium Dodecyl Sulphate: A Molecular Tool for Remediation

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Irene Axarli ◽  
Ariadne Prigipaki ◽  
Nikolaos E. Labrou
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Reaction Rate ◽  
Sodium Dodecyl ◽  
Cytochrome P450s ◽  
Ph Values ◽  
Maximum Value ◽  
Endogenous Compounds ◽  
Ph Range ◽  
Bell Shaped Curve

Bacterial cytochrome P450s (CYPs) constitute an important family of monooxygenase enzymes that carry out essential roles in the metabolism of endogenous compounds and foreign chemicals. In the present work we report the characterization of CYP102A2 from B. subtilis with a focus on its substrate specificity. CYP102A2 is more active in oxidation of sodium dodecyl sulphate (SDS) than any other characterized CYP. The effect of SDS and NADPH concentration on reaction rate showed nonhyperbolic and hyperbolic dependence, respectively. The enzyme was found to exhibit a bell-shaped curve for plots of activity versus pH, over pH values 5.9–8.5. The rate of SDS oxidation reached the maximum value approximately at pH 7.2 and the pH transition observed controlled by two ps in the acidic and basic pH range. The results are discussed in relation to the future biotechnology applications of CYPs.

The Beryllium Group

2010 ◽  
Author(s):  
George K. Schweitzer ◽  
Lester L. Pesterfield
Keyword(s):  
Charge Density ◽  
Principal Quantum Number ◽  
The Other ◽  
Outer Electron ◽  
Protective Oxide ◽  
Ph Values ◽  
Figure Legend ◽  
Alkaline Earths ◽  
Ph Range ◽  
Reactive Metals

The elements which constitute the Be Group of the Periodic Table are known as the alkaline earths. They are beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra. All six of the elements have atoms characterized by an outer electron structure of ns2 with n representing the principal quantum number. The elements exhibit marked resemblances to each other with Be differing considerably. This deviation is assignable to the small size of Be which causes the positive charge of Be+2 to be concentrated, that is, the charge density is high. The higher charge-density ions attack HOH to attach OH− and to liberate H+, that is, they hydrolyze readily. All of the elements exhibit oxidation numbers of 0 and II, with their chemistries being dominated by the oxidation state II. The six metals are exceptionally reactive, being strong reductants, reacting with acids, HOH, and bases at all pH values to give H2. The other product of such reactions are M+2 ions and M(OH)2, the ions being present at lower pH values and the hydroxides being present at higher pH values. The transition from M+2 to M(OH)2 occurs at increasing pH values from Be to Ra, such that the hydroxide of Sr is slightly soluble and those of Ba and Ra are soluble. These soluble hydroxides are strong bases. Ionic sizes in pm for the members of the group are as follows: Be (59), Mg (72), Ca (100), Sr (132), Ba (135), and Ra (148). The E° values for the M+2/M couples are as follows: Be (−1.97 v), Mg (−2.36 v), Ca (−2.87 v), Sr (−2.89 v), Ba (−2.91 v), and Ra (−2.91 v), indicating that they are very reactive metals. a. E–pH diagram. The E–pH diagram for 10−1.0 M Be is presented in Figure 6.1. In the figure legend are equations which describe the lines separating the species. It can be seen that Be is thermodynamically unstable with respect to H+, HOH, and OH−. However, Be is relatively inactive in the middle pH range due to a protective oxide coat. To dissolve Be, dilute acids such as HCl or H2SO4, or bases such as NaOH or KOH are required.

Solubility of Niobium(V) under Cementitious Conditions: Importance of Ca-niobate

2004 ◽  
Vol 824 ◽  
Author(s):  
Caterina Talerico ◽  
Michael Ochs ◽  
Eric Giffaut
Keyword(s):  
Solid Phase ◽  
Empirical Relation ◽  
Oxide Phase ◽  
X Ray Diffraction ◽  
Ph Values ◽  
Wide Range ◽  
Ph Conditions ◽  
Predicted Values ◽  
Ph Range ◽  
Good Agreement

AbstractThe solubility of niobium was investigated for Ca and pH conditions relevant for cementequilibrated solutions. For the pH range considered (9.5-13.2), the dissolved Nb concentration decreases with increasing pH. Overall, experiments lead to Nb concentrations between 2·10-5 M and 2·10-9 M. For all pH values, the dissolved Nb concentration also decreases systematically with increasing Ca concentration. X-ray diffraction measurements of selected experiments confirmed the presence of a solid Ca-Nb-oxide phase, with CaNb4O11·8H2O (hochelagaite) being the most likely composition. On the basis of these findings an empirical regression model for the prediction of Nb solubility data as a function of pH and Ca concentration was derived. This empirical relation is consistent with the presence of a solubility limiting Ca-Nb solid phase and permits to predict aqueous Nb solubility values in cementitious environments over a relatively wide range of conditions. Predicted values are in good agreement with independent experimental results.

Agglomerate formation during drying

2003 ◽  
Vol 18 (2) ◽  
pp. 495-506 ◽  
Author(s):  
Alejandro Vertanessian ◽  
Andrew Allen ◽  
Merrilea J. Mayo
Keyword(s):  
Zeta Potential ◽  
Isoelectric Point ◽  
Direct Consequence ◽  
Ph Values ◽  
Diffusion Limited ◽  
X Ray Scattering ◽  
Primary Particles ◽  
Small Primary ◽  
Ph Range ◽  
Size Scales

The evolution of agglomerate structure during drying of particles from suspension has been studied for a nanocrystalline Y2O3 (8% mol fraction)-stabilized ZrO2 powder. Agglomerates in drying and dried suspensions were examined at the smallest size scales (1 nm to 1 μm) using ultra-small angle x-ray scattering (USAXS) and at the largest size scales (100 nm to 10 μm) using scanning electron microscopy. The results were correlated with the degree of particle dissolution in each suspension (measured by flame absorption spectroscopy of the suspension filtrate) and the zeta potential of the particles in suspension prior to drying. Results show that large agglomerates readily form across a pH range from 2 to 9. The fact that Y+3 ion dissolution varies by over four orders of magnitude in this range leads to the conclusion that there is little direct correlation between the degree of Y dissolution and agglomeration in this system (Zr ion dissolution was below the detection limit at all pH values studied). The observation of large agglomerates well before the introduction of air-water interfaces into the drying mass likewise leads to the conclusion that capillary forces are not essential to agglomerate formation. Instead, agglomerates appear to form as a direct consequence of increasing suspension concentration. Zeta potential also plays a role. Specifically, there was a notable change in agglomerate morphology as the isoelectric point was approached, at approximately pH 8. Here USAXS shows the particles in suspension to have a layered interior structure, with small primary particles aggregated in sheets to form each blocky particle. This is in contrast to the more rounded agglomerates formed away from the isoelectric point, which appear to be composed of the same primary particles arranged in chainlike structures. USAXS of powders from the dried suspensions confirms that the structures seen after drying are the same as those present in suspension. The two structural morphologies are attributed to diffusion-limited (sheets) versus reaction-limited (chains) aggregation, respectively.

scholarly journals Spectrophotometric determination of pyridoxal and pyridoxal 5′-phosphate with 3-methyl-2-benzothiazolone hydrazone hydrochloride, and their selective assay

1969 ◽  
Vol 114 (3) ◽  
pp. 629-633 ◽  
Author(s):  
Kenji Soda ◽  
Takamitsu Yorifuji ◽  
Haruo Misono ◽  
Mitsuaki Moriguchi
Keyword(s):  
Absorption Spectra ◽  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
The Other ◽  
Selective Determination ◽  
Characteristic Absorption ◽  
Ph Values ◽  
Alkaline Conditions ◽  
Ph Range

A spectrophotometric method with 3-methyl-2-benzothiazolone hydrazone hydrochloride was developed for the determination of pyridoxal and pyridoxal 5′-phosphate, and for the selective determination of each in the presence of the other. Pyridoxal and pyridoxal 5′-phosphate react with the reagent to yield the azine derivatives, which give characteristic absorption spectra. The highest extinction values are obtained when pyridoxal and pyridoxal 5′-phosphate are incubated at pH values of about 3·4 and 8·0 respectively; their maxima are at 430nm. (∈ 2·74×104) and 380nm. (∈ 2·24×104) respectively. The azine of pyridoxal is only slightly soluble under the neutral and alkaline conditions, whereas that of pyridoxal 5′-phosphate is substantially insoluble in the acid pH range. This difference in solubility of the azines made possible the selective determination of pyridoxal and pyridoxal 5′-phosphate. α-Oxoglutarate and pyruvate are among the substances shown not to interfere with the assay of pyridoxal; their derivatives absorb appreciably only at wavelengths below 420nm. For the assay of pyridoxal 5′-phosphate in the presence of these compounds measurement at 390nm. is necessary.

scholarly journals Optimization of Tungsten Carbide Opposite Anvils Used in the In Situ High-Pressure Loading Apparatus

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Zhang Ying ◽  
Chen Xiping ◽  
Sun Guangai ◽  
Lu Yuping ◽  
Gong Jian ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Tungsten Carbide ◽  
The Other ◽  
Von Mises Stress ◽  
Pressure Loading ◽  
Support Ring ◽  
Maximum Value ◽  
Von Mises ◽  
Good Agreement

In order to optimize the structure of anvils, finite element method is used to simulate two kinds of structures, one of which has a support ring but the other one does not. According to the simulated results, it is found that the maximum value of pressure appears at the center of culet when the bevelled angle is about 20°. Comparing the results of these two kinds of structures, we find that the efficiency of pressure transformation for the structure without support ring is larger than that for the structure with support ring. Considering the effect of von Mises stress, two kinds of tungsten carbide opposite anvils have been manufactured with bevelled angle of 10°. The experimental results for these two anvils are in good agreement with the simulation.

The Malachite Green Biodegradation in Bioreactors on Various pH Domains

2019 ◽  
Vol 70 (8) ◽  
pp. 2996-2999
Author(s):  
Viorel Gheorghe ◽  
Catalina Gabriela Gheorghe ◽  
Andreea Bondarev ◽  
Vasile Matei ◽  
Mihaela Bombos
Keyword(s):  
Malachite Green ◽  
Contact Time ◽  
Dominant Species ◽  
Wastewater Treatment Plants ◽  
Organic Substances ◽  
Biological Degradation ◽  
Growth Promoters ◽  
Ph Values ◽  
Biological Sludge ◽  
Ph Range

In the experimental study was studied the malachite green colorant biodegradation in biological sludge with biological activity. The biodegradability tests were carried out in laboratory bioreactors, on aqueous solutions of green malachite contacted with microorganisms in which the dominant species is Paramecium caudatum, in a pH range between 8 and 12, temperatures in the ranges 25-350C, using pH neutralizing substances and biomass growth promoters. The colorant initial concentrations and those obtained after biological degradation depending on the contact time, at certain pH values, were established through UV-Vis spectrometry. The studies have shown the measure of possible biological degradation of some organic substances with extended uses, with largely aromatic structure, resistance to biodegradation of microorganisms, commonly used in wastewater treatment plants.

Removal of Trace Metals From Wastewater by Activated Carbon

1973 ◽  
Vol 8 (1) ◽  
pp. 110-121
Author(s):  
A. Netzer ◽  
J.D. Norman
Keyword(s):  
Activated Carbon ◽  
Trace Metals ◽  
Organic Compounds ◽  
The Other ◽  
Published Data ◽  
Ph Adjustment ◽  
Nickel Silver ◽  
Ph Range ◽  
Carbon Treatment ◽  
Cobalt Copper

Abstract The merits of activated carbon for removal of organic compounds from wastewater have been well documented in the literature. On the other hand there is a lack of published data on the use of activated carbon for the removal of trace metals from wastewater. Experiments were designed to assess the possibility that activated carbon treatment would remove aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, silver and zinc from wastewater. All metals studied were tested over the pH range 3-11. Greater than 99.5% removal was achieved by pH adjustment and activated carbon treatment for most of the metals tested.

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