scholarly journals Biodepression of Copper-Activated Pyrite with Acidithiobacillus ferrooxidans in Flotation with Fresh and Seawater

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1039
Author(s):  
Francisca San Martín ◽  
Ignacio Valles ◽  
Willy Kracht ◽  
Tomás Vargas ◽  
Claudio Aguilar
Keyword(s):  
Acidithiobacillus Ferrooxidans ◽  
The Other ◽  
Industrial Scale ◽  
Xps Analysis ◽  
Pyrite Surface ◽  
Depressant Effect ◽  
Other Hand ◽  
Common Process ◽  
Ph Range

Acidithiobacillus ferrooxidans has been shown to be a good depressant of pyrite in freshwater and seawater flotation. However, the effect of these bacteria over copper-activated pyrite has not been studied. At the industrial scale, the activation of pyrite with copper is a common process that occurs because Cu2+ ions, released from other minerals, react with pyrite. This is a problem because Cu2+ ions facilitate the reaction of pyrite with the xanthate collectors, becoming hydrophobic and reaching the froth. In this study, microflotation experiments in a Hallimond tube were conducted to evaluate the depressant effect of A. ferrooxidans over non-activated and Cu-activated pyrite in freshwater and seawater flotation. The experiments were carried out at pH 4, 6, 8, 10 and 12 and pyrite was mixed with CuSO4 at 2.5×10−5 and 5×10−5 M in order to activate its surface. Considering the results obtained in the microflotation tests, it is possible to conclude that Acidithiobacillus ferrooxidans is able to depress non-activated and Cu-activated pyrite at the entire pH range studied (4–12) in freshwater. On the other hand, the use of bacteria in flotation with seawater proved to be effective to depress non-activated and Cu-activated pyrite at pH 8 and 10 with better results achieved at pH 10. At this pH, the non-activated pyrite recovery dropped from 96% to 15%, and the recovery of Cu-activated pyrite dropped from 95% to 32% when the activation was carried out at 2.5×10−5 M, and from 87% to 50% when the activation was conducted at 5×10−5 M of CuSO4. The XPS analysis showed that chalcopyrite and copper (II) hydroxide were formed on the pyrite surface when it is contacted with CuSO4.

scholarly journals The removal of Mg2+ and Ca2+ and turbidity from aqueous solution employing copolymerization of ethyl acrylate onto guar gum

2020 ◽  
Author(s):  
I. O. Ntwampe
Keyword(s):  
Guar Gum ◽  
Mine Drainage ◽  
Ethyl Acrylate ◽  
The Other ◽  
Adsorption Efficiency ◽  
Adsorption Removal ◽  
Other Hand ◽  
Calcium Removal ◽  
Ph Range ◽  
Magnesium Removal

Abstract Acid mine drainage collected from decant in Krugersdorp, South Africa, was treated in a series of laboratory experiments using synthesized copolymer of guar gum-g-polymer (GG) for the removal of calcium and magnesium and turbidity. 250 mL of sample and 25 mL distilled water were added into 16 Erlenmeyer flasks. The samples were irradiated in a micro-oven at 900 W for 3 min and the mixtures were placed in a soxhlet extractor for homopolymerization, after which they were dried and crushed. The results showed an exponential increasing adsorption efficiency of calcium removal with increasing pH range 2–4, and a slight increase between the pH range 4–8. On the other hand, the results showed a continuous increasing adsorption removal efficiency of magnesium with increasing pH in a range 2–8. The results showed a slight increasing adsorption efficiency of calcium removal with increasing dosage between 15 and 25 mg/L of GG, an exponential increase between 15 and 35 mg/L and resuming a slight increase between 45 and 55 mg/L dosage. On the other hand, the results showed an exponential increasing adsorption efficiency of magnesium removal between 15 and 54 mg/L dosage and slight increasing trend between 45 and 55 mg/L dosage.

scholarly journals Revisión: Aspectos fundamentales de la flotación de apatita, calcita, hematita, magnesita y cuarzo usando la bacteria Rhodococcus opacus

2019 ◽  
pp. 59-67
Keyword(s):  
Rio De Janeiro ◽  
Van Der Waals ◽  
Decisive Role ◽  
The Other ◽  
Rhodococcus Opacus ◽  
Sem Images ◽  
Other Hand ◽  
Wide Ph Range ◽  
Negative Surface ◽  
Ph Range

Revisión: Aspectos fundamentales de la flotación de apatita, calcita, hematita, magnesita y cuarzo usando la bacteria Rhodococcus opacus Carlos Alberto Castañeda Olivera1,2, Jhonatan Gerardo Soto Puelles2 1 Escuela Profesional de Ingeniería Ambiental, Universidad César Vallejo, Av. Alfredo Mendiola 6232, Los Olivos, Lima, Perú 2 Departamento de Ingeniería Química y de Materiales, Pontificia Universidad Católica de Rio de Janeiro, Rua Marquês de São Vicente, 225 – Gávea - Rio de Janeiro – CEP: 22453-900, Brasil Recibido 3 de agosto. Revisado 8 de diciembre. Aprobado 17 de diciembre 2019. DOI: https://doi.org/10.33017/RevECIPeru2019.0009/ Resumen Este artículo presenta una revisión sobre los estudios de la bacteria Rhodococcus opacus como bioreactivo en la flotación de minerales. La microflotación de apatita, calcita, hematita, magnetita y cuarzo mostró que la bacteria Rhodococcus opacus tiene potencial como un bioreactivo en la flotación mineral. Además, las mediciones electrocinéticas indicaron que la interacción electrostática juega un papel determinante en la adhesión bacteria-mineral. Por otro lado, la espectroscopía infrarroja con transformada de Fourier (FTIR), detectó una cantidad significativa de grupos carboxílicos y amino en la pared celular bacteriana; la disociación de estos grupos puede ser responsable de la carga superficial negativa de las bacterias en un amplio intervalo de pH, así como su punto isoeléctrico (PIE) ácido, alrededor de 2,5. Otros estudios como la teoría XDLVO y el enfoque termodinámico, informaron que las interacciones hidrofóbicas/hidrofílicas, así como las fuerzas de van der Waals también están implicados en los fenómenos de adhesión. Finalmente, las imágenes microscopía electrónica de barrido (MEB) confirmaron la afinidad y selectividad de la bacteria Rhodococcus opacus sobre las superficies minerales. Descriptores: Flotación, Rhodococcus opacus, bioreactivo, mineral. Abstract This article presents a review on the studies of the Rhodococcus opacus bacteria as bioreagent in mineral flotation. The microflotation of apatite, calcite, hematite, magnesite and quartz showed that the Rhodococcus opacus bacteria has potential as a bioreagent. In addition, electrokinetic measurements indicated that electrostatic interaction plays a decisive role in bacterial-mineral adhesion. On the other hand, On the other hand, Fourier transform infrared spectroscopy (FTIR) detected a significant amount of carboxylic and amino groups in the bacterial cell wall; the dissociation of these groups can be responsible for the negative surface charge of the bacteria over a wide pH range, as well as their isoelectric point (IEP) acid, around 2.5. Other studies, such as the XDLVO theory and the thermodynamic approach, reported that hydrophobic/hydrophilic interactions as well as van der Waals forces are also involved in adhesion phenomena. Finally, scanning electron microscopy (SEM) images confirmed the affinity and selectivity of the Rhodococcus opacus bacteria on the mineral surfaces. Keywords: Flotation, Rhodococcus opacus, bioreagent, mineral.

Non-equivalent preparations of the same drug

1971 ◽  
Vol 9 (17) ◽  
pp. 65-68
Keyword(s):  
Therapeutic Effect ◽  
Therapeutic Response ◽  
Body Fluids ◽  
The Other ◽  
Blood Levels ◽  
Biological Availability ◽  
Other Hand ◽  
Poorly Soluble ◽  
Ph Range

Pharmacopoeial standards for preparations of drugs have largely been developed on the assumption that tests of purity of the ingredients and of the amounts present would ensure uniformity of therapeutic effect. However, differences in formulation may affect the biological availability of the ingredients and the subsequent therapeutic response in many ways.1 2 For example two batches of a preparation which chemically can be shown to contain identical amounts of a drug may produce different blood levels and even dissimilar effects,3 especially where the drug is poorly soluble in water in the pH range of body fluids. On the other hand, with some drugs even a twofold difference in blood levels is clinically unimportant. It has been stated that “until ‘equivalence’ of products has been proven, ‘non-equivalence’ of two formulations of the same drug should be assumed”.4 But there are always likely to be minor variations between different formulations of the same drug, and it would probably be difficult to achieve ‘equivalence’ or to demonstrate that it had been attained.

scholarly journals Attachment of Acidithiobacillus ferrooxidans to pyrite in fresh and saline water and its fitting to Langmuir and Freundlich isotherms

2019 ◽  
Author(s):  
Francisca San Martín Robbiano ◽  
Karem Tello
Keyword(s):  
Fresh Water ◽  
Adsorption Isotherms ◽  
Acidithiobacillus Ferrooxidans ◽  
Saline Water ◽  
The Other ◽  
Freundlich Isotherms ◽  
A Value ◽  
Other Hand ◽  
Langmuir And Freundlich Isotherms ◽  
Langmuir And Freundlich Models

Attachment of bacteria Acidithiobacillus ferrooxidans to pyrite was investigated in two different environment: fresh water and saline water (water with 35 g/L of NaCl), in both cases at pH 4. Adsorption isotherms were ?tted to the Langmuir and Freundlich models. The results showed that the bacteria adhere to pyrite to a greater extent in fresh water than in saline water. The Langmuir and Freundlich models ?tted well the data obtained in fresh water, showing a coeffcient of determination (R2) approximately equal to 0.8 for both models. On the other hand, in saline water the models did not show a good coeffcient of determination with a value approximately equal to 0.4 for both models.

Purification and characterization of cycloisomaltotetraose-forming glucanotransferases from Agreia sp. D1110 and Microbacterium trichothecenolyticum D2006

2021 ◽  
Vol 85 (3) ◽  
pp. 600-610
Author(s):  
Akihiro Fujita ◽  
Akira Kawashima ◽  
Yuuki Mitsukawa ◽  
Noriaki Kitagawa ◽  
Hikaru Watanabe ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Culture Supernatant ◽  
Coupling Reaction ◽  
The Other ◽  
Purification And Characterization ◽  
Other Hand ◽  
Sds Page ◽  
Ph Range ◽  
Hydrolysis Of

ABSTRACT Glucanotransferases that can synthesize cyclo-{→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→} (CI4) from dextran were purified to homogeneity from the culture supernatant of Agreia sp. D1110 and Microbacterium trichothecenolyticum D2006. The molecular mass of both enzymes was estimated to be 86 kDa by SDS-PAGE. The glucanotransferase, named CI4-forming enzyme, from Agreia sp. exhibited the highest activity at pH 6.0 and 40 °C. The enzyme was stable on the pH range of 4.6-9.9 and up to 40 °C. On the other hand, the enzyme from M. trichothecenolyticum exhibited the highest activity at pH 5.7 and 40 °C. The enzyme was stable on the pH range of 5.0-6.9 and up to 35 °C. Both enzymes catalyzed 4 reactions, namely, intramolecular α-1,6-transglycosylation (cyclization), intermolecular α-1,6-transglycosylation, hydrolysis of CI4, and coupling reaction. Furthermore, the CI4-forming enzyme produced CI4 from α-1,6-linked glucan synthesized from starch by 6-α-glucosyltransferase. These findings will enable the production of CI4 from starch.

A Simple Co Salicide Process Using Silicidation by N2/H2 RTA

1998 ◽  
Vol 514 ◽  
Author(s):  
Mitsuru Sekiguchi ◽  
Masaru Moriwaki ◽  
Shinji Fujii ◽  
Shuichi Mayumi
Keyword(s):  
Sheet Resistance ◽  
The Other ◽  
Xps Analysis ◽  
Oxidation Of Co ◽  
Diffusion Layers ◽  
Residual Oxygen ◽  
Other Hand ◽  
Cap Layer ◽  
Standard Deviations

ABSTRACTFor Co salicide process, a TiN cap layer is widely used to prevent oxidation of Co layers during silicidation by RTA. In this study, N2/H2 mixture ambient is used to eliminate the need for the TiN cap layer. The sheet resistance for the sample fabricated by N2 RTA without TiN cap layer shows large standard deviations for narrow N+ diffusion layers and shows 20% higher values and large standard deviations for P+ diffusion layers. On the other hand, the samples with N2/H2 RTA provides the same low and stable sheet resistance as those of the samples with TiN cap layer. XPS analysis shows that N2/H2 RTA suppresses oxidation of Co during the 1st RTA because of reduction by H2. B impurity in PMOS regions is known to retard silicidation of Co at 500°C. The retardation of silicidation seems to enhance oxidation of Co in PMOS regions by residual oxygen in the RTA chamber.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

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