Factors affecting chromium(VI) reduction by Thiobacillus ferrooxidans

Poisonous heavy metals in air, water, and soil produce global environmental problems that are considerable threats to humankind. To meet the local and international guidelines for heavy metal release, companies often use different approaches, such as chemical precipitation, chelating agents, or activated carbon produced by adsorption. One of these heavy and toxic metals is chromium(VI). Chromium(VI) is commonly used in many applications, such as dye fixation in the textile industry or as an anticorrosive agent in paints. The aim of this paper is to explore the factors affecting the removal of one of these deadly heavy metals, chromium(VI), from aqueous solutions. For this purpose, activated carbon from Turkish Tunçbilek lignite is prepared with both chemical and physical activation methods to investigate the adsorption behavior of chromium(VI). The effects of initial chromium(VI) concentration, adsorption temperature, and pH on adsorption are studied using a design of experiments method with a full 24 factorial design with center points. The Freundlich and Langmuir adsorption isotherms that are commonly used in chemical engineering are also applied both for predicting the amount of chromium(VI) adsorbed and confirming the validity and advantages of the obtained regression model. The results indicate that the design of experiments and regression can explain and support the design of new materials by using linear and physically meaningful equations instead of local nonlinear and empirical models that are usually insufficient. Additionally, three experiments were carried out in the liquid phase to test the activated carbon samples: chromium, chromium and sucrose, and chromium-sucrose-ion. A change in adsorption capacities of the activated carbon samples was observed. Sucrose was chosen for the experiments because it contains six carbon atoms in a slightly soluble structure. The results indicated that Tunçbilek lignite exhibits good adsorption capability.

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FACTORS AFFECTING METABOLISM AND FERROUS IRON OXIDATION IN SUSPENSIONS AND BATCH CULTURES OF THIOBACILLUS FERROOXIDANS: RELEVANCE TO FERRIC IRON LEACH SOLUTION REGENERATION

Metallurgical Applications of Bacterial Leaching and Related Microbiological Phenomena ◽

10.1016/b978-0-12-511150-8.50008-3 ◽

1978 ◽

pp. 19-44 ◽

Cited By ~ 30

Author(s):

D.P. Kelly ◽

C.A. Jones

Keyword(s):

Ferrous Iron ◽

Ferric Iron ◽

Thiobacillus Ferrooxidans ◽

Iron Oxidation ◽

Leach Solution ◽

Factors Affecting ◽

Batch Cultures ◽

Ferrous Iron Oxidation

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Factors Affecting the Adsorption of Chromium (VI) on Activated Carbon

Journal of Environmental Science and Health Part A ◽

10.1080/10934520600779265 ◽

2006 ◽

Vol 41 (9) ◽

pp. 1967-1980 ◽

Cited By ~ 17

Author(s):

REHA YAVUZ ◽

İLKÜN ORBAK ◽

NILGÜN KARATEPE

Keyword(s):

Activated Carbon ◽

Factors Affecting ◽

Chromium Vi

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Two factors affecting on iron-oxidizing activities of Thiobacillus ferrooxidans.

Agricultural and Biological Chemistry ◽

10.1271/bbb1961.45.393 ◽

1981 ◽

Vol 45 (2) ◽

pp. 393-403 ◽

Cited By ~ 5

Author(s):

Tsuyoshi SUGIO ◽

Tatsuo TANO ◽

Kazutami IMAI

Keyword(s):

Thiobacillus Ferrooxidans ◽

Factors Affecting ◽

Two Factors

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Progress In The Practical Application Of Automated Image Analysis To Tem Negatives

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078614 ◽

1977 ◽

Vol 35 ◽

pp. 214-217

Author(s):

F. A. Heckman ◽

E. Redman ◽

J.E. Connolly

Keyword(s):

Image Analysis ◽

Image Quality ◽

Exposure Time ◽

Image Contrast ◽

Automated Image Analysis ◽

Practical Application ◽

Factors Affecting ◽

High Image Quality ◽

Qualitative Evidence ◽

Comprehensive Study

In our initial publication on this subject1) we reported results demonstrating that contrast is the most important factor in producing the high image quality required for reliable image analysis. We also listed the factors which enhance contrast in order of the experimentally determined magnitude of their effect. The two most powerful factors affecting image contrast attainable with sheet film are beam intensity and KV. At that time we had only qualitative evidence for the ranking of enhancing factors. Later we carried out the densitometric measurements which led to the results outlined below.Meaningful evaluations of the cause-effect relationships among the considerable number of variables in preparing EM negatives depend on doing things in a systematic way, varying only one parameter at a time. Unless otherwise noted, we adhered to the following procedure evolved during our comprehensive study:Philips EM-300; 30μ objective aperature; magnification 7000- 12000X, exposure time 1 second, anti-contamination device operating.

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Scanning Electron Microscope Study of Bacteria on Mineral Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100090634 ◽

1976 ◽

Vol 34 ◽

pp. 130-131

Author(s):

V.K. Berry

Keyword(s):

Oxidation Reaction ◽

Electron Microscope Study ◽

Elemental Sulfur ◽

Thiobacillus Ferrooxidans ◽

Physical Contact ◽

Metal Sulfides ◽

Low Grade ◽

Mineral Surfaces ◽

Mineral Surface ◽

Scanning Electron Microscope Study

There are two strains of bacteria viz. Thiobacillus thiooxidansand Thiobacillus ferrooxidanswidely mentioned to play an important role in the leaching process of low-grade ores. Another strain used in this study is a thermophile and is designated Caldariella .These microorganisms are acidophilic chemosynthetic aerobic autotrophs and are capable of oxidizing many metal sulfides and elemental sulfur to sulfates and Fe2+ to Fe3+. The necessity of physical contact or attachment by bacteria to mineral surfaces during oxidation reaction has not been fairly established so far. Temple and Koehler reported that during oxidation of marcasite T. thiooxidanswere found concentrated on mineral surface. Schaeffer, et al. demonstrated that physical contact or attachment is essential for oxidation of sulfur.

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Factors affecting microstructural scale in liquid crystalline polymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100174230 ◽

1990 ◽

Vol 48 (4) ◽

pp. 220-221

Author(s):

Christine M. Dannels ◽

Christopher Viney

Keyword(s):

Liquid Crystalline ◽

Liquid Crystalline Polymers ◽

Factors Affecting ◽

Crystalline Polymers ◽

Thermal Expansion Coefficients ◽

Low Thermal Expansion ◽

Lower Viscosity ◽

Fine Microstructure ◽

Planar Orientation ◽

Strength And Stiffness

Processing polymers from the liquid crystalline state offers several advantages compared to processing from conventional fluids. These include: better axial strength and stiffness in fibers, better planar orientation in films, lower viscosity during processing, low solidification shrinkage of injection moldings (thermotropic processing), and low thermal expansion coefficients. However, the compressive strength of the solid is disappointing. Previous efforts to improve this property have focussed on synthesizing stiffer molecules. The effect of microstructural scale has been overlooked, even though its relevance to the mechanical and physical properties of more traditional materials is well established. By analogy with the behavior of metals and ceramics, one would expect a fine microstructure (i..e. a high density of orientational defects) to be desirable.Also, because much microstructural detail in liquid crystalline polymers occurs on a scale close to the wavelength of light, light is scattered on passing through these materials.

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