Chromium, the seventh most abundant element on earth is a transition metal from group VI-B .It is found in nature as the bound form constituting approximately 0.1 – 0.3 mg.g-1 of the earth’s crust. The name of the element is derived from the Greek word "chroma" meaning color, because many of its compounds are intensely colored. Cr is able to exist in several oxidation states, of which the trivalent Cr (III) and hexavalent Cr (VI) species are the most stable and abundant forms (Zayed & Terry et al., 2003).
The most stable form of chromium is its trivalent oxidation state which is primarily found geologically as chromite (FeCr2O4) (Cervantes et al., 2001). Cr (III) is naturally occurring, whereas Cr (VI) is of anthropogenic origin. This is as a result of the dissolution of chromite and the subsequent oxidation of Cr (III) to aqueous Cr (VI) in the presence of the common manganese mineral, birnessite (Oze et al., 2007). Cr (VI) usually associates with oxygen to form the oxyanions chromate (CrO42-) and dichromate (Cr2O7 2- ). Cr (VI) compounds are highly soluble and therefore mobile within aquatic systems, whereas derivatives of Cr(III) in the forms of hydroxides, oxides and sulphates, are water insoluble and exist mostly bound to organic matter in soils and aquatic systems(Cervantes,C et al.,2001; Zayed & Terry, 2003).
Chromium differs widely in physicochemical properties and biological reactivity with respect to its oxidation states. While Cr (VI) species and dichromate’s are extremely water soluble and mobile in the environment, Cr (III) species are much less soluble and comparatively immobile (Viamajala et al., 2004).
Chromium is an essential micronutrient required for the growth of many microorganisms for the mainten...
... middle of paper ...
... heavymetals (Ha et al., 2010).Majority of the bacteria used in the biosorption systems produce EPS plays a key role as bio-sorbents for metal remediation and recovery (Sheng GP et al.,2010).. There are several negatively charged functional groups such as hydroxyl, carboxyl, phenolic and sulfhydryl present in the EPS which help in the adsorption of chromium (Sethuraman P et al., 2010). Exopolysaccharides (EPS) which help in attachment, tolerance and reduction of hexavalent chromium (Ozturk et al., 2009).
Studies relating to reduction of hexavalent chromium to trivalent form by native microbial species isolated from different sources have been reported in past (Sethuraman P et al., 2010; Wei-hua XU et al., 2009; K. Sundar et al., 2011). The pivotal role of EPS along with the cell in the adsorption and reduction of chromium has been noted (K. Sundar et al., 2011).
One of the more recent improvements to GKN’s safety and health is the regulation of Chromium. Where GKN uses Chromium, is in their paint booths, clean and prime line, and chemical processing areas. Additionally, chromium is released in areas that sand, grind or drill on primed parts. Many areas have products containing chrome, but do not use them in large quantities.
The existence of Cyanobacteria is of vital importance to all life on planet earth. The process by which the amospehere of planet earth changed, from its early atmosphere to what it is present day is due to the process of photosynthesis, which is originated in a Cyanobacterium. Oxygenic photosynthesis is what made Cyanobacteria unique among the early organisms on planet earth whereby it used Carbon dioxide from the atmospehere and water as an electron donor to produce carbohydrates, releasing oxygen as a byproduct. In comparison, other early organisms on planet earth produced energy via
...Coauthor, ChemBioChem 2006, 7, 1-10; b) A. Author, B. Coauthor, Angew. Chem. 2006, 118, 1-5; Angew. Chem. Int. Ed. 2006, 45, 1-5.))
Another study proposed that CR slowed aging process by increasing resistance to hyperoxidation. As aging progressed in yeast and other animals, the presence of free radicals increased in the cells. Usually, the levels of the...
As a species, Cyanobacteria are chemically diverse, and owe their bluish colour to the pigment phycocyanin, which is used to capture light for photosynthesis. Because they are able to photosynthesize, they are able to...
An element in chemistry is more than just an element; at least Chlorine is more than just an element. It is very useful in many ways that help people today. Chlorine is a common nonmetallic element belonging to the halogens; it is a heavy yellow irritating toxic gas; it is used to purify water and as a bleaching agent and disinfectant; occurs naturally only as a salt. People should know more about the uses of chlorine and why chlorine is used in many processes, for example; bleaching, and why we use it today. Everything has to start somewhere, and chlorine was produced many years ago.
The purpose of this experiment is to use our knowledge from previous experiments to determine the theoretical, actual, and percent yields of the lead chromate from the reaction of solutions of potassium chromate and lead nitrate (Lab Guide pg. 83).
Dyes, the complicated aromatic substances mostly used to colorize different materials. Sometimes they combine on structural area with heavy metals, are examined to have comparatively unsatisfactory results on the nearby environment because of its inhibitory and toxic response (Mohan et al., 2005).
Thickett, Geoffrey. Chemistry 2: HSC course. N/A ed. Vol. 1. Milton: John Wiley & Sons Australia, 2006. 94-108. 1 vols. Print.
There are several types of treatment methods present but biological treatment methods have gained much traction in the recent years due to their low operation costs, comparatively benign effects on the environment and their ease of handling and maintenance. Biological wastewater treatment methods can be subcategorized into dispersed growth systems and attached growth systems. Biofilms fall under the latter category (Sehar & Naz, 2016)
2. Thompson, Stephen. PSU Version of Chemtrek: August 2000 to July 2001. Englewood Cliffs: Prentice Hall, 2000.
Numerous works (Abreu &Campana-Filho, 2009; An, Dung, Thien, Dong, &Nhi, 2008; Anitha et al., 2009; Ge&Luo, 2005; Hjerde, Varum, Grasdalen, Tokura, &Smidsrod, 1997; Kittur, Harish Prashanth, UdayaSankar, &Tharanathan, 2002; Mourya, Inamdar, &Tiwari, 2010; Muzzarelli, Tanfani, &Emanuelli, 1984; Rinaudo, Dung, Gey, &Milas, 1992; Xu, Xin, Li, Huang, & Zhou, 2010) have been carried out on CM-chitosan. Du &Hsieh(2008) showed that longer alkalization and ca...
However, when the pH levels reach a certain stage, the iron can then precipitate out, coating sediments with the characteristic yellow, red or orange colourings (D.E.P. 2, 2002; U.S.G.S. ; U.S.E.P.A., 2002). The rate that A.M.D. advances is also influenced by the presence of certain bacteria (Doyle; U.S.G.S). A.M.D. that has dissolved heavy metals such as copper, lead and mercury can contaminate ground and surface water.
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
V. Amarnath, D. C. Anthony, K. Amarnath, W. M. Valentine, L. A. Wetterau, D. G. J. Org. Chem. 1991, 56, p. 6924-6931.