Chromium, environmental impact

Chromium lignosulfonates are the biggest contributions to heavy metals in drilling fluids. Although studies have shown minimal environmental impact, substitutes exist that can result in lower chromium levels in muds. The less used chromium lignites (trivalent chromium complexes) are similar in character and performance with less chromium. Nonchromium substitutes are effective in many situations. Typical total chromium levels in muds are 100-1000 mg/1. 

The environmental impact of the two most toxic pollutants, nickel and chromium, is briefly presented in the following.11617 Significant concentrations of these elements pass through conventional treatment plants. 

Heavy metals are widely used as catalysts in the manufacture of anthraquinonoid dyes. Mercury is used when sulphonating anthraquinones and copper when reacting arylamines with bromoanthraquinones. Much effort has been devoted to minimising the trace metal content of such colorants and in effluents from dyemaking plants. Metal salts are used as reactants in dye synthesis, particularly in the ranges of premetallised acid, direct or reactive dyes, which usually contain copper, chromium, nickel or cobalt. These structures are described in detail in Chapter 5, where the implications in terms of environmental problems are also discussed. Certain basic dyes and stabilised azoic diazo components (Fast Salts) are marketed in the form of tetrachlorozincate complex salts. The environmental impact of the heavy metal salts used in dye application processes is dealt with in Volume 2. 

The liquid and solid effluents are well characterized. As the ACW I Committee noted in its original and supplemental reports, the gaseous process emissions will have to be characterized for health risk assessments and environmental risk assessments required by EPA guidelines (NRC, 1999, 2000a). These results, along with the results of analyses of metals emissions (including chromium VI), can be used to assess the environmental impact of a facility through accepted risk-assessment methods (EPA, 1998). 

Selenium (masses 74, 76, 77, 78, 80, and 82 Table 1) and chromium (masses 50, 52, 53 54 Table 1) are treated together in this chapter because of their geochemical similarities and similar isotope systematics. Both of these elements are important contaminants in surface and ground water. They are redox-active and their mobility and environmental impact depend strongly on valence state and redox transformations. Isotope ratio shifts occur primarily during oxyanion reduction reactions, and the isotope ratios should serve as indicators of those reactions. In addition to environmental applications, we expect that there will be geological applications for Se and Cr isotope measurements. The redox properties of Se and Cr make them promising candidates as recorders of marine chemistry and paleoredox conditions. 

Although both copper and, to a greater extent, chromium (Cox and Richardson, 1978 Richardson and Cox, 1985) have associated environmental impacts, particular concerns have been expressed regarding the use of arsenic. 

Figure 9.1 compares the synthesis of acetophenone by classic oxidation of 1-phenylethanol with stoichiometric amounts of chromium oxide and sulphuric acid, with an atom efficiency of 42%, with the heterogeneous catalytic oxidation with O2, with an atom efficiency of 87%, and with water as the only by-product. This is especially important if we consider the environmental unfriendliness of chromium salts the potential environmental impact of reactions can be expressed by the environmental quotient (EQ), where E is the E-factor (kg waste/kg product) and Q is the environmental unfriendliness quotient of the waste. If Q is... 

Acid rain is a threat to our environment because it can increase the concentration of toxic metal ions, such as Cd and Cr, in rivers and streams. If cadmium and chromium are present in sediment as Cd(OH)2 and Cr(OH)3, write reactions that demonstrate the effect of acid rain. Use the library to find the properties of cadmium and chromium responsible for their environmental impact. 

The production volume as well as the atom economy is widely used for the classification of chemical processes. The atom economy describes the number of atoms of all starting materials, which are transferred into the product [4]. But these criteria include not all aspects of chemical processes, for example loss of solvents (amount of waste), type of waste and energy balance. An additional aspect to include in these criteria is the E-factor (environmental factor). The E-factor was first discussed by R. A. Sheldon and is defined as kg by-product per kg product. The E-factor is associated with type of waste, because 1 kg of sodium chloride or 1 kg of sodium cyanide or chromium oxide will have different environmental impacts as waste products [5-8]. 

One environmental concern is that around the world there are landfill areas where over the years chromite ore processing residues (COPR) have been dumped, and chromium from these landfills is being leached into the ground water. The environmental impact of chromium in soils and sediments is dependent on specia-tion and on the response of the matrix to biological and physico-chemical conditions. These factors control the mobilization of chromium from the solid into the aquatic phase and uptake and transfer into living systems (Hursthouse 2001). 

Bianchi has suggested that the accepted inactivity of chromium(III) as a genotoxic agent should be questioned, and that the environmental impact of chromiu-m(III) accumulation is worth reconsidering (Bianchi and Levis 1988). Data needs in several areas of chromium exposure have been identified (Agency for Toxic Substances and Disease Registry 1998). 

EnvirOTimental trends are having an impact on electrical applications. Waste legislation includes WEEE (Waste of Electrical and Electronic Equipment) directive 2002/%/EC which holds producers responsible for collection and recovery of materials at end of Ufe. Additionally, materials that contain bromine-based flame retardants must be removed from the waste and handled separately. In restrictions on use of hazardous substances (ROHS) directive 2002/95/EC, the use of various hazardous materials is restricted. These include lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ether. Since the introduction of Blue Angel in Germany in 1978, several other eco-labels have been implemented. These include TCO (Sweden), Nordic Swan, Milieukeur (Netherlands), and the EU Ecolabel. The general purpose of these labels is to provide cmisumers with information relating to the environmental impact of the products they purchase. 

Chromate(VI)-based pre-treatments have historically been used to protect aluminium alloys. When the Cr(VI) species comes into contact with an aluminium substrate, a complex chromium oxide film is formed which provides excellent corrosion protection. Unfortunately, due to their toxicity and adverse environmental impact, these types of pre-treatment will be banned within Europe and North America. Many reports have shown that chromium(VI) is a carcinogen, and can cause kidney and liver damage, and even death [2,3]. Henee, there is an urgent need to provide corrosion protection systems for aluminium, and other active systems, that are accepted as being environmentally-compliant . 

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