Chrome pigments

As a result of variation shown in toxicity, the evaluation of technologies applicable for discharge control, and treatment by some compounds within the industrial chemicals, the SIC 281 groups are further subdivided into 11 subcategories.23 They are aluminum fluoride, chlor-alkali, chrome pigments, copper sulfate, hydrofluoric acid, hydrogen cyanide, nickel sulfate, sodium bisulfate, sodium... 

Water is used in the chrome pigment industry mainly to cool most of the equipment such as heat exchangers, generate steam in the boilers, make slurry of raw materials, scrub the reactor vent... 

Results of raw waste load found in verification sampling of a chrome pigment plant are given in Table 22.10. 

In addition to the heavy metals stated in Table 22.10, ferro- and ferricyanide are also part of the pollutants in the wastewater generated in a chrome pigment plant. These wastes are generally combined and treated through reduction, precipitation, equalization, and neutralization to be followed by clarification and filtration processes. Most of the heavy metals are precipitated using lime or caustic soda at specific pH. Chromium is reduced by S02 to a trivalent form, wherein it is precipitated as chromium hydroxide at specific pH. Sodium bisulfide is also employed to precipitate some of the metals at a low pH. The treated water is recycled for plant use while the sludge is sent to landfills (Figure 22.7). 

Some other types of treatment processes can be employed in the chrome pigment industry in order to achieve safer industrial practices in terms of pollution. Processes such as ion exchange, biological oxidation, and use of glass for filtration before settling have potential application in this industry. 

Summary of Raw Waste Loadings Found in Verification Sampling of Chrome Pigment... 

FIGURE 22.7 General wastewater treatment process flow diagram at a typical chrome pigment plant. 

NIOSH Current Intelligence Bulletin 4, Chrome Pigment. 6 pp. Cincinnati, OH, US Department of Health and Human Services, 1976... 

The fifth volume of Advances in Heterocyclic Chemistry surveys the chemistry of four well-defined groups of compounds pyrrolizidines (N. K. Kochetkov and A. M. Likhosherstov), aromatic quinolizines (B. S. Thyagarajan), 1,2,4-thiadiazoles (F. Kurzer), and the amino-chrome pigments (R. A. Heacock). 

Toxicity and health effects Occupational exposure to chromium through inhalation occurs more with stainless steel welding, chromate production, chrome plating, and chrome pigment industries, primarily to hexavalent chromium. Chromium (HI) is an essential nutrient that helps the body use... 

Benzimidiazolone yellows have good opacity, very good heat resistance, good solvent resistance (little tendency to bleed) and very good lightfastness. Pigment yellow 151 (Fig. 7.8) is an example, which is used as replacements for the lead chrome pigments. 

Chemical Reduction and Filtration Used in Inorganic Chemical Industry (Chrome Pigment)... 

Data source Effluent Guidelines Point source Inorganic chemicals Subcategory Chrome pigment... 

The highest exposures occur occupationally. The National Occupational Hazard Survey conducted by the National Institute for Occupational Safety and Health from 1972 through 1974 concluded that some 2.5 million workers could be exposed to chromium and its compounds in the workplace. The National Occupational Exposure Survey conducted a decade later from 1981 through 1983 estimated a total of almost 200 000 workers were exposed to hexavalent chromium compounds (barium chromate, calcium chromate, chromium trioxide, lead chromate, strontium chromate, and zinc chromate). Occupational exposure occurs primarily from stainless steel production and welding, chromate production, chrome plating, ferrochrome alloys, chrome pigment and tanning industries. 

Hexavalent chromium compounds are classified as substances known to be carcinogenic to humans. This is based upon sufficient evidence of carcinogenicity in humans exposed in chrome production facilities, chromium-alloy facilities, in the chrome plating industry as well as in chrome pigment industries. This exposure results in an increased incidence of lung cancer among these workers. The incidence of cancers at other sites may be increased in these occupational workers There is not sufficient evidence to show that barium chromate, calcium chromate, chromium trioxide, lead chromate, sodium dichromate and strontium chromate are carcinogenic in humans. 

Use Dyeing of textiles, waterproofing, varnishes, lead driers, chrome pigments, gold cyanidation process, insecticide, antifouling paints, analytical reagent, hair dye. 

Chrome pigments chrome green, chrome yellow, chrome orange, and zinc yellow... 

Chrome Pigments. Chrome pigments based on lead chromate and mixed lead molybdenum salts have been the basis for yellow and orange pigments since their discovery in the 19th century. 

The most severe blow to the continued use of chrome pigments has come from the proponents of safety in banning the use of even insoluble lead pigments in any paint that might be approached by children. However, even without legislative requirements, many automotive and other industrial finishes are being formulated without chrome colors. 

Termodur. [G>lstable lead chrome pigment... 

Dichromate anion has the formula Cr207, in which chromium ion occurs in the -1-6 oxidation state. It also occurs in the same valence state (-1-6) oxidation state. It also occurs in the same valence state (4-6) in chromates, Cr04. Sodium and potassium dichromates of formula Na2Cr207 and K2Cr207 and CAS numbers [10588-01- 9] and [7778-50-9], respectively, are of commercial importance. These compounds are used for bleaching resins, oils, and waxes in chrome tanning of hides in the manufacture of chrome pigments in pyrotechniques and safety matches and as corrosion inhibitors. 

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