Carbon monoxide contamination

Fig. 3.29 Resistances of the 38 sensor segments of a Sn02-microarray equipped with Si02-membrane during alternating exposure to carbon monoxide contaminated humid air and clean air with the same relative humidity...

The carbon monoxide contamination is very severe in the case of both LaNis and Feo.gsMno isTi alloys (Fig. 12.18). There is a steep decay in the hydrogen transfer property as seen in Fig. 12.14. It is postulated that a Ni(CO)4 layer forms due to reaction with CO gas [53]. To summarize, the AB5 hydrides (LaNis) are resistant to extrinsic impurities such as O2 and H2O, but not CO gas. The (Fe, Mn)Ti are generally not resistant to any of these impurities they are slightly resistant to CO gas. 

Earlier PEFC research by the National Institute of Advanced Industrial Sciences Technology in Japan [3] had resulted in the development of a new high-performance catalyst to replace platinnm-ruthenium alloy catalysts. The researchers achieved a world-record for high carbon monoxide contamination resistance by using a low-cost organometallic complex as an auxiliary catalyst to platinum. By eliminating ruthenium and using less platinum it was possible to reduce costs to one-third of their former level. 

A cylinder should be considered empty when its internal cylinder pressure reaches 25 p.s.i.g., unless the cylinder contains a gas having an extremely low vapor pressure. Withdrawal of the entire cylinder contents should be avoided as this may allow entry of moisture or contaminants that can result in delivery of impure gases when the tank is next refilled, or more seriously, in damage to the tank itself. For example, carbon monoxide contaminated with water vapor under pressure can cause stress-corrosion of the cylinder. 

A fermentation route to 1-butanol based on carbon monoxide employing the anaerobic bacterium, Butyribacterium methjlotrophicum has been reported (14,15). In contrast to other commercial catalytic processes for converting synthesis gas to alcohols, the new process is insensitive to sulfur contaminants. Current productivities to butanol are 1 g/L, about 10% of that required for commercial viabiUty. Researchers hope to learn enough about the bacteria s control mechanisms to be able to use recombinant DNA to make the cells produce more butanol. 

Carbon dioxide can cause product contamination through ammonium carbonate formation. Ammonium carbonate may also form by oxidation of carbon monoxide by cupric ion (eq. 27) ... 

Prevention of carbon monoxide poisoning is best accompHshed by providing good ventilation where contamination is a problem. If good ventilation is not possible, a self-contained breathing apparatus, such as a Scott Air-Pak, must be used. The use of gas masks containing an adsorbent is generally not recommended since it is difficult to know when the adsorbent is exhausted. 

Lateritic Ores. The process used at the Nicaro plant in Cuba requires that the dried ore be roasted in a reducing atmosphere of carbon monoxide at 760°C for 90 minutes. The reduced ore is cooled and discharged into an ammoniacal leaching solution. Nickel and cobalt are held in solution until the soflds are precipitated. The solution is then thickened, filtered, and steam heated to eliminate the ammonia. Nickel and cobalt are precipitated from solution as carbonates and sulfates. This method (8) has several disadvantages (/) a relatively high reduction temperature and a long reaction time (2) formation of nickel oxides (J) a low recovery of nickel and the contamination of nickel with cobalt and (4) low cobalt recovery. Modifications to this process have been proposed but all include the undesirable high 760°C reduction temperature (9). 

In electrochemical cells sample oxidation produces an electric current proportional to the concentration of test substance. Sometimes interferences by other contaminants can be problematic and in general the method is poorer than IR. Portable and static instruments based on this method are available for specific chemicals, e.g. carbon monoxide, chlorine, hydrogen sulphide. 

Direct reading samplers include simple devices such as colorimetric indicating tubes in which a color change indicates the presence of the contaminant in air passed through the tube, or instruments which are more or less specific for a particular substance. In the latter category are carbon monoxide indicators, combustible gas indicators (explosimeters) and mercury vapor meters, as well as a number of other instruments. 

In densely populated areas, traffic is responsible for massive exhausts of nitrous oxides, soot, polyaromatic hydrocarbons, and carbon monoxide. Traffic emissions also markedly contribute to the formation of ozone in the lower parts of the atmosphere. In large cities, fine particle exposure causes excess mortality which varies between one and five percent in the general population. Contamination of the ground water reservoirs with organic solvents has caused concern in many countries due to the persistent nature of the pollution. A total exposure assessment that takes into consideration all exposures via all routes is a relatively new concept, the significance of which is rapidly increasing. 

In Mexico City, several air quality parameters are measured continuously by an Automated Monitoring Network operated by the Under Secretariat of Ecology. Carbon monoxide, particulate matter, sulfur dioxide, nitrogen oxide, and ozone are the contaminants exceeding Air Quality Standards. Emissions produced by 2.7 million vehicles and 35,000 commercial and industrial outfits are not easily dispersed in a Valley located at 2240 m and surrounded by two mountain chains which hinder air circulation. An Integral Program, recently established to alleviate pollution, is briefly described. 

Carbon monoxide poses no significant residual risk. If metal carbonyls have been released, all foodstuffs in the area should be considered contaminated with residual metal decomposition products. Unopened items packaged in glass, metal, or heavy duty plastic and exposed only to agent vapors may be used after decontamination of the container. Opened or unpackaged items, or those packaged only in paper or cardboard, should be destroyed. 

Structural firefighters protective clothing is recommended for fire situations only it is not effective in spill situations or release events. Although carbon monoxide is primarily an inhalation hazard, metal carbonyls may pose a percutaneous risk. If chemical protective clothing is not available and it is necessary to rescue casualties from a contaminated area, then structural firefighters gear will provide limited skin protection. Contact with liquids and solutions should be avoided. 

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