Irreversible contamination

Answer 17.3 That man exploits a little less than the amount that is renewed, e.g., pumping so that some groundwater still drains to the ocean. And, second, that man does not deteriorate surface and groundwater systems by irreversible contamination. 

With respect to H2S contamination, it has been recognized for many years that the major impact is upon the fuel cell electrode kinetics [40], When H2S is added to humidified H2, EIS can be used to study the H2S contamination. Information gathered includes the effects of the H2S concentration, the exposure time, and the reversibility of the contamination. H2S can strongly adsorb on a Pt catalyst surface, blocking the active sites and then causing irreversible contamination. 

The direct injection of biological samples onto the chromatographic column without any sample preparation is in most cases highly problematic and may lead to an irreversible contamination of the separation columns, which reduce selectivity and column performance. A powerful asset to circumvent all the named problems is the implementation of RAM for sample preparation. RAMs, a combination of SEC with adsorptive chromatography, have foimd widespread use in the analysis of drug metabolites and other low-MW compounds, but have... 

Irreversible contamination of graphite parts and their surrounding areas by Cr, Mg, Mo, Ni, Pd or V modifiers, which precludes their subsequent determination as analytes. 

Thin-layer plates are only used once, while in column chromatography the stationary phase is used repeatedly. Therefore even samples highly contaminated by the matrix can be directly applied on the plate without being cleaned up. In column chromatography an irreversible contamination of the stationary phase has to be taken into consideration. 

Semiconductor charged particle detector Energy measurement -isotope ratios. Very convenient-capable of high resolution. Requires low geometry for high resolution. Detector may become irreversibly contaminated by volatile radioactivity. 

Which part of the hydrosphere is most subject to long-term, largely irreversible contamination from the improper disposal of hazardous wastes in the environment ... 

As you might appreciate, the worst that can happen to a catalytic converter, apart from its theft, is for the all-important metal surface to become irreversibly contaminated. That is one reason why leaded petrol is no longer used, for when the lead tetraethyl it contained decomposed into ethyl radicals (Reaction 13) and lead atoms, the latter stuck irreversihly to the metal and sealed it against further action. 

Despite all these safeguards to extend the service life of the antifreeze, fluid replacement is requited periodically. Typically, fluids are replaced because of irreversible damage caused by one of four conditions contamination, gel formation because of glycol/siUcate reaction, extensive glycol degradation caused by overheating or excessive oxygen exposure, or inhibitor depletion. 

In many of the other processes that use base metal catalysts, irreversible poisoning of the catalyst occurs as a result of deposition of metal contaminants from the process feedstock onto the catalyst surface. These catalysts are not considered to be regenerable by ordinary techniques. 

IDLH means immediately dangerous to life and health. This is a concentration at which immediate action is required. The exac4 effect on an individual depends on the individuals physical condition and susceptibility to the toxic agent involved. It is the maximum airborne contamination concentration from which one could escape within 30 min without any escape-impairing symptoms or irreversible health effects (developed by NIOSH). 

Physisorption occurs when, as a result of energy differences and/or electrical attractive forces (weak van der Waals forces), the adsorbate molecules become physically fastened to the adsorbent molecules. This type of adsorption is multilayered that is, each molecular layer forms on top of the previous layer with the number of layers being proportional to the contaminant concentration. More molecular layers form with higher concentrations of contaminant in solution. When a chemical compound is produced by the reaction between the adsorbed molecule and the adsorbent, chemisorption occurs. Unlike physisorption, this process is one molecule thick and irreversible... 

Deactivation of zeolite catalysts occurs due to coke formation and to poisoning by heavy metals. In general, there are two types of catalyst deactivation that occur in a FCC system, reversible and irreversible. Reversible deactivation occurs due to coke deposition. This is reversed by burning coke in the regenerator. Irreversible deactivation results as a combination of four separate but interrelated mechanisms zeolite dealu-mination, zeolite decomposition, matrix surface collapse, and contamination by metals such as vanadium and sodium. 

Immediately Dangerous to Life or Health (IDLH)—The maximum environmental concentration of a contaminant from which one could escape within 30 minutes without any escape-impairing symptoms or irreversible health effects. 

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