Adsorbate mercury

Figure 8.18 X-ray photoelectron spectrum of gold foil with adsorbed mercury. (Reproduced with permission, from Brundle, C. R., Roberts, M. W., Latham, D. and Yates, K., J. Electron Spectrosc., 3, 241, 1974)...

The toxic nature of mercury and its compounds has caused concern over environmental pollution, and governmental agencies have imposed severe restrictions on release of mercury compounds to waterways and the air (see Mercury). Methods of precipitation and agglomeration of mercurial wastes from process water have been developed. These methods generally depend on the formation of relatively insoluble compounds such as mercury sulfides, oxides, and thiocarbamates. MetaUic mercury is invariably formed as a by-product. The use of coprecipitants, which adsorb mercury on their surfaces facihtating removal, is frequent. 

Mattigod, S., Mercury remediation A tiny solution to a big problem—using nanotechnology for adsorbing mercury, Water and Wastewater Products, 9, 20-24. 

Thus glass which adsorbs the various constituents of the air more readily than it adsorbs mercury is not wetted by the metal, but if the adsorbed gas be removed from the surface, e.g. with the aid of a high vacuum such as obtains in a MacLeod gauge, the mercury may be caused to adhere to the glass. 

Ceftazidime was accumulated at HMDE at pH 9.5 and potential of +0.1 V in the form of the adsorbed mercury salt. The reduction peak potential at —0.7 V was used in cathodic stripping voltammetric determination of this compound [189]. 

The recovery and isotopic analysis of the mercury compound require special precautions since the presence of small amounts of natural mercury, as a contaminant, may give misleading results for the isotopic composition of the combined mercury. Therefore, the Hg>CU or HgO product has to be freed from adsorbed mercury prior to dissolution. Ten... 

Literature data on the surface capacitance of gold for mercury vary from 0.7 to 1.5 pg Hg(0)/cm2 [15,18,19] the mean value corresponds to about 0.3 nm2 per mercury atom. This density is about twice less than the density of gold atoms in the crystal lattice, i.e., it corresponds to about a half of the monolayer. An increasing of temperature decreases the amount of the adsorbed mercury [14]. 

The mercury contamination of significant amounts of mustard agent stockpiled at TOCDF is another factor influencing potential carbon disposition. TOCDF is implementing a pollution abatement system filtration system (PFS) that will trap mercury on carbon. The resulting secondary waste stream consisting of carbon with adsorbed mercury will present a unique disposal problem.14... 

Tab. 1. Fractional elimination and amount of adsorbed mercury/g of adsorbant asa function of initial mercury concentration.

To address this concern, several organic and inorganic reagents were evaluated as precipitants for heavy metals in a 10-34-0 (N-P2O5-K2O) fluid fertilizer and WPA. Trisodium trithiocyanuric acid (TMT-15), sodium polythiocarbonate (Thio-Red II), and sodium trithiocarbonate (5% Na2 CS3) precipitated arsenic, cadmium, copper, mercury, lead, and zinc from 10-34-0. Ammonium cyanurate was ineffective in removing cadmium from 10-34-0. Thio-Red II and 5% Na2CS3 precipitated mercury, lead, cadmium, copper, and chromium from WPA. A water-insoluble starch xanthate adsorbed mercury, copper, and lead from 10-34-0 and WPA. Sodium sulfide, sodium polysulfide, and potassium ferrocyanide were tested as inorganic precipitants. The polysulfide was twice as effective as the sulfide alone, and concentrations of less than 10 ppm of arsenic, cadmium, mercury, and lead were achieved in 10-34-0. Ferrocyanide reduced the concentrations of cadmium and nickel to less than 10 ppm in WPA. 

Mercury, copper, lead, and cadmium can be precipitated from 10-34-0 by adding TMT-15. The TMT-15 and Thio-Red II precipitated at least 94% of the copper and mercury present in the 10-34-0 manganese and chromium were not precipitated. The WI starch xanthate adsorbed mercury, copper, and lead from 10-34-0, while the adsorption of arsenic, cadmium, chromium, manganese, and zinc was negligible. 

Runoff as well as rainout carries soluble and adsorbed mercury into freshwater bodies and oceans. The very low levels of mercury available from the small solubility of humates and other mercury complexes are the source of mercury for land and water plants. Aquatic organisms derive a part of the mercury by ingestion of water plants, such as phytoplankton. Another source of mercury for aquatic organisms is zooplankton, which derives its mercury by ingestion of clay particles. These clay particles are agglomerated and then sedimented as part of the plankton excrement. 

Fine eolian dust carried over the ocean and precipitated by rain (60, 61) may also adsorb mercury from the atmosphere. Pelagic organisms may account for the agglomeration of the fine suspended matter in the ocean (3, 62), and thus the mercury generated over continents can be transferred to the midocean (63). Dissolved mercury in the oceans can be concentrated by phytoplankton (64), thus ofiFering another route for the removal and sedimentation of mercury in the midocean. As a result of this removal oceanic surface waters are depleted in this element (3, 65, 66) relative to deeper strata, and sediments are accordingly enriched. 

The undoubtedly most serious source of errors in the determination of mercury is in its mobility and hence independent of the technique used for its determination. Many materials adsorb mercury readily from higher concentrated solutions and desorb it again when they come into contact with a mercury-free solution. Contamination from the laboratory environment is also a big problem which requires special care. Closed systems with small surface areas and made from inert materials are of great advantage for an accurate determination of low levels of mercury. FI systems can come closest to these requirements if they are designed properly for CVAAS. 

In the case of petroleum gas and liquid feeds the usage of activated carbon impregnated with a catalyst, e.g. sulphur (for gasses) or iodide (for liquids) is very often practiced (O Dowd et al. 2006). Moreover, it is also proven that ionic liquids, particularly Solid Supported Ionic Liquids (SSILs), can capture all types of mercury in a single step more efficiently than other techniques (Mahpuzah Abai 2011). SSILs can adsorb mercury three times more than other commercially available adsorbents even without modifications to the plant infrastructure (Shariff 2011). 

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