Oxide contaminant removal

Techniques for handling sodium in commercial-scale appHcations have improved (5,23,98,101,102). Contamination by sodium oxide is kept at a minimum by completely welded constmction and inert gas-pressured transfers. Residual oxide is removed by cold traps or micrometallic filters. Special mechanical pumps or leak-free electromagnetic pumps and meters work well with clean Hquid sodium. Corrosion of stainless or carbon steel equipment is minimi2ed by keeping the oxide content low. The 8-h TWA PEL and ceiling TLV for sodium or sodium oxide or hydroxide smoke exposure is 2 mg/m. There is no defined AID for pure sodium, as even the smallest quantity ingested could potentially cause fatal injury. 

A significant problem is the dehydrocoupling reaction, which proceeds only at low yields per pass and is accompanied by rapid deactivation of the catalyst. The metathesis step, although chemically feasible, requires that polar contaminants resulting from partial oxidation be removed so that they will not deactivate the metathesis catalyst. In addition, apparendy both cis- and /ra/ j -stilbenes are obtained consequendy, a means of converting the unreactive i j -stilbene to the more reactive trans isomer must also be provided, thus complicating the process. 

Technology Description In-situ chemical treatment uses the same principles employed for above-ground chemical processes. Materials are added to neutralize, oxidize or remove contaminants in groundwater or soils in order to avoid digging or pumping of the contaminated waste above ground for... 

For organic contaminant removal from surface water packed-tower aeration, granular activated carbon (GAC), powdered activated carbon (PAC), diffused aeration, advanced oxidation processes, and reverse osmosis (RO). 

At many plants, fluxes are added to the metal to reduce hydrogen contamination, remove oxides, and eliminate undesirable trace elements. Solid fluxes such as hexachloroethane, aluminum chloride, and anhydrous magnesium chloride may be used, but it is more common to bubble gases such as chlorine, nitrogen, argon, helium, and mixtures of chlorine and inert gases through the molten metal. 

The fourth factor is the current density. At an inert anode and for 100% Faradaic efficiency for water oxidation, the density of the current controls the flux of H+ ions. The cathodic current density and the species available in its vicinity establish the efficiency of the reduction processes (Pb2+ —> Pb). These vary to a greater extent than the anode process, because the pH and the species reaching the cathode vary with processing time. Thus, control of the current density is critical to ensure optimal EO efficiency and contaminant removal. 

The excess triphenylphosphine used in the preparation can be recovered by addition of water to the ethanol filtrates until precipitation begins. After allowing the solutions to stand 2 to 3 days in a stoppered flask, the triphenylphosphine crystallizes out. Recrystallization from ethanol and ethanol-benzene (1 1) removes triphenylphosphine oxide contaminant. 

Abdul-Sada, A. K. Avent, A. G. Parkington, M. J. et al. The removal of oxide impurities fi om room-temperature halogenoaluminate ionic bquids, J. Chem. Soc., Chem. Commun., 1987, 1643-1644 Abdul-Sada, A. K. Avent, A. G. Parkington, M. J. et al. Removal of oxide contamination from ambient-temperature chloroaluminate(III) ionic bquids, J. Chem. Soc., Dalton Trans., 1993, 3283-3286. 

Phase-transfer oxidation is a technology for destruction of organic contaminants. It was developed to treat contaminated liquid streams using adsorption for contaminant removal and advanced oxidation processes for spent adsorbent regeneration. It was used in testing to treat the contaminated effluent from groundwater extraction technologies. 

Contaminated soil is fed into a rotary dryer where the temperature is raised to between 500 and 800°F. As the soil is heated, moisture and volatile organic compounds (VOCs) are vaporized. The heated exhaust gases from the dryer are forced through a baghouse where soil fines and dust particles are removed. Exhaust gases are then passed through a catalytic oxidizer to remove hydrocarbons. 

TerraTherm Environmental Services, Inc., a subsidiary of Shell Technology Ventures, Inc., has developed the in situ thermal desorption (ISTD) thermal blanket technology to treat or remove volatile and semivolatile contaminants from near-surface soils and pavements. The contaminant removal is accomplished by heating the soil in sim (without excavation) to desorb and treat contaminants. In addition to evaporation and volatilization, contaminants are removed by several mechanisms, including steam distillation, pyrolysis, oxidation, and other chemical reactions. Vaporized contaminants are drawn to the surface by vacuum, collected beneath an impermeable sheet, and routed to a vapor treatment system where contaminants are thermally oxidized or adsorbed. 

During the continuous photocatalytic oxidation of organic contaminants, the rate of contaminant removal has been commonly observed to decline over time, some-... 

It was expected that, because the contamination products were concentrated within the surface oxide layer, removal of the latter would eliminate radioactive contamination. Steel samples with oxide layers up to 100 pm in width were processed [1]. 

ConocoPhillips, 177, 247, 258, 496 contaminants, removing trace. See oxidation, preferential conversion, types of, 6 loss, 4... 

Cadmium [7440-43-9] M 112.4, m 321.1 , b 767 , df 8.642. Any oxide contaminant is removed by filtering the molten metal, under vacuum, through quartz wool. Its solubility in Hg is 5.2% (18°), and it is soluble in mineral acids. [Wagenknecht Juza in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1092 7965.]... 

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