Removal halogenated organics

AC filtration does remove some organic chemicals that can be harmful if present in quantities above the EPA Health Advisory Level (HAL). Included in this category are trihalomethanes (THM), pesticides, industrial solvents (halogenated... 

Solvent extraction shows effectiveness in the removal of organic wastes such as PCBs, VOCs, halogenated solvents, and petroleum wastes, but is less effective in removing inorganic compounds.39 The removal of organic contaminants depends on the nature of the extracting solvent. Organic bound metals can become a constituent of the concentrated waste, which is undesirable because it can restrict both disposal and recycle options. 

Removal of soluble toxic halogenated organic compounds... 

It has to be noted that the various processes mentioned are especially aimed at removing or destroying halogenated organic pollutants. If, in addition to halogenated pollutants, large amounts of non-halogenated... 

Quench elbow and secondary scrubber. This system is used to remove acid gases formed from the catalytic oxidation of halogenated organic compounds. The operation of the secondary scrubber is identical to that of the primary scrubber with the exception of a recirculation cooler that maintains scrubber exit gas temperature at 120°F. The secondary scrubber has a constant liquid blowdown that is collected in holding tanks and tested for agent prior to release. 

The Universal Demercurization Process, or UNIDEMP , is an ex situ process for removing mercury from a variety of solid and aqueous mercury waste streams such as metals, concrete, soils, asbestos, plastic, and cable as well as amalgams and mercury compounds. The process can also treat polychlorinated biphenyls (PCBs) and halogenated organics. UNIDEMP is a mobile system that volatizes and condenses mercury in a countercurrent rotating furnace at temperatures from 550 to 650°C. Celsius. 

Researchers believe that the PSVE technology can be used to remove volatile organic compounds (VOCs), halogenated volatile organic compounds (HVOCs), and total petroleum hydrocarbons (TPH). Some chemicals treated with PSVE include carbon tetrachloride, vinyl chloride (VC), chlorobenzene, 1,1-dichloroethane, dichloroethene (DCE), trichloroethane (TCA), and benzene, toluene, ethylbenzene, and xylene (BTEX). 

Irradiation was also successful in the decomposition of THMs to chloride and bromide ions (Cooper et al., 1993b). Toxic organic by-products such as haloacetic acid, aldehyde, ketones, or halogenated organic compounds were formed after irradiation. It has also been proven effective in the destruction of halogenated ethenes such as TCE and PCE. Removal rates decreased 20-fold in the presence of methanol as opposed to its absence. Aldehydes and formic acid were found when low solute concentrations of TCE and PCE were irradiated however, at high concentrations no more than 5% formic acid was found. Complete conversion of organic chlorine to chloride ion can be achieved. 

Bornhardt, C., J.E. Drewes, and M. Jekel. 1997. Removal of organic halogens (AOX) from municipal wastewater by powdered activated carbon (PAC)/activated sludge (AS) treatment. Water Sci. Technol. 35 147-153. 

Since the detection of halogenated organics in potable waters much research effort has been directed towards finding water treatment processes to remove such organics and their precursors and toward finding disinfectants other than chlorine. Great interest has been focused upon ozonisation because both disinfection and organic removal can be accomplished with this process. As ozonated end-products will occur in water produced by such processes and these could be potentially toxic and would accumulate in waste water after repeated cycles of use it is necessary to ascertain what end-products occur in water that has been ozonated and subsequently chlorinated. 

The metabolism of halogenated organic compounds is related directly to their environmental impact and toxicology. Accordingly, there has been extensive research into metabolic mechanisms, some of which detoxify and remove environmental pollutants, others which are responsible for in vivo toxicity. A brief overview in this subject will be given in this section. 

In the electroreductive treatments of halogenated organic pollutants the goal is either the complete dehalogenation (mostly hydrodehalogenation) of the substrates to ease their further treatment (e.g. improve their biodegradability), or their transformation into value-added compounds (e.g. selective removal of halogens, carboxyla-tion/carbonylation). 

The percentage of halogenated organics removal (PR, %), space-time yield (STY, kgm-3 h-1), current efficiency (CE, %) and energy consumption (ECN, kWh kg-1) are used to evaluate the HDH process performance. They are defined as ... 

Percentage of Halogenated Organics Removal and Space-Time Yield... 

Organic halides are known to be subject to hydrogenolysis in the presence of a catalyst, such as Pd/C or Raney nickel. This catalytic hydrogenolysis is one of the more convenient ways of removing halogens under mild conditions and numerous examples have been reported. Several reviews dealing with this subject have been published. 

The reduction of alkyl halides by solutions of dissolved metals like, e.g. sodium in ammonia or alkali metal naphthalenides in tetrahydrofuran, provides a convenient means of removing halogens to produce hydrocarbons or to prepare alkali metal organic compounds. It is generally accepted that these reductions involve free radical intermediates R pathway A, Scheme 12) . 

Cleaning Up Combine all reaction mixtures in a beaker, add a few drops of acetone to destroy any unreacted iodine in potassium iodide reagent, remove the iodoform by suction filtration, and place it in the halogenated organic waste container. The filtrate can be flushed down the drain after neutralization (if necessary). 

Under normal operating conditions H2O and CO give no response, while CO2 and NO2 are formed in very low concentrations and cause little interference. A scrubber is used to remove halogen gases. Therefore, the HECD is almost entirely selective for sulphur. The HECD has about the same sensitivity to inorganic sulphur compounds as the FPD however, it is much more sensitive to organic sulphur compounds than the FPD (Farwell et al., 1981). 

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