Salt waste stabilization

Although these reactions are highly versatile, so far they have not found significant industrial applications. The main reasons for this are relatively low thermal stabilities and turnover numbers of the catalytic systems, and the salt waste problem. However, Hoechst is trying to develop an industrial process for the manufacture of 6-methoxy 2-vinylnaphthalene by reaction 7.31. The precatalyst used is the dimeric phosphapallada cycle 7.63, which operates below a pressure of 20 atm and temperature of 130°C. 

Of the contaminants listed in Table 17.1, the hrst three are radioactive. The last one is benign but still is an issue for waste stabilization because the salts are easily... 

Cs, Sr, and Ba are mostly found in salt waste streams as chlorides, nitrates, and sulfates and hence are soluble in water. Even Cs oxide is very soluble. Therefore, they readily react during phosphate stabilization and are chemically immobilized. We shall see in the case studies later in this chapter that such stabilization is very effective in a CBPC matrix. 

Ceramicrete stabilization of Tc, partitioned from high-level tank wastes, was demonstrated by Singh et al. [11]. The waste stream was a product of a complexation-elution process that separates Tc from HLW, such as supernatant from salt waste tanks at Hanford and Savannah River. A typical waste solution generated during the complexation-elution process contains 1 M NaOH, 1 M ethylenediamine, and 0.005 M Sn +. 

Synthesis of salicylic acid by the Kolbe-Schmitt process (see above) is an example for the direct carboxylation of aromatics.34 At the same time, it is also an example for the limitations of such reactions. Formal insertion of C02 into a C-H bond can usually be achieved with compounds containing active hydrogens (such as phenolates), and perhaps more importantly, the product carboxylic acids have to be stabilized by salt formation. Liberation of the free acid from such carboxylates requires a mineral acid and produces 1 equiv of inorganic salt (waste) (Scheme 6.1). 

Since intratubular hydrostatic pressure does not differ significantly from controls in euvolemic and volume expanded animals, it is unlikely that intratubular obstruction plays an important role in early, cispl-atin-induced acute renal failure. Following withdrawal of the drug, renal insufficiency stabilizes but remains indefinitely impaired. The cisplatin-induced hypofil-tration is usually associated with tubular proteinuria. Severe salt-wasting with orthostatic hypotension has been observed after cisplatin administration in a minority of patients [18]. 

Spent pickle liquor is considered a hazardous waste (K062) because it contains considerable residual acidity and high concentrations of dissolved iron salts. For example, spent pickle liquor and waste acid from the production of stainless steel is considered hazardous. The hazardous constituents in K062 are lead, nickel, and hexavalent chromium. Waste pickle liquor sludge generated by lime stabilization of spent pickle liquor is not considered hazardous unless it exhibits one or more of the characteristics of hazardous waste. An estimated 6 million tons of spent pickle liquor are generated annually in the U.S.1... 

Wastes containing high levels of halogenated salts, zinc, lead, or mercury may pose problems for this technology due to volatilization and/or incomplete incorporation into the stabilized matrix. 

During the course of the experimental program, many phenomena will be investigated in detail. Most of these studies will address details of waste/salt interaction, radionuclide migration and salt stability. Results may affect the mode of long-term operation and design of the repository. 

The US Navy has also investigated the use of biodegradation for the disposal of TNT containing rinse w ( pink water ) (Ref 41). Likewise, the combined disposal in stabilization ponds of monomethyl hydrazine, nitrate and nitrite salts and nitrogen tetroxide waste liquors... 

Again, as in the case of hazardous contaminants discussed in Chapter 16, the solubility of a radioactive contaminant plays a major role in its stabilization in a phosphate matrix. Therefore, one needs to understand the aqueous behavior of a radioactive contaminant prior to selecting the acid-base reaction that will form the CBPC used for fabricating the waste form matrix. In this respect, actinides, fission products, and salts have unique solubility behavior. This behavior is discussed below. 

Salts of actinides are very common in waste streams. In particular, nitrates, chlorides, and sulfates are found in tank waste streams that were formed by neutralization of highly acidic solutions at several DOE sites, such as Hanford and Savannah River. The aqueous solubility of these salts is very high, and hence, it is a challenge to stabilize them. As we shall see in case studies, the CBPC matrix has good promise in handling these waste streams. 

Unlike Portland cement, the Ceramicrete slurry sets into a hard ceramic even in the presence of salts such as nitrates and chlorides hence, the Ceramicrete process has a great advantage over conventional cement technology with respect to the stabilization of some difficult waste streams, such as those from Hanford and Savannah River tanks. Wagh et al. demonstrated this advantage in several studies, wherein they produced monolithic Ceramicrete solids by using concentrated sodium nitrate and sodium chloride solutions in place of water to stabilize the waste streams. Details of some of these studies may be found in Ref. [21]. 

Several additional favorable properties of CBPCs make them an even better candidate for stabilization. The waste form is a dense matrix, generally with very good mechanical properties. Also it is nonleachable, does not degrade over time, is neutral in pH, converts even flammable waste into nonflammable waste forms, performs well within acceptable levels in radiolysis tests, and can incorporate a range of inorganic waste streams (solids, sludge, liquids, and salts). 

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