Immobilization phosphate stabilization

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. 

Special considerations chemical composition of filler surface affects nucleation of filler traces of heavy metals decrease thermal stability and cause discoloration siuface free energy of fillers determines interaction large difference in thermal properties of fillers and polymer may cause stress hydrotalcite is used as acid neutralizer with stabilizing packages anatase titanium dioxide decreases UV stability presence of transition metals (Ni, Zn, Fe, Co) affects thermal and UV stability calcium carbonate and talc were found to immobilize HALS stabilizers in PP with organic masterbatches such as ethylene diamine phosphate V-0 classification can be obtained with 20-25 wt%, at the same time tensile strength and impact strength are substantially reduced... 

Immobilized enzyme stability was assayed by using 0.4 g of the immobilized CALB on fiber or 0.01 g of Novozyme 435 in successive batches of methyl butyrate hydrolysis. The operational conditions were the same as described for the assay of hydrolytic activity. At the end of each batch, the immobilized lipase was removed from the reaction medium, washed with phosphate buffer to remove any remaining substrate or product, dried under vacuum (10 min), and assayed again. The residual activity of the biocatalyst was calculated in terms of percentage of activity (U) of the immobilized enzyme measured after each cycle compared with the activity of the immobilized enzyme before the first cycle. 

Figure 3.13 shows the thermal stability of immobilized ODN and PNA. The signal for the Thy- and Cyt-bases obtained with temperature-programmed (TP) SIMS starts to decrease at approximately 150 °C for ODN and 200 °C for PNA. This variance is caused by the different strengths of binding between the bases and the sugar-phosphate and peptide backbones, respectively. 

Tricalcium phosphate was also used as an enzyme embedding matrix. Das and coworkers [229] demonstrated that acid phosphatase and amylase immobilized on Ca3(P04)2 retained their activities with increased thermal stability. 

The immobilization of trimeric LHCII is demonstrated in Fig. 13(B). After the nickel ion activation (5), a 1 pM solution of trimeric recombinant LHCII prepared in NaP + DM buffer (20 mM sodium phosphate, pH 7.4, 0.1 % (w/v) n-dodecyl-/ -D-maltoside) was introduced into the flow cell (1). For each cycle, the protein solution was incubated in the loop for 30 min, followed by buffer rinse (2), EDTA (3), and SDS (4) regeneration. EDTA was used to competitively chelate the nickel ions and break the linkage between NTA and Histidine. SDS, as mentioned in Section 4.2, was used to detach any remaining physically adsorbed proteins. As shown in Fig. 13(B), the immobilization/regeneration cycles from (1) to (5) can be well reproduced and the baseline after every cycle stabilized at a response close to the starting level. This indicates that the... 

Inorganic contaminants are immobilized by washing the waste with soluble phosphates. This treatment uses a very small amount of phosphate, does not change other characteristics of the waste such as its granular nature or volume, and is relatively inexpensive. If the waste contains radioactive contaminants, phosphate washing is not sufficient because the dispersibility of the radioactive contaminant powders needs to be reduced, and hence, the waste needs to be solidified. Solidification requires generating phosphate ceramics of the waste in the form of a CBPC. In the case of radioactive waste, both stabilization and solidification are needed because they not only immobilize the contaminants, but also solidify the entire waste. As we will see in this and the next chapter, whether phosphate treatment is used only for stabilization or for both stabilization and solidification, it is very effective for a wide range of waste streams. 

The samples were stored for 3 weeks for curing. Each sample was then crushed and was subjected to the TCLP test. The TCLP test results on both the waste stream and the treated CBPC waste form are given in Table 16.6. The results on the untreated waste streams show that the leaching levels far exceed the regulatory limits. The results for the waste forms, on the other hand, are an order of magnitude below the EPA limit. These results indicate superior stabilization of Hg in the phosphate ceramic waste forms coupled with sulfide immobilization. 

As discussed in Chapter 16, chemical stabilization is a result of conversion of contaminants in a radioactive waste into their insoluble phosphate forms. This conversion is solely dependent on the dissolution kinetics of these components. In general, if these components are in a soluble or even in a sparsely soluble form, they will dissolve in the initially acidic CBPC slurry and react with the phosphate anions. The resultant product will be an insoluble phosphate that will not leach into the groundwater. On the other hand, if a certain radioactive component is not soluble in the acid slurry, it will not be soluble in more neutral groundwater, because the solubility of such components is lower in neutral than in acidic solutions. Such a component will be simply microencapsulated in the phosphate matrix of the CBPC. Thus, the solubility of hazardous and radioactive components is key to chemical immobilization. 

---