Iodine solid adsorbent

Although the majority of soil iodine remains adsorbed to the soil solid phase, its release into the Hquid and gaseous phases does occur, enabling potential transfer pathways that are likely to increase human exposure to iodine. 

MOR depends on whether the silver is reduced. Table 14.9 summarizes the solid adsorbents available for iodine capture. The silver-based alumina, silica, and mordenite adsorbents have comparable characteristics and are the currently preferred sorbents. An advantage of the mordenite is that the regeneration of the sorbent is possible, thereby utilizing the silver over the course of several cycles. The stripped iodine is then available for sorption using a cheaper metal or conversion to a waste form preferred for long-term storage. 

Bromine. In this experiment with bromine the absorption equilibrium between the solid phase and the liquid phase was attained after 1 hr for chitin but after 5 days for H-alg. Although the limited solubility of bromine in water precludes measurements at high concentrations, as shown in Figure 6, these saccharides absorb bromine (A) and bead form Ca-alg. has a high binding ratio corresponding to the concentration of bromine (B). Being different from chitin, chitosan absorbs bromine in water up to 1.12 molar bromine per two hexosaminyl residues [14] and neither bromine nor iodine is adsorbed on A-acetylchitosan [14]. The latter conflicts with our results for the chitin-iodine and chitin-bromide adducts. 

Figure 37. Experimental results and least-squares fits of data (solid lines) for a Pt/C LSM covered with an electrodeposited layer of copper and an adsorbed layer of iodine. Topmost curve IL fluorescence middle curve copper Ka fluorescence bottom curve reflectivity.

A number of solute-solid isotherms were determined over the next 20 years including those for the uptake of iodine and various dyes by charcoal and other adsorbents, but many of the investigators still believed that the process involved penetration into the solid structure. Freundlich, in 1907, was one of the first to... 

Figure 33. Experimental results and least squares fit of data (solid lines) for a Pt/C LSM covered with an electrodeposited layer of copper and an adsorbed layer of iodine. Topmost curve /j. fluorescence. Middle curve copper K, fluorescence. Bottom curve reflectivity. (From Abruna, H. D., White, J. H., et al., J. Phys. Chem. 92, 7045 (1988), with permission.)...

For permanent fixation of 1 adsorption on silver-loaded adsorbents, such as zeolites, silica, or alumina, will be the choice [PI, W2]. The process is simple, the bed temperature may be relatively high, the product is a dry solid, the chemisorbed iodine is highly insoluble, and the adsorbent is very efficient in removing both organic and inorganic iodine from gas streams. 

Iodine adsorbed on vacuum sublimed calcium fluoride is brown and its spectrum is shifted toward shorter wavelengths compared to that of ordinary solid iodine (9). On barium fluoride the surface color is more yellow, indicating that the spectrum is even further shifted towards the blue. The visually observed color is due to the combination of the absorption bands for unperturbed iodine and for an electrostatically adsorbed surface species. The spectrum of iodine on calcium fluoride at low coverage is sharp and consists (Fig. 10) of two bands at 3600 A... 

The vast majority of soil iodine is most likely adsorbed to the soil solid phase, although appreciable amounts may be released into the hquid and gaseous phases, particularly under anoxic soil conditions. 

Several reports have pointed out that iodination of proteins may affect their adsorption to solid surfaces and their chromatographic behavior (40-43). Consequently, we have chosen to determine the quantum yield of unlabeled, adsorbed lysozyme via fluorescence lifetimes. We are currently in the process of modifying our fluorescence equipment to obtain such fluorescence lifetimes. 

UV-VIS spectroscopy in the first place is sensitive to alterations in the electronic structure. Studies of molecular interactions on soUd surfaces started much later than those in solution. It is of historical interest that already in the early 1930s, UV-VIS spectroscopy was one of the first techniques appUed to a zeolite, as shown in Fig. 13 for iodine adsorption on chabazite [17]. The figure shows the spectrum of iodine on chabazite compared to those of iodine as vapor, as a solid, dissolved in benzene and adsorbed on calciiun fluoride. As illustrated by these examples, four main effects of interaction on the spectriun can be established [15,16] ... 

Fig. 13. Historical UV-VIS spectra of iodine adsorbed on chabazite and calcium fluoride compared to solid I2,12 vapor (broken line) and h dissolved in benzene. Reprinted from [17] with kind permission of R. Oldenbourg Verlag GmbH, Miinchen...

Immunoaffinitv assay The Irnmunoaffinity assay which Involves the use of an antibody column that traps the mycotoxins has been used for AFBl, AFMl and OTA (8, 9, 13, 36, 83,84). The toxin can be then eluted from the column for subsequent analysis or adsorbed In a solid-phase to which the fluorescence Is then read directly. Thus, the affinity column serves as a specific cleanup and concentration tool for the analysis. Recent advances In Improvement of Instrumentation of fluorescence detection and post-column derlvatlzatlon have led to a wider application of this method for AF detection. An AOAC collaborative study showing good result has been completed (85). In such an assay, AF extracted from the sample Is first diluted with buffer at pH 7.0 and then subjected to a disposable affinity column containing antl-AF antibody Sepharose gel. After washing, AF Is removed from the column with methanol, subjected to treatment with Iodine solution, and the fluorescence determined. Nevertheless, this method cannot be used for mycotoxins, such as TCTCs, which do not have high fluorescence or a chromophore. 

Itaya, K., Batina, N., Kunitake, M. etal. (1997) In situ scanning tunneling microscopy of organic molecules adsorbed on iodine-modified Au( 111), Ag( 111), and Pt( 111) electrodes. Solid-Liquid Electrochemical Interfaces. ACS Symposium Series, 656, 171-188. 

Anandan et al. reported that PVDF was used as a component in fabrication of DSCs [211]. For such a purpose, heteropolyacid was impregnated in PVDF polymer with iodine/iodide as a solid polymer electrolyte for DSCs in order to effectively decrease the back-electron transfer reaction TiOi nanoparticles were used as dye-adsorbants. The solar cell, composed of new polymer electrolyte (PVDF), Ti02 nanoparticles (photoanode) and conducting carbon cement, was cemented on conducting glass (photocathode). An overall energy conversion efficiency of up to 8% was reported [211]. 

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