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We have continued experiments on the reaction of iodate with sphagnum peat moss. We have established that iodate added to a suspension of peat moss undergoes reduction and to a significant extent is incorporated in to the peat moss. We have confirmed the incorporation of iodine into the peat matrix using pyrolysis GC/MS. In addition, we have performed a scaled up pyrolysis using the preparative GC system that was described in a previous report. This instrument consisted of a packed column gas chromatograph (SRI 8010) with a TCD detector and injector valve equipped with a thermal desorber. Pyrolysis experiments were performed in a 6” tube furnace manufactured by Carbolyte. This programmable furnace has a 0.5” diameter process tube that can hold 8-100 mg samples of peat or ion exchange resin. During sample heating helium stream sweeps products from the tube furnace to the carbosieve trap located in the thermal desorber unit. Volatile materials that are collected on the carbosieve trap can be transferred to the gas chromatograph by actuating the valve and activating the thermal desorption oven. Chromatography is initiated by thermally desorbing trapped volatiles from the carbosieve trap to the GC column (2mm x 2m, Porapak Q). The instrument was calibrated with by injecting methyl iodide into the thermal desorber trap. The response factor and retention time of methyl iodide were thus determined. Pyrolysis experiments with 8-12 mg of organic matter have been conducted using this experimental apparatus. Experimental results for a two series of incubations are shown in Figure 1. Results for experiments with a peat sample incubated at 40oC and pH 4.3 are shown. In addition, the results for a commercially available humic acid at pH 2 are presented. The low pH was used to prevent dissolution of the humic material.

During this last quarter we have investigated the influence of pyrolysis temperature on the yield of methyl iodide. We have done experiments with the analytical pyrolysis unit described in previous reports and with the preparative GC. The results of these studies are illustrated in Figures 2 and 3 and demonstrate optimum methyl iodide production at 400oC. The peat (350 mg) was incubated in 20 mL of 2.7*10-3M KIO3. The suspension pH was established with phosphate buffer and the sample was held in a constant temperature incubator. In most cases the amount of methyl iodide produced by pyrolysis increased with an increase in heating time. Previous reports indicated that organically bound iodine went through a maximum during heating experiments and then slowly decreased. This maximum was not apparent in the pyrolysis results.


Iodine — Isotopes; Peat mosses; Pyrolysis; Radioactive wastes; Reactor fuel reprocessing; Sorbents

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Iodine--Isotopes; Peat mosses; Radioactive wastes


Analytical Chemistry | Chemistry | Oil, Gas, and Energy | Physical Chemistry

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