[en] This paper explains the technology developed to produce Self-Assembled Mercaptan on Mesoporous Silica (SAMMS) for mercury removal from aqueous wastewater and from organic wastes. The characteristics of SAMMS materials, including physical characteristics and mercury loading, and its application for mercury removal and stabilization are discussed. Binding kinetics and binding speciations are reported. Preliminary cost estimates are provided for producing SAMMS materials and for mercury removal from wastewater. The characteristics of SAMMS in mercury separation were studied at PNNL using simulated aqueous tank wastes and actual tritiated pump oil wastes from Savannah River Site; preliminary results are outlined. 47 refs., 16 figs., 16 tabs

[en] This report describes a logical approach to resolving potential safety issues resulting from the presence of organic components in hanford tank wastes. The approach uses a structured logic diagram (SLD) to provide a pathway for quantifying organic safety issue risk. The scope of the report is limited to selected organics (i.e., solvents and complexants) that were added to the tanks and their degradation products. The greatest concern is the potential exothermic reactions that can occur between these components and oxidants, such as sodium nitrate, that are present in the waste tanks. The organic safety issue is described in a conceptual model that depicts key modes of failure-event reaction processes in tank systems and phase domains (domains are regions of the tank that have similar contents) that are depicted with the SLD. Applying this approach to quantify risk requires knowing the composition and distribution of the organic and inorganic components to determine (1) how much energy the waste would release in the various domains, (2) the toxicity of the region associated with a disruptive event, and (3) the probability of an initiating reaction. Five different characterization options are described, each providing a different level of quality in calculating the risks involved with organic safety issues. Recommendations include processing existing data through the SLD to estimate risk, developing models needed to link more complex characterization information for the purpose of estimating risk, and examining correlations between the characterization approaches for optimizing information quality while minimizing cost in estimating risk

[en] A study was conducted to demonstrate the effectiveness of a novel adsorber, the Self-Assembled Mesoporous Mercaptan Support (SAMMS) material to remove mercury (Hg) from potassium iodide/iodine (KI/I₂) waste streams. This study included investigations of the SAMMS material''s binding kinetics, loading capacity, and selectivity for Hg adsorption from surrogate and actual KI/I₂ waste solutions. The kinetics data showed that binding of Hg by the adsorber material occurs very rapidly, with 82% to 95% adsorption occurring within the first 5 min. No significant differences in the rate of adsorption were noted between pH values of 5 and 9 and at Hg concentrations of ∼100 mg/1. Within the same range of pH values, an approximate four-fold increase in initial Hg concentration resulted in a two-fold increase in the rate of adsorption. In all cases studied, equilibrium adsorption occured within 4 h. The loading capacity experiments in KI/I₂ surrogate solutions indicated Hg adsorption densities between 26 to 270 mg/g. The loading density increased with increasing solid: solution ratio and decreasing iodide concentrations. Values of distribution coefficients (1.3x10⁵ to >2.6x10⁸ ml/g) indicated that material adsorbs Hg with very high specificity from KI/I₂ surrogate solutions. Reduction studies showed that compared to metallic iron (Fe), sodium dithionite can very rapidly reduce iodine as the triiodide species into the iodide form. Adsorption studies conducted with actual KI/I₂ leachates confirmed the highly specific Hg adsorption properties (K_d>6x10⁷ to>1x10⁸ ml//g) of the adsorber material. Following treatment, the Hg concentrations in actual leachates were below instrumental detection limits (i.e., < 0.00005 mg/l), indicating that the KI solutions can be recycled

[en] Performance tests were conducted using novel getter materials that can immobilize or delay the transport of radioiodine that would be released during physical and chemical degradation of solidified low-level waste packages. The results showed that metal-capped novel getters such as Hg-thiol and Ag-thiol self-assembled monolayers on mesoporous silica (SAMMS), designed specifically to adsorb soft anions such as I^-, had very high affinities for adsorption of radioiodine (K_d ∝ 1 x 10⁴-4 x 10⁵ ml/g). The iodide adsorption performance of these novel getters was from one to two orders of magnitude better than many natural mineral and modified mineral getters. These data indicate that the novel getter materials are capable of significantly retarding the mobility of radioiodine leaching from physically and chemically weathered low-level waste glass packages during various physical and chemical weathering reactions expected during long-term disposal in the vadose zone. (orig.)

[en] X-ray and electron beam damage studies were performed on Br-terminated and methyl-terminated alkylsilane self-assembled monolayers. X-ray beam initiated damage was primarily limited to removal of the labile Br group and did not significantly damage the hydrocarbon chain. Some of the x-ray beam damage could be attributed to low-energy electrons emitted by the non-monochromatic source, but further damage was attributed to secondary electrons produced in the sample by x-ray exposure. Electron beams caused significant damage to the hydrocarbon chains. Maximum damage occurred with a beam energy of 600 eV and a dosage of 6x10^-3 C/cm²