The behavior of iodine in stabilized granular activated carbon and silver mordenite in cementitious waste forms.

Both granular activated carbon (GAC) and silver mordenite (AgM) are utilized for the removal of contaminants and radionuclides (e.g., radioiodine) from off-gas streams in nuclear fuel reprocessing and high temperature immobilization of nuclear waste. Following their service lifetimes, the GAC and AgM contain an inventory of contaminants and radionuclides and require stabilization in a matrix for disposal. GAC and AgM are referred to as solid secondary waste (SSW) materials. Cementitious waste forms can be used as the stabilization matrix for SSW, however, for successful stabilization, the inclusion of GAC and AgM should not negatively impact the physical behavior of the cementitious waste form or increase release of the contaminants/radionuclides compared to the baseline case without stabilization. The present work focuses on evaluation of cement formulations, with and without slag, for the stabilization of iodine-loaded GAC or AgM. The results showed that both a slag-containing and slag-free formulations were able to stabilize GAC and AgM, up to 30 vol%, without deleterious impacts on the bulk physical properties of the encapsulating matrix. When monolithic samples of the GAC or AgM containing cement formulations were subjected to leach tests, it was observed that iodide leached from the SSW) had limited sorption to either of the cement matrices. Nonetheless, the iodine can interact with the SSW materials themselves. Specifically, iodine retention within monolithic samples containing the iodine-loaded GAC or AgM was improved for AgM containing waste forms while no improvement was observed for the GAC containing waste forms. The improvement for the AgM containing waste forms was likely due to an enrichment of Ag at the interface between the AgM particles and the cement matrix that can impede iodine migration out from the waste form. The results are significant in highlighting the potential for long-term retention of iodine in specific cementitious waste forms.

Pearlescent Mica-Doped Alginate as a Stable, Vibrant Medium for Two-Dimensional and Three-Dimensional Art.

Emergent technologies are driving forces in the development of innovative art media that progress the field of modern art. Recently, artists have capitalized on the versatility of a new technology to create, restore, and modify art: additive manufacturing or three-dimensional (3D) printing. Additively manufactured art relies heavily on plastic-based materials, which typically require high heat to induce melting for workability. The necessity for heat limits plastic media to dedicated 3D printers. In contrast, biologically derived polymers such as polysaccharides used to create "bioinks" often do not require heating the material for workability, broadening the types of techniques available for printing. Here, we detail the formulation of a bioink consisting of mica pigments suspended in alginate as a new, vibrant art medium for 2D and 3D compositions. The properties that make alginate an ideal colorant binder are detailed: low cost with wide availability, nontoxicity and biocompatibility, minimal color, and an array of attractive physicochemical properties that offer workability and processing into 2D and 3D structures. Further, the chemical composition, morphology, and dispersibility of an array of mica pigment additives are characterized in detail as they pertain to the quality of an art medium. Alginate-based media with eight mica colors were formulated, where mica addition resulted in vibrantly colored inks with moderate hiding power and coverage of substrates necessary for 2D printing with thin horizontal and vertical lines. The utility of the media is demonstrated via the generation of 2D and 3D vibrant structures.