On the role of ultrasound and mechanical stirring for iodide adsorption by calcined layered double hydroxides.

10.1016/j.clay.2014.02.012Improving the adsorption of long-term radioactive species in the underground disposal of waste waters from nuclear reactors is a key issue. The natural metal oxides or hydroxides underground have the low retention ability of anionic species. Here, calcined Mg/Al LDHs were used as adsorbents. The influence on the adsorption capacity of different intercalated guest anions (carbonate (CO32 -) and nitrate (NO3-)) in the parent LDH was investigated, along with the effect of ultrasonication. Two Mg/Al molar ratios (3/1 and 2/1) were compared. Adsorption capacity was strongly affected by material textural properties, and the carbonate LDH-derived mixed oxides showed the largest adsorption capacity. Mixed oxides with an Mg/Al molar ratio equal to 3 presented higher iodide adsorption due to their lower charge density. The adsorption assisted by ultrasound increased iodide removal efficiency by reducing internal diffusion limitation. Two models were used to determine adsorption capacity: Langmuir and Freundlich. The iodide adsorption was best fitted by the Langmuir equilibrium model

Resolution and metallurgical studies with a scanning electron acoustic microscope

SIGLELD:9091.9F(AERE-R--10473) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Catalytic transformation of biomass-derived 5-hydroxymethylfurfural over supported bimetallic iridium-based catalysts

5-Hydroxymethylfurfural (HMF) is a biobased platform chemical that can be valorized into a spectrum of valuable products. In this report, supported Ir, Ir-Co, Ir-Ni, and Ir-Ru catalysts were investigated for this purpose. Only hydrogenation of HMF to 2,5-bis-(hydroxymethyl)furan (BHMF) occurred over all catalysts. The effect of the second metal (Co, Ni, and Ru) on Ir/SiO2was reflected by the kinetic constants being in the order Ir-Ni/SiO2> Ir-Co/SiO2> Ir-Ru/ SiO2. The oxophilic nature of the secondary metal improved the catalytic performance of the bimetallic catalysts compared to the monometallic iridium catalyst (Ir/SiO2). Addition of HCOOH and H2SO4 as cocatalysts is a strategy to reach one-pot conversion of HMF to 2,5-di-methylfuran (DMF). Over-hydrogenolysis products such as 2,5-dimethyltetrahydrofuran were formed when only H2SO4 was added, giving higher activity compared to addition of HCOOH. Simultaneous presence of acids gave the highest HMF conversion, promoting esterification to 5-formyloxymethyl furfural and allowing the one-pot transformation of HMF to DMF. Thermodynamic analysis of HMF transformations revealed that both hydrogenation and dehydration steps are feasible