Search

• Metal-oxide coated spinel-type manganese oxides as a Li ion sieve were synthesized. • Li adsorption capacity and acidic durability were higher than that of uncoated spinel. • Lower Mn dissolution should be caused by substituting Mn(III) by other elements. A series of surface-modified lithium ion adsorbents was synthesized in a pH-controlled solution using impregnation method; different oligomeric metal-hydroxide precursors were added on the surface of a spinel-type manganese oxide (Li 1.33 Mn 1.67 O 4), which was then heat treated. X-ray diffractometry indicated that the crystal structure of spinel was maintained after heating. Transmission electron microscopy revealed that their surfaces were partially covered with metal-oxide layers of 10–20 nm thickness. Loaded metal-oxide contents in mass % were 7.1 of Al and 11.8 of Ni, respectively. The effect of metal-oxide species on chemical stability of the resulting materials in 0.25 mol dm−3 H 2 SO 4 solution was investigated by inductively-coupled plasma spectrometry. Metal-oxide coated Li 1.33 Mn 1.67 O 4 showed lower manganese dissolution and higher lithium extraction, compared with that of the raw Li 1.33 Mn 1.67 O 4. [ABSTRACT FROM AUTHOR]

Abstract: Two hydrothermally synthesised allophanes (Si/Al=0.5 and 1) were modified by heating at 400°C. N-methyl-d-glucamine, a specific boron complexant, was grafted on the allophane material with Si/Al=0.5. The surface and structural properties of the different materials were characterised by infrared spectroscopy and 29Si CP MAS NMR spectroscopy. The porous characteristics of the different allophanes (specific surface area, pore size distribution) were determined by nitrogen adsorption at 77K using the BET equation and the BJH model. The adsorption of boron, i.e. boric acid/borate, by the modified allophanes was studied in aqueous solutions with boron contents of 1 to 100mgL−1. The pH-dependence of boron adsorption of all the sorbents showed a maximum at a pH value close to the pKa value of boric acid (pKa H3BO3/B(OH)4 − =9.26). The adsorption isotherms of boron by raw and modified allophanes were fitted with a double Langmuir equation, assuming the presence of two sets of adsorption sites. The grafting of N-methyl-d-glucamine did not improve the boron adsorption of the allophanes but the structural changes by heating at 400°C increased the adsorption. [Copyright &y& Elsevier]

The intelligent humidity control materials were synthesized using fumed silica and quaternary alkylammonium surfactant (decyl-, dodecyl-, tetradecyl- and hexadecyl-trimethylammonium chlorides) as a liquid-crystal template under hydrothermal conditions. X-ray diffraction and transmission electron micrographs indicate that a homogeneous hexagonal structure of SiO2 was formed for those products. The mesostructured products had high B.E.T. surface areas between 960 and 1300 m2/g, with uniform mesopore diameters of 2–4 nm. These physical quantities were controlled by varying the size of the organic template. Water vapor adsorption isotherms for these materials possess a sharp increase in adsorption when the relative water vapor pressure is at 40–60%. Over this range of pressures, the maximum amount of adsorbed water content is between 40 and 90%. These silicates have the potential to be effectively used as humidity control elements in construction materials. [ABSTRACT FROM AUTHOR]