The simplicity of calculus

The surface modification of papermaking fillers with compounds that promote a better bonding with the cellulosic fibres is nowadays one of the strategies used to increase the filler content in paper without sacrificing the mechanical properties. In this study precipitated calcium carbonate (PCC) was surface coated with poly(diallyldimethylammonium) using the layer-by-layer deposition method with alginate as an intermediate bonding polyelectrolyte. The deposition of small amounts of both polyelectrolytes at the surface of PCC was confirmed by different techniques, namely by zeta potential measurements and X-ray photoelectron spectroscopy. The filler particles coated with two layers (one layer of each polyelectrolyte) and with six layers (three alternating layers of each anionic and cationic polyelectrolyte) were used in laboratory papermaking tests. It was observed that the handsheets mechanical resistances were better with the six-layer coated PCC than with the reference PCC whereas the optical properties were not significantly affected. It is therefore possible to increase the filler content in paper using a new PCC-based filler obtained by a cheap and simple modification method

Catalytic oxidation of formaldehyde by ruthenium multisubstituted tungstosilicic polyoxometalate supported on cellulose/silica hybrid

Cellulose/silica hybrid material produced by a sol–gel method from cellulosic fibres and silica precursors (tetraethoxysilane and 3-aminopropyltriethoxysilane) was functionalized with α-[SiW9O37RuIII3(H2O)xCl3−x](10−x)− (Ru-POM), and thoroughly characterised by 13C and 29Si solid state NMR, FTIR spectroscopy, UV–vis reflectance spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), and chemical analysis. The supported Ru-POM exhibited catalytic activity for the gas phase heterogeneous aerobic oxidation of formaldehyde (ca. 830 ppm in polluted air) at room temperature, in a packed-bed reactor operating at a linear velocity ca. 0.33 m/s and ca. 0.5 s residence time. Maximum formaldehyde uptake was 1.10 g/min per kg of hybrid material doped with Ru-POM (ca. 1.4% w/w). More than 400 turnovers were achieved without significant loss of catalytic activity and the only detected oxidation products of formaldehyde were carbon dioxide and water. A plausible mechanism for the catalytic oxidation of formaldehyde by supported Ru-POM has been proposed and includes formaldehyde oxidation in oxygenated ruthenium complex

Novel charge transfer supramolecular assemblies with Keggin anions and 2-amino-5-nitropyridine

Several novel compounds with the non-linear optical chromophore 2-amino-5-nitropyridine (2A5NP) and Keggin polyoxoanions (alpha-isomers), having the general formula (2A5NP)(m)H-n[XM12O40]center dot xH(2)O, M = Mo, W, were synthesised. Compounds were obtained with X = P, n = 3, m = 3 and 4 and X = Si, n = m = 4 ( x = 2 - 6). Thus, for each of the anions [PMo12O40](3-) and [PW12O40](3-) two different compounds were obtained, with the same anion and organic counterpart but with a different stoichiometric ratio. These presented different charge transfer properties and thermal stability. All compounds were characterised by spectroscopic and analytical techniques. The single crystal X-ray diffraction structure of (2A5NP)(4)H-3[PMo12O40]center dot 2.5H(2)O center dot 0.5C(2)H(5)OH showed that the water solvent molecules and the organic chromophores are assembled via infinite one-dimensional chains of hydrogen bonds with formation of open channels, which accommodate [ PMo12O40] 3- and ethanol solvent molecules