Adsorption on magnetite

The above ideas that anion-cation pair sites are the surface sites for CO and CO2 adsorption on magnetite was verified directly by Udovic and Dumesic (43 ). These authors prepared films of magnetite on polycrystalline iron foils and varied the oxidation state of the surface by vacuum-annealing at different temperatures. In short, it was shown by Auger electron spectroscopy and X-ray photo-... 

Bychkova, A. V. Sorokina, O. N. Kovarski, A. L. Shapiro, A. B. Rosenfeld, M. A. The Investigation of Polyethyleneimine Adsorption on Magnetite Nanoparticles by Spin Labels Technique. Nanosci. Nanotechnol. Lett. (ESR in Small Systems), 2011,3, 591-593. 

Blesa, M.A. Maroto, A.J.G. (1986) Dissolution of metal oxides. J. chim. phys. 83 757—764 Blesa, M.A. Matijevic, E. (1989) Phase transformation of iron oxides, oxyhydroxides, and hydrous oxides in aqueous media. Adv. Colloid Interface Sci. 29 173-221 Blesa, M.A. Borghi, E.B. Maroto, A.J.G. Re-gazzoni, A.E. (1984) Adsorption of EDTA and iron-EDTA complexes on magnetite and the mechanism of dissolution of magnetite by EDTA. J. Colloid Interface Sci. 98 295-305 Blesa, M.A. Larotonda, R.M. Maroto, A.J.G. Regazzoni, A.E. (1982) Behaviour of cobalt(l 1) in aqueous suspensions of magnetite. Colloid Surf. 5 197-208... 

Clarke, N.S. Hall, P.G. (1992) Adsorption of water vapour by iron oxides. 3. Inelastic incoherent neutron scattering from water adsorbed on magnetite Evidence for an icelike structure. Langmuir 8 645-649... 

Hies, E. and Tombacz, E., The role of variable surface charge and surface complexation in the adsorption of humic acid on magnetite. Colloids Surf. A, 230, 99, 2004. 

Carbon monoxide, a soft base, is expected to interact with a soft acidic surface site (19), The octahedral iron cations (+2.5 average oxidation state) are the softer of the acid sites on magnetite and may be expected to provide CO adsorption sites. The initial interaction should result in a carbonyl surface species, and such species have been observed by infrared spectroscopy (20-22)t... 

The idea of competitive adsorption on pair-sites has also been used to describe the interaction of Ho and H2O with magnetite ( ). When isotherms were collected using M2/H2O mixtures following the same approach as discussed above, it was found that the data fit a model where H2 adsorbed dissociatively and H2O adsorbed associative-ly, with both species competing for pair-sites. These studies were conducted at water-gas shift reaction temperatures (e.g., 650 K) and as for the adsorption of CO and CO2, only a fraction of the magnetite surface was capable of adsorbing H2 and H2O. 

In closing, it is important to note that the CO/CO2 adsorption technique effectively titrates the active sites for WGS on magnetite catalysts which differ in activity by over an order of magnitude. Nitric oxide on the other hand titrates all of the surface cation sites and is unaffected by Si-substitution. Indeed, NO is known to chemisorb strongly on iron oxides and may even be able to reconstruct the surface. Thus, the combined use of NO and CO/CO2 adsorption provides information about the total magnetite surface area and fraction of the magnetite surface which is active for the WGS reaction. 

A new class of PS core/magnetite shell particles was produced by the sequential adsorption of magnetite nanoparticles and polyelectrolyte, a process that allowed the shell thickness and composition to be controlled with nanometer precision. The poly electrolytes were poly(diallyldimethylammonium chloride) or poly(allylamine hydrochloride). The influence of an external magnetic field on ordering of the composite PS core/magnetic shell particles was examined. 22 refs. 

Matrix or macromolecule coupled and mode of coupling" Immobilization of acetylcholine hydrochloride on an ion-exchange resin Adsorption onto magnetite Adsorption onto alumina Adsorption onto alumina coated with denatured bovine serum albumin... 

Doina Hritcu, Gianina Dodi, Marcel lonel Popa. Heavy Metal Ions Adsorption on Chitosan-Magnetite Microspheres. International Review of Chemical Engineering. 2012,4, 364-368. 

Natarajan, K. A., Riemer, S. C., Iwasaki, I., 1984. Influence of pyrrhotite on the corrosive wear of grinding balls in magnetite ore grinding. Inter. J. Miner. Process, 13(1) 73-81 Nesbitt, H. W., Bancroft, G. M., Pratt, A. R., Scaini, M. J., 1998. Sulfur and iron surface states on fractured pyrite surfaces. American Mineralogist, 83 1067 - 1076 Neeraj, K. M., 2000. Kinetic studies of sulphide mineral oxidition and xanthate adsorption. Doctor thesis of Virginia Polytechnic Institute and State University. A Bell Howell Company UMI dissertation Services... 

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