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Removal of methyl orange from aqueous solutions by magnetic maghemite/chitosan nanocomposite films: Adsorption kinetics and equilibrium

“…[10][11][12] Because of its excellent chemical stability and magnetic properties, 13 O 3 , and c-Fe 2 O 3 /polymer composites are also reported. [14][15][16][17] However, there have few reports on magnetic cross-linked chitosan based on maghemite (c-Fe 2 O 3 ), i.e. c-Fe 2 O 3 /chitosan composite as adsorbent for dye removal.…”

Surface and Catalytic Properties of NiO and Co3O4 Solids Doped with Cobalt and Nickel Ions

“…In fact, the dissolution of nickel species in Co 3 O 4 solid according to reaction (2) should be accompanied by a decrease in the specific surface area as a result of the contraction of the lattice due to the conversion of some of the divalent cobalt ions into trivalent cobalt ions, since the ionic radii of Co 2+ and Co 3+ ions are 0.78 Å and 0.68 Å, respectively (Greenwood 1964). Hence, the measurable increase in the S BET value of Co 3 O 4 due to doping with nickel species could result, mainly, from the creation of new pores through the liberation of nitrogen oxide gases during the course of the heat treatment of cobalt carbonate impregnated with nickel nitrate (El-Shobaky et al 1997, 2000b. The observed decrease in the particle size and degree of crystallinity of the Co 3 O 4 phase due to doping might also account for the resulting increase in its S BET value as a result of this treatment.…”

“…Cobaltic oxide, Co 3 O 4 , behaves as a p-type semiconductor (Kostad 1972) and is a double oxide having the formula CoO 2 2CoO (Remy 1956;Schmalzried 1962;Kostad 1972). The host lattice cations exist as Co 4+ and Co 2+ ions and so it is capable of acting as an active catalyst for oxidationreduction reactions (Kluz and Woitaszczyk 1978;Mekhandzhiev and Nikolova 1980;El-Shobaky et al 1982, 1983, 1987, 2001Al-Noaimi et al 1994;Fagal et al 1998). NiO also behaves as a p-type semiconductor especially when subjected to heat treatment at moderate temperatures *Author to whom all correspondence should be addressed.…”

“…The non-stoichiometric solid NiO contains Ni 2+ and Ni 3+ ions, the trivalent ions being considered as lattice defects which are responsible for the semiconducting and catalytic behaviour of the solid. Doping Co 3 O 4 and NiO solids with certain foreign oxides leads to significant modifications in their electrical, surface and catalytic properties (de Boer and Verwey 1937;Parravano and Boudart 1955;Bielanski and Nabjar 1972;Petro et al 1977;El-Shobaky 1978;El-Shobaky and Petro 1979;El-Shobaky et al 1982, 1983, 1987, 1999a,b, 2000a,b, 2001Fagal et al 1998). The most common dopant oxides used for modifying the physicochemical, surface and catalytic properties of Co 3 O 4 and NiO solids are Li 2 O, Na 2 O, Ag 2 O, MgO, ZnO, Al 2 O 3 , V 2 O 5 and MoO 3 .…”

Catalytic Conversion of Isopropyl Alcohol over CuO/MgO Treated with K2O

“…To improve the catalytic activity and selectivity of metal oxides employed in some important industrial reactions the following parameters (suitable support, exposure to radiation and doping with certain foreign cations) must be considered [3,4]. The loading on a suitable support-material results in an increase in the dispersity of catalytically active constituents [5] and increase their thermal stability via hindering their grain growth [6]. The catalytic activity of most of transition metal oxides can be greatly improved by supporting on a suitable carrier such as γ -alumina, magnesia.…”