Effects of pH and temperature of coprecipitation and thermal treatment on some physicochemical, surface and catalytic properties of nano-sized zinc ferrite

Zinc ferrite nanoparticles were prepared via thermal treatment of zinc-iron mixed hydroxides at 400-600 [degree sign] C. The mixed hydroxides were coprecipitated from their nitrates solutions using NaOH as precipitating agent. The effects of pH and temperature of coprecipitation and calcination temperature on some physicochemical, surface and catalytic properties of the prepared ferrites were studied. The prepared systems were characterized using TG, DTG, DTA, chemical analysis, atomic absorption spectroscopy [AAS], X-ray diffraction [XRD], energy dispersive X-ray [EDX] as well as texture properties based on nitrogen adsorption-desorption isotherms. The results revealed that solid- solid interaction between ZnO and Fe[2]O[3] took place at temperature starting from 400[degree sign] C to produce ZnFe[2]O[3] phase. The surface and catalytic properties of the produced ferrite phase were strongly dependent on coprecipitation conditions of the mixed hydroxides and on their calcinations temperature

Effect of Ag[2]O- and Mn[2]O[3]Doping of CuO/MgO-AI[2]O[3] on Its Surface and Catalytic Properties

Pure samples of CuO/MgO-Al[2]O[3] solids were prepared by wet impregnation method using a given weight of equimolar proportions of aluminum hydroxide and magnesium basic carbonate powders with calculated amounts of copper nitrate dissolved in the least amount of distilled water followed by drying and calcinations at 300 and 500°C. The doped samples were obtained by treating pure solids with a known weight of silver or manganese nitrate prior to impregnation with copper nitrate. The formulae of pure calcined solids were 0.05, 0.1 and 0.2 CuO/MgO-Al[2]O[3]. The dopant concentration was varied between 1-4 mol% Ag2[O] and 1-8 mol% Mn[2]O[3]. The results revealed that the specific surface areas of pure and doped solids decreased by increasing the calcination temperature from 300 to 500°C. The doping process resulted in a measurable increase in the BET-surface areas of all solids investigated. This process changed the catalytic activities of various solids in CO oxidation by O[2] and H[2]O[2] decomposition. Doping the solids investigated with both dopants brought about a considerable increase in the catalytic activity towards both H[2]O[2] decomposition and CO oxidation to an extent proportional to the amount of dopants added. The increase in the catalytic activity was, however, more pronounced for Ag[2]O-dopant. The increase in calcinations temperature from 300 to 500°C resulted in an increase in the catalytic activity of pure and doped solids. Activation energy calculations revealed that doping process did not modify the reaction mechanism of H[2]O[2] decomposition but rather changed the concentration of catalytically active sites without changing their energetic nature