Silver fine powder with different shapes and sizes were prepared by chemical reduction and characterized by scanning electron microscope. In this paper was presented the method for the preparation of the fine Ag powder with particles size smaller than 2.5 µm with suitability for the mass-production scale. Reduction was performed from nitrate solution directly by vigorous stirring at room temperature by three different reduction agents, with and without presence of two dispersants. Scanning electron microscopy revealed the preferred size of the particles obtained in all experiments with aim of the protecting agent. Larger particles and wider size distribution were obtained without surfactants although with average size of about 1 µm and small quantity of larger clusters of primary particles that is out of the fine powder classification. High purity, 99.999%, of silver was obtained in every experiment.
Sodium lead slag, generated during secondary lead production, is characterized as hazardous waste. The aim of the study was to investigate leaching mechanism and behaviour of lead and arsenic from sodium lead slag previously stabilized/solidified in concrete using additives: MgO, CaO, Ba(OH) 2 and gypsum. The influence of selected additives on pollutant release was also investigated. The results of the NEN 7375 leaching test indicate dissolution of lead and arsenic from the outer layer of specimens, followed by depletion of possible mobile forms. Analysis of leachates from samples with various compositions showed that proper selection of additives may reduce leaching of Pb and As below the specified limits.
The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K.
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