The results of studies on the influence of technological parameters (temperature, HCl concentration, etc.) on the separation rate of the liquid and solid phases of the reaction pulp from the hydrochloric acid decomposition of nepheline are presented. Based on the data obtained, optimal decomposition conditions were selected, under which the highest filtration rate was achieved: acid concentration 25–30 %; process temperature 85–95 °C; duration of loading nepheline into acid 3.03.5 hours with an additional exposure of 0.51 hour and the consumption of "seed" 1015 % of the mass of nepheline.
The article presents a method to obtain silica xerogels with developed specific surface based on nepheline concentrate acid decomposition in C2H5OH-H2SO4 system. It was found that the use of ethanol instead of water produces stable and steady silica gels. It is proved that the use of ethanol results in almost complete deposition of soda alum and aluminum potassium sulphate out of nepheline decomposition solution without its additional cooling, due to their extremely low solubility in alcohol solution. The morphology, structural and surface properties of synthesized xerogel sample with ~600 m2/g specific surface area (based on the analysis) were investigated; its mixed micro-and mesoporous structure was established. Electron probe microanalysis showed chemical purity of the resulting SiO2.
There is presented the method of silicon dioxide obtaining by its extraction from silica-containing solution from nepheline decomposition with the acetone and ethanol help with organic phase subsequent gelatinisation. Structural and surface properties of the obtained SiO2 samples were investigated. The specific surface area of the obtained samples depends on the preparation method and varies in the range from 559 to 626 m2/g. The particles average diameter varies in the given series of samples from 2.26 to 6.68 nm. It has been found that the use of extraction has no destructive effect on the SiO2 specific surface area and maintains its original microporous structure.
This paper presents the results of the studies on the effect of the surface tension of the intrapore liquid on the specific surface (SBET) and pore volume (VBJH) of hydrated aluminium oxide (HAO) obtained by treating aluminum potassium alum with ammonia. It has been found that replacing of water, the surface tension of which at the drying temperature is 57.87 mN/m, to acetone (13.19 mN/m) allows to increase both SBET and VBJH nearly 4 times. There are obtained equations, which connect specific surface area and specific pore volume of synthesized samples HAO with surface tension of intrapore area. It is found that in the initial presence of water in the aluminum hydroxide pores, the average pore diameter of the dried product is 3÷4 nm. Treatment of the synthesized sample with acetone increases the average pore diameter of the dried product to 5÷10 nm.
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