Removal of Aragonite Particles from Silica Balloons by Using Hot Flotation to Prepare the Heat Insulating Material
| Autor: | Yoshiaki Naruse, Masamitsu Komura, Eiichi Kuzuno, Balachandran Jeyadevan, Toyohisa Fujita |
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| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | Shigen-to-Sozai. 113:351-355 |
| ISSN: | 1880-6244 0916-1740 |
| DOI: | 10.2473/shigentosozai.113.351 |
| Popis: | Among nearly thirty types of calcium silicate hydrates, hydrothermally synthesized porous xonotlite is being used as fire resistant building material and heat resister. The molded body can be synthesized to have the necessary bulk density, strength and low thermal conductivity. When the porous amorphous silica (silica balloon) is synthesized through the removal of calcium from calcium silicate, the volume of ultrafine pores increases and the heat conductivity is further reduced. But, during the above process beside silica balloon, the needle shaped aragonite is also obtained. Since the aragonite not porous, the thermal conductivity of the slurry becomes five times that of silica glass. Therefore, to improve the thermal insulation aragonite has to dissolved using hydrochloric acid, a method that is costly and also the reuse of aragonite becomes impossible. In this study, we have examined the viability of separating aragonite and silica balloon using flotation and have arrived at the following conclusions.(1) When silica balloon and aragonite were floated separately with sodium oleate as collector, the floatability of aragonite was low and silica balloon did not float at all. But, in the flotation of aragonite-silica ballon mixture increment in floatability was observed in the case of aragonite due to large average diameter of the particle and the floatability of silica ballon also increased due to calcium ion activated surface and consequently the separation became difficult.(2) In the flotation of aragonite only, beside the collector sodium oleate, frother alcohol also was added. The floatability improved when the number of carbon atoms in the alkyl group was more than three. But, in the case of aragonite-silica mixture, silica balloon also floated due to the presence of dissolved calcium ions and the separation was difficult.(3) At the elevated temperatures the solubility of aragonite decreases leading to a decrease in the calcium ion concentration in the suspension. As a result the separation of aragonite and silica balloon becomes possible at temperatures higher than 353 K using sodium oleate as collector. |
| Databáze: | OpenAIRE |
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