Eiichi Kuzuno

Removal of Aragonite Particles from Silica Balloons by Using Hot Flotation to Prepare the Heat Insulating Material.

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.

Recovery of Palladium from Waste Ceramic Capacitor by Liquid-Liquid Extraction.

In the manufacturing process of multi layer ceramic chip capacitor, some unqualified products are produced and discarded as an industrial waste. Such a waste consists of barium titanate dielectrics and contains small amount of palladium as inner electrode. In order to recover and recycle palladium from the waste, liquid-liquid extraction was applied and investigated.Extraction behaviors of palladium and barium titanate were first examined using n -butanol, iso-octane and kerosene as organic phases at various pH. Palladium was extracted into n-butanol fairly well at the wide pH range of 1.0-10.5. On the contrary, barium titanate was not extracted almost entirely at the same conditions. Therefore, it was estimated that n-butanol was suitable organic phase for the separation of palladium from ceramics. When iso-octane or kerosene was used as an organic phase, large amount of barium titanate transferred into the oil phase at the wide pH range except high acidity, so that successive extraction of palladium from ceramics could not be expected except in high acidic medium. It was also shown that the addition of dodecylammonium acetate (DAA) as a collector was effective to promote the recovery of palladium in n-butanol.Then, the extraction was conducted for the practical waste of ceramic capacitor using n-butanol as an organic phase under the condition of 200mg·dm-3 DAA and pH 1.0. As a result, it was found that palladium was effectively separated with the recovery of 96.8% and the yield of about 10%, and that the product was upgraded to 34.4% palladium, about 10 times higher than the feed.