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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 35, Number 4
JKCSEZ 35(4)
August 20, 1991 

Alum and Hydroxide Routes to α-Al2O3 (Ⅰ) Calculation of Solubility Diagram for Extracting the Pure Alumina from Alumino-Silicate and its Experimetal Confirmation

명반 및 수산화 알루미늄을 이용한 α-Al2O3의 합성 (Ⅰ) 규산 알루미늄광으로부터 순수한 α-Al2O3 추출을 위한 용해도 모델 계산 및 실험적 검증
Jong-Seok Yoo, Jin-Ho Choy, Kyoo-Seung Han, Yang-Su Han, Chang-Kyo Lee, Nang-Ho Lee

유종석, 최진호, 한규승, 한양수, 이창교, 이낭호
천연규산 알루미늄광인 힐로이사이트 광물로부터 고순도 α-Al2O3를 합성하기 위해 황산용액을 사용한 습식합성법을 이용하였다. 추출된 황산 알루미늄 용액내에 존재하는 각종 불순물을 제거하기 위해 각 금속이온의 수산화물과 탄산화물의 형성을 고려, pH에 따른 용해도곡선을 도시하였다. 이를 기초로 α-Al2O3의 전구물질인 순수한 암모니움 명반은 pH = 1.5∼2.5에서, 수산화 알루미늄은 pH = 6∼8에서 각각 합성하였으며, 이로부터 얻어진 α-Al2O3의 순도는99.7%dhk 99.0%였다. 여기서 불순물에 대한 정제효과는 암모니움 명반으로부터 합성된 경우(Na = 0.047%, Si = 0.092%)가 수산화 알루미늄으로부터 합성된 경우Na = 0.29%, Si = 0.12%)보다 매우 높은 결과를 보였다.

High-purity alumina powder was prepared by extracting the natural alumino-silicate mineral (halloysite) in H2SO4 solution. For the selective precipitation of alum and aluminum hydroxide, the solubility diagram was prior calculated by also considering the formation of hydroxides and carbonates for all the metal ions in an aqueous solution, which allow us to control the contamination of impurities envolved in the natural minerals. Ammonium aluminum sulfate (alum) and alumium hydroxide could be successfully prepared at pH = 1.5∼2.5 and pH = 6∼8, respectively according to our solubility diagrams. The purity of alum-and hydroxide-derived α-Al2O3 was determined to be 99.7% and 99.0%, respectively, which indicates the former route would be more desirable for the large scale application. It is also worthy to note that the impurities like Na and Si were strongly reduced in the former (Na = 0.05%, Si = 0.09%) compared to the latter (Na = 0.29%, Si = 0.12%).

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