재용해법에 의한 고백색수산화알루미늄의 제조
Preparation of Ultra White Aluminum Tri-hydroxide by the Re-slurry Digestion Process
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초록
Bayer 공정에서 생산되는 일반 수산화알루미늄을 이용하여 고백색의 수산화알루미늄을 제조하고자 하였다. 수산화알루미늄을 용해 온도 100~160℃, 가성소다 용액 180~220 g/ℓ 조건에서 재용해하여 A/C비(Alumina/Caustic ratio) 0.55~0.75로 과포화된 소듐알루미네이트용액을 제조하였다. 이때 수산화알루미늄에 함유되어 있던 유기물이 소듐알루미네이트 용액중에 함유됨으로 이를 제거하기 위하여 소석회의 농도 5 g/ℓ, 반응온도 80℃, 반응시간 30 min의 조건에서 반응시킨후 GF/C 필터로 여과하여 유기물의 70%이상을 제거할 수 있었다. 정제된 소듐알루미네이트 용액을 이용하여 A/C비 0.60~0.69, 반응온도 52℃~88℃, 반응시간 24~72시간, 종자 5~40 g/ℓ, 종자입도 45 ㎛의 조건에서 석출시킨 결과 Al2O3 99.7% 이상, Na2O 0.20% 이하, Fe2O3 0.010% 이하, SiO2 0.01% 이하, CaO 0.01% 이하의 화학적 특성을 가지며, 백색도 97이상, 평균입도 65 내지 85 ㎛의 레디얼(Radial) 및 모자이크 구조(Mosaic)를 가진 고백색도의 수산화알루미늄을 제조할 수 있었다.
Abstract
A process to produce ultra white aluminium trihydroxide from a commercial grade aluminium trihydroxide produced by KC Corporation Ltd was developed. First of all, supersaturated sodium aluminate solution of A/C (Alumina/Caustic ratio, g/L) concentration 0.55~0.75 was produced by redissolving a commercial grade aluminium trihydroxide in sodium hydroxide solution (dissolution temperature 100~160℃, NaOH 180~220 g/L). Dissolved organics which influence the whiteness of aluminium trihydroxide was removed (more than 70% by precipitation) by adding calcium hydroxide (at 5 g/L), to the supersaturated slurry and stirring at 80°C for 30 minutes. The filtered sodium aluminate solution was then maintained at A/C 0.60~0.69, reaction temperature 52℃~88℃, reaction time 24~72 hours, for precipitation of the product to occur. Seeding using particles with an average size of 45 ㎛ was maintained at 5~40 g/L to facilitate the precipitation process. Ultra white aluminium trihydroxide was produced containing Al2O3 > 99.7%, Na2O < 0.20%, Fe2O3 < 0.010%, SiO2 < 0.01%, CaO < 0.01%, Whiteness > 97. The product produced from this process has a mean particle size within the range 65~85 ㎛ and is of radial or mosaic structure.
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