Taijiro Okabe

The precipitation of Ni3S2 from sulfate solutions

The formation conditions for the recovery of nickel from sulfate solutions as Ni3S2 have been investigated; this sulfide is more reactive than NiS in subsequent leaching operations. Hydrogen sulfide gas at atmospheric pressure is introduced into a NiSO4-Na2SO4-MgSO4-Al2(SO4)3 solution in the presence of reduced iron powder. Although the formation of Ni3S2 is compctitive with that of NiS, the nickel precipitation efficiency and the ratio of nickel as Ni3S2 to the total nickel precipitated reached 99.5 to 99.9 and 90 to 95 pct, respectively, under the following conditions: 363 K, Ph2s 31 kPa, Ni2+ 4.0 g · dm-3, 3[Feo]/[Ni2+] 1.25 to 1.5, H2S flow rate 70 to 100 cm3 · min-1, and 45 to 60 minutes retention time. Selective formation of Ni3S2 is achieved within 10 minutes, and a reaction on the surface of the iron is rate-determining during the early stages of precipitation. Since the iron is almost totally consumed after 1 to 2 hours of reaction, the precipitated Ni3S2 is gradually converted to NiS. Calculations considering the buffer action of sulfate ion and sulfate complex formation with polyvalent metal cations as well as with nickel ions confirmed that significant nickel precipitation as Ni3S2 should occur under the test conditions.

Sulfuric acid oxygen-pressure leaching of Ni3S2 prepared by a wet process

Abstract Ni3S2 prepared by a wet process was easily leached as nickel sulfate at 383 K, po2 1 MPa, and sulfuric acid concentration of 0.1–0.15 mol L−1. The leaching reaction proceeds through the intermediate formation of NiS prior to complete dissolution. A constant leaching rate was observed for most of the duration of the reaction, and this has been attributed to an increase in the specific surface area of the sulfide particles. A thin sulfur layer was formed on the sulfide; the diffusion of oxygen through the sulfur layer was found to be rate-determining.

Isolation of Iron- and Sulfur-Oxidizing Bacteria from Mine Water in Japan and Some Investigations on the Leaching of Sulfide Ores

The authors have studied the isolation of iron- and sulfur-oxidizing bacteria from mine water and carried out some investigations on the leaching of sulfide ores, in the hope that a technology of bacterial leaching of ores might be devised. The present paper is a brief summary of these results.

The Prevention of Oxidation of Sodium Sulfite in Aqueous Solution

The prevention of oxidation of sodium sulfite solution was investigated. As an antioxidant of sodium sulfite solution, Span 80 (a nonionic surfactant of the type of sorbitan fatty acids ester) was extremely effective. In the case of sulfite solution containing such metal ions as Fe2+, Ni2+, and VO43-, it was necessary to use a masking agent or a precipitant of metal ions in addition tothe above-mentioned antioxidant, and sodium tripolyphosphate and Allon 10 H wereespecially useful for a masking agent and a precipitant respectively.

Pressure Leaching of Tungsten Ores with Ammoniacal Ammonium Phosphate Solution

The pressure leaching of tungsten ores with ammoniacal ammonium phosphate solution was investigated at 160-220 C.The experimental results are summarized as follows(1) The tungsten extraction from scheelite and wolframite ores is 90 and 80%, respectively, under the optimum conditions viz. reaction temperature 200 C, reaction time 2hr, molar ratio of ammonium phosphate to tungsten in the ores: 8 and pulp density: 2g-ores per 8ml concentrated ammonia solution.(2) As the solubility of phosphate in concentrated ammonia solution containing several %of ammonium tungstate is less than 200 mg-P205/l, most of the phosphate in the leachate can be removed by merely blowing gaseous ammonia into it.(3) The ammonium phosphate method is inferior to the sodium carbonate one in the degree of the tungsten extraction, but has advantages that both ammonia and ammonium phosphate, which are decomposing agents, can be used circularly, and that the dissoiution, of silica can be suppressed.

Pressure Leaching of Alunite Ores with Aqueous Ammonia

ミョウバン石中のカリウムと硫酸根成分を抽出するため,安水(アンモニア水)加圧下で150～225℃の温度範囲にわたり,安水浸出を行なったものである。実験は1lのハステロイ- F ライニングしたステンレスオートクレーブを用い, 安水濃度, 使用安水モル比,ミョウバン石粒度,反応時間,反応温度等分解率に及ぼす影響について調べた。その結果ミョウバン石は適切な条件下でほぼ完全に分解することを見い出し,実操業の最適条件としては鉱石粒度-150～200mesh,反応温度200℃,使用安水モル比4,安水濃度8mol/lである。なお浸出液は硫安と硫酸カリウムを主成分とし,浸出残分はべーマイト態からなるアルミナを含み,前者は蒸発,結晶化により混合肥料として用いられ,後者は耐火物材料,アルミナセメント原料またはバイヤー法アルミナ原料として利用できる。またミョウバン石の安水浸出速度は鉱石の種類によって異なり,韓国黄山産がもっとも分解し易く,シリカ分の多い伊豆宇久須産と粘土質を含むアルゼンチン産は比較的分解が困難である。

Hydrometallurgy of Copper Using Complex Sulfide Ore

硫酸銅, 硫酸亜鉛混合溶液から, 経済的に銅を分離する方法, および塩基性硫酸銅の亜硫酸アンモニウムによる還元について研究した。硫酸塩形態の銅と亜鉛の分離法は種々考えられるが,本湿式銅製錬法には,アンモニアを用いる塩基性硫酸銅の分別沈殿分離が最適であり,銅の82%が沈殿するまで,塩基性硫酸銅の純度は平均95.5%である。更に得られる塩基性硫酸銅は亜硫酸アンモニウムによって容易に還元可能であり,反応温度,亜硫酸初濃度,Cu2+/SO32-モル比の還元に及ぼす影響は硫酸銅の亜硫酸アンモニウムによる還元と同様で,高収率で金属銅を得ることができる。