低品位红土镍矿焙烧-碱浸过程中硅的转化

针对目前红土镍矿碱法处理过程中存在的问题提出工艺改进，研究低品位红土镍矿焙烧活化-碱浸过程中含硅矿物的转化。考察了焙烧温度对红土镍矿活性的影响，探索了红土镍矿经焙烧后碱浸过程中温度、时间、搅拌强度、液固比以及碱初始质量浓度对硅转化的影响。结果表明，红土镍矿经650 °C焙烧2 h后，活性得到明显提高，红土镍矿经焙烧后采用初始质量浓度为60 g/L的碱溶液，在搅拌速度为400 r/min、浸出温度为140 °C、液固比为5∶1的条件下浸出120 min，硅的转化率可达89.42%。     

Leaching behavior of metals from a limonitic nickel laterite using a sulfation–roasting–leaching process

The leaching behavior of metals from a limonitic laterite was investigated using a sulfation–roasting–leaching process for the recovery of nickel and cobalt. The ore was mixed with water and concentrated sulfuric acid followed by roasting and finally leaching with water. Various parameters were studied including the amount of acid added, roasting temperature and time, sample particle size, addition of Na₂SO₄ and solid/liquid ratio in leaching process. More than 88% Ni, 93% Co and < 4% Fe are extracted under the determined conditions. Simultaneously, about 90% Mn and Cu, 70% Mg, 45% Al, 25% Zn, 4% Cr and Ca are extracted respectively. The pH of the leach solution is about 2. The leaching efficiency is independent of sample particle size due to decomposition of ferric sulfate formed during roasting. The roasted mass was characterized by various physico-chemical techniques such as DSC/TGA, XRD and SEM. This process provides a simple and effective way for the extraction of nickel and cobalt from laterite ore.     

Comparative leaching of minerals by sulphuric acid in a Chinese ferruginous nickel laterite ore

The Yuanjiang nickel laterite ore containing mainly maghemite, goethite and lizardite was leached by sulphuric acid at atmospheric pressure and the residues were characterized using X-ray diffraction and scanning electron microscopy/X-ray energy dispersive spectroscopy. The relationship was discussed between the extraction of nickel, cobalt, iron, magnesium, aluminum, and the dissolution behaviour of the laterite minerals; as well as the extent of congruency of nickel, cobalt and iron extraction. The results show that the solubility of the laterite minerals in sulphuric acid decreases in the following order: lizardite > goethite > maghemite > magnetite ≈ hematite > chromite ≈ ringwoodite. Lizardite dissolved rapidly in 0.6 mol/L sulphuric acid at 60 °C whilst goethite dissolved completely in 2.5 mol/L sulphuric acid at 80 °C. The dissolution of the primary mineral maghemite was slow, but increased with increasing acid concentration and leaching temperature. Magnetite dissolved more slowly than maghemite; and hematite was only dissolved in > 6.2 mol/L sulphuric acid at 105 °C. Chromite and ringwoodite were not dissolved. The leaching behaviour of the laterite minerals may be explained by the bond strength differences of Me–O and the substitution of metal cations in the mineral structure.     

Soda ash roasting of titania slag product from Rosetta ilmenite

A soda ash roasting process for upgrading titania slag product of Rosetta ilmenite to a high grade titanium dioxide (TiO₂) is presented. The roasting process was carried out at moderate to high temperatures to yield a reaction product that would be easily decomposed by subsequent leaching procedures. Factors affecting the roasting process; namely the soda ash ratio to the slag material, the roasting time and temperature were studied. The optimised conditions used a Na₂CO₃ to slag ratio of 0.55:1 at a roasting temperature of 850 °C for 0.5 h duration period. The impurities associated with the roasted slag were subjected to leaching with water and dilute hydrochloric acid solution leaving synthetic rutile (TiO₂) as insoluble residue. To improve the quality of the synthetic rutile, an alkaline leaching step was added to remove the excess silica present in the treated titania slag. This method is capable of producing high purity synthetic rutile assaying about 97% TiO₂.     

Studies on the leaching of an arsenic–uranium ore

Preliminary leaching studies were carried out to develop a suitable method for the recovery of uranium and the elimination of arsenic from a low grade carbonate/silicate ore containing 64 ppm U and 2446 ppm As, as well as some Cu, Pb, Ni and Zn. An examination of the mineralogy found mostly uranium(VI) minerals, such as uraninite, and various base metal sulfides and arsenates in veins and fissures. Roasting the ore at 500–800 °C to volatilize arsenic proved to be unsuitable. Therefore, the ground ore was subjected to direct leaching with sulfuric acid, sodium sulfide and ferric chloride at 80–90 °C with a liquid to solid ratio of 1:1. With sulfuric acid at a concentration of 180 kg/t ore, complete recovery of both uranium and arsenic was achieved giving undesirable arsenic in the leach liquor. The maximum recovery of uranium and arsenic by leaching with sodium sulfide was only 20% and 18%, respectively. However, 3 M ferric chloride leached approximately 92% U(VI) and precipitated arsenic as ferric arsenate. Therefore, maximum uranium can be extracted and arsenic eliminated as impurity by selective leaching with ferric chloride.     

Elevated-pH bioleaching of a low-grade ultramafic nickel sulphide ore in stirred-tank reactors at 5 to 45 °C

This study is a continuation of previous work designed to assess the effect of elevated-pH bioleaching on a low-grade ultramafic nickel sulphide ore from Manitoba, Canada. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as lizardite, making processing of the ore difficult with conventional pyro- and biohydrometallurgical techniques. This work has two objectives: to maximize nickel extraction, and to minimize magnesium mobilization. Five-week stirred-tank bioleaching experiments were conducted with finely ground ore (− 147 µm) at three pH levels (3, 4 and 5) and five temperatures (5, 15, 22.5, 30, and 45 °C). The initial rate of nickel extraction from pentlandite was observed to be inversely correlated to acidity at all temperatures, while the final extraction of nickel after 5 weeks was determined to be moderately correlated to acidity at high temperatures and negatively correlated to acidity at low temperatures. The advantage of elevated-pH bioleaching was most evident at 5 °C, in which the final extraction of nickel at pH 5 was approximately 250% greater than at pH 3. Electron probe X-ray microanalysis of the post-leach residues revealed that the un-reacted lizardite was enriched with nickel during experiments conducted at pH 5, and that the extent of enrichment was a strong function of temperature. The undesirable extraction of magnesium exhibited a strong negative pH–temperature interaction and the consumption of sulphuric acid directly tracked the extraction of magnesium over all experimental conditions. Bioleaching at elevated pH substantially increased the ratio of nickel to magnesium in the leachate, and resulted in a substantial reduction in sulphuric acid consumption.     

红土镍矿湿法冶金工艺现状及前景分析

随着硫化镍矿资源的不断消耗以及镍需求量的持续增长，红土镍矿将是未来镍的主要来源。红土镍矿具有储量丰富、易开采、便于运输等特点，成为研究开发的热点。对还原焙烧 氨浸工艺、加压酸浸工艺、常压酸浸工艺等湿法冶金处理红土镍矿的工艺特点及现状进行了阐述，并分析了各工艺的优势与不足，介绍了红土镍矿湿法冶金工艺的研究进展。最后探讨了未来红土镍矿湿法冶金工艺的发展前景，指出加压酸浸工艺将在今后红土镍矿湿法冶金中扮演重要角色。     

Intensification of sulphation and pressure acid leaching of nickel laterite by microwave radiation

The microwave is a clean and environmentally acceptable energy and various microwave-assisted metal extraction processes have been developed. The novel application of microwave irradiation for sulphation of the nickel laterite ore prior to pressure sulphuric acid leaching has been investigated. Under optimum conditions, about 92% of nickel can be extracted from the ore and above 90% of the iron precipitates as hematite with the residual acid content in the leachate lower than 31 g/L. The microwave sulphation proceeds rapidly and a relatively low leaching temperature and low mass ratio of sulphuric acid to ore can be used in the subsequent pressure leaching to achieve a satisfactory nickel extraction. This may potentially reduce the subsequent heavy capital and operation cost of the pressure acid leaching process.     

Leaching Ni and Co from Saprolitic Laterite Ore by Employing Atmospheric Acid Leaching Solution with High Concentration of FeCl 3 at Mild Conditions

Limonitic and saprolitic laterite ores are used to produce Ni by employing different kinds of processes. Acid leaching is an energy-saving process for pure Ni metal production. The high concentration of Fe in atmospheric acid leaching solution caused difficulties in metal-ions separation. In this work, saprolitic laterite ore was leached by atmospheric acid leaching solution of limonitic laterite ore at moderate temperatures. Conditions affecting the leaching of valuable metals and the conversion ratio of Fe were investigated. The results showed that optimal output was obtained after 1.5 h of leaching at 150°C with 1.0 liquid/solid ratio (volume/weight). X-ray diffraction analysis and mineral liberation analysis indicate that some nickel was adsorbed by leached residues, resulting in the loss of nickel. The physiochemical properties of leached residues could be changed due to the presence of Al and Cr. The decrease in zeta potential and the increase in specific surface area resulted in the increase of Ni adsorption.     

Reductive leaching of manganese from low-grade manganese ore in H2SO4 using cane molasses as reductant

Manganese extraction from a low-grade ore was investigated using cane molasses as a reducing agent in dilute sulfuric acid medium. The effects of concentrations of cane molasses and sulfuric acid, leaching temperature as well as reaction time were discussed. The results showed that high manganese recovery with low Fe and Al extraction yield could be obtained by analyzing the leaching efficiencies of Mn, Fe and Al during the leaching process. The optimal leaching condition was determined as 1.9 mol/L H₂SO₄ and 60.0 g/L cane molasses for 120 min at 90 °C while using particles smaller than 0.147 mm. The leaching efficiencies were 97.0% for Mn, whereas 21.5% for Al and 32.4% for Fe, respectively.