Decomposition mechanism of chromite in sulfuric acid-dichromic acid solution

The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly understood. In this work, binary spinels of Mg-Al, Mg-Fe, and Mg-Cr in the powdered and lump states were synthesized and used as raw materials to investigate the decomposition mechanism of chromite in sulfuric acid-dichromic acid solution. The leaching yields of metallic elements and the changes in morphology of the spinel were studied. The experimental results showed that the three spinels were stable in sulfuric acid solution and that dichromic acid had little influence on the decomposition behavior of the Mg-Al spinel and Mg-Fe spinel because Mg2+, Al3+, and Fe3+ in spinels cannot be oxidized by Cr6+. However, in the case of the Mg-Cr spinel, dichromic acid substantially promoted the decomposition efficiency and functioned as a catalyst. The decomposition mechanism of chromite in sulfuric acid-dichromic acid solution was illustrated on the basis of the findings of this study.     

硫酸中香蕉皮还原低品位锰矿的浸出行为及动力学模型

Manganese was leached from a low-grade manganese ore (LGMO) using banana peel as the reductant in a dilute sulfuric acid medium. The effects of banana peel amount, H₂SO₄ concentration, reaction temperature, and time on Mn leaching from the complex LGMO were studied. A leaching efficiency of ~98% was achieved at a leaching time of 2 h, banana peel amount of 4 g, leaching temperature of 120°C, manganese ore amount of 5 g, and sulfuric acid concentration of 15vol%. The phase, microstructural, and chemical analyses of LGMO samples before and after the leaching process confirmed the successful leaching of manganese. Furthermore, the leaching process followed the shrinking core model and the leaching rate was controlled by a surface chemical reaction (1 ? (1 ? x)1/3 = kt) mechanism with an apparent activation energy of 40.19 kJ·mol?1.     

Synergistic effect of microwave irradiation and CaF<Subscript>2</Subscript> on vanadium leaching

The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride (CaF₂) on the vanadium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when CaF₂ is present. The leaching rate of vanadium under microwave irradiation is increased by 8%-15% when 5wt% CaF₂ is added; by contrast, in the absence of CaF₂, the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation, whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover, a large amount of Al and V and a small amount of Si are dissolved from samples under microwave heating, as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When CaF₂ is present, the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer, resulting in a prominent effect of microwave irradiation.     

Preparation of manganese sulfate from low-grade manganese carbonate ores by sulfuric acid leaching

In this study, a method for preparing pure manganese sulfate from low-grade ores with a granule mean size of 0.47 mm by direct acid leaching was developed. The effects of the types of leaching agents, sulfuric acid concentration, reaction temperature, and agitation rate on the leaching efficiency of manganese were investigated. We observed that sulfuric acid used as a leaching agent provides a similar leaching efficiency of manganese and superior selectivity against calcium compared to hydrochloric acid. The optimal leaching conditions in sulfuric acid media were determined; under the optimal conditions, the leaching efficiencies of Mn and Ca were 92.42% and 9.61%, respectively. Moreover, the kinetics of manganese leaching indicated that the leaching follows the diffusion-controlled model with an apparent activation energy of 12.28 kJ·mol-1. The purification conditions of the leaching solution were also discussed. The results show that manganese dioxide is a suitable oxidant of ferrous ions and sodium dimethyldithiocarbamate is an effective precipitant of heavy metals. Finally, through chemical analysis and X-ray diffraction analysis, the obtained product was determined to contain 98% of MnSO₄·H₂O.     

Sulfuric acid leaching kinetics of South African chromite

The sulfuric acid leaching kinetics of South African chromite was investigated. The negative influence of a solid product layer constituted of a silicon-rich phase and chromium-rich sulfate was eliminated by crushing the chromite and by selecting proper leaching conditions. The dimensionless change in specific surface area and the conversion rate of the chromite were observed to exhibit a proportional relationship. A modified shrinking particle model was developed to account for the change in reactive surface area, and the model was fitted to experimental data. The resulting model was observed to describe experimental findings very well. Kinetics analysis revealed that the leaching process is controlled by a chemical reaction under the employed experimental conditions and the activation energy of the reaction is 48 kJ·mol-1.     

不同化学结合剂对铜氧化物的团聚和浸出行为

The chemical binder is one of the critical factors affecting ore agglomeration behavior and leaching efficiency. In this study, we investigated the effect of the type of binder and mass fraction of the H₂SO₄ solution used on the curing, soaking, and leaching behavior of agglomerations. The results revealed that Portland cement (3CaO·SiO₂, 2CaO·SiO₂, and 3CaO·Al₂O₃) was the optimal binder for obtaining a well-shaped, stable agglomeration structure. A higher extraction rate was achieved when using Portland cement than that obtained using sodium silicate, gypsum, or acid-proof cement. An excessive geometric mean size is not conducive to obtaining well-shaped agglomerations and desirable porosity. Using computed tomography (CT) and MATLAB, the porosity of two-dimensional CT images in sample concentrations L1–L3 was observed to increase at least 4.5vol% after acid leaching. Ore agglomerations began to be heavily destroyed and even to disintegrate when the sulfuric acid solution concentration was higher than 30 g/L, which was caused by the excessive accumulation of reaction products and residuals.     

铀矿堆浸过程的动力学模型及实验研究

通过浸出率与浸出时间的关系曲线,推导出铀矿硫酸堆浸过程的控制模式和化学反应常数。实验结果表明浸出率在小于60％以内,与浸出时间呈直线关系,得出浸出过程控制模式为化学反应控制的结论。实验数据计算得出在该实验中化学反应浸出速率常数为1．5×10^-7s^-1,液固相化学反应速率系数为3．6×10^-8m／s。实验结果在未加氧化剂的酸堆浸铀矿石中,最多只有40％的四价铀能氧化成六价铀,要想进一步提高铀的浸出率,必须加入氧化剂,提高氧化能力。     

从难处理金矿中回收金:黄铁矿对硫脲浸金体系稳定性的影响

The extraction of gold from refractory gold ores (RGOs) without side reactions is an extremely promising endeavor. However, most RGOs contain large amounts of sulfide, such as pyrite. Thus, investigation of the influence of sulfide on the gold leaching process is important to maximize the utilization of RGOs. In this work, the effects of pyrite on the stability of the thiourea system were systematically investigated under different conditions. Results showed that the decomposition rate of thiourea was accelerated sharply in the presence of pyrite. The effect of pyrite on gold recovery in thiourea leaching systems was then confirmed via a series of experiments. The decomposition efficiency of thiourea decreased by 40% and the recovery efficiency of gold increased by 56% after the removal of sulfide by roasting. Under optimal conditions, the efficiency of the gold recovery system increased to 83.69% and only 57.92% of thiourea decomposition was observed. The high consumption of thiourea by the leaching system may be attributed to not only adsorption by mineral particles but also catalytic decomposition by some impurities in the ores, such as pyrite and soluble ferric oxide.     

Extraction of vanadium from vanadium slag by high pressure oxidative acid leaching

To extract vanadium in an environment friendly manner, this study focuses on the process of leaching vanadium from vanadium slag by high pressure oxidative acid leaching. Characterizations of the raw slag, mineralogy transformation, and the form of leach residues were made by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The result shows that the vanadium slag is composed of major phases of fayalite, titanomagnetite, and spinel. During the high pressure oxidative acid leaching process, the fayalite and spinel phases are gradually decomposed by sulfuric acid, causing the release of vanadium and iron in the solution. Meanwhile, unreacted silicon and titanium are enriched in the leach residues. With the initial concentration of sulfuric acid at 250 g·L-1, a leaching temperature of 140℃, a leaching time of 50 min, a liquid-solid ratio of 10:1 mL·g-1, and oxygen pressure at 0.2 MPa, the leaching rate of vanadium reaches 97.69%.     

银金精矿的焙烧条件对焙砂中金银提取的影响

在热分析的基础上对吉林某浮选银精矿的预处理过程进行了研究。研究了焙焙烧温度、焙烧时间奶对金精矿中硫，碳脱除率的影响，着重研究了有添加剂存在时焙烧工艺条件对银精矿焙砂的金银提取性能的影响，并了添剂在硫酸化焙烧过程中的作用。试验结果表明：有添加剂存在时的焙少经稀硫酸预浸，其预浸渣于用硫脲法或氰化法浸金时，其金的浸率将大于９５％，争遥总浸出率也分别达９５％     

LiCoO2的化学分解浸取过程

废旧锂离子电池中钴的含量较高．钴具有较强的毒性,且资源稀少．为此,研究了废旧锂离子电池的湿法回收工艺过程,并分析了废旧锂离子电池中钴和锂在硫酸溶液中的漫取过程动力学．采用了解体电池塑料外壳、钢壳、正负极材料、N-甲基吡咯烷酮(NMP)分离铝箔与正极活性材料以及硫酸浸取钴与锂的回收工艺．结果表明,铝片的回收率接近100％,钴和锂的浸取率均超过99．6％,同时分析了漫取过程中的工艺参数对钴和锂的漫取率的影响．     

酸浸法提钒新工艺的研究

研究了用稀硫酸直接浸出—萃取—反萃—氨水沉钒—煅烧的提钒工艺。结果表明,采用稀硫酸直接浸出,原矿渣中总钒的一次浸取率可达95%以上;用萃取-反萃方式净化和浓缩浸出液,同时使用萃取促进剂处理酸浸液,使萃取效率比传统方法有明显提高,萃取级数大大减少;沉钒步骤摒弃了传统的铵盐沉钒工艺,使用氨水直接沉钒,提高了产品的纯度。钒的总回收率达86%以上,比传统提钒工艺效率提高了20%以上,同时由于避免了焙烧从而解决了传统提钒过程中因焙烧等产生的HCl、Cl₂等污染问题。     

Sulfuric acid leaching of high iron-bearing zinc calcine

Sulfuric acid leaching of high iron-bearing zinc calcine was investigated to assess the effects of sulfuric acid concentration, liquid-to-solid ratio, leaching time, leaching temperature, and the stirring speed on the leaching rates of zinc and iron. The results showed that the sulfuric acid concentration, liquid-to-solid ratio, leaching time, and leaching temperature strongly influenced the leaching of zinc and iron, whereas stirring speed had little influence. Zinc was mainly leached and the leaching rate of iron was low when the sulfuric acid concentration was less than 100 g/L. At sulfuric acid concentrations higher than 100 g/L, the leaching rate of iron increased quickly with increasing sulfuric acid concentration. This behavior is attributed to iron-bearing minerals such as zinc ferrite in zinc calcine dissolving at high temperatures and high sulfuric acid concentrations but not at low temperatures and low sulfuric acid concentrations.     

Deep cleaning of a metallurgical zinc leaching residue and recovery of valuable metals

Huge quantities of zinc leaching residues (ZLRs) generated from zinc production are dumped continuously around the world and pose a potential environmental threat because of their considerable amounts of entrained heavy metals (mainly lead). Most ZLRs have not been properly treated and the valuable metals in them have not yet been effectively recovered. Herein, the deep cleaning of a ZLR and recovery of valuable metals via a hydrometallurgical route were investigated. The cleaning process consists of two essential stages:acid leaching followed by calcium chloride leaching. The optimum conditions for extracting zinc, copper, and indium by acid leaching were a sulfuric acid concentration of 200 g·L-1, a liquid/solid ratio of 4:1 (mL/g), a leaching time of 2 h, and a temperature of 90℃. For lead and silver extractions, the optimum conditions were a calcium chloride concentration of 400 g·L-1, a pH value of 1.0, a leaching time of 1 h, and a temperature of 30℃. After calcium chloride leaching, silver and lead were extracted out and the lead was finally recovered as electrolytic lead by electrowinning. The anglesite phase, which poses the greatest potential environmental hazard, was removed from the ZLR after deep cleaning, thus reducing the cost of environmental management of ZLRs. The treatment of chlorine and spent electrolyte generated in the process was discussed.     

芦丁还原浸出低品位软锰矿的研究

为了研究糖蜜酒精废液中有机物还原浸出软锰矿的机理,采用芦丁为还原剂,在酸性介质中直接浸出低品位软锰矿。通过正交实验和单因素实验,研究了芦丁浓度、硫酸浓度、反应温度、浸出时间等因素对锰浸出率的影响,并对反应过程机理进行了初步探讨。实验结果表明,影响锰浸出率的主要因素依次为反应温度、硫酸浓度、浸出时间和芦丁浓度;当硫酸初始浓度2.35 mol/L,芦丁初始浓度0.041 mol/L,反应温度90℃,浸出时间90 m in时,锰浸出率达94.9%。     

冶金级硅酸洗提纯研究

冶金工艺被认为是非常有前途的一种有别于传统的西门子工艺而且能够满足市场对太阳能级硅需求的工艺.冶金级硅的预处理是冶金提纯工艺路径中非常重要的一个环节,因为酸洗可以有效地去除硅中的金属杂质例如铝、铁和钙等.通过系统性的对比试验对酸洗工艺去除硅中杂质的效果进行了详细的研究,分别探讨了酸的种类、酸的浓度、酸洗时间、酸洗温度以及硅粉颗粒粒径对杂质去除效率的影响.研究结果表明最佳的酸洗工艺参数为15%的盐酸,80℃,10h和100μm.在最佳酸洗工艺参数条件下金属杂质铝、铁和钙的去除率分别为70.90%、94.82%和82.69%.     

浸取环境对电解锰废渣中锰浸取的影响

在电解锰废渣中掺入锰矿粉,以提高锰废渣品位,探讨锰废渣中锰的硫酸法浸取回收效果.用单因素实验考察了矿渣比、液固比、浸取pH值、浸取温度和浸取时间等因素对锰浸取率的影响.实验结果表明,最佳浸取条件为：矿渣质量比3∶1、液固比3∶1（g/mL）、浸取液pH值2.0、浸取温度60 ℃和浸取时间3 h.最佳浸取条件下,锰浸取率达42.38%,与不加锰矿粉的浸取方法比较,锰浸取率提高了1.01倍.     

氧化铝赤泥酸浸提取镓的新工艺研究

研究了拜耳法赤泥硫酸浸出镓的过程。硫酸浸出镓的溶液,用氢氧化钠反应生成沉淀,再用盐酸溶解沉淀提取镓的过程。采用正交试验考察浸出过程中温度、时间、液固比、浓度对镓浸出率的影响的主次顺序以及最佳条件。结果表明,该方法比单纯用盐酸浸出镓的浸出率高。镓的高浸出率是保证高的回收率的基础。     

赞比亚低品位难处理铜钴矿湿法冶金新工艺

以赞比亚某低品位难处理铜钴矿石为研究样本,采用全湿法冶金方法,开展新工艺研究.研究可知:矿石Cu,Co和S质量分数分别为1.270%,0.071%,0.022%.矿石中铜矿物主要为假孔雀石和少量的孔雀石.钴矿物主要为钴锰矿和水钴矿,在褐铁矿和黑云母晶体中有少量铜、钴,矿石中铜钴元素赋存状态极其复杂.最佳的浸出条件为粒度小于74μm的矿粒所占比例70%、浸出温度65℃、浸出时间4 h、矿浆质量分数30%、硫酸加入量55 kg·t-1.该条件下铜浸出率可达74.34%左右,钴浸出率可达43.32%左右.充分利用萃余液中的硫酸可降低酸耗,硫酸用量减少20%以上.在搅拌浸出过程中加入适量还原剂Na_2SO_3或FeSO_4,可将钴的浸出率从43%提高到78%.     

用废旧电路板酸浸-电沉积法回收金属铜

为了既保障环保又达到最佳铜回收效果的目的,以废旧电路板经过初步破碎分离,得到铜金属富集产品为研究对象,采用硫酸-双氧水浸出结合电沉积工艺回收物料中的铜。考察了铜浸出率与硫酸质量浓度、双氧水用量、浸出时间、液固比之间的关系,进行最佳金属浸出条件实验。结果表明：硫酸物质的量浓度为3.5 mol/L、浸出时间3 h、双氧水用量为20 mL、液固比10∶1条件下,铜金属浸出率最高可达到97.58%。电沉积尾液循环用以浸出铜,铜离子循环质量浓度不低于18 g/L,平均电流效率高于97.60%。在沉积温度40℃,阴极材料为T2紫铜,电流密度小于800 A/m2时,电流效率可以保持在97%以上。实验中铜回收率达到了97.58%。