Inferring the distribution of iron oxidation species on mineral surfaces during grinding of base metal sulphides

Electrochemistry plays an important role in the flotation of base metal sulphide minerals. During grinding a galvanic interaction occurs between minerals and grinding media and controls the iron contamination on mineral surfaces, which depresses mineral flotation significantly. In this study, the galvanic interaction was quantified by measuring the iron oxidation species originated from grinding media by ethylene diamine-tetra acid (EDTA) extraction in single mineral and mixed mineral systems. It was found that the extent of galvanic interaction between minerals and grinding media was intimately associated with the electrochemical reactivity of minerals. The nobler the mineral, the stronger the galvanic interaction with grinding media, and the higher the amount of iron oxidation species from grinding media. For both galena and chalcopyrite a linear relationship was observed between the amount of iron oxidation species and flotation recovery in single mineral systems. This relationship was able to predict the iron oxidation species on galena and chalcopyrite surfaces when they were mixed with pyrite separately. The distribution of iron oxidation species onto the two minerals in the mixture changed with the ratio of the mineral surface areas and was correlated with mineral flotation recovery. The major cathodic mineral in the mixture was dictated by the combination of mineral surface area and reactivity and drew iron oxidation species from the grinding media.     

鞣酸体系下黄铜矿与黄铁矿浮选动力学分析

在铜硫硫化矿浮选实践中,一般通过添加大量的浮选药剂强压强拉以实现硫化铜和硫化铁矿物的浮选分离。利用铜硫硫化矿物在浮选药剂体系下浮选速率的差异,可以实现其清洁浮选分离。本文通过分批次刮泡浮选试验研究了鞣酸体系下黄铜矿及黄铁矿浮选行为和浮选动力学特性,计算了黄铜矿、黄铁矿在鞣酸体系下的浮选速率常数。研究结果表明,鞣酸能有效地抑制黄铁矿的浮选,而对黄铜矿的抑制作用较弱。在鞣酸体系下,黄铜矿的浮选速率明显大于黄铁矿的浮选速率,黄铜矿的平均浮选速率常数为0.80,而黄铁矿的平均浮选速率常数只有0.31。通过数学方法拟合了两种矿物在鞣酸体系下的浮选动力学模型,拟合结果表明,黄铜矿和黄铁矿浮选动力学均适用于改进的分速一级模型。     

Separation of chalcopyrite and pyrite from a copper tailing by ammonium humate

Copper tailings constitute a large proportion of mine wastes. Some of the copper tailings can be recycled to recover valuable minerals. In this paper, a copper tailing was studied through the chemical analysis method, X-ray diffraction and scanning electron microscope-energy dispersive spectrum. It turned out that chalcopyrite (Cu) and pyrite (S) were the main recoverable minerals in the tailing. In order to separate chalcopyrite from pyrite in low pulp pH, ammonium humate (AH) was singled out as the effective regulator. The depression mechanism of AH on the flotation of pyrite was proved by FTIR spectrum and XPS spectrum, demonstrating that there was a chemical adsorption between AH and pyrite. By Response Surface Methodology (RSM), the interaction between AH, pulp pH and iso-butyl ethionine (Z200) was discussed. It was illustrated that the optimal dosage of AH was 1678 g·t^-1 involving both the recovery of Cu and S. The point prediction by RSM and the closed-circuit flotation displayed that the qualified Cu concentrate and S concentrate could be obtained from the copper tailing. The study indicated that AH was a promising pyrite depressor in the low pulp pH from copper tailings.     

黄铁矿浮选的抑制与解抑活化研究进展

黄铁矿浮选问题是金属矿、煤矿以及某些非金属矿等开发利用过程中通常需要面临的问题,其浮选的抑制、解抑活化以及影响其浮选行为的一些因素一直是矿物加工领域的研究热点。本文分析了矿物学因素、难免离子和伽伐尼电偶作用对黄铁矿的浮选行为的影响,着重从浮选药剂与矿物的作用机理方面综述了黄铁矿的抑制与解抑活化;黄铁矿与不同种类的抑制剂作用后通过生成亲水膜、阻止黄药氧化、占据黄铁矿表面捕收剂能作用的活性位点、生成络合物以及多糖、蛋白质等微生物细菌胞外分泌物的吸附等作用对黄铁矿产生抑制作用;高碱环境下常用酸和盐类活化剂对受抑黄铁矿表面的亲水膜溶解进行活化,实现黄铁矿的回收利用。分析认为目前对矿物内部和矿浆的复杂环境研究仍不到位,应通过现代分析测试手段和计算机技术加强研究;黄铁矿不仅仅作为一种矿物资源,黄铁矿等环境矿物在环保领域的研究应用对缓解经济发展与环境保护的矛盾起着至关重要的作用。     

Semi-autogenous grinding mill pebbles as a vertically stirred mill medium

ABSTRACT

Semi-autogenous grinding pebbles were used as a grinding medium and compared to steel balls in terms of their effect the flotation behavior of the products and their industrial application. The pebbles increased the rate of copper recovery from the concentrated products by 3.30% to 86.89%. Industrial application showed that using pebbles instead of steel balls reduced over-comminution by 8.05% and increased the recovery rate by 1.81% when the copper grade of the concentrate was equal. Hence, pebbles are a viable and beneficial alternative to steel balls as the grinding medium in vertical mills.     

Study of metal ion sorption from acidic solutions

Acid mine drainage waters flowing out of the abandoned sulphide ore mine Smolnik in Slovakia represent a serious source of water and soils contamination. High concentrations of sulphate, iron, copper and other heavy metals are the result of pyrite oxidation connected with sulphuric acid production, which continuously dissolves rock minerals and produces a number of potentially toxic elements. The paper deals with the utilization of four types of natural and synthetic sorbents (produced mainly in Slovak Republic) for Fe, Cu, Al, Mn and Zn removal from acid mine drainage (shaft Pech, locality Smolnik, Slovakia). Prior to the kinetic study, the screening sorption experiment has been performed in order to determine optimum sorption pH. The turf brush sorbent Peatsorb has shown the satisfactory results for the removal of iron, copper, aluminium, zinc and manganese at pH below 4.     

Development of a galvanic sensor system for detecting the corrosion damage of the steel embedded in concrete structures: Part 1. Laboratory tests to correlate galvanic current with actual damage

The correlation between sensor output and corrosion rate of reinforcing steel was evaluated by laboratory electrochemical tests in saturated Ca(OH)₂ with 3.5 wt.% NaCl. In this paper, two types of electrochemical probes were developed: galvanic cells containing of steel/copper and steel/stainless steel couples. The corrosion behavior in saturated Ca(OH)₂ solution with and without 3.5 wt.% NaCl addition for the different electrodes was investigated by potentiodynamic test. Weight loss measurement and galvanic corrosion test were conducted to obtain the corrosion rate of reinforcing steel and the charge of sensor in saturated Ca(OH)₂ solution with 3.5 wt.% NaCl addition, respectively.

The results of the potentiodynamic test indicated the possibility of detecting an ingress point of chlorides by measuring the galvanic current. In galvanic corrosion tests, the galvanic current of steel/copper couple was higher than that of steel/stainless steel couple, i.e., the steel/copper sensor is more suitable for high resistance environment. The steel/stainless sensor showed a better linear correlation than the steel/copper sensor. Through the relationship between the sensor system output and the weight loss (mg/cm²) of steel, real corrosion damage of the steel embedded in concrete can be detected.     

Galvanic interaction of pyrite with Cu activated sphalerite and its effect on xanthate adsorption

In the presence of Cu ions, a packed bed electrochemical reactor (PBER) was employed to deliberately avoid or induce galvanic coupling between pyrite and Cu‐activated sphalerite. The effect of galvanic interaction on Cu ions uptake and xanthate adsorption were investigated. Solution chemistry and surface chemistry studies (ethylenediaminetetraacetic acid extraction and time of flight secondary ion mass spectrometry) have observed that when sphalerite and pyrite were galvanically coupled, Cu ions migrated from the pyrite surface to the surface of the sphalerite. Along with the marked decrease in the adsorption of Cu ions on pyrite, xanthate adsorption on the minerals also dramatically dropped. The pseudo‐adsorption rate constant for the minerals in the mixed mode is only 0.0583 s^?1, much less than that in the decoupled mode, which is 0.1368 s ^?1. This testing program shows that the galvanic coupling of minerals contributes to more copper transfer and Cu ions preferentially adsorbed by sphalerite rather than pyrite. This affects the pyrite surface and causes it to become xanthate unflavoured.     

Relation Between Base Metal Composition, Surface Composition, Pickling Rate, and Direct-On Adherence

Changes in residual alloy concentration, particularly increases in copper and nickel, which take place in pickling were found to be due to the formation of a pickling film through galvanic plating of these elements dissolved in the acid. Before pickling, the steel surface was actually higher in copper and nickel than was the interior, owing to preferential oxidation of iron during mill processing. Pickling film buildup (such as surface copper) was found to have no direct telation to adherence. Slow pickling steels, however, on which adherence was less easily obtained, built up more copper on the surface; hence, an apparent correlation existed. Fast pickling steels, which gave good adherence with less metal removal than was required for slow pickling steels, showed much more surface roughening for the same amount of metal removal. This increased roughening is felt to be a contributing factor toward good direct-on adherence.     

四川兴文先锋硫铁矿地质特征及成矿规律

先锋硫铁矿位于宜宾市兴文县。先锋硫铁矿主要矿石矿物为黄铁矿、白铁矿、胶黄铁矿;脉石矿物:高岭石、珍珠陶土等。矿石结构:半自形-自形晶粒结构、它形粒状结构、碎裂结构、变胶状环带结构;矿石构造:浸染状、条带状、网脉状、根须状、树枝状、团块状、结核状等构造。分析将从古地形初始、硫铁矿表生富集和硫铁矿成岩富集三个阶段。     

Development of a galvanic sensor system for detecting the corrosion damage of the steel embedded in concrete structure: Part 2. Laboratory electrochemical testing of sensors in concrete

The correlation between sensor output and the corrosion rate of steel bar was confirmed in concrete environment. Open-circuit potential, linear polarization resistance (LPR) measurement and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of steel bar embedded in concrete. Also, galvanic current measurements of designed sensors were conducted to obtain the charge of sensor embedded in concrete.In this study, the results of corrosion behavior of reinforcing steel showed a consistence among the data obtained by open-circuit potential monitoring, LPR and EIS measurements. Steel/copper sensor showed a good correlation in concrete environment between sensor output and corrosion rate of steel bar. However, there was no relationship between steel/stainless steel sensor output and corrosion rate of steel bar due to the low galvanic current output. Through the relationship between the steel/copper sensor output and the corrosion rate of reinforcing steel, the real corrosion damage of the reinforcing steel can be detected. Consequently, this confirms that the galvanic sensor system is a good method for detection of corrosion in reinforced concrete.     

铁矿石物相分析与研究

铁是地壳中分布最为广泛的元素之一。但具有工业价值的铁矿石则为数不多。铁矿石的物相分析工作,对我们采矿、选矿有着重要意义。铁矿物存在状态不同、晶体结构不同、风化程度不同。评价铁矿床的经济价值和矿床储量的计算不取决于铁的绝对含量,而与铁在矿石中的存在状态及其含量有关,铁矿物中有好多矿物还没有被我们开发利用。因为由同一元素组成的不同矿物,在工业处理上的难易程序和方法是不同的,所付出的经济代价也不相同,所以由该元素所组成的不同矿物是否能够全部被提取和利用率的大小也不相同,这就要求我们必须准确地确定由同一元素组成的不同矿物的百分含量。因此,按照我们测定菱铁矿、磁铁矿、磁黄铁矿、赤褐铁矿、黄铁矿、铁的硅酸盐的物相分析,研究其分离测定流程,是必不可少的,便于生产单位更好完成生产任务。     

Surface potential distribution over a zinc/steel galvanic couple corroding under thin layer of electrolyte

In this study, surface potential and surface pH changes over a zinc/steel galvanic couple corroding in artificial seawater (ASW) at 60 and 90% RH have been investigated. The results from surface potential and surface pH measurements were substantiated by the surface observation of the corroded sample during and after the corrosion test. The potential difference over the zinc and steel surface in 90% RH was very low (less than 200 mV) showing that whole steel surface was under galvanic protection. On the other hand, in 60% RH, after several days of corrosion the potential difference between the zinc coating and the steel surface was very high (more than 500 mV) and hence the galvanic protection was limited to interface region. The X-ray analysis of the sample corroded in 60% RH has shown that the zinc corrosion products were deposited on the steel surface near the interface, the same region has shown a low pH compared to than in other part of the steel surface. This led to conclude that with the progress of corrosion, the coating surface of zinc coated steel acidifies by the hydrolysis reaction of the dissolved zinc ions, and the iron surface showed the alkalinity by the oxygen reduction reaction. Moreover, the parts of the steel surface covered with zinc corrosion products had developed relatively less noble potential than other parts indicating that zinc corrosion products took a role to protect the base steel against corrosion. It was assumed that this behavior was related to a combination of the water absorbing capability of zinc corrosion products and adsorption of zinc ion on the steel surface due to low pH.     

A study on selective flotation in low and high pyritic copper sulphide ores

The effect of chemical reagent configurations was investigated on two different copper sulphide ore types, including high and low pyritic feeds. Three different combinations of collectors as isopropyl-n-ethyl thionocarbamate (C-4132), mixture of mercaptobenzothiazole and butyl sodium dithiphosphate (Flomin 7240) and sodium isopropyl xanthate (Z11) were used in flotation experiments. Solely using C-4132 was selected as the best pattern for both feed types with regard to achieving the highest copper grade and the lowest iron recovery. However, the selectivity index (SI) results showed that the combination of Z11+F7240 provides the highest selectivity of chalcopyrite against pyrite in either low or high pyritic ores.     

Applying One-Stage Grinding and Flotation to Improving Copper Recovery of a Fine-Grained Cu-Mo Sulphide Ore

This paper introduces the mineralogy of a fine-grained Cu-Mo sulphide ore, and the relationship between grinding fineness and flotation performance. Results show that the grinding fineness is a key factor affecting the recovery of copper and molybdenum. The result of one stage grinding and flotation is much better than that of grinding and flotation by stages, because an over grinding of chalcopyrite caused by regrinding of Cu-Mo bulk concentrate can be avoided. Finally, a simple flowsheet has been developed, that is, one-stage fine grinding of raw ore to 90% ?0.074 mm, and a bulk flotation to produce a bulk concentrate by one-stage roughing, two stages of cleaning and one-stage scavenging, followed by three times of Cu-Mo flotation separation. When the feed contains 0.50% Cu and 0.19% Mo, the obtained copper and molybdenum concentrates assay 19.23% Cu and 48.53% Mo with the recoveries of 85.5% and 90.96%, respectively.     

The role of silver minerals on the cyanidation of gold particles embedded within multi‐sulphidic mineral matrices

The effect of silver minerals on the dissolution behaviour of gold particles embedded within multi‐sulphidic minerals was investigated. A multi‐layer packed‐bed reactor approach was used to study the leaching behaviour of free gold (within silica) and gold associated with a series of synthetic multi‐mineral systems consisting of pyrite, silica, and successively, X = chalcopyrite, sphalerite, and stibnite. The reactor was filled with sieved powders of sulphidic minerals (pyrite, X), gold and silica and arranged as electrically‐isolated three‐layer //Pyrite//X//Silica// and two‐layer //Pyrite + X//Silica// systems. Gold powder was introduced successively in each layer of the three‐ and two‐layer mineral systems and the gold leaching behaviour was studied. The highest gold recovery was achieved for the gold particles within the pyrite layer while the lowest was within the silica layer. In case of the //Pyrite//Stibnite//Silica// system, the surface passivation inhibited gold leaching strongly. Gold cyanidation experiments were also performed with the addition of silver minerals, with both Au and Ag minerals dispersed in a three‐layer //Pyrite//X//Silica// and two‐layer //Pyrite + X//Silica// systems. Silver minerals addition proved beneficial for the pyrite‐sphalerite‐silica system. Gold leaching was severely retarded for the pyrite‐chalcopyrite‐silica and pyrite‐stibnite‐silica systems. Passivating films were observed at the surface of gold particles in case of gold cyanidation with pyrite‐chalcopyrite‐silica and pyrite‐stibnite‐silica systems.

     

改善新疆某铜镍矿半自磨机顽石积累

针对新疆某铜镍矿半自磨机顽石积累严重，磨矿产品细度不达标的问题，在测定矿石力学性质基础上，采用半自磨机磨矿循环的方法，以钢球介质配比作为单一变量，进行提高磨矿指标的磨矿对比研究，并采用离散元方法验证实验结论，最终确定半自磨机的最佳介质配比方案为?150:?120=1:2。结果表明，矿石比重平均值为3.36 g/cm3，硬度系数平均值为7.93有误单位，弹性模量平均值为3.11×104 MPa，泊松比平均值为0.26，矿石中等偏硬，伴有脆性、韧性较大的矿石存在；在相同磨矿条件下，半自磨机的推荐方案顽石25~80 mm粒级产率逐渐减少，现场方案反之。三次磨矿循环后，推荐方案较现场方案25~80 mm粒级产率低4.19个百分点，+100, ?2.5, ?0.074 mm三个粒级产率分别提高了0.25, 13.79, 4.80个百分点；与偏大方案相比，推荐方案同样表现出较好的研磨能力，在相同磨矿条件下，三次磨矿循环后顽石25~80 mm粒级产率低3.36个百分点，?0.074 mm磨矿细度高2.24个百分点。推荐方案25~80 mm粒级法向碰撞能量利用率为56.19%，较现场方案及偏大方案分别高1.82和2.30个百分点，推荐方案较其他两个方案顽石破碎能力更好，模拟仿真结果与实验结果一致。综合对比可知，推荐方案具有明显的优势，在保证磨矿产品细度维持在较好水平下，充分解决了顽石积累的问题，为相关厂矿同类问题提供可借鉴的方法。     

Bioleaching of copper via iron oxidation from chalcopyrite at elevated temperatures

The effect of elevated temperature on the bioleaching of copper from chalcopyrite (CuFeS₂) via iron oxidation using Acidithiobacillus ferrooxidans under mesophilic conditions was studied. It was shown that temperature tolerant and ore adapted strains of At. ferrooxidans could extract copper significantly better than non-adapted cultures at elevated temperatures. The presence of soluble iron and its oxidative state, as a determining factor in copper leaching were found to be closely related to pH and temperature.     

Spontaneous passivation observations during scale formation on mild steel in CO2 brines

Previous study revealed localized corrosion in CO₂ environments was driven by a galvanic cell established between pit surfaces and scaled surrounding area. In order to underpin the understanding of the galvanic mechanism of localized corrosion, the root cause of potential differences between these two surfaces, passivation of mild steel, in CO₂ environments was investigated using transmission electron microscopy technique and electrochemical techniques including potentiodynamic polarization, cyclic polarization and open circuit potential techniques. Potentiodynamic polarization experiments showed that the passivation of the carbon steel surface favorably occurred at pH > 7 and facilitated with the presence of FeCO₃ scale. Cyclic polarization tests showed that polarization rate had an important influence on passivation behavior. At a slower polarization rate, lower passivation potential and current density were observed. Spontaneous passivation was evidenced by a significant increase of corrosion resistance and an open circuit potential without any externally applied current or potential during electrode immersion. This process is affected by pH, temperature, presence of CO₂ and iron carbonate. Nevertheless, iron carbonate film is not the only one responsible for passivation, as demonstrated from depassivation tests where passivity was lost without losing the existing iron carbonate film. Transmission electron microscopy technique was used to determine the structure of the passive layer. An extra phase, most likely magnetite, was observed to be beneath the iron carbonate scale and at the crystal grain boundaries which passivated the mild steel.     

高压辊磨机在铁矿石加工中的应用

高压辊磨机因其在使用过程中可以省掉磨碎前的中细碎设备,而且可以不设中间矿仓,以及与其他粉碎设备配用可实现整个系统的最佳粉碎效果,所以其在铁矿石加工中的应用快速增长。本文介绍了高压辊磨机在铁矿石加工中的应用与选型,说明正确认识高压辊磨机的加工性能并采用合适的参数进行选型,可优化现有铁矿石加工工艺流程,达到节能降耗的效果。