Changes in the surface phase composition of sulfide minerals upon irradiation by high-power nanosecond pulses

The effect of high-power (high-voltage) nanosecond pulses on the phase composition and chemical state of atoms of surface layers of sulfide minerals with different semiconductor properties (galenite, molybdenite, and sphalerite) is investigated by means of XPES. Common patterns and characteristic features of the structural phase transformations of sulfide surfaces under the pulsed energetic effect are the formation and growth of a surface layer by the nonstoichiometric sulfur-enriched sulfide phase and Zn and Mo oxides and hydroxides; the staged character of the transformation of sulfur atoms in the composition of galenite and sphalerite surface layers; and the stability of the chemical state of sulfur in the molybdenite composition and lead atoms in the galenite composition.     

Adsorption of nitrogen oxide molecules to the surface of nanosized nickel clusters formed on the (111) surface of a magnesium oxide film

The properties of the systems formed on deposition of Ni atoms on the (111) surface of a MgO film of thickness equal to six monomolecular layers grown on a Mo(110) crystal face and the adsorption of NO nitrogen oxide molecules to the system surface have been studied by methods of electron spectroscopy (AES, XPES, LEED, LEIBSS) and reflective infrared absorption spectroscopy. On deposition of Ni atoms on the surface of MgO at a substrate temperature of 600 K, three-dimensional islands of Ni are formed. The subsequent adsorption of NO results in molecule dissociation even at 110 K. The efficiency of this process depends on the morphology of the Ni layer.     

A novel flotation technique combining carrier flotation and cavitation bubbles to enhance separation efficiency of ultra-fine particles

In this paper, a novel flotation technique that combines nano-scale bubbles generated by hydrodynamic cavitation (HC) and carrier flotation is proposed to promote the flotation efficiency of a high-ash (43%) ultra-fine coal sample (<45 µm). We investigated the mechanism by which cavitation bubbles enhance the separation efficiency of carrier flotation using focused beam reflectance measurements, polarizing microscopy, and extended Derjaguin–Landau–Verwey–Overbeek theory. The carrier particles (polystyrene (PS)) and fine coal were pre-treated in a venturi tube and then floated in a laboratory mechanical flotation cell. The flotation results indicate that the presence of cavitation bubbles significantly improved the carrier flotation performance of high-ash ultra-fine coal. This improvement was attributed to the presence of highly hydrophobic PS, which creates additional gas nuclei in the flotation system. The nano-bubbles, which were produced by the venturi tube and adhered to the fine coal particle surfaces, were conducive to the agglomeration of fine coal particles into large aggregates. Moreover, the nano-bubbles functioned as “bridges” of interaction between the carrier particles and large aggregates of fine coal particles. This paper mainly focused on the effect of carrier (PS) and HC on high-ash fine coal. The influence of different HC intensities on carrier (PS) flotation was discussed. Two models for the interactions between the coal particles, nano-bubbles, and PS during cavitation were proposed and were proved using the E-DLVO theory.     

Effect of the ultrasonic standing wave frequency on the attractive mineralization for fine coal particle flotation

Froth flotation for mineral beneficiation is one of the most important separation techniques; however, it has several challenges for processing fine and ultrafine particles. Attractive mineralization between particles and bubbles by ultrasonic standing wave (USW) is a novel and high-efficiency method that could assist fine particle flotation. Frequency is an important ultrasound parameter, whose effectiveness mechanisms on the attractive mineralization did not compressively address. This study explored the effect of the USW field with various frequencies on the fine coal flotation for filling this gap. Herein, a high-speed camera and a focused beam reflectance measurement (FBRM) were used to analyze three sub-processes of the attractive mineralization, including the microbubbles’ formation, the conventional flotation bubbles (CFBs)’ dispersion, and the particles’ movement. It was found that the maximum flotation metallurgical responses were obtained under the highest examined USW frequency (600 kHz). However, the flotation outcomes by a low USW frequency (50 kHz) were even lower than the conventional flotation tests. Observation and theoretical calculation results revealed these results were originated from the influence of frequency on the carrier bubbles’ formation and the action of the secondary acoustic force during USW-assisted flotation. These outcomes demonstrated that frequency is a key factor determining the success of attractive mineralization for fine particles’ flotation.     

Design of a flotation cell equipped with ultrasound transducers to enhance coal flotation

Ultrasonic treatment is widely used for surface cleaning during physical, chemical and physico-chemical processes in mineral processing. Several research papers and a few industrial applications about the subject suggest that the mechanism behind the positive effect of ultrasound for mineral processing and especially flotation is due to formation of cavitation by ultrasonic energy. Within this study, coal floatability is investigated by use of a specially designed flotation cell equipped with ultrasound transducers with different power, frequency and geometry. The results indicate that ultrasonic treatment during coal flotation positively affects the quality and quantity of the properties of floated coals while using of lesser amounts of reagent than a conventional flotation system.     

硫酸氢酯类药剂浮选铜的量子化学研究

我国矿产资源日益匮乏,对浮选药剂的选择性和安全性提出了更高的要求,设计新型药剂势在必行.运用密度泛函理论,选取B3LYP/6-311+G(d, p)方法基组,对碳原子数在15～21的硫酸氢酯类浮选药剂浮选铜离子进行了计算研究.通过几何参数优化、电荷密度分布及吸附能变化,探讨了碳原子数为15～21的硫酸氢酯类浮选药剂对铜离子浮选性能的改良,综合考虑各种因素, C_(17)(十七烷基硫酸氢酯)浮选效果较好.结论对研究浮选机理及分子模拟设计新型浮选药剂具有指导意义.     

Effect of ultrasonic standing waves on flotation bubbles

Ultrasonic flotation was an effective method to float fine coal. In this study, the effects of the standing waves with different frequencies on ultrasonic flotation were investigated. The dynamic processes of bubble and coal-bubble were revealed by a high-speed camera. The results showed that under the action of Bjerknes force, bubble aggregates were formed within 450 ms and coal bubble aggregates were formed within 20 ms. The bubble aggregates were statistically analyzed by image processing method. The number of aggregates and small bubbles in the ultrasonic field at 100 kHz was greater than those at 80 and 120 kHz. Besides, 100 kHz ultrasonic flotation achieved the highest yields of clean coal (35.89%) and combustible recovery (45.77%). The cavitation bubbles acted as either a “medium” or an “inclusion”, entrapping and entraining the coal particles in the flotation pulp. It promoted the aggregation of bubbles with coal particles, so the flotation efficiency was effectively improved in the presence of ultrasonic standing waves.     

红外拟合光谱分析微波对重晶石浮选的影响机理

目前浮选提高重晶石品位的方法通常采用新型浮选药剂从低品位重晶石矿中进行分选,采用微波加热预处理矿物可提高浮选回收率,但微波对浮选药剂与矿物的作用机理还不清楚。微波加热技术近年来用于矿物加工、冶金与材料制备等领域,具有反应速度快、产品指标高等优点。以油酸钠为捕收剂,对微波预处理后的重晶石纯矿物进行浮选,并对不同微波作用时间下的重晶石浮选样品进行红外光谱检测,通过红外拟合平滑光谱和二阶导数光谱计算分析,研究微波对重晶石浮选的影响机理。浮选试验结果表明,未经微波预处理的重晶石,在油酸钠用量为55 mg·L-1、pH值为8.0的条件下,浮选指标最佳,回收率为91.41%;而对比之下,经微波作用后的重晶石进行浮选,随着微波处理时间的增加浮选指标逐渐提高,且在微波作用60s时的回收率最高,达95.27%。基于浮选试验的红外光谱分析表明,重晶石未经微波预处理进行浮选,与油酸钠作用,在波数为3 004 cm-1处-CH₂-的对称伸缩振动峰、2 953 cm-1处-CH₃的反对称伸缩振动峰、1 119和1 077 cm-1处SO2-₄的非对称伸缩振动峰均发生了红移,说明油酸钠在重晶石表面发生化学吸附;而经微波预处理后的重晶石浮选时,在波数为2 853 cm-1处-CH₂-对称伸缩振动峰、2 923 cm-1处-CH₂-反对称伸缩振动峰、2 958 cm-1处-CH₃反对称伸缩振动峰、1 181,1 122和1 086 cm-1处SO2-₄非对称伸缩振动峰、982 cm-1处SO2-₄对称伸缩振动峰、635和610 cm-1处SO2-₄弯曲振动峰,其峰位并未发生红移,但峰强随着微波作用时间的增加明显加强,且微波作用60 s时其峰强增加最明显;对微波处理后的红外光谱进行拟合平滑光谱和二阶导数光谱计算发现,在波数为2 958,2 923,2 853,1 181,1 122,1 086,982,635和610 cm-1处峰面积均有不同程度的增加,且在微波作用60s时峰面积分别增加了1.84%,259.12%,761.15%,235.72%,145.61%,198.50%,641.16%,549.67%和744.97%,表明微波预处理并未诱发重晶石表面发生化学反应,但强化了捕收剂油酸钠与重晶石矿之间的化学吸附,使其与重晶石表面的化学吸附更加致密,吸附量增加,因此重晶石回收率增加,浮选指标提高。     

A review of effects and applications of ultrasound in mineral flotation

Ultrasound technology is widely applied in the flotation process. From the perspective of the theory of ultrasound, this article explains the effects and applications of ultrasound in the flotation process. To obtain a clear understanding of ultrasonic effects, we observe the phenomena of ultrasound using a high-speed camera and a CCD camera, and investigate potential applications in flotation. From these different phenomena, the ultrasonic effects are classified into three types of effect: the transient cavitation effect, stable cavitation effect, and acoustic radiation force effect. Based on these effects, the applications of ultrasound to mineral flotation are reviewed, including slime coating removal, oxidation film removal, desulfuration, tiny bubble generation, flotation reagent dispersion, and aggregation. In addition, the ultrasonic equipment and treatment methods applied in flotation are classified and compared based on their characteristics. Finally, we propose some potential directions in the study of the stable cavitation effect and acoustic radiation force effect, which are important, but are seldom mentioned in previous reports.     

Effect of ultrasonication on the flotation of fine graphite particles: Nanobubbles or not?

It has been reported that nanobubbles can be produced by ultrasonication. However, it remains unclear whether part of the contribution of ultrasonication on flotation performance can be attributed to the generation of nanobubbles. In this work, we systematically studied this point of ultrasonication by combining a series of techniques including flotation testing, AFM (atomic force microscope) measurement, and settling testing. AFM imaging showed that no surface nanobubbles were found at the HOPG-water interface before and after subjection to ultrasonication. Further, surface nanobubbles were generated with solution exchange before ultrasonciation and then they were subjected to ultrasonication. It was found that ultrasonication did not destroy the pre-existing surface nanobubbles at the HOPG (highly oriented pyrolytic graphite) -water interface. Settling tests and flotation tests indicate that ultrasonication has a negligible influence on the interaction between graphite particles and thus flotation performance. Nanobubbles were not one of the outcomes for ultrasonication.     

Wetting behavior of magnesite and dolomite surfaces

Magnesite and dolomite are salt-type minerals that show similar chemical composition and flotation behavior due to same crystal structure, and sparingly soluble nature. The surface properties of minerals play a major role in determining their separation from each other in processes such as flotation. During flotation process, selectivity problem arises between magnesite and associated gangue minerals such as dolomite. There is a close relationship between floatability of minerals and their contact angles. Therefore, surface hydrophobicity of magnesite and dolomite minerals was investigated by contact angle measurements in the absence and presence of flotation reagents.Magnesite and dolomite show hydrophilic properties and they have got a small contact angle (magnesite ∼10.4° and dolomite ∼6.6°) in distilled water in the absence of any surfactant. The contact angle values at the magnesite and dolomite surfaces remained at 9.7°-10.9° in the presence of petroleum sulphonates (R825 and R840) while sodium oleate affected hydrophobicity of magnesite, and the contact angle value increased up to 79°. The contact angle value of 39° at dolomite surface was obtained in the solution of sodium oleate, respectively.     

The role of bulk micro-nanobubbles in reagent desorption and potential implication in flotation separation of highly hydrophobized minerals

Micro-nanobubbles (MNBs) generated during hydrodynamic cavitation (HC) have been extensively studied in mineral processing field in the past two decades. Many researchers have claimed that MNBs can effectively promote the collection of fine particles in flotation, while studies on MNBs assisted mineral separation are rare. In this study, the role of bulk MNBs in desorbing flotation reagent was investigated, with the aim of illustrating the potential effects of MNBs on minerals separation. The results showed that bulk MNBs could efficiently remove the sodium oleate (NaOl) from diaspore surfaces, reducing the residual concentration of NaOl on solids, which was more significant when the amount of NaOl pre-adsorbed was relatively small. Furthermore, lower residual concentration of NaOl on solids caused by MNBs cleaning made the particles less hydrophobic and flocs more friable. Given that gangue entrapment in flocs was one of the main limits for high-selective flotation, the roles of MNBs in enhancing reagent desorption and associated flocs breakup and reorganization probably contribute to higher separation efficiency of different minerals, which was confirmed by the flotation results of diaspore/kaolinite mixture.     

氯化钠-十六烷基三甲基溴化铵体系分离富集-原子吸收光谱法测定湖泊沉积物中的镉

建立了碘化钾存在下氯化钠-十六烷基三甲基溴化铵体系分离富集-原子吸收光谱法测定湖泊沉积物中镉的新方法,最佳浮选分离条件为0.1mol.L-1HNO3、0.05mol.L-1KI、5.0×10-3mol.L-1CTMAC,NaCl用量为1.0%(W/V)。在最佳浮选分离条件下,镉的浮选率在94.1%—99.2%之间。合成样分离试验表明,体系能定量分离镉,而大量基体元素不被浮选。富集试验结果显示本法具有较好的富集效果,可明显提高测定的灵敏度。应用本法对湖泊沉积进行分离测定,结果满意。     

超声波强化煤泥浮选脱硫研究

叙述了超声波在选矿工程中的应用,研究了超声波处理对矿浆颗粒性质变化、矿浆中溶解氧和矿浆ｐＨ值的影响,探索了超声强化浮选脱硫的可行性,提出超声处理矿浆作为一种手段,配合适当的浮选工艺与黄铁矿抑制方法,能达到浮脱硫的最佳效果。     

红外光谱分析技术在浮选过程中的应用研究进展

随着浮选研究的深入发展,以捕收剂为核心的浮选药剂作用机理的研究逐渐成为研究焦点。红外光谱以速度快、成本低、无损等特点成为浮选药剂作用机理研究最为重要的手段之一。首先从文献报道数量和比例说明红外光谱在该研究中的重要地位,并总结了常见浮选药剂的红外光谱特征,最后分别阐述了红外光谱在捕收剂、抑制剂、活化剂等浮选药剂作用机理中的应用研究进展。归纳出红外光谱用于判定捕收剂在矿物表面作用三种机制的判据： 如果捕收剂作用后的矿物表面有新的吸收峰,则捕收剂在矿物表面发生了化学反应;如果仅有吸收峰的位置发生移动,并超过测试设备本身误差范围的移动量,则捕收剂在矿物表面形成的是化学吸附;排除上述产生的新红外特征吸收峰和红外特征峰的移动,且通过反复水洗即可清除表面沾染的捕收剂分子,则捕收剂在矿物表面发生的是物理吸附。并指出红外光谱在浮选过程中的应用研究存在的两大问题,一是将捕收剂与矿物表面的化学反应和化学吸附机理混淆;二是忽视红外光谱仪器吸收峰位移2～4 cm-1背景误差。展望未来红外光谱在浮选过程中的应用研究应该着眼于多种药剂混合用药在矿物表面作用机理的研究,该领域内红外光谱的定量分析研究及红外光谱吸收峰位移的背景误差分析等三方面。     

Effect of ultrasound pre-treatment on carbonaceous copper-bearing shale flotation

Although numerous studies have been implemented on identifying the impact of acoustic waves on mineral beneficiation, its fundamental aspects remain unclear in the literature. The present work, for the first time, systematically investigates the role of ultrasound pre-treatment (UPT) in the carbonaceous copper-bearing shale flotation. To this end, conditioning was carried out at different powers of applied ultrasound. Non-treated and UPT shale flotation tests were performed in the presence of frother (MIBC) and collector (KEX). To analyse particle surface charge variation and collector adsorption properties after application of UPT, zeta potential and ultraviolet–visible spectroscopy measurements were implemented, respectively. The generation of sub-micron bubbles due to the acoustic cavitation was characterised by laser-based particle size measurements. Shale hydrophobicity was determined using the sessile drop and captive bubble techniques.The micro-flotation results showed that the mass recovery increased by 40% at 20 W of applied ultrasonic power. The positive effect of UPT on the copper-bearing shale flotation was related to: i) generation of ultrafine bubbles due to the acoustic cavitation phenomenon and ii) the cleaning effect through transient bubble collapse. However, rigorous ultra-sonication diminished the recoverability of the sample owing to the less intensified number of ultrafine bubbles on the particle surfaces and formation of free H and OH radicals, which led to the oxidation of particle surfaces. These statements were correlated well with the observations of the zeta potential, particle size analysis and quantified ultrafine bubbles. Finally, we briefly highlighted fundamental knowledge gaps in flotation and ultrasound-related issues for future work.     

Ilmenite Mineral's Recovery from Beach Sand Tailings

The mineral ilmenite is the major source of rutile for industrial use and is of interest to paint and fertiliser industries. Enormous unutilised tailing dams lie on the eastern coast of the South Africa. Although covered by a simulation of the original indigenous vegetation, these tailings are still ilmenite bearing and of economic value. Tailings emanating from beach sand mineral slimes dams of the Kwazulu-Natal area (South Africa) have been processed. Screening, flotation, spiral concentration and magnetic separation methods were used either separately or successively. The present work sheds light on alternative routes for the extraction of the ilmenite, from these tailings. It moreover points out the usefulness of the Mössbauer spectroscopy in the mineral processing product monitoring. Tailings from the beach sands were used in the present study after the economic industrial minerals zirconia, ilmenite and rutile had been extracted in previous mining operations. About 61% natural ilmenite recovery was observed in the flotation concentrate of a Humphrey Spiral concentrate while a 62% recovery of hematite was found in the flotation tailings. The combination of screening, spiral concentration and magnetic separation, and flotation yielded a product with the highest ilmenite and hematite concentration being 71% and 19%, respectively. A natural ilmenite mineral, containing 87% ilmenite and 13% hematite, could be produced and extracted from the tailings of the flotation process, collected subsequently to the spiral concentration and the initial screening.     

硫氰酸铵-十二烷基二甲基苄基氯化铵-水体系浮选分离汞(Ⅱ)

研究了硫氰酸铵-十二烷基二甲基苄基氯化铵-水体系浮选分离汞(Ⅱ)的行为及其常见金属离子的分离条件。控制pH=5.0,当0.01mol/L硫氰酸铵溶液和0.01mol/L十二烷基二甲基苄基氯化铵(DDBAC)溶液的用量分别为0.30、0.50mL时,体系中形成的不溶于水的三元缔合物(DDBAC)2[Hg(SCN)4]可浮于水相上层形成界面清晰的液-固两相,分相过程中,Hg2+被定量浮选,而Zn2+,Cd2+,Mn2+,Ni2+,Co2+,Fe2+等离子在此条件下不被浮选,实现了Hg2+的定量分离。该方法对合成水样中微量Hg2+进行定量浮选分离测定,浮选率为96.0%—108.8%。     

沉淀浮选预分离/富集与FAAS联用测定粮食中痕量Cu和Mn的研究

提出了以8-羟基喹啉为沉淀剂,十二烷基苯磺酸钠为浮选剂,沉淀浮选预分离富集与火焰原子吸收光谱法联用测定痕量Cu和Mn的新方法。研究了浮选分离富集Cu和Mn的最佳条件。讨论了多种浮选条件对单一离子测定的影响及pH 9时混合离子浮选的相互影响,并考察了多种离子对Cu和Mn测定的影响。研究表明,pH为9时Cu的浮选率最大,在此条件下改变混合金属离子的浓度比,当Mn/Cu≥8时,Cu的回收率小于90%。方法简便,快速,灵敏度高,精密度理想,又可避免使用有毒的有机溶剂。铜的校准曲线线性范围为0.5～5.0 μg·mL-1,相关线性系数为0.999 6,方法检出限为1.59×10-3 μg·mL-1。锰的校准曲线线性范围为0.5～5.0μg·mL-1,相关线性系数为0.9987,方法检出限为3.52×10-3 μg·mL-1。该法应用于粮食中铜锰含量的测定,加标回收率达到87.6%～100.7%,结果令人满意。     

Effect of High-Voltage Nanosecond Pulses on the Physicochemical and Technological Properties of Rare-Metal Minerals

The mechanism of the structural and chemical state modification of columbite, tantalite and zircon surface under the effect of high-voltage nanosecond pulses is investigated using a set of precision physical and chemical methods (e.g., XPS, FTIR, SEM–EDX, potentiometric titration, electrophoretic light scattering, AFM–Kelvin force probe microscopy, and microhardness). An effective mode of preliminarily treating rare-metal minerals with high-voltage nanosecond pulses to produce directional changes in their physicochemical, electrical, mechanical, and technical properties is validated that increases mineral flotation and sorption activity and greatly improves the flotation technological characteristics of columbite and zircon.