The Limits of Fine and Coarse Particle Flotation

The flotation behaviour of quartz particles was studied over the particle size range from 0.5 µm to 1000 µm and for advancing water contact angles between 0° and 83°. Flotation was performed in a column and in a Rushton turbine cell. Particle contact angle threshold values, below which the particles could not be floated, were identified for the particle size range 0.5–1000 µm, under different hydrodynamic conditions. The flotation response of the particles, either in a column or in a mechanically agitated cell with a similar bubble size, was comparable. Turbulence plays a role, as does bubble‐particle aggregate velocity and bubble size. The stability of the bubble‐particle aggregate controls the maximum floatable particle size of coarse particles. For fine particles, the flotation limit is dictated by the energy required to rupture the intervening liquid film between the particle and bubble. Flotation of very fine and large particles is facilitated with small bubbles and high contact angles. These results greatly extend our earlier observations and theoretical predictions.     

Picobubble Enhanced Fine Coal Flotation

Abstract

Froth flotation is widely used in the coal industry to clean ?28 mesh fine coal. A successful recovery of particles by flotation depends on efficient particle‐bubble collision and attachment with minimal subsequent particle detachment from bubble. Flotation is effective in a narrow size range beyond which the flotation efficiency drops drastically. It is now known that the low flotation recovery of particles in the finest size fractions is mainly due to a low probability of bubble‐particle collision while the main reason for poor coarse particle flotation recovery is the high probability of detachment. A fundamental analysis has shown that use of picobubbles can significantly improve the flotation recovery of particles in a wide range of size by increasing the probability of collision and attachment and reducing the probability of detachment.

A specially designed column with a picobubble generator has been developed for enhanced recovery of fine coal particles. Picobubbles were produced based on the hydrodynamic cavitation principle. They are characterized by a size distribution that is mostly below 1 µm and adhere preferentially to the hydrophobic surfaces. The presence of picobubbles increases the probability of collision and attachment and decreases the probability of detachment, thus enhancing flotation recovery. Experimental results with the Coalberg seam coal in West Virginia, U.S.A. have shown that the use of picobubbles in a 2″ column flotation increased fine coal recovery by 10–30%, depending on the feed rate, collector dosage, and other flotation conditions. Picobubbles also acted as a secondary collector and reduced the collector dosage by one third to one half.     

Adsorbing Flotation of Copper Hydroxo Precipitates by Pyrite Fines

Abstract

The removal of copper ions from dilute aqueous solutions by the addition of mineral (pyrite) fine particles was undertaken by following an adsorbing (scavenging) flotation mechanism. Pyrite generally constitutes a residual or a solid industrial waste by-product in mixed sulfides processing plants. This paper suggests a further utilization for pyrite. The dissolved-air method was applied for solid/liquid separation when the mineral particles were in the fine (subsieve) size range. Various unconventional collectors for pyrite flotation were also examined.     

Time dependent wettability of mineral and metal surfaces in the presence of thiol surfactants

The decrease in wettability of mineral and metal surfaces due to the adsorption of surfactants is crucial for flotation recovery and upgrading of these materials in mineral processing. Because of limited residence time in flotation processing, the kinetics of the wettability changes of the mineral surface becomes an important issue. The time dependent wettabilities of silver and galena (PbS) surfaces in aqueous solutions of di-isobutyl dithiophosphinate, a commercial flotation reagent, were determined from in situ measurements of advancing and receding bubble contact angles. Kinetic parameters were calculated from these data. By comparing the in situ measurements with ex situ measurements of water contact angles and external reflection FTIR of the adsorbed organic films on silver, a physical interpretation of the wettability data is given in terms of the evolution of these thin organic films on the mineral surfaces.     

The influence of frother types and concentrations on fine particles’ entrainment using column flotation

Entrainment which is the characteristic feature of fine particles is closely related to water recovery. It is based on the changes depending on the establishment of linear relationship between water recovery and solid recovery. This paper deals with the investigation of the effect of frother types and concentrations on fine particles’ entrainment using column flotation. Entrainment of fine particle using a mixture of artificial ore (celestite:calcite; 1:1) was investigated in column flotation. In a two-phase system (water/air), the variation of bubble diameters and gas hold-up with a superficial air rates using different frother types and concentrations were tested. The results showed that the frother types and concentrations had significant effect on the grade and recovery, superficial air rate, gas hold-up and fine gangue entrainment. Entrainment factors for frother types and concentrations were compared in flotation column. Kirjaveinen^[11] model was used for describing the specific entrained factor (P_i) of hydrophilic particles. It has been found that Kirjaveinen model supports the results of this study.     

浮选设备流体力学特征参数研究现状

浮选设备是矿物加工工程领域一种重要的气液反应装置，主要包括浮选机和浮选柱。浮选设备应用已有百年历史，随着选矿技术水平的提高，浮选设备逐渐向自动化、大型化的方向发展。近年来对浮选设备内流体力学特征参数的研究解析越来越多，进一步促进了设备的合理放大和优化。本工作在简要介绍目前浮选设备的发展和应用现状后，总结了国内外学者对浮选设备内气泡尺寸、气含率和气泡速度3个重要流体力学特征参数的检测方法和研究现状，提出了在今后研究中，开发以机器视觉为核心的检测技术和强化侵入式检测装置的适用性是流体力学特征参数检测手段的发展方向之一。     

Modeling of flotation process in dispersed systems

Mathematical model of flotation in dispersed mixture of liquid, solid, and gas phases has been designed within the considerations of the mechanics of multiphase media with the assumption of the degree of mineralization of the bubble surface. The application of the designed model has been demonstrated based on the example of one-dimensional stationary flotation and it has been shown that the equations that describe the emergence of bubbles are singularly disturbed (“rigid”). The effect of size and concentration of bubbles, as well as volume content of dispersed particles, on flotation has been analyzed.     

Separation Characteristics of Inorganic Particles from Rainfalls in Dissolved Air Flotation: A Korean Perspective

Abstract

Many reservoirs have been constructed in Korea to store water resources utilizing the terrain of the land. In general, dam source waters contain algae species that have densities close to that of water. Consequently algae are difficult to remove by conventional gravity sedimentation (CGS), while dissolved air flotation (DAF) is known to be an effective process for the purpose. The same source waters usually also have high turbidities due to mineral soil particles in the wet summer season. Systematic studies on the effect of high turbidity on the DAF process are very limited. In this work, DAF and CGS experiments were carried out to investigate water treatment characteristics and removal efficiencies under various COD/SS and chlorophyll‐a/SS ratios. A kinetic DAF process model was employed to describe bubble‐floc collision and agglomeration, as well as the rising velocity of bubble‐floc agglomerate. Our results showed that the initial collision‐attachment efficiency for the clay floc size range of 100?400 µm was a relatively low value of 0.3. The removal efficiency by DAF was greater than by CGS when chlorophyll‐a/SS ratio was high. It was also found that sedimentation prior to flotation is required for the effective separation of large clay flocs caused by runoff. Our experimental and theoretical results also suggest that the DAF process requires carefully operation in Korea, especially, in the rainy summer season.     

Application of colloidal gas aphrons for pollution remediation

Colloidal gas aphrons (CGAs), first described by Felix Sebba in his book Foams and Biliquid Foams—Aphrons in 1987, consist of a system of spherical microbubbles with diameters mostly above 25 µm and classified as kugelschaums (ball foam). They possess some colloidal properties and can be pumped at uniform rate through pipes and channels, much like liquids. Also, they have high stability due to very small size and thick surfactant shells. Research work published over the past two decades indicate effective applications of CGAs for clarification of particles and microorganisms, protein separation, gas and nutrient transfer and pollutant separation from water and soil matrices. In this review paper, the techniques for generating CGAs and their application to pollution abatement are discussed. Some mineral separation processes by CGA flotation have also been reviewed because of their relevance to contaminant removal processes. The CGAs were found to function on the principles of bubble entrained floc flotation, electrostatic and ionic interaction, diffusion of entrapped gas and hydrophobicity of the pollutant particles. Two tables have also been provided to present a comparative overview of the generation technologies and the effectiveness of pollution remediation techniques. Copyright © 2012 Society of Chemical Industry     

现代光学测量技术在矿物浮选中的应用及展望

为了解现代光学测量技术在细粒矿物浮选中的应用,在深入研究浮选理论的基础上,分析了以往研究浮选过程的测量方法,提出了近年来最为先进的流体力学光学测量技术PIV和高速动态显微摄像技术,利用其测量的高精度、高分辨率、无干扰等优势,可以实现对宏观、微观尺度的复原流场、矿化过程的测量。PIV可展现流场的流态,得到所需的各种指标、参数;高速动态显微摄像技术可直观观察到颗粒气泡在流场中运动、矿化过程。利用现代光学测量技术可深入研究流体动力学和选矿,实现流场稳定和最佳流态,也可研究强化矿化微观过程,最终实现浮选动力学的改进和分选指标的最优化。     

纳米气泡在微细粒矿物浮选中的应用研究现状

我国矿石资源禀赋差,很大一部分微细粒矿物资源难以回收.提高微细粒矿物资源的综合利用率是解决我国现阶段面临的矿产资源匮乏问题最有效的途径之一.文中主要对微细粒矿物的分选现状、纳米气泡的发展历程、形成方法、稳定性研究现状及在矿物浮选中的应用现状进行讨论与分析.纳米气泡浮选是针对微细粒矿物粒度小、质量轻、比表面积大、表面能高...     

Improving the dewetability characteristics of hydrophobic fine particles by air bubble entrapments

The present study deals with the role of surface hydrophobicity and air bubble entrapment on filtration / dewatering of fine coal particles (− 0.5 mm). The experimental results showed that hydrophobizing reagents increased the contact angle (or hydrophobicity) and decreased the filtrate surface tension, cake formation time and moisture content of the fine particles. In addition to these, when the air bubbles were introduced to the hydrophobic fine coal particles in water, the cake formation time and moisture content of the filter cake were further reduced, which may be attributed to the fact that micro/nano size air bubbles were entrapped on the surface of the fine particles in a slurry and increased the dewetting characteristics of the fine particles. As a result, this process may lower the amount of moisture trapped during the dewatering fine particles and increase the efficiency of the filters.     

The effect of different types of micro‐bubbles on the performance of the coagulation flotation process for coke waste‐water

BACKGROUND: Comparison experiments were carried out with three kinds of micro‐bubbles on the coagulation flotation process treatment of coke waste‐water under optimum coagulation conditions obtained from zeta potential measurement. RESULTS: Micro‐bubble flotation with ozone showed the best performance. The ozone micro‐bubbles exhibited high absolute zeta potential values, creating repulsion forces thus avoiding the coalescence of bubbles as well as creating attractive interaction between bubbles and particles in the waste‐water. Moreover, the fluorescence intensity of three micro‐bubble samples showed that the ozone micro‐bubble system produced the most hydroxyl radicals, which contributed to the degradation of organic material in the coke waste‐water. Compared with either air micro‐bubble flotation and oxygen micro‐bubble flotation processes, pyridine removal efficiency of the ozone micro‐bubble flotation process was, respectively, 4.5 and 1.7 times higher, and benzene removal efficiency 3.6 and 1.5 times higher. Finally, drainage models and oxygen diffusion models of the three kinds of micro‐bubble water samples verified the long persistence of the three kinds of micro‐bubbles in the water. CONCLUSION: The application of ozone micro‐bubble technology in coagulation processes may provide an efficient and cost‐effective approach to the treatment of waste‐water containing refractory organic compounds. Copyright © 2011 Society of Chemical Industry     

Role of Sodium Hexametaphosphate in the Flotation of Acanthite Fines from Finely Disseminated Ores

Abstract

The improvement of the flotation of acanthite fines from a finely disseminated ore through the addition of sodium hexametaphosphate (SHMP) as the dispersant has been studied in this work. This study was carried out on the silver scavenger concentrate from the Fresnillo concentration plant in Mexico. The experimental results have shown that the dispersion processing by adding SHMP as the dispersant greatly increased the separation efficiency and the flotation rate of acanthite fines from the ore. This increase was much more remarkable for smaller mineral particles. It has been found that the improvement might be attributed to the fact that SHMP increased simultaneously the electric double layer repulsion and steric repulsion between minerals (valuable and gangue) particles in aqueous suspensions upon the adsorption of polymetaphosphate anions on the mineral surfaces, and thus eliminated the hetero-coagulation of the fine mineral particles in the aqueous ore suspension.     

Effect of microbubbles and particle size on the particle collection in the column flotation

Particle-bubble collection characteristics from microbubble behavior in column flotation have been studied theoretically and experimentally. A flotation model taking into account particle collection has been developed by particle-bubble collision followed by the particle sliding over the bubble during which attachment may occur. Bubble size and bubble swarm velocity were measured as a function of frother dosage and superficial gas velocity to estimate the collision and collection efficiency. Separation tests were carried out to compare with theoretical particle recovery. Fly ash particles in the size range of <38, 38-75, 75-125, >125 mm were used as separation test particles. Theoretical collision and collection efficiencies were estimated by experimental data on the bubble behavior such as bubble size, gas holdup and bubble swarm velocity. Collection efficiency improved with an increase of the bubble size and particle size but decreased in the particle size up to 52 mm. Also, flotation rate constants were estimated to predict the optimum separation condition. From the theoretical results on the flotation rate constant, optimum separation condition was estimated as bubble size of 0.3-0.4 mm and superficial gas velocity of 1.5-2.0 cm/s. A decrease of bubble size improved the collection efficiency but did not improve particle recovery.     

微细气泡技术标准体系探究

微细气泡技术是面向未来、绿色可持续的技术.气泡尺寸小到微纳米级的微细气泡技术快速发展,其应用也越来越广泛,在矿物浮选分离、超声造影剂、污水处理、工业清洗和精细剥离、日用清洗和护肤、农业种植以及水产养殖、盐碱地改良和土壤修复等诸多领域,微细气泡技术均颇有建树.但是,就像其他新兴技术发展初期一样,伴随着微细气泡的研究和应用...     

双流态微泡浮选机气液两相流测试结果分析

介绍了双流态微泡浮选机的特点,采用激光粒子动态分析仪测量了该浮选机矿化器内微泡发生器段和矿化管部分以及浮选槽内的微泡时均速度、脉动速度和粒径分布情况,分析了不同充气量与药剂量对微泡的影响;对比表明,该机在宏观流态、紊动特性以及形成的微气泡尺寸、粒径分布和浓度等方面为微细粒煤泥浮选创造了最佳的流体动力学环境。     

Metal ion separation and recovery from environmental sources using various flotation and sorption techniques

Flotation is a gravity separation process that originated from processing of minerals, and has nowadays found wide application, for instance, in industrial waste‐water treatment. It is also useful in the concentration of a variety of dissolved chemical species often following a sorption process. The present review paper focuses on the removal of heavy metal ions from aqueous solution. The process mechanisms involved are either sorptive flotation where metal bonding agents, including biosorbents, are added and the subsequent complexes are separated downstream by flotation or other conventional flotation techniques, such as ion flotation are used. In the laboratory experiments described in this paper, zinc has been used as an example, but in addition copper, nickel, arsenic, etc. are considered. A new hybrid flotation–microfiltration cell is also introduced. Copyright © 2010 Society of Chemical Industry     

Effect of particle size on the surface oxidation and flotation behavior of galena particles in lime system

ABSTRACT

In this research, the effect of particle size on the surface oxidation and flotation behavior of galena in the lime system was studied. Coarse (?0.074 + 0.038 mm), intermediate (?0.038 + 0.025 mm) and fine (?0.025 mm) galena particles were used in the experiment. The dissolution tests, flotation tests, and sorption tests were accomplished. Through further analysis by XPS, the effect of particle size and lime was observed. The decrease of mineral particle sizes increased the adsorption ratio of collector and the dissolution of galena, while the hydrophilic product OH^?/Ca(OH)⁺ produced by dissolution occupied the dominant position, which led to the minerals hydrophilic.     

Removal of Resin from Mechanical Pulps by Selective Flotation: Mechanisms of Resin Flotation and Yield Loss of Fibers

Abstract

The amount of wood resin in mechanical pulp suspensions could be decreased using a selective flotation process. In selective flotation air‐bubbles are dispersed into low consistency pulp suspensions mechanically by an impeller or by injectors. Resin particles attach to the air‐bubbles and are lifted to the top of the pulp suspension from where they are removed, along with the flotation froth. The very small size of the resin particles (average diameter <1.0 micron) suggests that they are driven toward the air‐bubbles mainly by Brownian diffusion and that attachment of the resin particles to the air‐bubbles takes place through colloidal interactions. The resin flotation followed approximate first‐order kinetics. The mechanism of yield loss of fibers was entrainment, whereby they were hydraulically transported into the froth along with the water.