共查询到10条相似文献，搜索用时 140 毫秒
1.
《International Journal of Mineral Processing》2005,77(1):1-45
The properties of thin liquid films (TLF) are of paramount significance for colloidal disperse systems, and a number of industrial processes, including froth flotation. In flotation, the bubble–particle attachment is controlled by the thinning and rupture of the intervening liquid film between an air bubble and a mineral particle. The froth evolution and its transient stability are also a function of the drainage and rupture of liquid films between air bubbles. Surface-active substances (surfactants) are used as flotation reagents to control the behavior of the liquid films. This paper presents a review of our research in the area of surfactant adsorption, surface forces and liquid films. It mainly focuses on the validation, application and extension of the Stefan–Reynolds theory on the liquid drainage. The extension of the Stefan–Reynolds theory comprises surface forces (disjoining pressure), surface tension variation, caused by the adsorption and diffusion of surfactants. Both the experimental and theoretical results are mostly related to the free (foam) films formed between two bubbles but can be principally extended to emulsion films between two oil drops and wetting films between an air bubble and a solid surface. 相似文献
2.
Jose R. Hernandez-Aguilar Ryan CunninghamJames A. Finch 《International Journal of Mineral Processing》2006
Air bubbles of uniform size (ca. 1 mm diameter) were generated at a submerged orifice (glass capillary) under controlled frequency (down to ca. 0.06 s− 1) in aqueous solutions of frother (Dowfroth 250). The bubbles were sized with an imaging technique. One objective was to establish whether the Tate equation (static balance between buoyancy and capillary forces) could be used as a standard sizing calibration method. Another aim was to verify whether with decreasing surface tension (due to increasing frother concentration) the anticipated decrease in bubble size agreed with the equation prediction. An effect of frother was detected compatible with the role of surface tension but divided into two concentration regions, seemingly the result of a gradual change in bubble shape and wetting: > 6 ppm the bubble holds a spherical shape and the capillary appeared to be completely wetted while at ≤ 6 ppm a degree of non-wetting and bubble distortion (neck formation just prior to detachment) were apparent, supported by qualitative observations. In addition, at > 6 ppm the Tate value was only approached by decreasing the bubble frequency but not attained. Plausible causes for the failure to reach the predicted size are discussed. 相似文献
3.
为了提高空气扰动技术（air sparging,AS）的效果,做了一系列的实验,研究了表面活性剂强化空气扰动技术（surfactant-enhanced air sparging, SEAS）中表面活性剂的选择方法。结果表明：在气流运行方式以鼓泡为主要机制时,表面活性剂的加入强化了气泡的起泡性和稳泡性,使空气饱和度增加;在气流运行方式以微孔道为主要机制时,表面活性剂的加入因减小了表面张力而减小了空气驱替水所需的毛细压力,使空气饱和度增加。比较Tween-80、TritonX-100、SDS和SDBS在介质上的吸附损失,确定出在中砂中TritonX-100为优,在砾石中SDBS为优。 相似文献
4.
Bubble–particle encounter during flotation is governed by liquid flow relative to the rising bubble, which is a function of the adsorbed frothers, collectors, and other surfactants and surface contaminants. Due to surface contamination, the bubble surface in flotation has been considered as immobile (rigid). However, surface contamination can be swept to the backside of the rising bubble due to the relative liquid flow, leaving the front surface of the rising bubble mobile with a non-zero tangential component of the liquid velocity. The bubble with a mobile surface was considered by Sutherland who applied the potential flow condition and analyzed the bubble–particle encounter using a simplified particle motion equation without inertia. The Sutherland model was found to over-predict the encounter efficiency and has been improved by incorporating inertial forces which are amplified at the mobile surface with a non-zero tangential velocity component of the liquid phase. An analytical solution was obtained for the encounter efficiency using approximate equations and is called the Generalized Sutherland Equation (GSE). In this paper, the bubble–particle encounter interaction with the potential flow condition has been analyzed by solving the full motion equation for the particle employing a numerical computational approach. The GSE model was compared with the exact numerical results for the encounter efficiency. The comparison only shows good agreement between the GSE prediction and the numerical data for ultrafine particles (< 10 μm in diameter), the inertial forces of which are vanishingly small. For non-ultrafine particles, a significant deviation of the GSE model from the numerical data has been observed. Details of the numerical methodology and solutions for the (collision) angle of tangency and encounter efficiency are described. 相似文献
5.
《矿物学报》2013,(Z1)
In this study, the adsorption kinetics, equilibrium and thermodynamics of Fe3+ ions on natural (NAP) and synthetic (HAP) apaties were examined. The adsorption efficiency of Fe3+ onto the NAP and HAP was increased with increasing temperature. The kinetics of adsorption of Fe3+ ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 37.15 and 49.84 kJ·mol 1 for NAP and HAP, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin–Redushkevich (D–R) isotherm equations at different temperatures. RL separation factor for Langmuir and the n value for Freundlich isotherm show that Fe3+ ions are favorably adsorbed by NAP and HAP. Various thermodynamic parameters such as enthalpy (ΔH), Gibbs free energy (ΔG) and entropy (ΔS) changes were computed and the results showed that the adsorption of Fe3+ ions onto NAP and HAP were spontaneous and endothermic in nature. 相似文献
6.
通过一维砂柱实验研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对空气扰动技术(air sparging,AS)修复氯苯污染地下水的强化效果.结果表明,SDBS的加入降低了地下水的表面张力,减小了水气两相毛细压力,从而提高了地下水中的空气饱和度.当曝气量为100 mL/min,地下水的表面张力由72.2 mN/m降至49.5 mN/m时,地下水中空气饱和度由13.2%提高至50.1%,而后随着表面张力的进一步降低,空气饱和度不再提高,反而有小幅下降.通过污染物的去除实验发现,SDBS的加入大大提高了氯苯的去除率,且去除率的变化与空气饱和度的变化趋势基本相符.因此,表面活性剂的加入可以作为空气扰动技术一种十分有效的强化手段. 相似文献
7.
Conventional and non-conventional flotation for mineral processing and for water (and wastewaters) treatment and reuse (or recycling) is rapidly broadening their applications in the mining field. Conventional flotation assisted with microbubbles (30–100 μm) finds application in the recovery of fine mineral particles (< 13 μm) and flotation with these fine bubbles is being used as a solid/liquid separation to remove pollutants. The injection of small bubbles to conventional coarse bubbles flotation cells usually leads to general improvements of the separation parameters, especially for the ultrafines (< 5 μm) ore particles. Results obtained are believed to occur by enhancing the capture of particles by bubbles, one of the main drawbacks in fine ore flotation. It is believed that by decreasing the bubble size distribution (through the injection of small bubbles), increases the bubble surface flux and the fines capture. DAF or dissolved air flotation with microbubbles, treating water, wastewater and domestic sewage is known for a number of years and is now gradually entering in the mining environmental area. This technology offers, in most cases, advantages over settling, filtration, precipitation, or adsorption onto natural and synthetic adsorbents. The targets are the removal of oils (emulsified or not), ions (heavy metals and anions) and the reuse or recirculation of the process waters. Advantages include better treated water quality, rapid start up, high rate operation, and a thicker sludge. New applications are found in the mining vehicles washing water treatment and reuse, AMD (acid mining drainage) neutralization and high rate solids/water separation by flotation with microbubbles. This work reviews some recent applications of the use of microbubbles to assist the recovery of very small mineral particles and for the removal of pollutants from mining wastewaters. Emphasis is given to the design features of innovative devices showing the potential of conventional and unconventional DAF flotation. 相似文献
8.
Investigation on foaming properties of some organics for oily bubble bitumen flotation 总被引：1，自引：0，他引：1
Studies have shown that using organic coated bubbles (“oily” bubbles) could increase bitumen recovery rate in flotation. One way to coat bubbles is that used in the air-assisted solvent extraction process where solvent foam is formed and injected through a capillary to release solvent coated bubbles in a controlled manner into the aqueous system. To investigate adapting this approach, the foaming properties of some organics (Hexane, Heptane, Hexadecane, Petroleum Ether, Toluene, Benzene and Kerosene and their binary mixtures) of potential interest in oily bubble bitumen flotation were investigated. Silicone oil was found to be a good foaming agent in some cases. Bubble stability and film thickness experiments were carried out to help select candidate organics. Surface tension and dynamic viscosity measurements were conducted to examine the mechanism of foaming. Attachment studies showed that droplets of the selected organics readily attached to a bitumen surface compared to air bubbles. From a combination of criteria, 25:75 Hexadecane/Heptane appears to be a promising candidate. 相似文献
9.
The adsorption kinetics of methylene blue from aqueous solutions on purified palygorskite was investigated. The kinetics data related to the adsorption of methylene blue from aqueous solutions are in good agreement with the pseudo-second order equation in ranges of initial concentration of 120-210 mg/L, oscillation speed of 100-200 r/min and temperature of 298-328K. The experimental results show that methylene blue is only adsorbed onto the external surface of purified palygorskite, and the apparent adsorption activation energy is 13.92 kJ/mol. The relatively low apparent adsorption activation energy suggests that the adsorption of methylene blue involves in not only a chemical, but also a physical adsorption process, and it is controlled by the combination of chemical adsorption and liquid-film diffusion. 相似文献
10.
污灌土壤对铅的吸附和解吸特性 总被引：1，自引：0，他引：1
为了解污灌土壤对铅的吸附-解吸机制,进行不同条件下的吸附-解吸试验。结果表明：污灌土壤对铅的吸附量随铅初始浓度的增大,呈现先强烈吸附再缓和的过程。Langmuir模式对污灌土壤等温吸附铅的拟合效果最好,其饱和吸附量为7.84 mg/g。亚砷酸盐的存在会阻碍污灌土壤对Pb2+的吸附,亚砷酸盐加入前后污灌土壤对铅的吸附率从99.9％～100％下降到97.8％～99.0％。加亚砷酸盐条件下污灌土壤对铅的等温吸附模式以Freundlich模式的拟合效果最好。污灌土壤对吸附态铅的解吸量随解吸振荡时间的延长而不断增加,且解吸率随时间增加总体趋于降低。Elovich方程和幂函数方程均能很好地拟合污灌土壤对铅的解吸动力学过程,尤其是Elovich方程的拟合效果最为显著。 相似文献