N-(2-氨乙基)-月桂酰胺浮选铝硅酸盐矿物的研究

研究了N (2 氨乙基) 月桂酰胺对高岭石、伊利石和叶腊石等铝硅酸盐矿物的浮选行为.发现该表面活性剂对叶腊石的浮选回收率最高可达97.7％，对伊利石和高岭石的回收率相对较低，一般不超过82％.矿浆pH对高岭石、伊利石和叶腊石的回收率影响较小.酸性矿浆中表面活性剂通过静电引力吸附在矿粒表面；碱性矿浆中，表面活性剂通过氢键吸附在矿粒表面.红外吸收光谱证明，三种矿物表面中均存在－OH；在一个较宽的pH范围内，三种矿物矿浆的Zeta电位均为负值，表明矿粒表面荷负电.矿粒的扫描电镜（SEM）照片（×15000）表明，叶腊石主要呈薄片状颗粒，高岭石和伊利石颗粒呈不规则形状.     

A study on the ink-fiber interfacial interaction in waste printed paper I. The effect of a custom-designed polymeric additive on flotation de-inking of solvent-treated wastepapers

The effect of interaction between solvent and three different kinds of printed wastepaper has been studied. The solubility parameter of the solvent was found to be among the most important in order to obtain an optimum ink-fiber interfacial swelling, necessary for de-inking wastepaper. The degree of ink-fiber interfacial swelling was qualitatively estimated by examining the dispersity of ink particles using an optical microscope. FT-IR analyses were carried out to correlate the degree of dispersion and the ink composition in the printed wastepapers studied. The effect of a selective swelling solvent on the de-inking characteristics of a mixture of old wastepapers was investigated. The solvent treatment of these wastepapers prior to flotation de-inking failed to add any positive effect on the brightness of the de-inked pulp. On the other hand, the incorporation of a custom-designed polymer additive improved the pulp brightness without any solvent treatment. The same additive played a negative role in the presence of a swelling solvent. The function of the polymer additive in the flotation de-inking process is also described.     

The liquid flow force on a particle in the bubble-particle interaction in flotation

In this paper the problem of calculating the liquid flow force on a particle in interaction with an air bubble with a mobile surface in flotation as a function of the separation distance was solved. The force equation was obtained by first deriving the disturbed flow confined between the surfaces. The model for the force includes the separation distance between the bubble and the particle, the particle size, the bubble's Reynolds number, the bubble rise velocity, and the polar position of the particle on the bubble surface. The proposed equations provide an exact solution to the situation where the particle and the bubble are very close together. The attractive flow force and the surface forces are of similar orders of magnitude. Consequently, the models presented in this paper should provide a better estimate for calculating the forces on particles interacting with air bubbles in mineral flotation and other separation operations involving colloidal interactions.     

Hydrophobic attraction as revealed by AFM force measurements and molecular dynamics simulation

Spherical calcium dioleate particles ( approximately 10 mum in diameter) were used as AFM (atomic force microscope) probes to measure interaction forces of the collector colloid with calcite and fluorite surfaces. The attractive AFM force between the calcium dioleate sphere and the fluorite surface is strong and has a longer range than the DLVO (Derjaguin-Landau-Verwey-Overbeek) prediction. The AFM force between the calcium dioleate sphere and the mineral surfaces does not agree with the DLVO prediction. Consideration of non-DLVO forces, including the attractive hydrophobic force and the repulsive hydration force, was necessary to explain the experimental results. The non-DLVO interactions considered were justified by the different interfacial water structures at calcite- and fluorite-water interfaces as revealed by the numerical computation experiments with molecular dynamics simulation.     

LATERAL CAPILLARY FORCES AND TWO-DIMENSIONA ARRAYS OF COLLOID PARTICLES AND PROTEIN MOLECULES

This paper presents a review of our recent studies on the lateral capillary forces and on their role in the formation of two-dimensional ordered arrays of colloidal particles or protein molecules. To reveal the mechanism of protein ordering in liquid films we carried out model experiments with micrometer sized latex particles. The films were formed on solid or liquid substrates. By variation of the electrolyte concentration, the particle charge and volume fraction we proved that neither the double layer repulsion, nor the van der Waals attraction between the particles, was responsible for the formation of the two-dimensional arrays. Direct microscope observations revealed that the process of ordering was triggered by attractive lateral capillary forces due to the overlap of the menisci formed around the particles. Two types of lateral capillary forces, flotation and immersion, could be distinguished and theory of these interactions was developed. The lateral capillary forces between a floating particle and a wall were also studied; they could be employed for precise determination of the shear surface viscosity.     

Ordering of Colloidal Spheres Floating on the Surface of Glycol Film

The ordering of polystyrene colloidal particles floating on the surface of glycol film, forming a two-dimensional system,was studied via an optical microscope. We have observed that the interfacial colloidal particles crystallized to form a two-dimensional triangular lattice with lots of point defects and grain boundaries. The interactions between the interfacial colloidal particles are also analyzed.     

A modeling approach to describe the adhesion of rough, asymmetric particles to surfaces

A combined theoretical and experimental study of the adhesion of alumina particles and polystyrene latex spheres to silicon dioxide surfaces was performed. A boundary element technique was used to model electrostatic interactions between micron-scale particles and planar surfaces when the particles and surfaces were in contact. This method allows quantitative evaluation of the effects of particle geometry and surface roughness on the electrostatic interaction. The electrostatic interactions are combined with a previously developed model for van der Waals forces in particle adhesion. The combined model accounts for the effects of particle and substrate geometry, surface roughness and asperity deformation on the adhesion force. Predictions from the combined model are compared with experimental measurements made with an atomic force microscope. Measurements are made in aqueous solutions of varying ionic strength and solution pH. While van der Waals forces are generally dominant when particles are in contact with surfaces, results obtained here indicate that electrostatic interactions contribute to the overall adhesion force in certain cases. Specifically, alumina particles with complex geometries were found to adhere to surfaces due to both electrostatic and van der Waals interactions, while polystyrene latex spheres were not affected by electrostatic forces when in contact with various surfaces.     

Quantification of particle-bubble interactions using atomic force microscopy: A review

The attachment of particles to bubbles in solution is of fundamental importance to several industrial processes, most notably in the process of froth flotation. During this process hydrophobic particles attach to air bubbles in solution, which allows them to be separated as froth at the surface. The addition of chemicals can help to modulate these interactions to increase the yield of the minerals of interest. Over the past decade the atomic force microscope (AFM) has been adapted for use in studying the forces involved in the attachment of single particles to bubbles in the laboratory. This allows the measurement of actual DLVO (Derjaguin, Landau, Vervey and Overbeek) forces and adhesive contacts to be measured under different conditions. In addition contact angles may be calculated from features of force versus distance curves. It is the purpose of this article to illustrate how the colloid probe technique can be used to make single particle-bubble interactions and to summarise the current literature describing such experiments.     

Surfactant adsorption at the salt/water interface: comparing the conformation and interfacial water structure for selected surfactants

We report in situ spectroscopic measurements monitoring the adsorption of a series of carboxylate surfactants onto the surface of the semisoluble, ionic solid fluorite (CaF2). We employ the surface-specific technique, vibrational sum-frequency spectroscopy (VSFS), to examine the effect that surfactant adsorption has on the bonding interactions and orientation of interfacial water molecules through the alteration of the electric properties in the interfacial region. In addition, we report on the chain length and headgroup dependence of the formation of hydrophobic self-assembled monolayers on the surface of the solid phase. Differences in chain length and headgroup functionality lead to large changes in the adsorption behavior and structuring of the monolayers formed and the interactions of interfacial water molecules with these monolayers. Fundamental studies such as these are essential for understanding the mechanisms involved in the surfactant adsorption process, information that is important for industrially relevant processes such as mineral ore flotation, waste processing, and petroleum recovery.     

Measurement of dynamical forces between deformable drops using the atomic force microscope. I. Theory

Recent experimental developments have enabled the measurement of dynamical forces between two moving liquid drops in solution using an atomic force microscope (AFM). The drop sizes, interfacial tension, and approach velocities used in the experiments are in a regime where surface forces, hydrodynamics, and drop deformation are all significant. A detailed theoretical model of the experimental setup which accounts for surface forces, hydrodynamic interactions, droplet deformation, and AFM cantilever deflection has been developed. In agreement with experimental observations, the calculated force curves show pseudo-constant compliance regions due to drop flattening, as well as attractive pull-off forces due mainly to hydrodynamic lubrication forces.     

A concise review of nanoscopic aspects of bioleaching bacteria–mineral interactions

Bioleaching is a technology for the recovery of metals from minerals by means of microorganisms, which accelerate the oxidative dissolution of the mineral by regenerating ferric ions. Bioleaching processes take place at the interface of bacteria, sulfide mineral and leaching solution. The fundamental forces between a bioleaching bacterium and mineral surface are central to understanding the intricacies of interfacial phenomena, such as bacterial adhesion or detachment from minerals and the mineral dissolution. This review focuses on the current state of knowledge in the colloidal aspect of bacteria–mineral interactions, particularly for bioleaching bacteria. Special consideration is given to the microscopic structure of bacterial cells and the atomic force microscopy technique used in the quantification of fundamental interaction forces at nanoscale.     

Finite-size effects in dissipative particle dynamics simulations

We have performed dissipative particle dynamics (DPD) simulations to evaluate the effect that finite size of transversal area has on stress anisotropy and interfacial tension. The simulations were carried out in one phase and two phases in parallelepiped cells. In one-phase simulations there is no finite-size effect on stress anisotropy when the simulation is performed using repulsive forces. However, an oscillatory function of stress anisotropy is found for attractive-repulsive interactions. In the case of liquid-liquid interfaces with repulsive interaction between molecules, there is only a small effect of surface area on interfacial tension when the simulations are performed using the Monte Carlo method at constant temperature and normal pressure. An important but artificial finite-size effect of interfacial area on surface tension is found in simulations in the canonical ensemble. Reliable results of interfacial tension from DPD simulations can be obtained using small systems, less than 2000 particles, when they interact exclusively with repulsive forces.     

Measurement and modeling on hydrodynamic forces and deformation of an air bubble approaching a solid sphere in liquids

The interaction between bubbles and solid surfaces is central to a broad range of industrial and biological processes. Various experimental techniques have been developed to measure the interactions of bubbles approaching solids in a liquid. A main challenge is to accurately and reliably control the relative motion over a wide range of hydrodynamic conditions and at the same time to determine the interaction forces, bubble–solid separation and bubble deformation. Existing experimental methods are able to focus only on one of the aspects of this problem, mostly for bubbles and particles with characteristic dimensions either below 100 μm or above 1 cm. As a result, either the interfacial deformations are measured directly with the forces being inferred from a model, or the forces are measured directly with the deformations to be deduced from the theory. The recently developed integrated thin film drainage apparatus (ITFDA) filled the gap of intermediate bubble/particle size ranges that are commonly encountered in mineral and oil recovery applications. Equipped with side-view digital cameras along with a bimorph cantilever as force sensor and speaker diaphragm as the driver for bubble to approach a solid sphere, the ITFDA has the capacity to measure simultaneously and independently the forces and interfacial deformations as a bubble approaches a solid sphere in a liquid. Coupled with the thin liquid film drainage modeling, the ITFDA measurement allows the critical role of surface tension, fluid viscosity and bubble approach speed in determining bubble deformation (profile) and hydrodynamic forces to be elucidated. Here we compare the available methods of studying bubble–solid interactions and demonstrate unique features and advantages of the ITFDA for measuring both forces and bubble deformations in systems of Reynolds numbers as high as 10. The consistency and accuracy of such measurement are tested against the well established Stokes–Reynolds–Young–Laplace model. The potential to use the design principles of the ITFDA for fundamental and developmental research is demonstrated.     

Reexamining the functions of zinc sulfate as a selective depressant in differential sulfide flotation--the role of coagulation

Zinc sulfate is a well-known selective depressant for zinc sulfide minerals such as sphalerite during the flotation of complex Cu-Pb-Zn sulfide ores. It deactivates sphalerite flotation by substituting the activating metal ions, and depresses sphalerite flotation by forming hydrophilic coatings of zinc hydroxyl species on sphalerite surfaces. However, we recently observed that zinc sulfate could also induce coagulation of fine sphalerite particles and such coagulation significantly reduced the mechanical entrainment of the fine sphalerite. Therefore, it seems that the effectiveness of zinc sulfate as a selective sphalerite depressant is not only due to its ability to make mineral surface hydrophilic, which reduces genuine flotation, but also due to its ability to coagulate the mineral, which reduces mechanical entrainment. Zinc sulfate is a "dual function" selective flotation depressant.     

A review of zinc oxide mineral beneficiation using flotation method

In recent years, extraction of zinc from low-grade mining tailings of oxidized zinc has been a matter of discussion. This is a material which can be processed by flotation and acid-leaching methods. Owing to the similarities in the physicochemical and surface chemistry of the constituent minerals, separation of zinc oxide minerals from their gangues by flotation is an extremely complex process. It appears that selective leaching is a promising method for the beneficiation of this type of ore. However, with the high consumption of leaching acid, the treatment of low-grade oxidized zinc ores by hydrometallurgical methods is expensive and complex. Hence, it is best to pre-concentrate low-grade oxidized zinc by flotation and then to employ hydrometallurgical methods. This paper presents a critical review on the zinc oxide mineral flotation technique. In this paper, the various flotation methods of zinc oxide minerals which have been proposed in the literature have been detailed with the aim of identifying the important factors involved in the flotation process. The various aspects of recovery of zinc from these minerals are also dealt with here. The literature indicates that the collector type, sulfidizing agent, pH regulator, depressants and dispersants types, temperature, solid pulp concentration, and desliming are important parameters in the process. The range and optimum values of these parameters, as also the adsorption mechanism, together with the resultant flotation of the zinc oxide minerals reported in the literature are summarized and highlighted in the paper. This review presents a comprehensive scientific guide to the effectiveness of flotation strategy.     

The influence of stabilizing agents on the interaction between styrene/butadiene latex and calcium carbonate: a calorimetric and a dynamic electrokinetic study

The role of stabilizing agents in the interaction between styrene/butadiene latex and calcium carbonate particles has been studied using isothermal titration calorimetry (ITC) and an electrokinetic sonic amplitude (ESA) technique. It is demonstrated that the polyacrylate sodium salt (dispersing agent, referred to as NaPA) used as stabilizing agent for the calcium carbonate suspensions principally affects the interfacial properties of the calcite surface. An electrostatic barrier is created and this decreases the attractive interactions between the latex and the negatively charged mineral surface. The total enthalpy change observed when an emulsion of styrene/butadiene particles substantially free from surfactant was added to the dispersed calcium carbonate could be described via a relatively complex path. The process included (i) an exothermic response from the association of the latex particles (adsorption process) with the dispersed calcium carbonate surface and (ii) an endothermic bulk phase effect due to the adsorption on the latex particles of dissolved species originating from the calcium carbonate. Stabilization of the latex particles with sodium dodecyl benzene sulfonate (SDBS) or a non-ionic fatty alcohol ethoxylate surfactant did not significantly change the enthalpy of interaction. It was further demonstrated that SDBS had a very weak affinity for the dispersed calcium carbonate particles and that dissolution of species, such as calcium ions, from the calcium carbonate surface, allows further adsorption of SDBS onto the latex particles.     

A review of the fundamental studies of the copper activation mechanisms for selective flotation of the sulfide minerals, sphalerite and pyrite

A review of the considerable, but often contradictory, literature examining the specific surface reactions associated with copper adsorption onto the common metal sulfide minerals sphalerite, (Zn,Fe)S, and pyrite (FeS(2)), and the effect of the co-location of the two minerals is presented. Copper "activation", involving the surface adsorption of copper species from solution onto mineral surfaces to activate the surface for hydrophobic collector attachment, is an important step in the flotation and separation of minerals in an ore. Due to the complexity of metal sulfide mineral containing systems this activation process and the emergence of activation products on the mineral surfaces are not fully understood for most sulfide minerals even after decades of research. Factors such as copper concentration, activation time, pH, surface charge, extent of pre-oxidation, water and surface contaminants, pulp potential and galvanic interactions are important factors affecting copper activation of sphalerite and pyrite. A high pH, the correct reagent concentration and activation time and a short time delay between reagent additions is favourable for separation of sphalerite from pyrite. Sufficient oxidation potential is also needed (through O(2) conditioning) to maintain effective galvanic interactions between sphalerite and pyrite. This ensures pyrite is sufficiently depressed while sphalerite floats. Good water quality with low concentrations of contaminant ions, such as Pb(2+)and Fe(2+), is also needed to limit inadvertent activation and flotation of pyrite into zinc concentrates. Selectivity can further be increased and reagent use minimised by opting for inert grinding and by carefully choosing selective pyrite depressants such as sulfoxy or cyanide reagents. Studies that approximate plant conditions are essential for the development of better separation techniques and methodologies. Improved experimental approaches and surface sensitive techniques with high spatial resolution are needed to precisely verify surface structures formed after copper activation. Sphalerite and pyrite surfaces are characterised by varying amounts of steps and defects, and this heterogeneity suggests co-existence of more than one copper-sulfide structure after activation.     

电化学研究DDTC在脆硫锑铅矿表面的吸附(英文)

通过循环伏安法、交流阻抗法研究了二乙基二硫代氨基甲酸钠(以D表示)与脆硫锑铅矿的相互作用.在不同的电位条件下呈现出不同的电极过程.从-178～472mV(相对于标准氢电极),脆硫锑铅矿表面主要是DDTC,PbD2,S0等疏水性物质的吸附,界面电容也比较小.当电极电位高于472mV时,由于PbD2,S0等疏水性物质被氧化成Pb2+,SO32-,SO42-,PbSO4等亲水性产物,脆硫锑铅矿表面是亲水的.由此推测用DDTC做捕收剂浮选脆硫锑铅矿的电位范围为-178～472mV,最佳电位范围为60～222mV.     

THE ROLE OF INTERFACIAL INTERACTIONS IN THE PARTICLE/BUBBLE ATTACHMENT

The Van Oss surface thermodynamic theory of polar and apolar interfacial interactions was extended to the interaction between mineral surfaces and bubbles across liquid media. The acid base (polar) interfacial interactions are supposed to be responsible for the hydration repulsion between a hydrophilic mineral and a bubble as well as for the hydrophobic attraction between a hydrophobic mineral and the bubble.