2016, 147−154 Physicochemical Problems of Mineral Processing

Abstract: In this paper the importance of definition of hydrophobicity and aquaoleophilicity in terms of contact angle as well as the properties of water films in flotation and oil agglomeration were briefly presented. It was shown that the hysteresis of contact angle for a considered system depends on the way of measurement and geometry of the system due to the presence of other that excess pressure and capillary forces and buffering properties of the capillary force. It was suggested that, the measured advancing and receding contact angles should be, when possible, recalculated into the Young (rest, equilibrium) contact angle. It was discussed that quartz is not a good model of hydrophilic surface because its contact angle with a gas phase in water is not zero and that a spontaneous attachment between highly hydrophobic materials such as hydrocarbons and Teflon in dynamic system, such as flotation, does not occur

Application of near infrared sensors to preconcentration of hydrothermally-formed copper ore

Article© 2015. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Near infrared sensors can be a very useful technique for the qualitative analysis of complex ores, and thus could be useful for the preconcentration of ores. In this paper, individual particles of hydrothermally-formed copper ore sampled from a mine in the Los Pozos mining district, northern Chile, were classified as product, middling and waste based on their near infrared response. The classification of copper bearing minerals (product) from gangue (waste) was considered for vibration combination bands at longer wavelengths from 2000 to 2400 nm. This region exhibits characteristic features for carbonates and hydroxyl gangue bearing minerals. The near infrared features at 1400 and 1900 nm were not considered favourable for classification and subsequent discrimination because they can be influenced by moisture and other environmental factors and are easily suppressed by iron-rich minerals. Two near infrared preconcentration strategies were applied for particle discrimination. Results indicate that targeting only the calcite (carbonate) dominated particles for discrimination as waste provided the best option for preconcentration. The near infrared discrimination analysis correlates well with mineralogical (QEMSCAN® and XRD) and elemental (XRF) data classification. The results indicate that near infrared spectroscopy is a suitable preconcentration method for supergene copper ore

Classification of Flotation Frothers

In this paper, a scheme of flotation frothers classification is presented. The scheme first indicates the physical system in which a frother is present and four of them i.e., pure state, aqueous solution, aqueous solution/gas system and aqueous solution/gas/solid system are distinguished. As a result, there are numerous classifications of flotation frothers. The classifications can be organized into a scheme described in detail in this paper. The frother can be present in one of four physical systems, that is pure state, aqueous solution, aqueous solution/gas and aqueous solution/gas/solid system. It results from the paper that a meaningful classification of frothers relies on choosing the physical system and next feature, trend, parameter or parameters according to which the classification is performed. The proposed classification can play a useful role in characterizing and evaluation of flotation frothers

Surface roughness in bubble attachment and flotation of highly hydrophobic solids in presence of frother – experiment and simulations

In this paper, the kinetic of the three-phase contact (TPC) formation and the flotation recovery of highly hydrophobic solids with different surface roughness were studied in pure water and aqueous solutions of n-octanol. The surface roughness varied between 1 to 100 μm. It was found that there was a strong influence of surface roughness on both kinetics of TPC formation and flotation. The time of three phase contact formation and flotation rate were much faster for rough surfaces in both water and aqueous solutions of frother. Irrespective of the surface roughness, at above a certain frother dose, the attachment time increased and the flotation rate decreased. It was related to the presence of air at the hydrophobic solid surfaces. The mechanism of this prolongation of the time of TPC formation at the solid surfaces with different roughness due to the frother overdosage was discussed, and the experimental data were confirmed by numerical simulations

Kinetic separation curves based on process rate considerations

There are many graphical representations of separation results involving time as a crucial parameter determining the kinetics of a process. The graphical representations of results of separation are usually in the form of 2D plots relating two parameters which one of them is time. Time can also be utilized as a complex parameter such as a process rate. The plots involving time are called kinetic curves. Theoretically, the number of kinetic curves is infinite. The basic process kinetic curves, relating either yield (or recovery) and time can be modified to obtain numerous local and global efficiency curves. The global efficiency kinetic curves provide characteristic constants which do not change with the time and yield of a process. In this paper the local and global efficiency plots were created using experimental data which followed the so-called first order kinetics. It was shown that the integral 1st order kinetic equation provided the kinetic constant k which was numerically identical with the 1st order specific rate v, while their units were different (k, 1/min; v, %/(%·min). The global efficiency parameters plotted versus the maximum yield provided another type of plot, which can be called the limits kinetic curve. The limits kinetic curves are very useful for characterizing, quantification and classification of separation systems. The limits kinetic curves can be normalized providing one universal curve with a characteristic point, for instance, v50 indicating the specific rate (or kinetic) constant at the maximum recovery equal to 50%. The mathematical equation of the normalized limits kinetic curve was given in the paper

Control of glass surface wettability via esterification with n-alkyl alcohols

Surface wettability plays an essential role in many processes and materials applications. It depends mainly on the surface roughness and chemical composition, thus through a controlled modification of these parameters, the wettability can be restrained. Glass is an inorganic solid material, composed mainly of amorphous silica, which surface, due to the presence of reactive hydroxyl groups, can be quite easily chemically modified. This feature can be used to control the wettability of glass by reaction with organic compounds. In this study, the esterification of glass silanol groups with n-alkyl alcohols (Cn/H2n+1/OH, n=3, 4, 6, 8, 10) was employed to modify its wettability. The effect of such modification on the physicochemical properties of glass surface was comprehensively investigated and characterised by the water contact angle, surface free energy, zeta potential, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) measurements. We demonstrate that the wettability of the esterified glass surface is strongly dependent on both the chain length of used alcohol and modification time. The alcohol molecule binds to the glass surface through a Si-O-C bond, leading to the formation of a monolayer that does not significantly affect the surface morphology and zeta potential. Conducted studies provided a broader view of the influence of this technique for modifying surface wettability on its physicochemical properties

Concentration at the Minimum Bubble Velocity (CMV) for Various Types of Flotation Frothers

This paper presents the determination of a concentration at the minimum bubble velocity (CMV) for different types of frothers, such as straight and branched alkyl chain aliphatic alcohols, 1,ω-diols, poly(propylene glycol) and poly(ethylene glycol) alkyl ethers, n-alkyltrimethylammonium bromides, commercial frothers and others. The values of terminal rise bubble velocity were reviewed from the experimental data published in the literature for two different types of columns, i.e., a short PAS (used in Polish Academy of Sciences) of height (35 cm) and a long McGill of height (350 cm). The obtained empirical equation is universal and allows one to rapidly and accurately determine the CMV for all surfactants. The proposed empirical model can also be used to predict the terminal bubble velocity–frother concentration curve by knowing the maximum and minimum terminal velocities, as well as the values of CMV. Assessment and usefulness of frother characterization parameters (i.e., concentration at the minimum bubble velocity (CMV), dynamic frothability index (DFI) and critical coalescence concentration (CCC)) were shown in the flotation of coal

Local and global assessment of flotation kinetics

Most flotation data can be approximated with the first order kinetic equation. However, this equation frequently provides two, not one, parameters, that is the first order flotation rate constant k and maximum flotation recovery Rmax. Currently, the most often way of evaluation of a set of flotation data is by using efficiency eto = k·Rmax, being the slope of flotation kinetic curve at zero flotation time (t=0). This parameter has a local character and is useful only in very limited cases. It was proposed in this work to use a global flotation kinetic efficiency (e) which can characterize the whole set of kinetic curves. For the considered in this work flotation data, a simple relation Rmax = e·k was used. For other sets of flotation data, the global flotation kinetics efficiency very likely will be represented by another equation with the one-adjustable parameter

Critical Synergistic Concentration of Binary Surfactant Mixtures

This paper presents a simple method for determination of synergism in binary surfactant mixtures. A homologous series of cationic alkyltrimethylammonium bromides (CnTAB, with n = 8, 12, 16, 18) mixed with three non-ionic surfactants (n-octanol, methyl isobutyl carbinol, tri(propylene glycol) butyl ether) was chosen as a model system. In addition to the cationic-non-ionic system, the mixture of anionic-non-ionic surfactants (sodium dodecyl sulphate and tri(propylene glycol) butyl ether) was investigated. The foam behavior of one-component solutions and binary mixtures was characterized as a function of surfactant concentration, number of carbons (n) in alkyl chain of CnTAB as well as type of surfactant. It was shown that synergism in foamability could be produced by the ionic-non-ionic systems, and the concentration below the synergism occurs, called the critical synergistic concentration (CSC), that can be easily predicted based on the surface tension data on individual components

Effect of foamability index of short chain alkyl amines on flotation of quartz

Amines can be used for flotation of various minerals, especially quartz. The flotation efficiency of quartz depends on the amine type and dose. It was proved that the shorter alkyl amine, higher amine concentration has to be used to recover quartz at the same level. In flotation amines play a role of both collectors and frothers. The ability of a amine to collect particles can be expressed in the form of contact angle, while the foaming properties by different parameters including dynamic foamability index (DFI) and critical coalescence concentration (CCC). Determination of DFI and CCC requires advanced techniques and methods. Therefore, in this paper a rapid and facile method for determination of foaming properties of amines and also other surfactants was used. It was based on measuring the initial foam and froth heights in a conventional flotation machine at different concentrations of surfactants. The foam height-concentration curve was described by utilizing an empirical equation which was based on one-adjustable parameter called the foamability index (FI). In this work the foamability index was determined for butylamine (ButNH2), hexylamine (HexNH2) and octylamine (OctNH2) as examples of short chain alkyl amines. The determined foamability indices were 92, 12 and 4 mg/dm3 for ButNH2, HexNH2 and OctNH2, respectively. It was shown that when the flotation results of quartz were presented in the form of recovery versus normalized amine concentration in relation to the foamability index (c/FI), all the experimental data points converged to one curve. It indicates that amines act similarly but at different concentrations expressed as FI. The foamability index seems to be a useful parameter for characterizing any flotation frother