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Separation of naturally hydrophobic particles, such as coal, by flotation is known to be enhanced with the addition of salt solutions into the system. In this study, the flotation of bituminous coal in the presence of NaCl, KCl, CaCl2 and MgCl2 without use of any flotation chemicals was investigated in detailed. In addition, zeta potential and foam...
Citations
... Salt flotation can be also carried out at salt saturated aqueous solutions (Ratajczak and Drzymala, 2003). The presence of dissolved salt usually increases both the rate and final efficiency of flotation (Paulson and Pugh, 1996;Pugh et al., 1997;Kurniawan et al., 2011;Ozdemir, 2013;Laskowski and Castro, 2015;Zhang, 2015). ...
Flotation of copper-bearing shale in aqueous solutions of NaCl at their different pH values was investigated. The tests were carried out in a laboratory flotation machine. The pH range was between 5 and 10 while NaCl concentrations were 0.5M, 1.0M and 2.0M. It was observed that the flotation recovery of the copper shale was increasing with the increase of pH and concentration of the salt solution. On the basis of thermodynamic and hydrodynamic considerations it was postulated that the increasing surface tension was responsible for better shale flotation observed with increasing salt concentration. The observed improved shale flotation caused by increasing pH is most likely due to changes in the properties of the thin film between particle and bubble including mosaic structure of water on the surface of shale. It was shown that the zeta potential of shale particles, zeta potential of air bubbles, solution surface tension, and shale hydrophobicity were not responsible for the increasing with pH recoveries.
... Meanwhile, in the absence of particles, this structure is called foam and the stability is provided by the surfactants (frothers). Although frothers are the main chemicals used to control bubble coalescence, and thus bubble size and foam stability, studies have shown that some dissolved ions also inhibit bubble coalescence above a concentration called the transition concentration [16]. ...
... The effect of dissolved ions in flotation was mostly studied in the flotation of soluble salt minerals such as potash, trona, and borax [20][21][22][23][24]. However, there are also studies on nonsoluble ores [25][26][27][28][29] and coal [16]. ...
The aqueous ions influence the properties of air bubbles and, therefore, the recovery of flotation. This study aims to reveal the synergistic effect of frequently found ions in the flotation of Pb-Zn sulfide ores. In this context, dynamic surface tension measurements, bubble coalescence time, Sauter mean diameter (SMD), bubble size distribution (BSD), and dynamic foam stability (DFS) measurements were carried out using artificial process waters (APWs). APW with the minimum ion concentration is expressed as “APW1” with the ionic strength (I) of 0.03 mol/dm3. The concentration of the ions in APW1 was increased by 3, 5, and 10 times, and thus APW3 (I = 0.08 mol/dm3), APW5 (I = 0.13 mol/dm3), and APW10 (I = 0.26 mol/dm3) were prepared, respectively. The results of this study indicated that the surface tension increased slightly in the presence of APW related to the ion concentration. Potassium ethyl xanthate (KEX) at high concentrations was effective in the reduction of surface tension. As the APW concentration increased, finer bubbles were obtained with a narrower size range. The stability of the foam increased with butyl glycol (BG) and APW concentration. There was no need to use a frother (BG) for the flotation experiments in the presence of APW1 or APWs with higher ionic strength.
... The existence of these hydrophobic particles in the froth layer works on stabilizing the bubbles of this layer for a longer time [4,18]. In addition, the ionic species in the solution significantly affect the bubbles size and stability due to increasing the bubble surface charge that consequently prevents coalescence [4,9]. Figure 4 depicts the effect of pine oil at different pH values on ash % and coal recovery% in the floated fraction in the absence of MgCl2. ...
Coal flotation using inorganic salts receives special attention. It utilizes coal hydrophobicity to float coal without adding collectors. Although different salts were tested, chloride salts are the most promising ones. However, the stabilization of froth layer using the salts only is dubious. Therefore, in this study, the flotation of coal was tested using either magnesium chloride or pine oil as a frother to see if there is a difference in coal flotation between these reagents in terms of ash removal and coal recovery in the float fraction. Additionally, both magnesium salt and pine oil were added together to clarify their interactive effect using statistical design. The results proved that the presence of either reagent (i.e., pine oil or MgCl2) is significant in reducing the ash content and increasing coal recovery. Using the MgCl2 only reduced the ash to less than 4.3% with a coal recovery up to 28% while adding 1.0 kg/t pine oil along with 4 kg/t MgCl2 enhanced the reduction of ash to less than 3% with a coal recovery of up to 80% at pH 2.
... In a previous study using coal supplied from the same region as the coal used in this study, Ozdemir [31] conducted laboratory-scale collectorless flotation experiments with 100 g of coal particles (0.212×0.038 mm) using a 1.5 dm 3volume Denver (D-12) flotation cell in the presence of the same ions. Ozdemir [31] reported that the combustible recovery of the coal was 10% in the absence of ions. ...
... In a previous study using coal supplied from the same region as the coal used in this study, Ozdemir [31] conducted laboratory-scale collectorless flotation experiments with 100 g of coal particles (0.212×0.038 mm) using a 1.5 dm 3volume Denver (D-12) flotation cell in the presence of the same ions. Ozdemir [31] reported that the combustible recovery of the coal was 10% in the absence of ions. As found in the present study, although the coal was sufficiently hydrophobic in the absence of ions with a contact angle of 62°, the unsuccessful flotation of the coal can be explained by the lack of a sufficient number of stable bubbles in the flotation environment. ...
... Moreover, the results for the bubble-particle attachment time were correlated with the combustible recovery results of Ozdemir [31], and the relationship is given in Figure 6. As shown in Figure 6, the combustible recovery shows an increase when attachment time decreased. ...
... Kurniawan et al. used different salts, and the most stable froth and best flotation recovery were obtained with MgCl 2 [7]. Ozdemir comfirmed also that MgCl 2 showed the best recovery among the used salts i. e., NaCl, MgCl 2 , KCl and CaCl 2 when the influence of salts on flotation performance was investigated [8]. It was proved also that using MgCl 2 as single salt reduced ash content in concentrate more than its binary and tertiary mixtures with other chloride [9]. ...
The most frequently investigated salts in coal flotation are chlorides. However, seawater contains additional salts such as sulfates. In coal flotation, magnesium chlorides showed the best results in terms of higher yield and lower ash content compared to the other magnesium salts studied. Therefore, two magnesium salts were tested in this investigation, namely magnesium chloride and magnesium sulfate. The effect of the magnesium salts as well as the optimization of coal flotation were investigated by statistical design of experiments in terms of pulp density, particle size, conditioning time and different dosages of MgCl 2 and MgSO 4 . The flotation results obtained by statistical design show that the ash content was lowest at 8.2% when a mixture of 2 kg/t MgSO 4 and 2 kg/t MgCl 2 has been used, with pulp density 20%, particle size 400 lm and conditioning time 15 min. The particle size plays an important role in reducing the ash content when the conditioning time has been extended and pulp density has been reduced. The strong interaction between the salts hinders the reduction of the ash content to less than 8.2%.
... However, the mineralogical composition of some ores allows their processing using only a frother, without affecting mineral surfaces. An example is a native flotation of talc ore [4][5][6][7] or the collectorless flotation of sulfide minerals [8,9] and coal [10,11]. ...
This paper investigates the effect of sodium hexametaphosphate (SHMP) depressant/dispersant in the presence of methyl isobutyl carbinol (MIBC) frother and soluble starch (SS) depressant on the flotation kinetics of talc ore. Emphasis is on a comparison between the evaluation of a custom design of experiment (DoE) using the multilinear regression analysis (MRA) and response surface methodology (RSM) approach. Although analysis of variance (ANOVA) is a good first step in the evaluation of the effect of factors on froth flotation processing, it nonetheless only reveals the effects that are the same under all conditions. In the case of SHMP, its effect on separation efficiency is positive; however, if it is used along with SS, the effect is negative. Moreover, if a higher frother dosage is used, the effect of SHMP on separation efficiency is negligible.
... The collectorless flotation of naturally floatable sulfides is neither a new idea nor an unrealistic hypothesis (Brez ani et al., 2013). This concept had been proposed since virtually the start of this century (Ozdemir, 2013). Over the last few decades, numerous studies have exerted considerable efforts in understanding why certain minerals demonstrate natural floatability (Klimpel, 2000), and most of the studies were performed with isolated minerals in laboratory scale . ...
An economical and environmentally friendly beneficiation process is of great practical significance for the mining industry to achieve green and sustainable development. This study aims to optimize the traditional flotation process of Mo–Bi sulfide ore by using the difference in natural floatability of minerals for cleaner production. Single-mineral flotation tests demonstrate that the natural floatability of the sulfide minerals investigated decreased in the following order: molybdenite > bismuthinite > pyrite. Molybdenite displayed the best natural floatability in a wide pH range, and pyrite exhibited the least naturally floatable under alkaline conditions. The moderately natural floatability of bismuthinite was observed at the pH below 6, but decreased with the shift of pH to the alkaline region. Batch flotation tests indicate that the collectorless flotation of Mo–Bi sulfide ore resulted in lower flotation kinetics but higher selectivity than those of the collector flotation process. Industrial-scale tests illustrate that introducing collectorless flotation into the sequential flotation in industrial production was a feasible and reliable method of simultaneously increasing economic benefits and improving product quality. The grades of the Mo and Bi concentrates generated from the modified flotation process were 2.78% and 2.81% higher than those produced by the traditional flotation process. The daily consumption of chemical reagents in the modified flotation process decreased by more than 10%, reducing the annual cost of flotation reagent by approximately USD 60407.0. Given the characteristics of low reagents dosage, slightly environmental pollution, and high economic benefits, the modified flotation flowsheet is a promising separation process that can be extensively employed for mineral sources with similar mineralogical properties.
... Group A electrolytes of divalent and trivalent cations were found to give the best flotation response compared to electrolytes of group B (NaCl,LiCl,KCl,CsCl,NH4Cl), and group C (NaAc, NaClO4, HClO4, HCl, H2SO4, LiClO4). Kurniawan et al. (2011) found that in the presence of Dowfroth 250, MgCl2 gave the most stable froth, while NaClO3 showed the lowest froth stability that was similar to the recovery response (Kurniawan et al.,2011;Ozdemir 2013). conducted a review addressing the effect of saline water on the interfacial phenomena taking place in the flotation process, such as surface wettability, bubble-particle collision and attachment, mineral particle interactions and frothing. ...
Water plays a critical role in various stages of flotation, which brings a lot of pressure to the flotation processing plants resided in dry areas. In this regard, it will be of significance to explore the feasibility of using wastewater resources in mineral flotation. Coal gasification brine (CGB) that contains a high concentration of salts becomes the subject of interest of this study. In this study, a synthetic CGB solution, which was prepared by adding NaCl, MgCl2, and CaCl2 to ultrapure water based on the composition of salts in a real CGB, was used in the flotation of anthracite coal. The comparison results based on the first-order model showed that flotation in the presence of the synthetic CGB solution gave a higher flotation selectivity (SI =7.086) than that of flotation in ultrapure water (SI=3.545). Water recoveries and average bubble sizes in the froth showed that the addition of the three salt ions (Na+, Mg2+, and Ca2+) was conducive to diminishing the entrainment of gangue materials as a result of the reduction of water reporting to the froth. Additionally, the zeta potentials and induction time measurements indicated that only divalent ions of Ca2+ and Mg2+ significantly compressed the double electrical layer and enhanced the attachment between bubbles and coal particles according to DLVO theory, which was further confirmed by the calculation of interaction energy between coal and bubbles. The findings of the present work may promote the use of CGB as a potential water resource in coal flotation.
... Based on these data, we speculate that the foam tendency of GA solution can be changed with the addition of surfactant; however, the inorganic salt has little effect on its foam tendency. 25 In the process of ventilating, the surfactants arrange at the gas−water interface in a manner where hydrophilic ends come in contact with liquid and hydrophobic ends come in contact with gas ( Figure 3), 26−28 increasing the formation of foam and foam stability. On the one hand, with the addition of surfactants, the surface tension of GA solution is decreased, the lower the surface tension, the easier the foam formation. ...
The foam tendency of aviation coolants (ACs) can be greatly influenced by additives. This study investigates the effect of additives on foam behaviors based on four commercial ACs and glycol aqueous solutions added with different additives. Experimental results show that the foam tendency of ACs can be greatly influenced by surfactants; however, inorganic salts have little effect on foam tendency. The volume of generated foam reaches up to 350 mL after ventilation for an AC with a surfactant, much larger than 40 mL of an AC with an inorganic salt. The surface tension of ACs reduces with the addition of surfactants, the lower the surface tension, the more the foam formation. Furthermore, the presence of arranged surfactants at the gas–solution interface can increase the intermolecular forces and enhance the liquid and viscosity of film elasticity, thereby enhancing the foam stability. Besides, the surfactants would weaken the gas diffusion of foams and affect the defoaming property of ACs accordingly.
... Flotation can also be performed at high, one molar and more, salt concentration or even in salt saturated aqueous solutions (Ratajczak and Drzymala, 2003). The presence of dissolved salts usually increases both the rate and ultimate yield of flotation (Paulson and Pugh, 1996;Pugh et al., 1997;Ozdemir, 2013;Laskowski and Castro, 2015;Zhang, 2015). It was demonstrated in a previous study (Drzymala, 2018) that an Arrhenius-type equation can be used to relate the salt concentration and flotation kinetics, that is to link the value of incentive parameter with the value of a system response parameter, and determine the salt flotation activation energy. ...
A modified Arrhenius equation, in which thermal energy is replaced with chemical (Gibbs) potential, and a special calculation procedure were used to evaluate the flotation activation energy for salt solutions in the one molar range of concentrations. The proposed formula overcomes the difficulties of calculating the salt flotation activation energy caused by mathematical problems of finding 1/(ln(c/co)) for the standard salt concentration co=1 M (1 kmol/m3) and when the applied salt concentration c is in the vicinity of 1 M. The salt flotation activation energy was calculated for flotation of copper-bearing carbonaceous shale in the 0.25, 0.50, 1.00 and 2.00 M NaCl solutions performed in a laboratory machine as equal to 1.9 RT for standard salt solution equal to 1 M.
