Flotation Of Salts Research Articles

Investigation of flotation of salts in their saturated solutions

Flotation of NaCl, KCl and KPF6 in saturated aqueous solutions was investigated. The tests were carried out for salt particle sizes of >200, 100-200, 71-100 and <71μm. Flotation tests were performed in a Hallimond flotation cell. In addition, contact angle was estimated using a flotometric method and measured by the sessile drop technique. The angles were 5 degree for NaCl and KCl and 8 degrees for KPF6. Thus, there was mostly mechanical carryover of particles during the flotation test. However, an increase in the flotation yield of the tested salts with the increase of contact angle was observed.

Selective adsorption of octadecylamine hydrochloride on the surface of KCl crystal: adsorption energy based on density functional theory

Flotation has become a significant technique for the KCl separation from NaCl-containing complex systems, but the true nature of adsorption selectivity of collector on the crystal surface of KCl is still unclear. In this study, using density functional theory calculations, we investigated the adsorption behaviors of a commonly used collector, octadecylamine hydrochloride (ODA), on the crystal surfaces of KCl and NaCl, respectively. The results demonstrate that the structure of built crystals for calculation is validity and the crystal surfaces containing two-layer atoms are most stable. All adsorption energies of ODA+ cation and H2O molecule on the crystal surfaces of KCl and NaCl are negative with the decreased absolute value according to the sequence of KCl-ODA+ >NaCl-H2O > KCl-H2O > NaCl-ODA+, suggesting that the interaction between ODA and KCl is stronger than that in the other considered systems. The differences of interaction energies demonstrate the adsorption selectivity of ODA on KCl, resulting in the selectively flotation. Therefore, we construct accurate models to simulate the actual crystal surface structures of KCl and NaCl, and we provide adsorption energies as complementary evidences to interpret the floatability of KCl from the NaCl mixture, which can help to design new collectors for the flotation of soluble salts.

Specific anion effects on adsorption and packing of octadecylamine hydrochloride molecules at the air/water interface

The spread of collector molecules on bubble surfaces in salt solution is a fundamental phenomenon in the froth flotation of soluble salts, such as KCl, and consideration of ionic effects on adsorption behavior and packing of collector molecules at the air/solution interface is appropriate for study. In this work, specific anion effects on the adsorption and packing of one common collector (octadecylamine hydrochloride, ODA) at the air/water interface were investigated by employing a combination of surface pressure measurements, sum frequency vibrational spectroscopy (SFVS) and molecular dynamics simulations (MDS). The results from experiments and MDS showed that the addition of external anions disturbs the arrangement of ODA molecules due to the penetration of these anions from the water subphase into the ODA monolayer at the air/water interface. During monolayer compression, the penetrated anions might be driven back to the water subphase by electrostatic forces and the added compression force. These anions could screen the charge of NH3 groups resulting in a reduction of the minimum area of the ODA molecule (Amin) for the solid phase state of the monolayer. With the exception of the sulfate anion, the added anions increase hydrogen bonding of interfacial water molecules at the air/water interface. These results allow for a better understanding of the anionic effect on adsorption and packing of ODA molecules at the air/water interface, and might therefore provide new insights into froth flotation of soluble salts and should help to improve soluble salt flotation technology.

Erratum to: Effects of particle size and chain length on flotation of quaternary ammonium salts onto kaolinite

Erratum to: Effects of particle size and chain length on flotation of quaternary ammonium salts onto kaolinite

Effects of particle size and chain length on flotation of quaternary ammonium salts onto kaolinite

Effects of particle size and chain length on flotation of quaternary ammonium salts (QAS) onto kaolinite have been investigated by flotation tests. Dodecyltrimethylammonium chloride (DTAC) and cetyltrimethylammonium chloride (CTAC) were used as collectors for kaolinite in different particle size fractions (0.075 ~ 0.01 mm, 0.045 ~ 0.075 mm, 0 ~ 0.045 mm). The anomalous flotation behavior of kaolinite have been further explained based on crystal structure considerations by adsorption tests and molecular dynamics (MD) simulation. The results show that the flotation recovery of kaolinite in all different particle size fractions decreases with an increase in pH. As the concentration of collectors increases, the flotation recovery increases. The longer the carbon chain of QAS is, the higher the recoveries of coarse kaolinite (0.075 ~ 0.01 mm and 0.045 ~ 0.075 mm) are. But the flotation recovery of the finest kaolinite (0 ~ 0.045 mm) decreases with chain lengths of QAS collectors increasing, which is consistent with the flotation results of unscreened kaolinite (0 ~ 0.075 mm). It is explained by the froth stability related to the residual concentration of QAS collector in mineral pulp. In lower residual concentration, the froth stability becomes worse. Within the range of flotation collector concentration, it’s easy of CTAC to be completely adsorbed by kaolinite in the particle size fraction (0–0.045 mm), which led to lower flotation recovery. Moreover, it is interesting that the coarser particle size of kaolinite is, the higher flotation recovery is. The anomalous flotation behavior of kaolinite is rationalized based on crystal structure considerations. The results of MD simulations show that the (001) kaolinite surface has the strongest interaction with DTAC, compared with the (001) face, (010) and (110) edges. On the other hand, when particle size of kaolinite is altered, the number of basal planes and edge planes is changed. It is observed that the finer kaolinite particles size become, the greater relative surface area of edges and the more the number of edges are. It means that fine kaolinite particles have more edges to adsorb fewer cationic colletors than that of coarse kaolinite particles, which is responsible for the poorer floatability of fine kaolinite.

Flotation chemistry of soluble salt minerals: from ion hydration to colloid adsorption

In this paper, recent progress with respect to the flotation chemistry of soluble salt minerals is reviewed, and some of the more relevant issues including the hydration states of ions, the interfacial phenomena of salt surfaces and the flotation behavior of selected soluble salts are discussed. Due to the high solubility, the flotation of most soluble salts has to be carried out in their saturated brines. Anecdotal evidence has suggested that the hydration states of the ions have significant influence on the physicochemical properties of the solutions, the surface charge and wetting characteristics of the minerals, the collector adsorption states and, further, the flotation behavior of the soluble salts. In this regard, reviewing past research findings, efforts are made to establish a correlation between the ion hydration states with the flotation behavior of the soluble salts. Further, advances in understanding the significance of colloid adsorption involved in the soluble salt flotation process are addressed, and future research efforts to understand the soluble salt flotation chemistry are suggested.

Flotation and adsorption of quaternary ammonium salts collectors on kaolinite of different particle size

The flotation behaviors of decyltrimethylammonium (103C), dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC) and cetyltrimethylammonium chloride (CTAC) on kaolinite of different particle size fraction were studied. The adsorbed amount and adsorption isotherms of collectors on kaolinite were determined for painstaking investigation into the adsorption of quaternary amines at kaolinite–water interface by ultraviolet spectrophotometer methods. The flotation results show that the flotation recovery of kaolinite of different particle fraction increases with an increase in pH when 103C, DTAC, TTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. Particle size of kaolinite has a strong effect on flotation. The flotation recovery of fine kaolinite decreases with the carbon chain of quaternary ammonium salts collectors increasing, while coarse kaolinite is on the contrary. The adsorbed amount tests and adsorption isotherms show that adsorbed amount increases when the particle size of kaolinite increases or when the carbon chain length of quaternary ammonium salts increases. Within the range of flotation collector concentration, the longer the hydrocarbon chain, the more probable to be absolutely adsorbed by fine kaolinite particles and then the lower the collector concentration in the bulk, which leds to lower flotation recovery.

Bubble attachment time and FTIR analysis of water structure in the flotation of sylvite, bischofite and carnallite

Water structure is the most important parameter that influences the flotation of soluble salts. In this paper bubble attachment time measurements and FTIR analyses were performed to investigate the effect of water structure on the flotation behavior of sylvite (KCl), bischofite (MgCl2·6H2O) and carnallite (KMgCl3·6H2O). The results from bubble attachment time measurements suggest that collector adsorption at the surface of KCl induces flotation with either the cationic collector, ODA, or anionic collector, SDS. In contrast bubble attachment did not occur for bischofite (MgCl2·6H2O) or carnallite (KMgCl3·6H2O). Results show that the surface charge is not a determining factor in the flotation of soluble salts.Further, the interaction between water molecules and the three chloride salts dissolved in aqueous solution were studied by measuring the shift in the hydrogen-bonding of water molecules. The results indicate that KCl is a structure breaker salt, while MgCl2·6H2O and KMgCl3·6H2O are structure maker salts.Viscosities for the brines of these three salts were determined. The results give additional evidence of differences in water structure and are in good agreement with the FTIR and bubble attachment results. The findings provide further evidence that water structure plays an important role in the flotation of soluble salts.

Contact angle and bubble attachment studies in the flotation of trona and other soluble carbonate salts

Trona, Na 2CO 3 · NaHCO 3 · 2H 2O, is mined as the primary source for sodium carbonate production in the United States. Recent studies have shown that the flotation method can be used for pre-processing of trona ore to remove insoluble mineral contaminants for the production of soda ash (sodium carbonate). Studies with carbonate salts suggest that certain important factors can affect their flotation response, including viscosity of the brine and interfacial water structure. Flotation studies showed that contrary to the strong flotation of NaHCO 3 with both anionic and cationic collectors, Na 2CO 3 does not float at all. Based on the analysis of interfacial water structure in saturated brines, Na 2CO 3 was found to act as a strong water structure maker, whereas NaHCO 3 acts as a weak water structure maker. Bubble attachment time measurements suggest that collector adsorption at the surface of NaHCO 3 induces flotation; this is not the case for Na 2CO 3. Contact angle measurements indicated that the surface of Na 2CO 3 is hydrated to a great extent, whereas the NaHCO 3 salt surface is less hydrated. These results reveal that there is a strong relationship between the interfacial water structure and the contact angle of these salts. The less stable NaHCO 3 surface is ascribed to the interfacial water structure which allows for NaHCO 3 flotation with both anionic and cationic collectors.

Water structure and its influence on the flotation of carbonate and bicarbonate salts

Interfacial water structure is a most important parameter that influences the collector adsorption by salt minerals such as borax, potash and trona. According to previous studies, salts can be classified as water structure makers and water structure breakers. Water structure making and breaking properties of salt minerals in their saturated brine solutions are essential to explain their flotation behavior. In this work, water structure making–breaking studies in solutions of carbonate and bicarbonate salts (Na 2CO 3, K 2CO 3, NaHCO 3 and NH 4HCO 3) in 4 wt% D 2O in H 2O mixtures have been performed by FTIR analysis of the OD stretching band. This method reveals a microscopic picture of the water structure making/breaking character of the salts in terms of the hydrogen bonding between the water molecules in solution. The results from the vibrational spectroscopic studies demonstrate that carbonate salts (Na 2CO 3 and K 2CO 3) act as strong structure makers, whereas bicarbonate salts (NaHCO 3 and NH 4HCO 3) act as weak structure makers. In addition, the changes in the OD band parameters of carbonate and bicarbonate salt solutions are in agreement with the viscosity characteristics of their solutions.

Water structure in aqueous solutions of alkali halide salts: FTIR spectroscopy of the OD stretching band

Water structure making/breaking studies in solutions of five alkali halide salts (KF, KI, NaI, CsF and CsCl) in 4 wt% D 2O in H 2O mixtures have been performed by FTIR analysis of the OD stretching band in the full solubility range. The proposed method gives a microscopic picture of the water structure making/breaking character of the salts in terms of the hydrogen bonding between the water molecules in the solution. With the exception of CsCl, there is a very good correlation of the structure making/breaking character of the salts determined by FTIR analysis, and the viscosity coefficients of the solutions. The results fully support and explain previous studies of bubble attachment to microscopic salt particles of the above salts. The investigations support the primary importance of interfacial water structure in the explanation of the flotation of alkali halide salts in their brines.

FTIR analysis of water structure and its significance in the flotation of sodium carbonate and sodium bicarbonate salts

Abstract The production of soda ash from trona resources (sodium sesquicarbonate, Na 2 CO 3 ·NaHCO 3 ·2H 2 O) has completely displaced the production of synthetic soda ash in the USA. Further, the utilization of other trona resources is under consideration in China, Turkey, etc. Recent research has been concerned with the development of flotation technology for the trona industry. In this regard studies on the flotation behavior of sodium carbonate salts: trona, sodium carbonate monohydrate and decahydrate, as well as the flotation behavior of sodium bicarbonate, are reported for both cationic (dodecyl ammonium hydrochloride) and anionic (sodium dodecyl sulfate) collectors. It has been found that strong flotation of sodium bicarbonate (NaHCO 3 ) can be achieved with 100% recovery, while the other sodium carbonate salts do not float well. These results have been explained by FTIR analysis of aqueous solutions of Na 2 CO 3 and NaHCO 3 in a range of concentrations from very dilute to saturated conditions. The changes in the shape of the O–H stretching band of water are correlated with the flotation behavior of Na 2 CO 3 salts and NaHCO 3 . In addition, the absorption band of the carbonate ion at ca. 1385 cm −1 is used to monitor its interactions with water and/or other ions in solution. The infrared results demonstrate that Na 2 CO 3 acts as a water structure maker, leading to an extensively hydrated surface that accounts for the poor flotation of most sodium carbonate salts. In contrast, NaHCO 3 does not have this characteristic and consequently complete flotation is possible with both cationic and anionic collectors. These results support the previous water structure analysis for soluble salt flotation of alkali halides and other oxyanion salts.

Effect of thermal stability on the flotation response of sodium carbonate salts

Laboratory microflotation experiments show that flotation of certain sodium carbonate salts with cationic and anionic collectors is possible if the salts are thermodynamically stable under the prevailing experimental conditions. Sodium carbonate monohydrate can be floated up to 100% recovery with cationic dodecyl amine hydrochloride (DAH) and anionic sodium dodecyl sulfate (SDS) collectors at temperatures above 40 °C. Sodium carbonate decahydrate floats to a maximum yield of about 30% with 1×10 −3 M DAH and to 17% with 1×10 −4 M SDS even at room temperature where it is thermodynamically stable. Trona, the double salt of sodium carbonate and bicarbonate, does not float at room temperature in its saturated solution with either collector. Complete flotation of sodium bicarbonate in its saturated solution at pH 8.3 occurs with both DAH and SDS at all temperatures. Complementary data on flotation, viscosity and FTIR studies reveal that in addition to the thermal stability, the flotation response is dictated by the relative contributions of viscosity and water structuring properties of soluble carbonate salts.

Flotation of sodium carbonate and sodium bicarbonate salts from their saturated brines

The flotation behavior of sodium carbonates and sodium bicarbonate has been studied with dodecyl amine hydrochloride (DAH) and sodium dodecyl sulfate (SDS) as part of a research program to evaluate the potential of flotation technology for use in the trona industry. Laboratory microflotation experiments generally show that flotation of sodium carbonate salts is possible at least to some extent with cationic (DAH) and anionic (SDS) collectors if the salt is thermodynamically stable under the prevailing experimental conditions. Anhydrous sodium carbonate does not float at any collector concentration because of its instability at the temperatures considered. Sodium carbonate monohydrate can be floated to completion with DAH and SDS at temperatures higher than 40 °C where it is thermodynamically stable but not at lower temperatures. Sodium carbonate decahydrate is difficult to float (30% yield) even at room temperature where it is thermodynamically stable. Even modest flotation of decahydrate is not possible for temperatures exceeding 32 °C under which conditions the decahydrate salt becomes unstable. In general, the sodium carbonate salts are difficult to float even when they are thermodynamically stable because of their strong water structure making influence.In contrast, strong and complete flotation of sodium bicarbonate can be achieved with both DAH and SDS at all temperatures. Such a flotation response was expected since sodium bicarbonate is stable at these temperatures and since the sodium bicarbonate salt does not promote the formation of water structure. Addition of sodium carbonate to the saturated bicarbonate solution, however, destroys the flotation of sodium bicarbonate completely. It is evident that the amount of sodium carbonate in the saturated solution is a most important parameter which controls the flotation response of sodium bicarbonate.Finally trona, sodium sesquicarbonate, the double salt of sodium carbonate and bicarbonate, was found not to float at room temperature with either the DAH or SDS collectors. These flotation results are discussed with regard to interfacial water structure as influenced by salt properties.

The Significance of Interfacial Water Structure in Soluble Salt Flotation Systems

Flotation of soluble salts with dodecyl amine hydrochloride (DAH) and sodium dodecyl sulfate (SDS) collectors has demonstrated that the interfacial water structure and hydration states of soluble salt surfaces together with the precipitation tendency of the corresponding collector salts are of considerable importance in explaining their flotation behavior. In particular, the high concentration of ions in these soluble salt brines and their hydration appear to modify the bulk and interfacial structure of water as revealed by contact angle measurements and this effect is shown to be an important feature in the flotation chemistry of soluble salt minerals including alkali halide and alkali oxyanion salts. Depending on characteristic chemical features (salt type), the salt can serve either as a structure maker, in which intermolecular hydrogen bonding between water molecules is facilitated, or as a structure breaker, in which intermolecular hydrogen bonding between water molecules is disrupted. For structure making salts the brine completely wets the salt surface and no contact angle can be measured. For structure breaking salts the brine does not completely wet the salt surface and a finite contact angle is measured. In this regard it has been found that soluble salt flotation either with the cationic DAH or anionic SDS collector is possible only if the salt is a structure breaker.

Fundamental aspects of soluble salt flotation

The sign of the surface charge for alkali halides in their saturated brines has been established from nonequilibrium electrokinetic measurements. These surface charge results for alkali halides are generally as expected from simplified lattice ion hydration theory. Based on this electrokinetic information, it has been demonstrated that the flotation of alkali halide salts is due to the adsorption of oppositely charged collector colloids by heterocoagulation. For example, the classic flotation separation of KCl from NaCl with alkyl amines is thus explained. Now, the surface charge.collector colloid adsorption hypothesis has been extended to successfully explain the flotation behavior of certain alkali oxyanions including nitrates and sulfates as well as double salts including schoenite (K 2SO 4·MgSO 4·6H 2O) and kainite (KCl·MgSO 4·3H 2O). As was done previously for the alkali halides, the sign of the surface charge for these alkali oxyanion salts was established from nonequilibrium electrokinetic measurements by laser-doppler electrophoresis. These results together with the results from flotation/bubble attachment experiments indicate that the surface charge/collector colloid adsorption hypothesis accounts for the flotation response of many different soluble salt minerals when alkyl amines and carboxylates are used as collectors.

Surface Properties of Sodium Octyl Sulphate in Saturated Salt Solutions

As part of a study of the flotation of soluble salts the surface tension of sodium octyl sulphate has been measured1 in saturated solutions of lithium, sodium, potassium and ammonium chlorides at 20° C. No previous measurements are recorded for the surface tension of sodium octyl sulphate in saturated salt solutions or in water. This compound has very little effect on the surface tension in water, but in the saturated salt solutions the maximum lowering of surface tension is approximately 50 dynes cm.−1.