Hydrophobic Agglomeration Research Articles

Hydrophobic agglomeration of apatite fines induced by sodium oleate in aqueous solutions

Abstract In this work, the hydrophobic agglomeration of apatite fines induced by sodium oleate in aqueous solutions has been investigated through the measurement of agglomeration degree and fractal dimension. The results showed that the agglomeration degree of apatite fines and agglomerates morphology was strongly depended on sodium oleate concentration, pH, stirring speed and time. Better agglomeration degree and more regular agglomerates were achieved at sodium oleate concentration of 5 × 10−5 mol/L under neutral condition. The critical stirring speed for agglomerates rupture was 1000 rev/min, above which, prolonged stirring time would cause breakage and restructure of the agglomerates after a certain stirring time, resulting in lower agglomeration degree and more regular agglomerates. The agglomeration degree of apatite fines could be greatly enhanced with the addition of emulsified kerosene, but only if the apatite surface was hydrophobic enough.

Removal of graphene oxide from water by floc-flotation

Abstract In this work, floc-flotation has been introduced into the elimination of graphene oxide (GO) from water for the first time, so as to reduce its potential risk and biotoxicity. Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) were used to characterize the prepared GO, and the floc-flotation of GO have been studied both experimentally and theoretically. Extended DLVO theory has been applied to predict the hydrophobic agglomeration of GO, while the effects of dodecylamine hydrochloride (DAH) concentration, pH and stirring strength on the floc-flotation have been discussed. It has been found that the addition of DAH could induce GO surfaces hydrophobic, while appropriate stirring strength provided the kinetic energy for overcoming the energy barrier between the approaching particles. As a result, the hydrophobic agglomeration of GO could be greatly promoted and then the flotation separation of flocs from water could be efficiently realized. This processing could remove up to 98% of the GO nanoparticles form water, resulting in a much less environmental concern for GO in natural water bodies.

Hydrophobic agglomeration of talc fines in aqueous suspensions

In this work, hydrophobic agglomeration of fine talc particles in aqueous solutions under mechanical conditioning and without any addition of surfactants has been experimentally studied. A method of in-situ measurement of turbidity of flocs suspension in the settlement process has been applied, and the turbidity as a function of settling time has been attempted to fit a certain function so as to assess the hydrophobic agglomeration behaviors. Effects of kerosene dosages, stirring rate, and wettability of talc particles on the hydrophobic agglomeration behaviors have been investigated. The results show that the addition of kerosene can greatly enhance the aggregation of colloidal talc in aqueous suspensions. Besides, the stirring strength and duration make an enormous influence on the aggregation through providing the kinetic energy for overcoming the energy barrier between the approaching particles. It is also found that the wettability of talc is closely related to the aggregation degree. More hydrophobic talc particles show a much stronger aggregation behaviors.

Hydrophobic agglomeration kinetics of fine kaolinite particles in aqueous suspensions

ABSTRACTThe hydrophobic agglomeration kinetics of kaolinite has been studied through the in-situ turbidity meter measurement system. The effects of surfactant dosage, stirring rate and particle size on the hydrophobic agglomeration dynamics have been investigated. Appropriate surfactant concentrations provided the strongest hydrophobicity, modest stirring rate offered a higher agglomerates formation rate and a lower disruption rate, and smaller particles had lower energy barrier and higher attachment efficiency. The best hydrophobic agglomeration conditions have been determined and a kinetic model of hydrophobic agglomeration has been proposed by experimental results. The kinetic model has been turned out to be fitted to the dynamic process well and can characterize as well as assess the hydrophobic agglomeration kinetics appropriately.

Design and regulation about composition of minerals and TiO2 particles

To guide the composition of mineral and TiO2 particles by hydrophobic agglomeration, a relationship between interaction energy of particles (van der Waals energy, electrostatic energy and hydrophobic interaction energy) and their distance between these particles in aqueous medium was established according to the extended Derjaguin–Landau–Verwey–Overbeek theory and hydrophobic agglomeration theory. In this paper, a CaCO3-TiO2 composite material (CaCO3 particle was coated by TiO2 particles) was prepared to verify the correctness of the theory through surface-induced hydrophobic interactions. The performance and structure of this composite were characterised by scanning electron microscope, energy dispersive X-ray analysis, ultrasonic strength test, particle size analyser, whiteness, hiding power and oil absorption. The experiment results about the coating situation are agreement with the calculation analysis. These results are significant to guide the experiment for preparation of the CaCO3-TiO2 composite by hydrophobic agglomeration compound.

KINETICS OF HYDROPHOBIC AGGLOMERATION OF MOLYBDENITE FINES IN AQUEOUS SUSPENSIONS

The kinetics of hydrophobic agglomeration of molybdenite fines in aqueous suspensions has been studied in this work. This study was performed on minus 5 µm molybdenite particles through turbid- ity measurements and imaging. The results have showed that stirring strength and kerosene addition greatly affected the agglomeration rate of molybdenite fines in aqueous suspensions. The higher was the stirring strength, the larger the agglomeration rate was. Kerosene addition enhanced not only the agglom- eration rate, but also the agglomerates structure. It was recommended to use radial impeller for the for- mation of hydrophobic agglomeration, because it produced a stronger shear field in impeller zone.

Morphology of Hydrophobic Agglomerates of Molybdenite Fines in Aqueous Suspensions

In this work the morphology of agglomerates formed in the hydrophobic agglomeration of molybdenite fines in aqueous suspensions has been studied by measuring fractal dimension with image analysis method. The results have shown that the morphology closely correlated with the mechanical conditioning in the hydrophobic agglomeration. The higher the stirring speed and the longer the stirring, the more spherical and more compact the agglomerates. Also, kerosene addition could make the agglomerates to be more spherical and compact.

HYDROPHOBIC AGGLOMERATION OF MINERAL FINES IN AQUEOUS SUSPENSIONS AND ITS APPLICATION IN FLOTATION: A REVIEW

Hydrophobic agglomeration is originated from the hydrophobic attraction between particles, which is essentially different from electrolyte coagulation and polymer flocculation. It is applied to mineral processing in floc-flotation process to improve the recovery of mineral fines. In this paper, the applications of this phenomenon in mineral fines were summarized, including the origin of hydrophobic agglomeration, the main factors affect hydrophobic agglomeration (particle hydrophobicity, shear rate and duration, nonpolar oil and tank geometry), as well as hydrophobic agglomeration based separation processes (carrier flotation and floc-flotation).

Hydrophobic agglomeration of colloidal kaolinite in aqueous suspensions with dodecylamine

The stability of colloidal kaolinite dispersions in the presence of dodecylamine (DDA) has been studied in this work through the measurements of aggregation degree, zeta potential and adsorption. The experimental results show that DDA can induce a strong aggregation of colloidal kaolinite in aqueous suspensions even though the particles are highly negatively charged. This aggregation closely correlated to the adsorption of DDA cation on kaolinite surfaces and the hydrophobicity, so that it should belong to hydrophobic agglomeration. The adsorption isotherm of DDA on kaolinite surfaces showed two regions in which the adsorption density sharply increased, which might correspond to the hemi-micelle and bilayer adsorption of DDA cation on the surfaces. In addition, the hydrophobic agglomeration could be weakened by the addition of NaCl, which was due to the decrease of DDA adsorption on kaolinite surfaces.

Flotation of molybdenite fines as hydrophobic agglomerates

The flotation of molybdenite fines as hydrophobic agglomerates has been studied through micro-flotation and microscopy observations in this work. The hydrophobic agglomeration was achieved with a strong mechanical conditioning and a small amount of kerosene addition. The experimental results showed that floc-flotation is much more effective than conventional flotation for the beneficiation of molybdenite fines. At the same flotation time, floc-flotation reached the flotability of 90%, while conventional flotation only did 35%. The most important parameters in the floc-flotation were mechanical conditioning strength and kerosene addition. A good floc-flotation could be achieved by applying a high-speed stirring for a short time. The kerosene enhancement of the floc-flotation closely correlated with droplet size of kerosene emulsion. The smaller were the droplets, the better the floc-flotation was.

Quantitative assessment of hydrophobic agglomeration performance

The process of agglomeration is quantitatively described by the use of two factors: (i) the hydrophobic compatibility between the solid and the liquid, and (ii) an agglomeration coefficient. If in an agglomeration system, the gap between the hydrophobicities of the agglomerants (i.e. the solid and the liquid) exceeds certain tolerances, it is difficult for the agglomeration process to proceed properly, especially to produce appropriately sized, dense, agglomerates. By the use of certain organic surfactants, it is possible to adjust agglomerant compatibilities and make the agglomeration system work well. This promotion action of surfactants is explained in terms of the interfacial interactions and the immersion energy of the system. In addition, the agglomeration efficiency of different agglomerants can be evaluated by the ‘agglomeration coefficient’, which is measured by the capillary rise method and reflects the physical properties of the liquid and the mutual interactions between the solids and the liquid.

Fine particle processing by magnetic carrier methods

Methods for selectively enhancing the magnetic properties of fine particles to be recovered or removed by subsequent magnetic separation are reviewed. The comparison of magnetic carrier separation with carrier flotation is also discussed. The influences of physicochemical extent in the adsorption of fine magnetite onto particle surfaces are briefly described. It is concluded that the selectivity of magnetic reagent for the fine particles and the hydrophobic interaction between the particles treated with chemicals and the carriers (e.g. magnetite laden oil or magnetic reagent) depends on factors similar to those in other mineral separation techniques such as hydrophobic agglomeration and shear flocculation. A large number of applications of the magnetic carrier methods in various are also introduced.

Water content and air flow behavior of coal slurries treated with cationic organofunctional silanes

The effect of cationic organofunctional silanes on fine coal slurries has been studied. A series of aminofunctional and quaternary ammonium silanes was examined with bituminous coals of different rank. The properties measured were cake moisture, and normalized air flow (correlating factor). The former was a direct measure of mechanical dewatering enhancement, and the latter was an indirect measure of the degree of aggregation in the cake. Behavior is compared to silicone surfactants and polymers already known to be effective coal dewatering agents. Hydrophilic aminofunctional silanes increase the moisture content and decrease the correlating factor in the highest rank, most hydrophobic coal. This suggests possible application as coal/water slurry stabilizers in such cases. They have only modest dewatering effects on lower rank coals. Hydrophilic quaternary ammonium silanes have little effect on any of the coals studied. The only cationic silane included in this study with a significant hydrophobic entity, the octadecyl group, had a considerable effect on decreasing the moisture content and increasing the correlating factor. This behavior implies that hydrophobic agglomeration plays a significant role in its mechanism of action. The more effective aminofunctional polydimethylsiloxane polymer emulsions function in a similar manner.

The activation mechanisms of wolframite by Ca 2+ and Fe 3+ ions in hydrophobic agglomeration, using sodium oleate as collector

Ca 2+ or Fe 3+ ions are used to activate wolframite in a hydrophobic agglomeration and their mechanisms are explored by means of hydrophobic agglomeration tests, zeta potential, adsorption of activators, Auger spectra, etc., and the crystalline structure of wolframite is also referred to. The results show that the adsorption of Ca 2+ is physisorption at pH values between 5 and 10 and is reversible, and the Fe 3+ hydroxy complex of high molecular weight, carrying positive charges and also positively charged Fe(OH) 3 colloids, may form on the surface at pH values between 2.7 and 7.5 and its adsorption is irreversible.

Hydrophobic agglomeration and spherical agglomeration of wolframite fines

New beneficiation processes for treating wolframite fines by means of hydrophobic agglomeration and by spherical agglomeration have been developed in this work. An artificial mixture of wolframite and quartz fines, assaying 6.83% WO 3 and having a size of − 15 μm, can be separated by these new processes. The wolframite concentrate obtained by means of hydrophobic agglomeration using sodium oleate as the agglomeration reagent with separation from the dispersed quartz by sedimentation assays 57.61–59.64% WO 3 with a recovery of 90.37–93.76%. The wolframite concentrate obtained by means of spherical agglomeration using sodium oleate as collector and fuel oil as combining liquid and separated by screening assays 69.72–70.65% WO 3 with a recovery of 90.95–91.62%. The major influences on these processes are the amount of reagents used and the time and the speed of agitation.