Flotation Mechanisms of Boron Minerals

Abstract

The development of reagent strategies for the flotation of boron minerals requires an understanding of flotation chemistry of reagent/mineral interactions. The floatability of a typical boron mineral, colemanite, was investigated in a microflotation cell by using anionic and cationic surfactants as collectors and tannic acid as a depressant. The results obtained with zeta potential measurements together with flotation tests reveal that colemanite is floatable with both anionic and cationic surfactants at its natural pH of 9.3. While the floatability of colemanite with anionic surfactants decreases with increasing pH, that with a cationic surfactant exhibits a maximum at pH 10.2, indicating the major role of electrostatic interactions in the system.     

The Separation of Collectors Used as Coprecipitants of Trace Elements in Seawater by Adsorption Colloid Flotation

Abstract

Nine surfactants are screened for their ability to float six collectors, which have been used to coprecipitate trace metallic species in seawater, to the surface of seawater by adsorption colloid flotation as a function of pH.     

Investigations of Kinetics of Removal of Trivalent Chromium Salts from Aqueous Solutions Using lon and Precipitate Flotation Methods

Abstract

Trivalent chromium salt solutions were flotated using cationic and anionic surfactants. The results indicate that the course of ion and precipitate flotation in the range of parameters investigated can be described by an equation analogous to a first-order rate equation. In the region of precipitate flotation the flotation rate constant reaches a maximum at a definite pH value. Increases in the surfactant concentration result in decreases in the flotation rate. Flotation of chromium at higher surfactant concentrations results in a delay effect which increases with the concentration of the surface-active agent. Increases in the flotation gas flow rate result in increases in the rates of ion and precipitate flotation.     

Powdered Activated Carbon Separation from Water by Foam Flotation

Abstract

Powdered activated carbon was separated from dilute aqueous suspensions (200–1000 mg/L) by foam flotation using surfactants (anionic or cationic). The effects of surfactant type, pH value of the suspension, initial carbon and surfactant concentrations, flotation time, and air flow rate on the dispersed-air flotation of powdered activation carbon were investigated. In optimum conditions the powdered activated carbon separation was almost complete. The ζ-potential of powdered activated carbon was also measured in the presence and absence of surfactants. Finally, carbon flotation was examined after the carbon had adsorbed chromate ions from an acidic solution (pH 2). Almost complete separation of Cr(VI)-loaded carbon was obtained by using an anionic surfactant.     

Electrical Aspects of Adsorbing Colloid Flotation. XV. Adsorption Isotherms of Mixed Surfactants

Abstract

A theory is developed for the calculation of absorption isotherms of binary mixtures of surfactants A and B on solid-water interfaces. The effects of the relative magnitudes of the interaction energies of A-A, A-B, and B-B nearest neighbor pairs are explored. The theory makes use of the random approximation in order to overcome mathematical difficulties which arise in the general case. The possibility of reducing surfactant costs in precipitate and adsorbing colloid flotation by the use of mixed surfactants is suggested.     

Recovery of Metals from Process Streams of Deep-Sea Ferromanganese Nodules by Adsorptive Bubble Techniques

Abstract

A method for the separation of Cu, Co, Ni, and Zn with varying degrees of selectivity from chemically treated deep-sea ferromanganese nodules is described. Quantitative removal of these species is achieved primarily by precipitate flotation of insoluble sulfides. Recovery of residual metal values of Cu, Co, Ni, and Zn in process rejects of the nodules is also possible. The quantitative removal of Pb and V, which are the most abundant toxic elements in nodules and tailings, is achieved simultaneously. Cationic and anionic surfactants are employed for collection depending on zeta potentials of the flocs generated upon addition of Na₂S to sample solutions. Separations are more selective and efficient at lower pH than previously reported for flotation of metals from nodules as insoluble hydroxides. Modifications resulting in slight improvements over previously employed high temperature sulfation processes are also described.     

Solvent Sublation and Adsorptive Flotation/Sublation of Diphenyl

Abstract

Diphenyl is readily removed from aqueous systems by solvent sublation into mineral oil. The process is slightly enhanced by increasing aeration rate, added salts, and surfactants, and slightly retarded by organic solvent. A new technique, adsorptive flotation/sublation, was found to be more effective in removing diphenyl from aqueous solution than either adsorbing colloid flotation or solvent sublation. Over 99% of diphenyl can be removed from the solution in 30 min by a three-step batch process of adsorptive flotation/sublation.     

Mechanism of Selective Flotation of Sodium-Calcium Borates with Anionic and Cationic Collectors

Abstract

The major boron minerals, colemanite and ulexite, are frequently found together in boron deposits. Similarities in their chemical compositions create problems in the selective flotation of these minerals. The surface properties of the above boron minerals have been determined by solubility, microflotation, and zeta potential measurements using typical anionic and cationic surfactants. The isoelectric point (iep) of colemanite is 10.5, while ulexite exhibits no iep in a practical pH. Anionic surfactants thus easily float colemanite but fail to float ulexite at a natural pH. This knowledge is used to find the optimum conditions for the selective separation of colemanite from ulexite at a natural pH of 9.3. Cationic surfactants work well but are adversely affected by the presence of clay-type minerals in the boron ore which hinder the floatability of borates by the formation of a slime coating. The mechanism of slime coating onto boron minerals is also elucidated.     

Separation of Metals from Sulfated Deep-Sea Ferromanganese Nodules by Adsorbing Colloid Flotation

Abstract

Adsorbing colloid flotation (ACF) is applied to aqueous leach solutions of sulfated deep-sea ferromanganese nodules and their process tailings. Metal cations of Cu, Co, Ni, Mn, Al, and Zn are separated simultaneously by flotation with hydroxide collectors and cationic surfactants from the leach liquors of sulfated ferromanganese nodules. Applications of ACF to the nodule tailings also makes possible the recovery of residual Cu, Co, Ni, Ti, Zn, Al, Fe, Mn, and the separation of Pb and V, the most abundant toxic species in the nodules and tailings.     

Surfactant Recovery in Adsorbing Colloid Flotation

Abstract

The displacement of surfactants from floc–water interfaces by salts is examined by statistical mechanical methods. The effect of added salts on the adsorption isotherm is exhibited, and it is found that surfactant condensed films can readily be displaced. This may markedly improve the economics of adsorbing colloid flotation by facilitating surfactant recovery. Preliminary experimental results supporting the theory are presented; Na₂CO₃ is used to displace sodium lauryl sulfate from Fe(OH)₃. The viscous drag forces on floc particles attached to rising bubbles are calculated for bubbles having diameters in the range 0 to 1 mm. At the upper end of this range these forces appear to be large enough to reduce the efficiency of foam flotation.     

Flotation Using Microgas Dispersions for the Removal of Pentachlorophenol from Aqueous Solutions

ABSTRACT

Microgas dispersions called colloidal gas aphrons (CGAs) were generated using cationic, anionic, and nonionic surfactants, and were used in an adsorptive bubble flotation process in a semibatch mode to remove pentachlorophenol (PCP) from the aqueous phase. The aqueous solution was maintained at pH values by using buffers. CGAs generated with Tergitol, which is a nonionic surfactant, were found to be the most efficient for the removal of PCP; the efficiency remained nearly independent of pH. In the case of an anionic surfactant, sodium dodecylbenzene sulfonate (DDBS), the efficiency of removal improved from 15 to 36% with a change in pH from 10.1 to 3.0. For a cationic surfactant, hexadecyltrimethylammonium bromide (HTAB), the removal at pH 10.1 was 81%, which decreased to 68.1% at pH 3.0. The charges on the encapsulating film of CGAs may explain the higher percentage of adsorption of PCP on the CGAs generated using HTAB as compared to CGAs generated using DDBS. For all the surfactants, an increase in concentration improved the removal efficiency. These results were compared with the removal efficiencies using conventional flotation techniques used by other researchers. Solvent sublation appears to be effective in the removal of PCP, but even in the presence of a surfactant it required 300% more air volume per volume of liquid when compared with CGA flotation.     

Surface Activity of Monomeric and Polymeric (3-alkyloxy aniline) Surfactants

ABSTRACT

The adsorption and micellization processes of 3-alkyloxy aniline namely [3-decyloxy aniline (C10M), 3-dodecyloxy aniline (C12M) and 3-cetyloxy aniline (C16M)] and their polymers [C10P, C12P and C16P] have been investigated using surface tension (γ) measurements at different temperatures. The synthesized monomers and polymers have been characterized by IR and elemental analysis. The surface and thermodynamic parameters of these monomeric and polymeric surfactants are investigated. The results show that the critical micelle concentration (CMC) of the polymeric surfactants is lower than that of monomers. The CMC values decreases as the hydrophobic chain lengthens for both monomeric and polymeric surfactants. The surface parameters show the ability of monomeric and polymeric surfactants to adsorb at the air/water interface and decrease the surface tension. The thermodynamic parameters reveal that the micellization process is spontaneous for all investigated surfactants. The specific conductance measurements show that the specific conductance increases with increasing chain length of the substituted alkyl groups, the synthesized polymeric surfactants have higher values of specific conductance than the corresponding monomers and the specific conductance increases with rising solution temperature.     

An Electrokinetic Study on the Oil Flotation of Oxidized Coal

Abstract

The objective of this investigation was to study the electrokinetic behavior of oxidized coals and of hydrocarbon emulsion droplets of flotation reagents to indicate the feasibility of separating the oxidized coals from ash materials and pyrite by an oil flotation process. The effects of surfactants and hydrolyzed metal ions were also included. The electrokinetic behavior of the oxidized coals and the hydrocarbon emulsion droplets were studied by an electrophoresis technique. Generally the isoelectric point (IEP) of the coals decreased with increasing degree of oxidation.

A model of selective flotation of oxidized coal is postulated on the basis of the electrokinetic results. This model simply states that in the presence of a suitable amount of collector and frother, the optimal selective flotation of oxidized coal will occur at the IEP of the oxidized coal. To achieve this condition at the coal surface, it is necessary to adsorb heavy metal hydroxide ions prior to flotation and to absorb hydrocarbon oil droplets containing positively charged organic functional groups during flotation. Oxidized coal becomes more hydrophobic at its IEP because most of its surface is relatively non-polarizable. In contrast, pyrite and ash minerals have relatively polarizable surfaces and remain in suspension even when they are at an IEP.     

Removal of Resin from Mechanical Pulps by Selective Flotation: Mechanisms of Resin Flotation and Yield Loss of Fibers

Abstract

The amount of wood resin in mechanical pulp suspensions could be decreased using a selective flotation process. In selective flotation air‐bubbles are dispersed into low consistency pulp suspensions mechanically by an impeller or by injectors. Resin particles attach to the air‐bubbles and are lifted to the top of the pulp suspension from where they are removed, along with the flotation froth. The very small size of the resin particles (average diameter <1.0 micron) suggests that they are driven toward the air‐bubbles mainly by Brownian diffusion and that attachment of the resin particles to the air‐bubbles takes place through colloidal interactions. The resin flotation followed approximate first‐order kinetics. The mechanism of yield loss of fibers was entrainment, whereby they were hydraulically transported into the froth along with the water.     

Coagulation and Flotation of Colloidal Titanium Dioxide

Abstract

The foam separation of dispersed and coagulated titanium dioxide was investigated using anionic and cationic collector surfactants in a batch flotation system. Aluminum sulfate was used as the coagulating agent, and ethanol served as the frother. Removal was studied as a function of pH with coagulant and collector concentrations as parameters.     

Separation Using Foaming Techniques

Abstract

Separation of various chemical components from each other is often the most difficult step in analytical procedures. The problems attached to separation become further magnified when the species concentations are extremely low. A group of techniques that has proven useful especially in dilute solutions for separating and concentrating metallic as well as nonmetallic ions and complexes, proteins, microorganisms, particulates, etc. is the adsorptive bubble separation techniques. Minerals have indeed been treated using some of these techniques for decades. The success of these processes is primarily dependent upon differences in the natural surface activity of various species or particulates in the system or in their tendency to associate with surfactants. The efficiency of the process is determined by such variables as solution pH, ionic strength, concentration of various activating and depressing agents, and temperature. A proper control of variables offers an opportunity to separate a variety of metallic and nonmetallic species and particulates. In this paper the principles governing various foam separation techniques, particularly froth flotation, are presented along with the recent results on the role of variables that can be controlled to achieve complete removal of species and particulates for analytical purposes.     

Precipitate Foam Flotation of Copper,Nickel, Cobalt,and Manganese with LIX Reagents

Abstract

The precipitate flotation of copper, nickel, cobalt, manganese, zinc, and cadmium with LIX65 and LIX63 (hydroxyoxime compounds) and carrier surfactants hexadecyltrimethylammonium bromide and TX100 was investigated. The effects of pH and possibly interfering ions (sulfate, phosphate, EDTA) were studied. LIX65 was found to give good results with copper, nickel, cobalt, and manganese; LIX63 was less satisfactory.     

Selective Floatation of Inorganic Ions

Abstract

On the basis of both the literature data and the results of our own studies, some chemical and physicochemical aspects of selective flotation of inorganic ions was discussed. Classification of properties and events that determine the flotated ion separation, such as ionic charge, base-acid equilibria, complexation processes, solubility of ion-collector compounds, and ion affinity to surfactants have been described and exemplified.     

Synthesis,Characterization and Electrical Conductivity of Polyesters Containing Azomethine Linkages

Abstract

The synthesis and characterization of some polyesters containing azomethine linkages are reported here. The electrical conductivity of these polyesters is measured and the results are explained with simple Pariser-Parr-Pople calculations. The polymers are doped with Ag and the electrical conductivity of most of the doped polymers is found to register significant increase. Attempts are made to explain this increase in electrical conductivity.     

Calcium Chelating Sugar-Based Surfactants for Hard-Water Detergency

Hard water can decrease the detergency efficiency of surfactants due to a significant concentration of divalent cations as Ca²⁺ or Mg²⁺. The formulation of a cleaning detergent must be modified and it is usual to add more surfactants or a huge quantity of sequestrating agents. This supplementary addition can have deleterious effects on the environment and increases the price of the formulation. A surfactant, presenting both detergency capacities in the presence of Ca²⁺ and Ca²⁺ chelating properties, would be of great interest. In this paper, we report on Ca²⁺ extraction with sugar-based chelating surfactants using an experimental device, namely a flotation column, as both chelating properties and foaming properties in the presence of Ca²⁺ are important in the flotation process as well as in detergency. Among all the sugar-based surfactants tested, a few of them were able to extract calcium and thus demonstrated the expected characteristics.