Flotation of metal hydroxide precipitates. I. Flotation of copper hydroxide

Flotation of copper hydroxide precipitate has been investigated at total initial copper concentration 10^?2M with sodium dodecylbenzenesulphonate (DBSNa) and dodecyldimethylbenzylammonium bromide (DDMBABr), both at initial concentration 10^?4M. In particular, granulometric analysis of the precipitate and measurement of its electrokinetic potential were carried out over a wide range of the acidity of aqueous precipitate suspension in order to establish essential factors governing flotation of the precipitate. Moreover, adsorption of the flotation collectors by the precipitate as well as the rate of precipitate sedimentation were measured. The cationic collector (DDMBABr) neither influenced the electrokinetic potential of copper hydroxide precipitate nor adsorbed on its surface. Consequently, no flotation of copper hydroxide was observed with (DDMBABr). On the other hand, the anionic collector (DBSNa) influenced the electrokinetic potential of copper hydroxide within the same pH range where adsorption of DBSNa on the precipitate was observed and flotation was effective. The rate of flotation varied with the pH of the aqueous suspension. This dependence was irregular and presumably governed by the aggregation of precipitate grains since the rate of flotation increased with the size of the aggregates.     

Precipitate flotation. IV. Flotation of silver,uranium and gold

The conditions for the flotation of silver using α-nitroso-β-naphthol and β-nitroso-α-naphthol, that of uranium using α-nitroso-β-naphthol and benzoylacetone, and that of gold using phenyl-α-pyridylketoxime were examined. Recoveries of over 90% were possible from 5 × 10^?5 M solutions of silver, 10^?4 M solutions of uranium (VI) and 3 × 10^?4 M solutions of gold (III). Extractions were best in the pH range 7–9, 6–9 and 3–5 respectively. Silver could be separated from 10-fold molar excesses of copper, zinc and lead; uranium from 10-fold molar excesses of gold and iron and 100-fold molar excesses of sulphate and manganese: gold from a 10-fold molar excess of uranium. Methods are suggested whereby redispersion in precipitate flotation of the second kind can be avoided. The efficiency of this kind of flotation is considered.     

A kinetic study of precipitate flotation of Zinc(II), Cobalt(II) and Copper(II) hydroxides

An experimental kinetic study has been completed on precipitate flotation of Zn(II), Co(II) and Cu(II) hydroxides (initial metal concentration 1 × 10^?-2M) with the anionic surfactant, sodium dodecyl benzenesulphonate (1 × 10^?-4M), at varying equilibrium pH. An original radioactive isotope procedure was applied and proved to be sufficiently accurate. Kinetic equations of Rubin and co-workers were found to be relevant for precipitate flotation of hydroxides. From the flotation rate constant (k_p) determined at varying equilibrium pH of floated suspensions it appeared that the selective flotation of individual compounds from mixed precipitate was possible as a result of the ‘kinetic effect’.     

Precipitate Flotation II. Separation of palladium from platinum,gold, silver,iron, cobalt and nickel

Palladium is completely removed from 5 × 10^?5 M-PdCl₂ solutions using the new technique of precipitate flotation of the second kind, in which no surfactant is used to float precipitates. Recoveries were best at pH 1–2 and were not markedly dependent on temperature. Increase in ionic strength had no deleterious effect, unlike conventional precipitate flotation. Palladium can be completely separated from a 400-fold excess of nickel, a 100-fold excess of platinum, iron and cobalt, a 10-fold excess of gold but not from silver in the presence of chloride ions. Equimolar amounts of palladium, nickel and platinum were completely separated from each other by successive flotations. Photographs taken of the bubbles during flotation showed that, at a flow-rate of 3.1 litre/hour, a mean surface area of 2.07 metre² passed through the cell per minute.     

The low gas flow rate foam separation of cerium (III) from dilute aqueous solutions

Two low gas flow rate foam separation techniques, ion and precipitate flotation, have been investigated for the separation of trivalent cerium from solutions with initial cerium concentrations ranging from 1 × 10^?8 to 1 × 10^?4M in the pH range of 1.8–12 using the anionic collector sodium lauryl sulphate and the cationic surfactant cetyl trimethyl ammonium bromide. In addition to the type of collector, the pH and the cerium ion concentration, and other factors which can affect flotation results, viz. the time period of bubbling, the rate of gas flow, the ageing of both the cerium and the collector ions, the ionic strength, and the concentration of the collector ions have been investigated and optimum conditions have been established. Under optimum conditions removals as high as 98.5% can be achieved.     

Electrical Aspects of Adsorbing Colloid Flotation II. Theory of Rate Processes

Abstract

The kinetic and equilibrium factors affecting the rate of precipitate flotation are analyzed by means of the Gouy-Chapman model. Kinetic effects are found to be extremely rapid, and the rate of precipitate flotation is due to equilibrium considerations. Removal efficiency as a function of inert salt concentration goes through a maximum at about 10^?5 M for films 300 Å thick. Removal efficiency increases with increasing zeta potential of the film surface and with increasing charge on the precipitate particles.     

Electrokinetic Properties of Acid-Activated Montmorillonite Dispersions

In this study, the influence of pH, electrolyte concentration, and type of ionic species on the electrokinetic properties (zeta potential and electrokinetic charge density) of the acid-activated montmorillonite mineral have been investigated using the microelectrophoresis method. The electrokinetic properties of acid-activated montmorillonite dispersions have been determined in aqueous solutions of mono-, di-, and trivalent salts and divalent heavy metal salts. Zeta potential experiments have been performed to determine the point of zero charge (pzc) and potential determining ions (pdi). The zeta potential values of the acid-activated montmorillonite particles were negative and did not vary significantly within the pH range studied. Acid-activated montmorillonite dispersions do not have point of zero charge (pzc). The valence of the electrolytes has a great influence on the electrokinetic behavior of the suspension. A gradual decrease in the zeta potential (from ?25 mV to ?5 mV) occurs with the monovalent electrolytes when concentration increased. Divalent and heavy metal electrolytes have less negative z-potentials due to the higher valence of ions. A sign reversal of z-potential has been observed at AlCl₃, FeCl₃, and CrCl₃ electrolytes (potential determining ions) and zeta potential values have had a positive sign at high electrolyte concentrations.

The electrokinetic charge density of acid-activated montmorillonite has shown similar trends for variation in mono- and divalent electrolyte solutions. Up to concentrations of ca. 10^?3 M, it has remained practically constant at approximately 0.5 × 10^?3 C m^?2 For higher concentrations of monovalent electrolytes more negative values (?16 × 10^?3 C m^?2) were observed. It has less negative values in divalent electrolyte concentrations according to monovalent electrolytes (?5 × 10^?3 C m^?2). For low concentrations of trivalent electrolytes, the electrokinetic charge density of montmorillonite particles is constant, but at certain concentrations it rapidly increased and changed its sign to positive.     

Precipitate flotation I. Removal of nickel from dilute aqueous solutions and its separation from cobalt

A new technique, called precipitate flotation of the second kind, in which no surfactant is used to float precipitates, is described. Nickel is completely removed from 1.5 × 10^?5 m-NiCl₂ solutions in 3 minutes using a tenfold excess of nioxime. Flotation improves with increasing temperature between 21° and 40° if the pH is in the range 8–11. Increase in ionic strength has no deleterious effect, unlike conventional precipitate flotation. Nickel can be completely separated from a hundredfold excess of cobalt by complexing the latter with nitroso-R-salt before flotation. Iron does not float on its own but recoveries of 50% can be achieved by entrainment of ferric hydroxide in nickel nioximate.     

Flotation of phosphorus(V), molybdenum(VI), and rhenium(VII) oxyanions

Efficiency and intensity of the flotation of isostructural, tetrahedral oxyanions with the cationic (R)4N⁺ type surfactant were examined, exemplified by the case of the diluted aqueous solutions of phosphorus(v), molybdenum(vi) and rhenium(vii) at concent rations of 1 × 10^?4, 5 × 10^?5 and 1 × 10^?5 kmol m^?3. No direct relation was found between the flotation efficiency and the charge and size of the examined ions. For ions of equal charge, the Grieves entropy criterion¹⁵ was obeyed in most cases.     

Flotation of perrhenates with cationic surfactants: Effect of surfactant's structure

An experimental investigation is presented on the flotation of perrhenate anions from diluted aqueous solutions (5.10^?5 M ) with numerous cationic surfactants of systematically varying molecular structure. Alkyltrimethyl-ammonium bromides, alkoxycarbonylmethyl-trimethylammonium chlorides, alkoxycarbonylmethyl-dimethylbenzylammonium chlorides, ethoxycarbonylmethyl-dimethylalkylammonium chlorides, N-substituted dodecylamines, and diquaternary ammonium bromides were investigated at their initial concentrations in the feed solution, 1.10^?4 M or 2.10^?4 M . It was found that both the length of the main hydrocarbon chain and of the short hydrocarbon groups govern the affinity of a cationic surfactant towards perrhenate anions. In order to achieve the effective flotation of perrhenate or similar anions the value of C:N atomic ratio for a tertiary or a quaternary ammonium surfactant should be in the range 15 to about 26. This value can be used as a primary criterion for the sufficient flotation capability of an alkylammonium surfactant.     

The Effect of Surfactant Concentration on the Flotation of Hydrocarbons from Their Emulsions. I. Removal of Mesitylene

Abstract

The removal of mesitylene from its aqueous emulsions by the foaming method was investigated. As frothing agents, sodium dodecylbenzenesulfonate (NaDBS) and cetyltrimethylammonium bromide (CTMABr) were used. The influence of the concentration of those compounds on the removal effect of mesitylene is presented. It was found that the effective index of the surfactants is best when their concentration in the foamed mixture is the lowest possible one. Taking into account the foam stability, these concentrations equal 1.0 × 10^?4 mol/dm³ for CTMABr and 1.7 × 10^?4 mol/dm³ for NaDBS. The effect of the initial mesitylene concentration in the emulsion on its removal was also determined.     

Synthesis and characterization of fluorescent PEG-polyurethane with free carboxyl groups

An innovative spherical poly(vinyl alcohol)(PVA)/peat/clay porous composite bead was prepared and shown to be suitable for use as an adsorbent. The mass transport process for the adsorption of metal ions onto this composite bead in an aqueous system was investigated. In the external mass transport process, the diffusion coefficient (D₁) of Cu⁺² and Zn⁺² ions increased with increasing initial metal ion concentration and the increasing effect was more pronounced in the initial metal ion concentrations range of 18?×?10^-3 to 22?×?10^-3?M. The diffusion rate of Zn⁺² ions was faster than that of Cu⁺² ions. In the intraparticle diffusion process, the diffusion coefficient (D₂) decreased with increasing initial metal ion concentration in the initial concentration range of 1?×?10^-3 to 4?×?10^-3?M, and the value of D₂ maintained an almost constant value in the initial concentration range of 8?×?10^-3 to 22?×?10^-3?M. The rate of ion diffusion within the adsorbent for Cu⁺² ions was faster than that for Zn⁺² ions. The adsorption mechanism was controlled by the intraparticle diffusion process. The adsorption followed the Langmuir adsorption isotherm model. The maximum amount of adsorbed metal ions for Cu⁺² and Zn⁺² ions were 22.57 and 13.62?mg/g composite bead, respectively.     

Electrical Aspects of Adsorbing Colloid Flotation. X. Pretreatments,Multiple Removals,Interferences, and Specific Adsorption

Abstract

The compatibility of the adsorbing colloid flotation of Cu(II) with Fe(OH)₃ and sodium lauryl sulfate with a variety of precipitation pretreatment techniques was studied. Procedures were developed which permitted precipitation pretreatment and effective foam flotation polishing. The interferences of glycerol, ClO₄ ^?, NO₃ ^?, C1^?, CN^?, CNS^?, F^?, SO4₄ ^2?, HPO₄ ^2?, HAsO₄ ^2?, C₂O₄ ^2?, (PO₃)₆ ^6?, and EDTA with the precipitate flotation of ferric hydroxide by sodium lauryl sulfate were studied. The simultaneous adsorbing colloid flotation of Cu(II), Pb(II), and Zn(II) with Fe(OH)₃ and sodium lauryl sulfate was found to be effective in the pH range 6 to 7 at ionic strengths below 0.1 mole/l. A model was analyzed for calculating surface potentials for floe surfaces having the charge distributed at discrete sites in the presence of electrolytes. Plots of surface potential versus adsorbable ion concentration were calculated for various values of the model parameters.     

Electrochemical remediation of BPA in a soil matrix by Pd/Ti and RuO2/Ti electrodes

This study aimed to investigate the bisphenol A (BPA) degradation performance of an electrokinetic process coupled with Pd/Ti (PT) and RuO₂/Ti (RT) binary metallic oxidation electrodes under a potential gradient of 2 Vcm^?1 for 5 days. Fifteen experiments conducted with five processing fluids, namely deionized water (DW), Na₂SO₄, citric acid (CA), NaOH and NaCl, and two binary metallic oxidation electrodes, Pd/Ti and RT, were investigated in this study. Electroosmosis permeability of 3.2 × 10^?6–4.7 × 10^?6, 4.0 × 10^?6–4.9 × 10^?6, and 3.7 × 10^?6–6.8 × 10^?6 cm² V^?1 s^?1 were observed in the electrokinetic system with Ti, PT, and RT electrodes, respectively. A significant detachment of the coated metals was observed in BMOEEK–PT system with Na₂SO₄, CA, and NaOH processing fluids. A higher BPA treatment efficiency of 52.2–67.3 % was found in the BMOEEK–RT system, which was 1.4–1.8 times greater than in the EK–Ti system with DW as the processing fluid. The best treatment efficiency was found in the system with NaCl as the processing fluid, which may mostly result from less detachment of the coated metal from electrode and increased hypochlorite (OCl^?) generation in the anode reservoir. The primary treatment mechanism in the BMOEEK system with NaCl procession fluid was degradation by anodic oxidation. It was concluded that both the binary metallic electrode and processing fluid played key roles in enhancing the electrochemical degradation of BPA. The electrode characteristics (progressive cyclic voltammogram and SEM micrograph with EDAX), electrokinetic behavior (specimen pH and current density), and treatment mechanism were also discussed in this study.     

Precipitate flotation. III. Parameters of precipitate flotation of the first kind

Precipitates of strontium carbonate (10^?3 mole litre^?1) were floated using dodecylpyridinium chloride, hexadecylpyridinium bromide, hexadecyltrimethylammonium chloride and a dialkyldimethylammonium chloride. Flotations were performed at a gas flow-rate of 7 litre hour^?1 for 3 minutes or 2 litre hour^?1 for 20 minutes. Complete recoveries were possible by both methods, provided optimum concentrations of collector were used. If too little collector was present, redispersion of precipitate occurred because the foam formed was insufficient to support it. With too much collector, the precipitate was excluded from the bubbles and also became coated by a double layer of collector which gave a hydrophilic surface. Increase of temperature and of time allowed for precipitation, improved recoveries because of increased particle size. Flotations were not complete below 10^?3 m unless the strontium carbonate was co-precipitated in calcium carbonate, when 10^?8 m could be recovered. Increased ionic strength reduced recoveries because it caused precipitation to be slower, attachment of collector to the precipitate to be less secure, flotation of the collector to be more rapid and foam drainage, and hence redispersion, to increase.     

Electrical Aspects of Adsorbing Colloid Flotation. XVI. Double-Layer Relaxation

Abstract

A mathematical model for studying relaxation processes in the electric double layer adjacent to a plane charged surface is developed and analyzed. The model is nonlinear and nonideal. A time constant of roughly 7 × 10^?8 s qualitatively describes the relaxation processes. Increased applied potentials yield nonlinear responses, which are investigated by Fourier analysis. The effects of ionic size are determined. The relaxation rate is fast enough so that the local equilibrium assumption in foam flotation is amply justified.     

Influences of nonionic poly(ethylene glycol) polymer PEG on electrokinetic and rheological properties of bentonite suspensions

The determination of the electrokinetic properties of colloidal systems is very important for the chracterization of these systems. Colloidal systems have high adsorption performance due to the carrying of negative charges and the colloid structure. The control of the electrokinetic properties of the bentonite–water system are important not only from a technological point view; they are also important from a scientific point of view. Knowing the electrokinetic and rheological properties of bentonite minerals is important for the estimation of the behavior of clays under various environmental conditions. The purpose of this study was to interpret the effect of the nonionic poly(ethylene glycol) (PEG) polymer on electrokinetic and rheological properties. Zeta potential and viscosity measurements were done as a function of PEG molecular weights (400, 3000, and 8000) and their concentrations (2.5 × 10^?5 to 1.25 × 10^?2 mol/L). We interpreted the experimental data, taking into account these two parameters. X‐ray diffaction studies were done together with the electrokinetic and rheological measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 341–346, 2002     

Ion Flotation of Chromium(VI) Species: pH,Ionic Strength,Mixing Time,and Temperature

Abstract

Batch foam separation experiments of Cr(VI) anions with the cationic surfactant, ethylhexadecyldimethylammonium bromide, show a sharp increase in the flotation stoichiometry from 1.0 to 2.0⁺ over pH 6-8, corresponding to the conversion of Cr₂O₇ ^2?(HCrO₄ ^?) to CrO₄ ^2? with pH. In the acidic region for approximately 1.0×10^?3 M Cr(VI) solutions, the maximum increase in the flotation stoichiometry and decrease in the fractional removal of Cr₂O₇ ^2? is 12% over a fortyfold increase in ionic strength, varied with four different monoand divalent salts; the effect is produced by a small increase in the solubility of the (EHDA)₂Cr₂O₇ precipitate. In the basic region, a twentyfold increase in ionic strength with NaCl produces greater than 100% changes in the same flotation parameters, indicating a foam fractionation mechanism and competition between Br^?, Cl^? and CrO₄ ^2? for surfactant exchange sites. A temperature increase from 23 to 33°C in the acidic region has no effect on the flotation, and the lack of the effect of the mixing time between the Cr(VI) and surfactant solutions over the full range of variables permits all reported data points to be the average of four replicates, within ±3%.     

The Elimination of Channeling and Foam Overturning in Continuous Mode Adsorbing Colloid Flotation with a Sodium Dodecylsulfate/Dodecanoic Acid Mixture

Abstract

The effect of hydraulic loading, surfactant concentration, and air flow rate on the removal of Cr(III), Ni(II), and Zn(II) from chromium stream electroplating wastewater by adsorbing colloid flotation using a sodium dodecylsulfate/dodecanoic acid mixture was investigated. Typically, heavy metal concentrations of 81 ppm Cr(III), 55 ppm Ni(II), and 3.3 ppm Zn(II) were reduced to 1.2 ppm Cr(III), 3.2 ppm Ni(II), and 0.05 ppm Zn(II) at a hydraulic loading of 22.9 m³/m²·h (3 L·min^?1), an air flow rate of 45.8 m³/m²·h (6 L·min^?1), 40 ppm dodecanoic acid, and 80 ppm sodium dodecylsulfate, and using a 10-cm inner diameter column. A novel mode of operation (high liquid carryover) was used whereby a large proportion of the liquid entering the column leaves the column with the foam.     

A New Sensor for Determination of Anionic Surfactants in Detergent Products with Carbon Nanotubes as Solid Contact

A new solid‐state sensor for potentiometric determination of surfactants with a layer of multi‐walled carbon nanotubes was prepared. As a sensing material, 1,3‐didecyl‐2‐methylimidazolium–tetraphenylborate ion‐pair was used. The investigated sensor showed a Nernstian response for both dodecylbenzenesulphonate (DBS, 57.6 mV/decade of activity between 5 × 10^?7 to 1 × 10^?3 M) and sodium lauryl sulfate (LS, 58.4 mV/decade of activity between 2 × 10^?7 to 2 × 10^?3 M). It responded in 8–10 s for each ten‐fold concentration change in the range of 1 × 10^?6 to 3 × 10^?3 M. The detection limits for DS and DBS were 2 × 10^?7 and 3 × 10^?7 M, respectively. The sensor revealed a stable response (signal drift 2.6 mV/h) and exhibited satisfactory selectivity performances for LS over most of the anions generally used in surfactant‐based commercial detergents. The main application of this sensor was the end‐point determination in potentiometric titrations of anionic surfactants. The (diisobutyl phenoxy ethoxy ethyl)dimethyl benzyl ammonium chloride (Hyamine), cetyltrimethylammonium bromide, hexadecylpyridinium chloride monohydrate (HDPC) and 1,3‐didecyl‐2‐methylimidazolium chloride were tested as potential cationic titrants, and all exhibited analytically usable titration curves with well‐defined equivalence points. The standard solution of HDPC was used as a cationic titrant by all potentiometric titrations. The operational life‐time of the sensor described was prolonged to more than 3 months.