Studies on the Separation of Cadmium from Solutions by Foam Separation. I. Foam Separation of Cadmium Cations

Abstract

The efficiency of Cd²⁺ foam separation with sodium lauryl sulfate and sodium laurate from sodium sulfate and sodium nitrate solution was tested. Foam fractionation of Cd²⁺ with lauryl sulfate in the form of a hydrated ion pair 2C₁₂H₂₅SO₄, Cd²⁺ is ineffective because of a low recovery and high hydration of the foam. But ion flotation of Cd²⁺ as a low-solubility salt (C₁₂H₂₅COO)₂Cd is highly effective. The presence of electrolyte in the solution has a negative influence on Cd²⁺ foam fractionation with lauryl sulfate because of an increase of inert salt concentration which causes competition for the collector between colligend Cd²⁺ and the added Na⁺ ions, and because of simultaneous increase in the thickness of water sheaths around the gas bubbles. In the case of ion flotation with sodium laurate, the presence of electrolyte improves Cd²⁺ recovery and decreases the thickness of the water sheaths around the gas bubbles. The interpretation of the results is based on the exchange of the collector counterions as well as on the properties of the reaction products.     

Studies on the Separation of Cadmium from Solutions by Foam Separation. III. Foam Separation of Complex Cadmium Anions

Abstract

The effects of thiocyanate and iodide concentrations, acidity and nature of the acid, and various alcohols on the removal of cadmium and liquid in the foam separation process were studied. Moreover, the surface tension and electric surface potential of some solutions were measured. The results of foam separation and changes of the surface properties of the solutions were interpreted on the basis of the ratio of concentrations of cadmium complexes and the exchange of the collector bromide counterions for the ligand anions, complex cadmium anions, or acid anions.     

Removal of Cu(II) from Aqueous Solutions by the Foam Separation Techniques of Precipitate and Adsorbing Colloid Flotation

Abstract

Experimental investigations on the removal of Cu(II) from aqueous solution were carried out through two foam separation techniques: precipitate flotation and adsorbing colloid flotation with Fe(III). The optimum pH for good removal was found to be about 9 for the former and about 7 for the latter. The effects of surfactant (sodium lauryl sulfate), foreign ions (Na⁺, Ca²⁺, NO^? ₃, and SO^2- ₄), and Al(III) addition on the efficiency of Cu(II) removal are discussed.     

Removal of Cadmium from Dilute Solutions by Hydroxyapatite. II. Flotation Studies

Abstract

Dissolved-air flotation has been investigated in the present paper as a suitable solid/liquid separation technique, applied downstream for hydroxyapatite ultrafine particles which were used in a preliminary stage for the removal by sorption of toxic cadmium cations. The main parameters affecting this process were evaluated, including the necessary quantity of sorbent material in the dispersion, the proper pH values of Cd solutions, the type and concentration of supplementary inorganic flocculant agents (ferric chloride and aluminum sulfate), and the presence of additional surfactant added. The results obtained were considered to be promising. Under optimum conditions, over 95% of Cd-loaded hydroxyapatite particles were separated in a very short retention time.     

Foam Fractionation and Precipitate Flotation of Zinc(II)

Abstract

The hydrolytic behavior of a metal can be related to its removal by foaming. In this study the effect of pH and ionic strength on the foam separation of 0.1 mM zinc (II) was investigated using different concentrations of sodium lauryl sulfate as the collector. At low pH Zn²⁺ ion was removed by foam fractionation while above pH 8 Zn(OH)²(s) was removed by precipitate flotation. The results demonstrate that precipitate flotation is a more efficient removal process than the foam separation of soluble metal species.     

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.     

Separation of Some Dyes from Aqueous Solutions by Flotation

Abstract

Separation of the dyes brilliant green, neutral red, eriochrome black T, and eosin from aqueous solutions by flotation was studied using oleic acid surfactant. Nearly 100% of the investigated dyes could be floated under the optimum conditions. The effect of pH on the flotation efficiency was studied in particular. At pH ≤ 2, 7.5, ≤ 5, and ≤ 6, the maximum flotation was achieved for brilliant green, neutral red, eriochrome black T, and eosin, respectively. The effects of oleic acid and dye concentrations, some ions, and temperature on the floatability were examined. Moreover, the selective separation of some dyes was attempted.     

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.     

Foam Separation of Mercury(II) and Cadmium(II) from Aqueous Systems

Abstract

Mercury(II) and cadmium(II) were separated from aqueous systems by a number of batch-type precipitate flotation and adsorbing colloid flotation techniques. HgS, CdS, and Cd(OH)₂ were removed by precipitate flotation; Fe(OH)₃, Al(OH)₃, FeS, and CuS were used as adsorbing colloids. Sodium lauryl sulfate and hexadecyltrimethylammonium bromide (HTA) were used as collectors. Dependence of separation efficiency on pH and ionic strength was investigated. Floc foam flotation of both metals with CuS and HTA was found to be quite effective, resulting in residual Hg(II) levels as low as 5 ppb and residual Cd(II) levels as low as 20 ppb. Floc foam flotation of Cd(II) with FeS and HTA yielded residual Cd(II) levels as low as 10 ppb.     

Manganese Removal from Water by a Precipitate Flotation Technique

Abstract

Microgas dispersions were used to remove manganese from dilute aqueous solution by a precipitate flotation technique. Manganese in its coagulated oxide form is difficult to remove from water by other methods, such as filtration. Flotation processes appear to be more suited to continuous manganese dioxide removal than other conventional methods. Taking advantage of the tendency for manganese dioxide to coagulate, manganese removals as high as 98% were observed for continuous flotation when the metal was present in only trace quantites (2 to 5 mg/L).     

Removal of Cadmium from Dilute Solutions by Hydroxyapatite. III. Flocculation Studies

Abstract

Synthetic hydroxyapatite in a fine particulate dispersion has been used previously for the removal of Cd²⁺ cations from dilute aqueous solutions. In the present work the flocculation of these hydroxyapatite particulates was examined with and without the presence of Cd²⁺ ions by applying the conventional inorganic flocculents ferric chloride and aluminum sulfate. An optical technique was applied in order to monitor the flocculation dynamics of the dispersed particles, complemented by electrophoretic and turbidity measurements. The relative size of aggregates formed during flocculation, expressed as a “flocculation index,” could be continuously measured by this technique. Results indicated that the flocculation index provided important information about flocculation mechanisms. The main parameters examined included flocculent dose, solution pH, and mixing intensity. The optimum conditions for efficient flocculation were determined.     

Chelation and Foam Separation of Metal Ions from Solutions

Abstract

An experimental study was conducted on the chelation and foam separation of trace amounts of cadmium, zinc, and lead from their water solutions. The chelation agents ethylenediaminetetraacetate (sodium salt), sodium diethyl-dithiocarbamate, and citric acid were used with sodium dodecylsulfate (SDS) as a foam-producing agent. The chelation agents did not produce metal complexes that were very surface active. The foam-producing agent produced metal ion complexes that were surface active and resulted in appreciable separation of the metal ions. The use of 100 ppm SDS resulted in separation of 90% of the zinc ions from solution containing 2 to 20 ppm zinc. At concentrations below and above this, the removal efficiency dropped significantly     

泡沫浮选分离技术应用进展

综述了泡沫浮选在分离固体粒子、分离溶液中的离子、分子,处理工业废水、油田开发、脱墨、土壤的清洗、回收、浓缩生物活性物质、分离全细胞的应用,并提出将来的发展方向。     

Interaction Free Energy Studies on Floe Foam Flotation

Abstract

The Gouy-Chapman theory of the electric double layer is applied to the calculation of interaction free energy of a charged surface film and a solid surface of opposite charge immersed in a solution of electrolyte. The interaction energies calculated with a constant surface charge density model and a constant surface potential model are compared. A constant surface charge density model for floe foam flotation is found to result in less effective binding energy than the constant surface potential model. The constant surface potential model can be found to account for the decrease in efficiency of floe foam flotation which is observed experimentally when ionic strength is increased. However, studying the binding energy at various ionic strengths with the constant surface charge density model gives results that are contradictory to the experimental results. We can thus conclude that the floe foam flotation system is better analyzed with a constant surface potential model.     

Removal of Copper from Aqueous Amminecopper(II) Solution by Foam Flotation

Abstract

Copper is removed from aqueous amminecopper(II) solution by adsorbing colloid flotation. Iron(III) hydroxide is used as the adsorbing carrier floc, and an anionic surfactant sodium dodecyl sulfate is used as the collector. Optimal flotations are achieved at the pH of maximum adsorption of copper on the resultant flocs. Adsorption of copper on the flocs enhances their floatability. Rapid and efficient removal of copper can be obtained by a batch operation under controlled dosing of iron(III) for samples in various concentrations of total ammonia. A two-step batch method has the advantages of higher efficiency and lower copper residue when dealing with samples of high copper concentration (>200 ppm) and low total ammonia (<0.15 M).     

泡沫浮选法处理含氰废水

本文研究了在含氰废水中按化学计量比加入Fe~(2+)和Fe~(3+)离子以生成无毒的亚铁氰化铁絮状物沉淀,然后采用泡沫浮选进行分离的除氰方法。操作过程中拟加入一定量的阳离子表面活性剂,采用5~#烧结玻璃板作气体分布器,在pH值为4.0～6.5之间,能获得较高的分离效率。操作宜在阳光直射不到的阳暗处进行以避免亚铁氰化铁沉淀的光解反应发生。     

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.     

Removal of Direct Red from Aqueous Solution by Foam Separation Techniques of Ion and Adsorbing Colloid Flotation

Abstract

Experimental investigations on the removal of Direct Red from an aqueous solution were carried out through two foam separation techniques: ion flotation and adsorbing colloid flotation with Fe(III). The residual concentration of Direct Red can be lowered to below 0.5 ppm in 3 minutes by ion flotation and below 0.1 ppm in 2 minutes by adsorbing colloid flotation. The optimum pH for the removal of Direct Red was found to be 4 for ion flotation and 3–5 for adsorbing colloid flotation. The effects of surfactant, foreign ions, and Al(III) addition on the removal of Direct Red are discussed.     

Simultaneous Removal of Nickel(II) and Chromium(VI) from Aqueous Solutions and Simulated Wastewaters by Foam Separation

The present investigation was carried out to study the feasibility of foam separation for simultaneous removal of two types of inorganic hazardous contaminants, nickel(II) cations and chromium(VI) anions, from aqueous solutions and simulated wastewaters. The effects of pH of the solution, Ni/Cr ratio, collector and frother concentrations, induction and flotation time, and solution ionic strength on the co-removal efficiency of nickel(II) and chromium(VI) were studied. At the optimum conditions, removals more than 99.5% were obtained for nickel(II) and chromium(VI). The concerned contaminants were effectively removed when they coexisted at low as well as at high concentrations. Coflotation of nickel(II) and chromium(VI) from tap water and simulated electroplating wastewater resulted in removal percentages higher than 99.5% with residual concentrations below their permissible limits in potable water. High removal percentages, DFs, ERs, and VRs were achieved for their radionuclides, ⁶³Ni(II) and ⁵¹Cr(VI), from simulated radioactive process wastewater. The results obtained in this study suggest the feasibility of the developed foam separation process for treatment, in a single-step, of wastewaters contaminated with cationic and anionic inorganic pollutants.     

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.