Ion and Adsorbing Colloid Flotation of Auramine

Auramine, a cationic dye, was removed from synthetic wastewater by ion flotation of auramine‐sodium lauryl sulfate complex. Over 98% of auramine was removed from the solution in 15 min. A stoichiometric amount of surfactant (1 mol of surfactant to 1 mol of dye) was found to be most effective for auramine removal. The rate of separation and ultimate removal of auramine increased with increasing the rate of air flow and decreased with increasing concentration of NaNO₃. Auramine was also removed by adsorbing colloid flotation technique using ferric hydroxide as the coagulant. Sodium lauryl sulfate was used as the collector, and over 95% of auramine was removed in 10 min. The separation efficiency decreased with increasing ionic strength of the solution. The deleterious effect of neutral salt was compensated somewhat with the aid of aluminum ions as the activator. Both ion flotation and adsorbing colloid flotation are promising approaches for the removal of cationic dye from wastewater.     

Adsorbing colloid flotation separation and polarographic determination of Mo(VI) in water

A method is described for the flotation and determination of Mo(VI) in water at ng/ml levels. Mo(VI) is preconcentrated and separated by adsorbing colloid flotation employing aluminium(III) hydroxide as collector and sodium lauryl sulphate as surfactant at pH 5.3 ± 0.1. The molybdenum content in the froth is estimated by using the catalytic wave of Mo(VI) in the presence of nitrate by charging current compensated d.c. polarography (CCCDCP) or differential pulse polarography (DPP). The effect of variables such as pH, ionic strength, concentration of collector and surfactant, time of stirring and gas flow-rate on the recovery of Mo by flotation is reported. The effects of various cations and anions on the flotation and determination of Mo are studied. This method is employed for the determination of molybdenum in natural fresh water samples.     

CORRELATION OF DISPERSION STABILITY WITH SURFACTANT CONCENTRATION AND ABRASIVE PARTICLE SIZE FOR CHEMICAL MECHANICAL POLISHING (CMP) SLURRIES

The preparation of stable colloidal slurries is often difficult in industries where many chemical components are added into the slurries. A critically acclaimed example of such an industry is the chemical mechanical polishing (CMP) industry which involves polishing slurries with several chemical additives. In the present work, the stabilization of a slurry used for CMP of metals is investigated in detail. This high ionic strength slurry has been stabilized using an optimaJ combination of sodium dodecyl sulfate (anionic surfactant) and Tween 80 (nonionic surfactant). The amount of surfactant needed to impart stability has been investigated in this study for two different sizes of abrasive particles. It has been found that the amount of surfactant needed to stabilize the slurry increases as the total surface area per gram of panicles increases. Slurry stabilization has been correlated with particle size measurements. It has been found that the average panicle size of the slurry decreases as the stability of the slurry increases. Stable slurries have been found to have particle sizes close to those of the particles before agglomeration. It is proposed that the stabilized CMP slurries can lead to reduced defects in wafers by preventing agglomeration of panicles.     

The effect of triethylenetetraamine (Trien) on the ion flotation of Cu(2+) and Ni(2+)

Ion flotation is a separation process involving the adsorption of a surfactant and counterions at an air/aqueous solution interface. It shows promise for removing toxic heavy metal ions from dilute aqueous solutions. Here we report the effect of a neutral chelating ligand, triethylenetetraamine (Trien), on the ion flotation of cations with dodecylsulfate, DS(-), introduced as sodium dodecylsulfate, SDS. Ion flotation in the aqueous SD-Cu(II)-Ca(II)-Trien system gave strongly preferential removal of Cu(II) over Ca(II), which is a reversal of the order of selectivity seen in the SDS-Cu(II)-Ca(II) system containing no Trien. The removal rates of Cu(2+) and Ni(2+) with DS(-) were much faster in the presence of Trien than for simple aquo ions, and the final metal concentration was significantly lower. Surface tension measurements showed that Trien enhanced the surface activity and adsorption density for SDS-Cu(II) and SDS-Ni(II) solutions. The overall change in the Gibbs free energy for adsorption resulting from complexation was -3.60 kJ/mol for Cu(II) and -3.50 kJ/mol for Ni(II). This included the effects of hydrophobic interactions between the metal-Trien complexes at the air/solution interface, along with changes in the amount of dehydration associated with cosorption of the metal-Trien complex with DS(-) at the air/solution interface.     

Rapid separation of humic acid in fresh waters by coprecipitation and flotation

After removal of suspended matter in 1 liter of water by flotation with a cationic surfactant, humic acid at theg/l level is separated from fulvic acid by coprecipitation with milligram quantities of iron(III) hydroxide at pH 7 followed by flotation with anionic surfactants. The iron(III) hydroxide is dissolved in 2M hydrochloric acid, and the acid-insoluble humic acid is filtered off on an ultrafilter and then dissolved in 10 ml of 0.1M potassium hydroxide solution for measurements of absorption spectra, molecular weight distribution and complexing ability. The time required for the separation is ca. 1 h.     

Removal of Safranine from Aqueous Solution by Using Adsorptive Bubble Separation Techniques

Safranine, a cationic dye, was removed from synthetic wastewater by ion flotation. Over 98% of safranine was removed from the solution in 10 min. A stoichiometric amount of surfactant (1 mol of surfactant to 1 mol of dye) was found to be most effective for safranine removal. The separation efficiency of safranine decreased with increasing concentration of NaNO3. Safranine was also removed by adsorbing colloid flotation technique using Fe(OH)3 as the coagulant. Sodium lauryl sulfate was used as the collector, and over 97% of safranine was removed in 5 min. The separation efficiency decreased with increasing ionic strength of the solution. The deleterious effect of neutral salt was compensated somewhat with the aid of Al^3 as the activator. Both ion flotation and adsorbing colloid flotation may be applicable in the removal of safranine from wastewater.     

Dilational Rheological Properties of Non-Ionic Surfactants at the Water–Decane Interface: Effect of Unsaturated Hydrophobic Group

The interfacial tensions and dilational properties of adsorbed films of two non-ionic surfactants with different hydrophobic groups, polyoxy-ethylene sorbitan stearate (Tween 60) and polyoxy-ethylene sorbitan monooleate (Tween 80), at the water–decane interface have been investigated by the drop-shape analysis method. The effects of dilational frequency and bulk concentration on the interfacial properties were expounded. The influence of low temperature on the interfacial tensions and dilational properties have also been researched. The experiment results show that the interfacial activity of Tween 80 is rather large compared with Tween 60. The minimum area per molecule at the water–decane interface (A_min) value of Tween 80 is little large than that of Tween 60, which is due to the steric effect of unsaturated double bond in Tween 80 molecule. The dilational data show that the ethylene oxide groups of non-ionic surfactant form a stable sub-layer, which results in the increase of modulus and the decrease of phase angle for both Tween 60 and Tween 80 than those of common ionic surfactants. Moreover, the unsaturated hydrophobic group of Tween 80 is much flexible, which is easily crosslinked and entangled. Therefore, dilational modulus of Tween 80 is higher and phase angle is lower than that of Tween 60. Low temperature decreases the flexibility of unsaturated hydrophobic group and lessens the influence on the interaction of saturated hydrophobic group. Saturated surfactant molecules of Tween 60 almost lose temperature response.     

Effect of Emulsifier Type on the Characterization of O/W Emulsions Using a Spectroscopy Technique

The droplet size distribution (DSD) of emulsions is the result of two competitive effects that take place during emulsification process, i.e., drop breakup and drop coalescence, and it is influenced by the formulation and composition variables, i.e., nature and amount of emulsifier, mixing characteristics, and emulsion preparation, all of which affect the emulsion stability. The aim of this study is to characterize oil-in-water (O/W) emulsions (droplet size and stability) in terms of surfactant concentration and surfactant composition (sodium dodecyl benzene sulphonate (SDBS)/Tween 80 mixture). Ultraviolet-visible (UV-vis) transmission spectroscopy has been applied to obtain droplet size and stability of the emulsions and the verification of emulsion stability with the relative cleared volume technique (time required for a certain amount of emulsion to separate as a cleared phase). It is demonstrated that the DSD of the emulsions is a function of the oil concentration and the surfactant composition with higher stability for emulsions prepared with higher SDBS ratio and lower relative cleared volume with the time. Results also show that smaller oil droplets are generated with increasing Tween 80 ratio and emulsifier concentration.     

Removal of Zn(II) from dilute aqueous solutions and radioactive process wastewater by foam separation

Ion, precipitate and adsorbing colloid flotations of zinc(II) from dilute aqueous solutions have been investigated over a wide pH range using the anionic surfactant Aerosol OT or the cationic collector cetyl pyridinium chloride. In case of adsorbing colloid flotation (ACF) iron oxyhydroxide and aluminium hydroxide were used, either separately or together, as coprecipitants. The precipitate flotation curves were compared with the corresponding theoretical one calculated from the data published for Zn(II) hydrolysis. In addition to the effect of pH on the percent removal the effects of collector concentration, ionic strength, bubbling time and metal ion concentration were investigated and the optimum conditions were established. High removals could be achieved especially with ACF. The results obtained are discussed with respect to the chemical state of zinc, the ionization behaviour of the collectors and properties of the coprecipitants. The developed ACF process was applied to the removal of⁶⁵Zn from radioactive process wastewater.     

Separation and determination of traces of heavy metals complexed with humic substances in fresh waters by sorption on diethylaminoethyl-sephadex a-25

Copper(II), lead and cadmium complexed with humic and fulvic acids in filtered 1-l samples of fresh water are sorbed on a column containing 0.5 ml of the macroreticular weak-base anion exchanger, diethylaminoethyl-Sephadex A-25 at a flow rate of 20 ml min^?1. Simple metal cations are not sorbed at all. The sorbed trace metals are quantitatively desorbed with 4 M nitric acid batchwise and determined by graphite-furnace atomic absorption spectrometry. For synthetic aqueous solutions containing traces of heavy metals and humic acid, the results are in conformity with those obtained by cationexchange separation. About 80% of the sorbed humic substances are eluted with 0.5 M sodium hydroxide solution from the A-25 column and its quantity is estimated spectrophotometrically at 400 nm.     

Ion-pair formation of a copper(II)-ammine complex with an anionic surfactant and the recovery of copper(II) from ammonia medium by the surfactant-gel extraction method.

The extraction and separation of copper(II), zinc(II), cobalt(II), and cadmium(II) were investigated. Both copper(II) and zinc(II) formed ammine-complexes, while cadmium(II) and cobalt(II) formed hydroxide precipitates in an ammonia medium. By the addition of sodium dodecylsulfate (SDS), a copper(II) complex formed an ion-pair (copper-ammine-DS), which was extracted into the SDS phase. However, a zinc(II) complex did not form an ion-pair, and was soluble in water. Copper(II) ion was recovered by stripping (back-extraction) after the addition of hydrochloric acid. This method was applied to the separation of copper(II) in a brass alloy.     

Electrophoretic separations in poly(dimethylsiloxane) microchips using mixtures of ionic,nonionic and zwitterionic surfactants

The use of surfactant mixtures to affect both EOF and separation selectivity in electrophoresis with PDMS substrates is reported, and capacitively coupled contactless conductivity detection is introduced for EOF measurement on PDMS microchips. First, the EOF was measured for two nonionic surfactants (Tween 20 and Triton X‐100), mixed ionic/nonionic surfactant systems (SDS/Tween 20 and SDS/Triton X‐100), and finally for the first time, mixed zwitterionic/nonionic surfactant systems (TDAPS/Tween 20 and TDAPS/Triton X‐100). EOF for the nonionic surfactants decreased with increasing surfactant concentration. The addition of SDS or TDAPS to a nonionic surfactant increased EOF. After establishing the EOF behavior, the separation of model catecholamines was explored to show the impact on separations. Similar analyte resolution with greater peak heights was achieved with mixed surfactant systems containing Tween 20 and TDAPS relative to the single surfactant system. Finally, the detection of catecholamine release from PC12 cells by stimulation with 80 mM K⁺ was performed to demonstrate the usefulness of mixed surfactant systems to provide resolution of biological compounds in complex samples.     

Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam

A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction, conditions for the separation of zinc from cadmium, influence of other cations and anions on the zinc sorption by PU foam, and required conditions for back extraction of zinc from the PU foam. The results show that zinc traces can be separated from large amounts of cadmium at pH 3.0±0.50, with the range of thiocyanate concentration from 0.15 to 0.20 mol l⁻¹, and the shaking time of 5 min. The back extraction of zinc can be done by shaking it with water for 10 min. Calcium, barium, strontium, magnesium, aluminum, nickel and iron(II) are efficiently separated. Iron(III), copper(II) and cobalt(II) are extracted simultaneously with zinc, but the iron reduction with ascorbic acid and the use of citrate to mask copper(II) and cobalt(II) increase the selectivity of the zinc extraction. The anions nitrate, chloride, sulfate, acetate, thiosulphate, tartarate, oxalate, fluoride, citrate, and carbonate do not affect the zinc extraction. Phosphate and EDTA must be absent. The method proposed was applied to determine zinc in cadmium salts using 4-(2-pyridylazo)-resorcinol (PAR) as a spectrophotometric reagent. The result achieved did not show significant difference in the accuracy and precision (95% confidence level) with those obtained by ICP–AES analysis.     

Micellar-enhanced ultrafiltration of cadmium ions with anionic–nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The micellar-enhanced ultrafiltration of cadmium from aqueous solution was studied in systems of anionic surfactant and mixed anionic/nonionic surfactants. The micelle sizes and zeta potentials were investigated by dynamic light scattering measurements. The effects of feed surfactant concentration, cadmium concentration and the molar ratio of nonionic surfactants to sodium dodecyl sulfate (SDS) on the cadmium removal efficiency, the rejection of SDS and nonionic surfactants and the permeate flux were investigated. The rejection efficiencies of cadmium in the MEUF operation were enhanced with higher SDS concentration and moderate Cd concentration. When SDS concentration was fixed at 3 mM, the optimal ranges of the molar ratios of nonionic surfactants to SDS for the removal of cadmium were 0.4–0.7 for Brij 35 and 0.5–0.7 for Triton X-100, respectively. With the addition of nonionic surfactants, the SDS dosage and the SDS concentration in the permeate were reduced efficiently.     

Effect of ionic surfactants on bauxite residues suspensions viscosity

Measurement of the rheological property of bauxite residue sample received from an Australian alumina refinery, treated with a number of cationic and anionic surfactant in laboratory has been carried out using a Brookfield viscometer for the assessment of the effect of surfactants on the residue viscosity. Sodium laurate, prepared with an excess of sodium hydroxide, was found to be effective while direct addition of anionic surfactants (lauric acid and sodium laureth sulphate) and cationic (cetyl trimethyl ammonium bromide) produce only moderate effect on the red mud suspension apparent viscosity at 65 degrees C. The experimental data appear to confirm the crucial role of the cation sodium in the process of adsorption of anionic surfactants on the flocculated red mud particles.     

Rice Bran as an Excellent Sorbent for Heavy Metals from Aqueous Media, 1. Optimization of Conditions

In this two‐part report, the efficiency of rice bran in removal of heavy metals such as cadmium, lead, zinc, nickel, copper and iron(III) from aqueous solution is investigated. The different experimental conditions such as pH, temperature, volume of solution, bran amount, particle size, exchange time, stirring speed, etc. are studied, and the optimum conditions are selected in part 1 of this series of reports. The efficiency of bran in removal of heavy metals is presented with and without treatments. For treatment, heat or acid, alkali and salt solutions were used. The results obtained show that after treating with saturated sodium chloride solution, its efficiency for Ni²⁺ and Zn²⁺ improves. At pH 5, all studied cations have recoveries more than 93% (lead and cadmium 100%). The exchange speed is very high and has preference over the classical ion exchangers.     

乳状液膜体系分离锌(Ⅱ)

研究了span80(失水山梨醇单油酸脂)-SDS(十二烷基磺酸钠)与span80-AOT(2-乙基己基琥珀酸酯磺酸钠)两种乳状液膜体系对锌(Ⅱ)分离效果的比较。分别讨论了液膜体系中表面活性剂和内相试剂浓度、乳水比和油内比对锌(Ⅱ)去除率的影响。试验了锌(Ⅱ)与共存组分的分离。     

Effect of surfactants on bauxite residues suspensions viscosity

Measurement of the rheological property of bauxite residue samples received from an Australian alumina refinery (red mud and neutralised mud suspension) has been carried out using a Brookfield viscometer. The plant samples were treated with two anionic surfactants (sodium polyphosphate and sodium laurate) in the laboratory and the effect of the surfactants on the residues viscosity was determined. It was found that the addition of sodium laurate, prepared with an excess of sodium hydroxide causes reduction of the viscosity of both red mud and neutralised mud while sodium polyphosphate shows very little effect on either samples. The suspensions exhibit non-Newtonian behaviour and obey the power law model over a range of solid concentrations at 75 °C.     

Computational study of cation substitutions in apatites

Density-functional theory plane-wave modeling of fluor- and hydroxyapatites has been performed, where one or two calcium ions per unit cell were replaced with cadmium or zinc cations. It was found that cadmium ions favor Ca(1) positions in fluorapatites and Ca(2) positions in hydroxyapatites, in agreement with experiment. A similar pattern is predicted for zinc substitutions. In the doubly substituted cases, where only hydroxyapatites were modeled, a preference for the substituting ions to be located in Ca(2) position was also observed. Displacement of the hydroxide ions from their symmetrical positions on the hexagonal axis can be used to explain the preferred configurations of substituting ions around the axis.     

Effect of Micelle Composition on Acidic Drugs Separation Behavior by Micellar Electrokinetic Capillary Chromatography

Micellar electrokinetic capillary chromatography (MECC) is a branch of capillary electrophoretic techniques, in which surfactant micelles are added to the electrolyte solution as pseudostationary phase. Separation in MECC is based on electrophoretic mobilities of the analytes when partitioned into micelles1. In this work, four acidic drugs similar in structure with aryl carboxylic acid were separated by MECC. The effects of type of surfactant, such as anionic surfactant SDS, nonionic …